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PC50

INFLUENCE OF XEROGEL STRUCTURE ON SWELLING KINETICS

B. ADNADJEVIC^a, J. JOVANOVIC^b

Hydrogels are three-dimensional, water-swollen structures composed mainly of hydrophilic homopolymers or copolymers [1]. They are rendered insoluble by chemical or physical cross-links. Cross-links provide the network structure and physical integrity. Although hydrogels have a wide range of applications and numerous papers have been published on this topic dealing with the swelling kinetics of various types of hydrogels, there are lack of investigation concerning the hydrogel, i.e xerogel structure .

In this paper the basic structural properties of the used PAA hydrogels were defined: xerogel density, cross-links density, macroporosity, molar mass between cross-links and network mesch size. A several synthetic procedures for preparing poly(acrylic acid) hydrogel with different structural properties were developed. Swelling kinetics at temperature range from 20^o to 45^oC of structurally different xerogels was investigated. Based on the temperature changes of swelling rates constants the swelling kinetic parameters, activation energy (E_a) and pre-exponential factor (A), were determined. Correlation relationship between the structural properties of the hydrogels and the selling kinetics parameters were determined. A possible mechanism of hydrogel swelling of structurally different hydrogels was suggested.

[1] N.A. Peppas, A.G.Mikos, "Hydrogels in Medicine and Pharmacy", Vol. I: Fundamentals, CRC Press, Boca Raton, Florida 1986. p. 2-23;

PC51

PREPARATION AND CHARACTERIZATION OF NONSTOICHIOMETRIC POLYELECTROLYTE COMPLEXES USING CHITOSAN AND PEG MONOSUCCINATE.

T.W. SON ^a, B.G. KIM^a, B.S. KIM ^b, S.M. SUNG ^b

In this study, water-soluble polymer complex prepared from chitosan and poly(ethylene glycol)(PEG)-monosuccinate was established by two-step reaction. PEG-monosuccinate was synthesized by one to one mol ratio of PEG and succinic anhydride. Then, novel water-soluble chitosan-polymer complex was prepared. The chemical structure of polymer complex synthesized from chitosan and PEG-monosuccinate was analyzed through the elemental analysis(EA), FT-IR, ¹H NMR and ¹³C NMR. The result, it was found that the observed EA, FT-IR, ¹H NMR and ¹³C NMR data were good agreement with the new polymer complex. Also, chitosan-polymer complex after synthesized shows excellent solubility in the water.

The present paper is focused on both the preparation of water-soluble, biocompatible, biodegradable and non-toxic polyelectrolyte complex and establishment of best condition in a novel nonstoichiometric polyelectrolyte complexes formed by interaction between two high-molecular weight compounds.

PC52

RHEOLOGICAL PROPERTIES OF CHITOSAN-ALGINATE COMPLEX HYDROGELS

T.W. SON ^a, S.M. SUNG^b, B.S. KIM ^b, B.G. KIM ^a

Natural polymers as biotechnological or biomedical resources have been widely investigated because of their unique properties which include nontoxicity, degradability, and biological compatibility. Especially, hydrogels have been used in the medical device industry as contact lenses, artificial corneas, dressings as coating for sutures and electrode sensors.

Natural polymer hydrogels of polyelectrolyte complexes which have received increasing attention recently. Native chitin itself is known to be insoluble in polar solvent, due to extensive intermolecular hydrogen bonding, however, the chitosan is dissolved in the acid to form a hydrogels of electrolyte complex with a counter-ion polymer such as alginic acid, k-carrageenan, xanthane etc..

Hydrogelswere prepared by mixing the chitosan aqueous solution and the alginic acid solution. The chitosan was dissolved in an aqueous solution of Lactic acid and the alginic acid in a solution of alginate and then the two solutions were mixed to form a homogeneous hydrogel.

According to the results of rheological measurement the hydrogels showed increase in G,' G", viscosity at raising temperature however, tan＆delta is reduce slightly. The gelation results from the interaction of oppositely charged electrolytes to give a polyelectrolyte complex gel.

PC53

EFFECT OF STOICHIOMETRY ON PROPERTIES OF END-LINKED NETWORKS

B. MEISSNER, L. MATĚJKA

The effects of the initial ratio r of crosslinker-to-precursor functional groups concentration on the extent of an end-linking reaction at a constant reaction time were calculated analytically on the basis of the second order reaction kinetics. They were found to be in a close agreement with a recent result of a Monte Carlo simulation (Gilra et al. [1]) which supplied discrete data at a constant number of Monte Carlo steps.

Using the analytical approach, dependences of sol fraction on r measured on poly(tetrahydrofuran) networks (Takahashi et al. [2], diallyl-terminated polymer + tetrathiol crosslinker) could be quantitatively described in the framework of the theory of branching processes [3,4], the only parameter being the rate constant of the thiol - allyl end-linking reaction. Experimental observation that under the condition of a constant reaction time a non-stoichiometric ratio generates a more perfect network with a higher modulus and a lower sol fraction is thus quantitatively explained, for this type of network, by kinetic limitation which prevents the near-stoichiometric systems to achieve high extent of reaction in a reasonable time.

On the other hand, for hydrosilylation end-linked polysiloxane networks kinetic limitation does not seem to be of importance, most probably due to the high rate of the Pt-catalyzed silane-vinyl reaction. Another phenomenon which was anticipated from the mechanism of a disproportionation side reaction has been observed with these networks: an increase in the effective silane crosslinker functionality before or during the end-linking reaction. It has been found to play a significant role in the region of an excess of silane groups.

[1] Giltra et al. J Chem Phys 2000;112:6910-6916.

[2] Takahashi H et al. Macromolecules 1995;28:8824-8828.

[3] Miller DR, Macosko CW. Macromolecules 1976;9:206-211.

[4] Dušek K. Adv Polym Sci 1986;78:1-59.

PC54

A STUDY ON THE EMULSION POLYMERIZATION AND ELECTRICAL CHARGE OF PARTICLES IN PREPARATION OF FINE TONER

S.S. KIM, S.J. LEE

In order to manufacture of PVA particle toner, PVA/PVAc particle was synthesized by emulsion polymerization and surface saponification reaction. Particle size distribution is studied with a particle size analyzer and glass transition temperatures(Tg) are determined with differential scanning calorimeter. Fine spherical PVAc particle with emulsifier initiator V-50 (2, 2'- azo bis (2- amidinopropane) dihydrochloride) was manufactured by emulsion polymerization.

After emulsion polymerization, the PVAc was carried with surface saponification in 10% NaOH for 48hrs. PVA/PVAc skin core particle was obtained under some given saponification conditions. PVA/PVAc particles were dyed with C. I. Reactive Red 2. In dyeing of PVA/PVAc particles with reactive dye, PVA skin side showed high colour value at 0.5g/100ml dye concentration, for 1hr and at 30℃. In order for toner particles to be workable in electrophotography, proper thermal and electrical properties are essential. Electrical charge is measured with a zeta potential measurement apparatus. The variation of electrical charge of PVA toner particles also measured with CCA concentration.

PC55

POLYMERIZATION AND NETWORKING AS A METHOD OF PERMANENT HOLOGRAPHIC RECORD FORMATION

M. KVĚTOŇ^a, A. HAVRÁNEK^b

Processes of radical polymerization and networking are successfully used in mechanisms of holographic record formation and long-time stabilization in novel photopolymer recording materials. Optical holography is a method which makes possible to record and read full 3D optical information (both amplitude and phase of the electromagnetic wave). The holographic image is stored in the material in the form of quasi-periodical modulated refractive index distribution. The typical photopolymer recording material, where the image arises during exposition process, is composed of monomer, initiator and polymer binder. The advantage of the photopolymer material consists in its self-developing characteristics; it does not need wet chemical developing process to reach high quality and stable image. Material is going to be a progressive recording medium for applications as diffractive optical elements for optics communications, high capacity holographic memories and recording media for image holography.

Illumination of the material by the help of interference field starts processes of light induced radical polymerization and diffusion of monomer molecules. Monomer molecules diffuse from dark to bright regions where they polymerize and increase the refractive index. We have prepared and tested material based on acrylamide (monomer), erythrosine B with triethanolamine (initiator) in polyvinyl alcohol matrix (binder). Alternatively N, N'-methylene-bis-acrylamide (cross-linker) and acrylic acid (plasticizer) has been added. Diffraction gratings (simple hologram with periodical refractive index modulation) have been exposed in thin layers of this recording material and the diffraction efficiency grow-curves have been detected. We have tested the response of the material to its composition and illumination parameters. Especially the role of cross-linker has been investigated; it seems that branching and cross-linking, i.e. formation of a network, is necessary for obtaining a stable hologram.

PC56

POLYMER GROWTH DETECTED BY HOLOGRAPHIC METHOD

M. KVĚTOŇ ^a, J. HAVRÁNKOVÁ ^b, A. HAVRÁNEK ^c

In our previous contribution (Květoň, Havránek: Polymerization...) we have described how a hologram may be created by photo-polymerization and we have presented the results of our experimental investigations of the process. We have tried to solve the question whether the polymer creating the hologram is linear, branched, or if it forms a network.

For better understanding the experimentally obtained curves describing the growth of a holographic grating, we put down the theory of the early stages of polymer growth. This theory completes the usually used diffusion theory especially in the cases where the role of low-mers (di-mers, tri-mers etc.) is not negligible. The main idea of the theory is that the growing polymer chain looses its mobility and so it stabilises its position in the bright regions of the recorded interference field. In the framework of the theory we have discussed the curves of hologram diffraction efficiency for various compositions of the layers and for various intensity and time profiles of exposition. We have tried to find the conditions for obtaining the best hologram.

In this contribution we shall concentrate ourselves on the inverse problem. If the diffraction efficiency growth is in close connection with the growth of the polymer, we may investigate the kinetics of the polymer growth by measuring the increase of the hologram efficiency. We have the equipment, which allows us to measure the immediate values of diffraction efficiency, and so we have a tool for investigation of polymer kinetics. The theory of the early stages of hologram growth gives us some introductory orientation in the problem. The theory is now solved only for linear polymers but in reality the effect of branching cannot be omitted. We hope that we will be able to give some new results to this more complex problem in our poster presentation.

PC57

POLYPEPTIDE INCORPORATION IN OPPOSITELY CHARGED MICROGELS

H. BYSELL, M. MALMSTEN

The aim of this project was to investigate the electrostatic interactions of different sized polylysine (pLys) and oppositely charged microgels made from polyacrylic acid (PA) and to study the effect of pH and ionic strength on these interactions. Due to their extensive swelling/deswelling behavior such microgels have potential as drug delivery vehicles, e.g. for protein drugs and it is therefore of great importance to outline the mechanisms of interactions between such microgels and polypeptides.

The deswelling kinetics of PA microgels was studied with light microscopy/micromanipulation techniques and the distribution of pLys within the gel network was studied with confocal microscopy. A study on sequential adsorption of different sized pLys as well as oppositely charged polypeptides on PA microgels was also performed using this later technique. The uptake of pLys in microgel particles was measured spectrophotometrically.

Results obtained so far indicate that pLys of low to intermediate molecular weight penetrate the entire network (fig 1) thereby causing a rapid deswelling of the microgel already at fairly low concentrations. A high molecular weight pLys distributes to the surface of the microgel particle, creating a dense surface layer (fig 2) which appear to induce a charge reversal of the surface. This surface layer seems to create an electrostatic but not steric barrier for other polypeptides to enter the microgel particle. The effect of pH and ionic strength on the interactions of pLys and PA microgels seems quite moderate.

FIG. 1	FIG. 2

PC58

TEMPERATURE- AND SOLVENT-SENSITIVE HYDROGELS BASED ON N‑ISOPROPYLACRYLAMIDE AND N,N-DIMETHYLACRYLAMIDE

K. PAGONIS, G. BOKIAS

Water-soluble polymers and hydrogels responsive or sensitive to external stimuli like temperature, pH, ionic strength, solutes or solvent composition, represent nowadays an important and active research area, due to the many possible applications of such smart materials in diverse technological fields. Recently, research focus on multi-stimuli materials, i.e. to polymers or hydrogels responsive or sensitive to more than one external stimuli.

In order to prepare hydrogels sensitive both to temperature and solvent composition we have exploited the cononsolvency properties of poly(N-isopropylacrylamide), PNIPAM, and poly(N,N-dimethylacrylamide), PDMAM, in mixtures of water with polar organic solvents, like dioxane. It is known that the homopolymer PNIPAM exhibits a Lower Critical Solution Tenperature (LCST)-type conosolvency behavior in water-dioxane mixtures rich in water, i.e. PNIPAM phase separates from such water-dioxane mixtures upon heating. In addition, we have recently shown that the homopolymer PDMAM exhibits the inverse cononsolvency behavior in water-dioxane mixtures, i.e. PDMAM phase separates from water-dioxane mixtures rich in dioxane upon cooling (Upper Critical Solution Temperature (UCST)-type cononsolvency).

To combine the UCST-type conosolvency properties of PDMAM with the LCST-type cononsolvency properties of PNIPAM in water-dioxane mixtures we have prepared a series of hydrogels containing N-isopropylacrylamide, NIPAM, and N,N-dimethylacrylamide, DMAM, by random copolymerization in water of the two monomers in the presence of N,N-methylenebisacrylamide. The NIPAM-content of the hydrogels varied between 0 up to 100 mol%. The degree of swelling of these hydrogels in water-dioxane mixtures was studied as a function of temperature and solvent composition. Depending on the hydrogel composition, the swelling ability of the hydrogels is found to be sensitive to temperature and solvent composition, exhibiting either an LCST- or a UCST-type cononsolvency behavior. Moreover, for some hydrogels both LCST and USCT-type cononsovency properties are observed, depending on the solvent composition.

PC59

AQUEOUS DISPERSIONS BASED ON POLYURETHANE/ POLYMETHACRYLATE SEMI-INTERPENETRATING NETWORKS

A. ANŽLOVAR, M. ŽIGON

In this contribution we extended our studies of polyurethane/ polymethylmethacrylate semi-IPNs (SIPNs) to aqueous dispersions with the aim to prepare solvent free IPNs for coatings and adhesives. Two series of SIPN aqueous dispersions were synthesized: in the first series we varied the NCO/OH ratio and consequently the molecular weight of the PU component while in the second one the molar ratio between carboxylic and tertiary amine groups were varied. The linear PU component was quantitatively polymerized in the acrylic monomer and solution was dispersed in deionized water. The polymerization and cross-linking of the acrylic component took place inside the particles. The synthesized SIPN dispersions were stable for at least three months. The molecular weight averages of the synthesized PU components were determined by the size exclusion chromatography (SEC) and the content of the residual acrylic monomers was determined by the GC-MS. Weight average molecular weights varied between 19000 and 51000 while the methacrylic monomer concentration in SIPN dispersion was below 0.5 wt. %. The particle size distributions of SIPN dispersions were determined by the photon correlation spectroscopy. The particle diameters of the first series were in the range between 45 and 60 nm while in the second series they increased from 55 nm to 100 nm by increasing the concentration tertiary amine groups. This was also confirmed by the scanning electron microscopy (SEM) which showed that the SIPN particles are spheres with diameters between 100 and 200 nm. The miscibility of PU and PM components in SIPN aqueous dispersions were studied by the shifts of glass transition temperatures determined by the differential scanning calorimetry (DSC). DSC curves of SIPNs showed two glass transitions (between -45 and 70 ^oC and between 55 and 120 ^oC) indicating that polyurethane (PU) and polymethacrylic (PM) components form separate phases. The introduction of tertiary amine functional groups enhanced the miscibility of both components in SIPNs due to the interaction between the carboxylic groups of the PU and the tertiary amine groups of the PM component. However, in all the samples two glass transitions were observed indicating that despite the enhanced miscibility the resulting semi-IPNs are two phase systems.

PC60

NOVEL HYBRID HYDROGELS SELF-ASSEMBLED FROM HPMA COPOLYMERS CONTAINING COILED-COIL PEPTIDE GRAFTS

J. YANG^a, C.XU^a, C.WANG^b, J.KOPEČEK^a,c

Peptide/protein self-assembly is an increasingly used strategy for the synthesis of new nanostructured materials. In this presentation, a series of leucine-zipper peptides that self-assemble into homo- and/or heterodimers and serve as physical crosslinkers of hybrid hydrogels were investigated. These peptides were synthesized by the solid-phase method and characterized by reversed-phase high-performance liquid chromatography, amino acid composition analysis, and mass spectrometry. The ability of these peptides to form α-helical structures and to adopt the two-stranded α-helical coiled-coil conformation was studied by circular dichroism spectroscopy and sedimentation equilibrium experiments. The results demonstrated that the formation of the coiled-coil structure is highly dependent on the sequence and chain length of peptides as well as environmental factors, such as pH and temperature.

These peptides were covalently attached to N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer backbone containing pendant maleimide groups. Microrheology was utilized to monitor the gelation process. The results revealed that the assembly of these materials is controlled not only by the structure of peptide motifs but also the solution conditions. The minimum length of the peptides for the formation of hydrogel is three heptads, which corresponds to the minimum size needed for coiled-coil folding. This suggested that self-assembly of graft copolymer hydrogels was mediated by folding associations of coiled-coil domains. It appears that a stimuli-responsive and reversible system was rationally designed and will have potential in tailoring supramolecular structures for drug delivery, tissue engineering, and other biomedical applications.

The research was supported in part by NIH grant EB005288.

PC61

NOVEL AZO BOND-CONTAINING PH-SENSITIVE IPN HYDROGELS: DESIGN, CHARACTERIZATION, AND APPLICATION

P. CHIVUKULA^a, K. DUŠEK^b, D. WANG^a, M. DUŠKOVÁ-SMRČKOVÁ^b, P. KOPEČKOVÁ^a, J. KOPEČEK^a

Novel interpenetrating network (IPN) hydrogels, composed of pH-sensitive, aromatic azo group containing network as one component (Network A), and a hydrolyzable network as the other (Network B) were prepared by a sequential process. The structure - property relationship of interpenetrating network (IPN) hydrogels was investigated.

The first network was formed by crosslinking of a reactive polymer precursor (copolymer of N,N-dimethylacrylamide, acrylic acid, N-tert.butylacrylamide, and N-methacryloylglycylglycine p-nitrophenyl ester) with an aromatic azo group containing diamine ((N,N'-ε-aminocaproyl)-4,4'-diaminoazobenzene). The second network was formed by radical crosslinking copolymerization of N-(2-hydroxypropyl)methacrylamide with N,O-dimethacryloylhydroxylamine. Hydrogels synthesized in this manner were homogeneous and showed no evidence of phase separation. The composition of the hydrogels was manipulated to determine the influence of hydrogel composition on the equilibrium degree of swelling, modulus of elasticity in compression, and on the rate of degradation of network B. To mimic the conditions in the gastrointestinal tract, properties of the hydrogels were evaluated after abrupt change of pH from pH 2.0 to pH 7.4. The analysis of IPN structure revealed that crosslinking efficiency of radically polymerized networks B (10-30%) was lower than that of step polyaddition networks A. In the IPN gels, the crosslinking efficiency was even lower and was close to 10%. Factors contributing to the low crosslinking efficiency of IPN include higher dilution at network formation and possible negative effect of the components of network A on radical polymerization of network B. The major advantage of IPN hydrogels, when compared to traditional pH-sensitive networks, is the linear swelling profile following abrupt change of pH from 2 to 7.4. This indicates the suitability of IPN hydrogels as carriers for drug delivery to the colon.

At present, the application of IPN hydrogels in noninvasive colorectal cancer screening and positron emission tomography imaging is being evaluated.

PC62

NEW FINDINGS IN THE PHASE BEHAVIOUR OF AQUEOUS SODIUM OLEATE SYSTEM. STRUCTURAL ANALYSIS BY RHEOLOGY, DSC AND NMR

A. ABREU ¹,F.E. ANTUNES², L. COPPOLA¹, D. GAUDIO¹, C. OLIVIERO¹, I. NICOTERA¹*

The phase behaviour of the aqueous solution of sodium oleate binary system is being used for different studies using this surfactant. However, the reference literature which supports such studies is from several decades ago. An approach to sodium oleate phase diagram was made in 1939. Our purpose of this investigation is to revisit the binary system, applying modern techniques to the study: Optical polarizing microscopy, micro differential scanning calorimetry (DSC), ²H-NMR spectroscopy, PFG-NMR and Rheology, starting from 0.01 and up to 30 wt% sodium oleate and within the temperature interval 5-70°C. The experiments show a structural evolution in the micellar phase and two different regions in this phase induced by temperature.

PC63

Fabrication of Ag-PVA hydrogel nanocomposites BY Gamma irradiation

A. Krklješ, J. Nedeljković, Z. Kačarević-Popović

Hybrid systems consisting of metal nanoparticles and organic polymers exhibit novel combination of particle and polymer properties and have great potential in technological and biomedical applications. PVA has received much attention in pharmaceutical, biomedical, and biochemical applications. On the other hand metal nanoparticles such as Ag provide a very interesting research area because they have close-lying conduction and valence bands in which electrons move freely. Radiolytic reduction of aqueous metal ions is a simple, clean, important technique for producing homogeneous colloidal dispersions of small metal particles Moreover, not much work has been reported so far on the radiolytic formation of metal clusters in hydrogel matrix which offers many advantages.

The Ag-PVA nanocomposit films with different contents of inorganic phase have been prepared by gamma radiolyticaly reduction of Ag⁺ ions in a PVA hydrogel matrix which was previously obtained at one gamma dose. Optical properties of the Ag-PVA nanocomposite investigated by UV-visible absorption spectroscopy revealed the presence of surface plasmon absorption band at 413 nm and no absorption band in the longer wavelength region of 500-700 nm, which is usually assigned to higher aggregates. Molecular structure of the nanocomposite has been investigated by the IR spectroscopy. Thermal and thermooxidative properties of the Ag-PVA nanocomposites were affected by the content of the nanofiller.

PC64

STRUCTURE DEVELOPMENT DURING THE FORMATION OF MULTIPHASE POLYURETHANE NETWORKS

J.L. STANFORD*, P.A. COOKSON

The formation of water-blown flexible polyurethane foam, from liquid monomers and oligomers, involves a complex combination of chemical and physical events. From room temperature and in less than five minutes, a liquid mixture of relatively low molar mass components is transformed into a material with a supramolecular architecture in the form of a cellular solid. The chemical reactions occurring during foam formation lead to the formation of a segmented block copoly(urethane-urea), of the -(H_mS)_n- type, where H_m represents the polyurea hard segment with a degree of polymerisation m, and S is the poly(ether-urethane) soft segment: n is the degree of polymerisation of the block copolymer.

As copolymerisation proceeds, the core of the rising polyurethane foam becomes self-insulated by the surrounding polymerising mixture creating, in effect, a quasi-adiabatic temperature environment. The emphasis in the present studies has been on the measurement of adiabatic temperature rise profiles for individual foam systems to provide an accurate kinetics basis for subsequent forced-adiabatic temperature FTIR spectroscopy to establish the sequence of chemical events and the role that the kinetics of polymerisation and microphase separation play in the development of morphology and structure in flexible polyurethane foams. The apparent microphase-separation transition was shown to occur between 80 and 120 s at an isocyanate conversion of p_NCO = 0.57±0.05, well before the formation of a covalent polymer network.

Real-time rheological measurements were also made under forced-adiabatic temperature conditions to give modulus development and normal force changes occurring during polyurethane foam formation.

Correlating the data from the time-resolved analytical techniques gives a quantitative description of the complete sequence of chemical, physical and morphological events that occur during the reactive processing of these multiphase polyurethane networks.

PC65

EFFECTS OF BISMALEIMIDE RESIN ON DIELECTRIC, DYNAMIC THERMAL DEGRADATION AND DYNAMIC MECHANICAL PROPERTIES OF EPOXY-AMINE BASED GLASS-FABRIC-REINFORCED NETWORKS/COMPOSITES

L. RAJABI¹*, R. MIRABDOLBAGHI², GH. MALEKZADEH ³

Effects of Bismaleimide, BMI, Resin (4, 4'-Bismaleimido diphenyl methane) on Dielectric properties [Permittivity (e'), Loss factor (e") and Ionic Conductivity (σ)] is measured during Dynamic curing (over a temperature range 20-300°C) of two different epoxy-amine resin systems using DEA. Dynamic thermal degradation studies of the same resin systems is performed by TGA and the dynamic mechanical properties [flexural storage and loss moduli (E' and E") and shear storage and loss moduli (G' and G")] of the glass-fabric reinforced composites (laminates) of the above mentioned resin matrices is carried out by DMA.

Double exothermic curing peaks are observed for the formulations with DDS as curing agent. For each system, that region of the curve in which the value for ionic conductivity displays a frequency-dependency, indicates that, the measurement is strongly influenced by dipole relaxations. At temperatures near or below T_g, dielectric properties of resins are dominated by the molecular dipoles (frequency-dependent response). Ionic conductivity increases largely on using DDS as curing agent for DGEBPA over MDA however, addition of BMI to DDS- and MDA-cured thermosets decreases the ionic conductivity in the former and increases in the later resin systems.

Addition of bismaleimide (BM) resin in three different concentrations to the glass-fabric DGEBPA: MDA and DGEBPA: DDS laminates, increased T_g, T_g∞ and flexural and shear storage moduli (E' & G') considerably with an exception of the DGEBPA: DDS/BM (15%) laminate.

Key Words: Epoxy-amine, Composite, Bismaleimide, DEA,TGA, DMA.

PC66

ASPECTS OF GELATION ON POLYSULFIDE PREPOLYMERS BY NUMERICAL SIMULATION

K.H. TSOI, B.W. DARVELL

Polysulphide prepolymers have many applications such as dental impression materials, sealants and adhesives. These applications involve the polymerization from prepolymer fragments to polymer. In this process, gelation is a key factor affecting the mechanical properties of the polymer.

From some previous studies, low molecular weight fragments were found to be predominant, including loops, in the prepolymer fragment distribution. Such a distribution differs from some common distributions, and could cause gelation to behave differently. Some experiments using rheology and titration to study gelation of prepolymers have given poor results due to wrong assumption on the prepolymer fragment structures, and errors inherent in the method on the experiments. Computer simulation may be a powerful tool for investigating the effects and occurrence of gelation.

In this study, numerical simulation using Monte Carlo techniques were used to emulate a system containing polysulphide monomers with various proportions of branching trifunctional monomer. The monomer array size was five million. These monomers were initially 'bonded' randomly to represent full polymerization. Then this 'polymer' was randomly 'debonded' to various extents, to yield the prepolymer fragments. The molecular weight distribution of fragments was determined by counting.

The simulation data results fragment number and weight distributions, fragment structures, and gelation profile, for the various prepolymer. With these simulated data, a general gelation relationship is established for this type of prepolymer.

PC67

ELECTROSTATIC INTERACTIONS BETWEEN PROTEINS AND MICROGEL PARTICLES

C. JOHANSSON, M. MALMSTEN

Microgel particles are polymer networks that swell/deswell as a response to changes in the environment. As a model for studying electrostatic interactions between protein drugs and polyelectrolyte microgels, we study the interactions between lysozyme and microgel particles of loosely cross-linked poly(acrylic acid).

When lysozyme (positively charged) is distributed into the negatively charged microgel, the microgel deswells, embracing the protein. We study how ionic strength and pH affect the interactions between protein and microgel. Binding isotherm studies show the effect on protein loading, and confocal microscopy show the effect on protein distribution.

A micro pipette equipment is used to study time dependent volume changes of specific microgels being loaded with lysozyme, and to study the effect of pH and ionic strength on these volume changes. Experiments show that the V/V0-decrease is more pronounced when lysozyme is incorporated at low ionic strength.

Protein incorporation is generally higher at low ionic strength. At high ionic strength, lysozyme incorporation increases strongly with decreasing pH. This pH-dependence is less pronounced at lower ionic strength. Binding isotherms show that lysozyme incorporation mostly is governed by protein charge alone, rather than by some combined charge contrast.

Altogether, we try to give an overview on how pH and ionic strength affect the electrostatic interactions between protein and microgel.

PC68

Binding and Unbinding of LysozymE to a Poly(styrenesulfonate) gel

M. ANDERSSON, P HANSSON

The project deals with the binding and unbinding of charged proteins with oppositely charged polymer gels. Our aim is to find key factors determing determing the stability of the complex salt formed, including how the structure of the complex salt depend on the presence of salt, on pH changes, and variations in charge density on the components. Specifically we are looking at the model system of egg-white lysozyme and covalently crosslinked gels of poly(styrene sulfonate).

The main technique used is micromanipulator assisted flouresent light microscopy, using sub-mm sized (~50-100µm) gel beads, in aqueous solutions; Result from time resolved meassurements is presented (looking at the changes of particle volume, induced by complex fomation from binding of the protein), together with studies on equilibrium volume in varied environments (e.g. different pH and ion-strenght). Also the results from Small Angle X-ray Spetroscopy of the system will be presented. Intermediateate structures formed on a macroscopic scale, eg. phase separations in the network, is looked at, as is the influence of such on the dynamics of binding and unbinding.

PC69

Surfactant-induced DESWELLING of polyacrylate gels

P. NILSSON*, P. HANSSON

Earlier studies have shown that crosslinked polyacrylate gels spontaneously absorb cationic surfactants [1]. The strong interaction between the cationic surfactant micelles and the anionic polyacrylate network [2] limits the osmotic swelling of the gels, resulting in volume changes of up to 100 times compared to a surfactant free system. Since the amount of surfactant available is kinetically limited by stagnant layer diffusion, the entire gel cannot collapse at once. Instead, the outer part of the gel will collapse first, forming a dense, rubber-like skin around a swollen core. Since the two phases (skin and core) are part of the same network, they cannot separate like the non-crosslinked polymer would and they therefore influence each other's equilibrium states, resulting in a less swollen core and less dense skin [3]. Describing the partial collapse of the network as well as the deswelling kinetics is crucial to understanding the interaction of the surfactant and the crosslinked polymer.

We have now studied the interaction of micrometer sized (radius~70 microns) polyacrylate gels and dodecyltrimethylammoniumbromide (DoTAB) by light microscopy under conditions of forced convection. The gels were handled using a micromanipulation system and digital images of the deswelling gels were captured, allowing the deswelling behaviour to be evaluated over time. A semi-empirical model based on the equilibrium of the osmotic swelling and the deformation of both the gel network and the skin was used to theoretically predict the deswelling [4]. In order to test the model, parameters such as gel size, surfactant concentration and flow rate were varied. The model could account for all these variations, and the effect on the deswelling was correctly predicted.

The aim of the work is to build a base for future development of controlled release drug vehicles, using the dense collapsed phase as a diffusion barrier.

References:

[1] Hansson, P., Langmuir, 1998, 14, 2269

[2] Hansson, P., Langmuir, 2001, 17, 4167

[3] Hansson, P.; Schneider, S.; Lindman, B., J. Phys. Chem. B, 2002, 106, 9777

[4] Göransson, A.; Hansson, P., J. Phys. Chem. B, 2003, 107, 9203

PC70

SYNTHESIS AND SWELLING BEHAVIOR OF pH- AND TEMPERATURE-SENSITIVE POLY[2(DIMETHYLAMINO)ETHYL METHACRYLATE-co-2-ACRYLAMIDO-2-METHYLPROPANE-1-SULFONIC ACID] HYDROGELS

S. ÇAVUŞ, G. GÜRDAĞ

Poly(dimethylaminoethyl methacrylate-co-2-acrylamido-2-methyl-1-propane sulphonic acid) [poly(DMAEMA-co-AMPS)] hydrogels were prepared by free radical copolymerization in water at 60 ^oC for 24 hour in the presence of tetraethyleneglycol diacrylate (TEGDA) as cross-linking agent. Freshly prepared ammonium persulphate (APS) solution and N,N'-tetramethylethylenediamine (TEMED) were used as initiator and accelerator, respectively. Hydrogels with different feed compositions were prepared by keeping the total monomer concentration constant as 1 and 0.5 M. While the crosslinking agent, TEGDA, was used in the 3 and 2 mol % of total amounts of the monomers, APS and TEMED were 1 mol % of total monomer content.

In order to observe the effect of pH of swelling medium on the swelling values, equilibrium swelling values of these hydrogels were determined both in distilled water and in different buffer solutions (pH=2.8, 5.3, 7.0, 10.0, and 12.40) with constant ionic strength (I = 0.08 M) at room temperature. The influence of temperature and comonomer (DMAEMA/AMPS) molar ratios on the swelling behavior of [poly(DMAEMA-co-AMPS)] were also investigated.

The appearance of the hydrogels depends on the feed composition and it becomes opaque with the increase in dimethylaminoethyl methacrylate (DMAEMA) content in feed composition.

PC71

STRUCTURE FORMATION IN POLYACRYLONITRILE-PROPYLENE CARBONATE SOLUTIONS IN GELATION.

S.A. UDRA, V.I. MASHCHENKO, L.A. KAZARIN, V.V. SOROKIN, V.I. GERASIMOV

A structure formed on gelling influence on structure and properties of materials based on the gels. Therefore knowledge of structureformation features in gelation allow to control properties of end materials.

In this investigation, behavior of an ultra high molecular weight polyacrylonitrile-propylenecarbonate (PAN-PC) system was examined. On using methods of small-amplitude oscillatory shear rheology and turbidity spectra kinetic of processes led to physical gelation in PAN-PC solutions was studied.

Using properties of critical gels times of gelation were determined with rheological metod and the temperature dependence was plotted.

Character of appearance and development of heterogeneities during phase separation in the system under investigation was cleared up with a turbidity spectra method.

It was defined how dimensions of the heterogeneities connect with the process of gelation characterized from the rheological data. Gelformation at 70^оС result in the most heterogeneous structure in compare with the other temperatures. Both increasing and decreasing of temperature relatively of 70^оС lead to visible reduction of the sizes of the heterogeneities before gelation. These data correlate with the recently ones obtained with SEM. Sizes of the heterogeneities in the micrographs of xerogels obtained from the gels are also the largest at 70^оС.

This work was supported by the Russian Foundation for Basic Research (project 05-03-32711-а), Programs "Universities of Russia" (project No. UR-06-02-550) and «Leading science schools» (project No. 902-2003-3).

PC72

SYNTHESIS AND PROPERTIES OF HYDROGELS BASED ON POLYACRYLAMIDE

F. KUČERA, E. KOSTELECKÁ

The current knowledge of cross-linking kinetics in polyacrylamide networks was reviewed. The experimental part of this work was focused on synthesis of polyacrylamide gels and on kinetics of network formation.

Polyacrylamide gels were prepared by free radical copolymerization of acrylamide and N,N´-methylenebisacrylamide in aqueous solution at 23°C. The influence of concentration of cross-linking agent on the kinetics of polymerized system was investigated. The double bonds conversion and critical double bonds conversion at gel point were calculated. The positive substitution effect was observed, i.e. the critical conversion decreased with increasing concentration of cross-linking agent. The amount of sol and gel content in prepared samples was determined using liquid extraction. It was observed; that with increasing concentration of cross-linking agent amount of sol decreased.

Acknowledgements:

This work was supported by the Ministry of Education, contracts: MSM0021630501.

PC73

SYNTHESIS OF FLEXIBLE NETWORK POLYMERS CONSISTING OF CENTIPEDE-TYPE PRIMARY POLYMER CHAINS BY ALLYL POLYMERIZATION

H. ITO, H. AOTA, A. MATSUMOTO

Department of Applied Chemistry, Faculty of Engineering and HRC, Kansai University, Suita, Osaka 564-8680, Japan (amatsu / ipcku.kansai-u.ac.jp)

We have been concerned with the free-radical crosslinking polymerization and copolymerization of multivinyl monomers, mainly focused on the elucidation of network formation mechanism. In this study, we attempted to prepare the novel homogeneous network polymers with abundant dangling chains as an extension of multiallyl crosslinking polymerization which provides network polymers consisting of short primary polymer chains.

Thus, allylic prepolymers having different amounts of pendant allyl groups and different molecular weights were prepared by allyl methacrylate (AMA) homopolymerization and AMA/alkyl methacrylate (RMA) copolymerizations in the presence of lauryl mercaptan as a chain transfer agent; they were subjected to the post-copolymerizations with allyl benzoate (ABz)/vinyl benzoate monomer mixtures. The gelation depended significantly on the allylic prepolymer concentration and the amount of pendant allyl groups of prepolymers. Notably, this type of network polymer contains short primary polymer chains having abundant oligomeric side-chains as a reflection of characteristic allyl polymerization.

In addition, we tried to prepare the novel centipede polymers as primary polymer chains of network polymer having abundant dangling chains by utilizing allyl polymerization. Thus, AMA/RMA precopolymers were copolymerized with ABz to provide novel centipede polymers by the suppression of the intermolecular crosslinking reaction. Moreover, the preparation of novel inhomogeneous network polymers with abundant dangling chains was done by employing densely-netted AMA/RMA/ethylene dimethacrylate precopolymers. The characteristic swelling behavior of resulting lipogels is discussed.

PC74

Kinetic INVESTIGATION of free-radical crosslinking vinyl/divinyl copolymerizations resulting in hydrophilic network polymers by ir spectra

K. NAKAMURA, H. AOTA, A. MATSUMOTO

As part of our continuing studies concerned with the mechanistic discussion of 3-dimensional network formation in the free-radical monovinyl/divinyl copolymerizations, we have reported the preparation of novel amphiphilic network polymers consisting of short primary polymer chains and long crosslink units with opposite polarities.¹ In this study, our previous work was further extended to the mechanistic discussion of hydrophilic network polymer formation in an aqueous solution crosslinking monovinyl/divinyl copolymerization.

Here, we used the ReactIR reaction analysis system. ReactIR has the outstanding function of offering us IR spectra at regular time intervals throughout the entire course of chemical reactions. Thus, it was applied to the in-situ, real-time analysis of free-radical crosslinking methacryloyloxyethyltrimethylamm-onium chloride (METMAC) /tricosaethylene glycol dimethacrylate (PEGDMA-23) copolymerizations. The reaction was pursued by employing the absorption band at 1250 cm^-1 assigned to the backbone methyl groups of the resulting polymer (Fig. 1). Especially, this method is powerful for the detailed kinetic study of the free-radical crosslinking polymerization at an early stage of polymerization before gelation.

The present work is mainly focused on the primary polymer chain dependency of network formation governed by Flory-Stockmayer gelation theory. In addition, various crosslinking monovinyl/divinyl copolymerizations are explored by employing 2-hydroxyethyl methacrylate in place of METMAC and by changing the crosslinker from PEGDMA-23.

1) M. Doura et al., Macromolecules, 36, 8477 (2003); J. Polym. Sci.: Part A: Polym. Chem., 42, 2192 (2004).

PC75

GELATION BEHAVIOR AND PROPERTIES OF POLY(VINYL ALCOHOL) AND POLY(ACRYLIC ACID)

J. H. KIM^a, J. S. YEO^a, H. C. KIM^a, S. H. KIM^a, D. S. KIM^a

The gelation behaviors of poly(vinyl alcohol)(PVA) and poly(acrylic acid)(PAA) were investigated with various gel-forming condition. The gel of PVA was formed physically and by chemical cross-linking either. We also prepared the blend gel of PVA and PAA with the reaction of cross-linking agent. The properties of gels of the polymers were studied in terms of processing condition and environment.

The rate of gelation and the rate of phase separation of PVA solutions were observed with the mixed solvent of DMSO/water at the quenching temperature of 0℃ and 25℃. The gelation time was gradually shortened with increasing DMSO ratio in the solvent up to 60/40(DMSO/water)(Fig. 1). PVA solutions at 0℃ showed high transparency except 0/100, 90/10, and 100/0(DMSO/water) solutions.

Particularly, the solution in the solvent of 80/20 (DMSO/water) still maintained its transparency after 20,000 min. From the results of gelation experiments, it could be inferred that the internal structure of PVA gel formed from 80/20(DMSO/water) solution is the most stable. The other results were also discussed with some variables of the gels.

Fig. 1. Rate of gelation t_gel^-1 (●) and rate of phase separation t_ps^-1 (○) of Poly(vinyl alcohol) at 25 ℃.

PC76

Monitoring of crosslinking reaction of collagen hydrolysate with glutaraldehyde by optical method

M. NAVRÁTIL, V. KŘESÁLEK

The nature of the reaction between collagen and cross-linking agents is important in leather technology. The question how to control the reaction is still unanswered because at the present there is no suitable or reliable measure of its progress. From the many cross-linking type reactions that occur, it is convenient to monitor the reaction of glutaraldehyde because the condensing reaction is accompanied by a change in colour. It would be very useful to explore and determine the relationship between degree of cross-linking and change optical properties. The paper describes some of the important measurement which is focused on optical sensor design.

PC77

FORMATION-STRUCTURE-PROPERTIES RELATIONS IN EPOXY NETWORKS REINFORCED WITH POLYHEDRAL OLIGOMERIC SILESQUIOSCANES (POSS)

I. KROUTILOVÁ, L. MATĚJKA, J. PLEŠTIL, M.STEINHART, M. ŠLOUF

Along with increased use of synthetic polymers more demanding requirements have come, such as higher temperatures of use and greater resistance to oxidation. A recent approach has been the development of new materials that have properties intermediate between those of traditional organic systems (i.e. polymers) and those of traditional inorganic systems (i.e. ceramics).

Here we describe some of our preliminary efforts to prepare well-defined, nanoreinforced, polymeric hybrids with enhanced properties, that can be understood and tailored at the molecular level. We have studied classical epoxy networks based on diglycidyl ether of Bisphenol A (DGEBA) and poly(oxypropylene)diamine (Jeffamine D2000) reinforced with various types of polyhedral oligomeric silsesquioxane (POSS). According to the functionality of POSS monomer (mono-, di-, tetra- and octaepoxide) POSS units can be incorporated into the network either as dangling units or parts of the chain backbone or network junctions. The aim of this investigation was to explain an effect of POSS on thermal and mechanical properties of the network, determine supermolecular structure of the system and POSS interactions contributing to the reinforcement. The organic-inorganic (O-I) systems were characterized by SAXS, WAXS, TEM and DMA.

The relationships between formation, structure and thermomechanical properties of these hybrid materials are discussed. The main factor affecting the O-I network structure and mechanical properties is the interaction between POSS nanosized units resulting in aggregation and possible self-assembly.

PC78

ORGANIC-INORGANIC HYDROGELS WITH THERMORESPONSIVE PROPERTIES

M. UCHMAN, B. STRACHOTOVÁ, M. ŠLOUF, L. MATĚJKA

The thermoresponsive organic-inorganic (O-I) hydrogels based on cross-linked poly(N-isopropylacrylamide) (PNIPA) were prepared and characterized. The inorganic phase, silica or silsesquioxane domains, was formed in-situ via sol-gel process during PNIPA network formation. The goal of the investigation was to obtain heterogeneous PNIPA-based gels with fast response to temperature change and with improved mechanical properties. We have prepared two types of materials: interpenetrating networks and gels with covalently bonded silsesquioxane domains, using tetrametoxysilane (TMOS) or (3-methacryloxypropyl)trimetoxysilane (MPTMOS) as precursors of the inorganic phase. Both types of hydrogels were prepared under homogeneous as well as under heterogeneous conditions, i.e., at polymerization temperature above lower critical solution temperature.

The introduction of the inorganic phase resulted in a significant acceleration of swelling-deswelling kinetics in comparison to non-modified PNIPA, and in improved mechanical properties of the hydrogels. The interpenetrating O-I networks prepared using TMOS showed larger response to temperature change than the materials with covalently bonded silsesquioxane domains formed by copolymerization of NIPA with MPTMOS. The latter showed a fast but small response. In both types of hydrogels the heterogeneous conditions of preperation resulted in further acceleration of swelling-deswelling kinetics.

PC79

Crosslinked methacrylate-based polymer gels as supports for immobilized metal affinity chromatography (IMAC)

K. Kráčalíková^a,b, M. Bleha ^a

Crosslinkedpolymer gels in form of spherical particles were prepared from 2,3-epoxypropyl methacrylate (GMA), 2-(2-hydroxyethoxy)ethyl methacrylate (DEGMA) and ethylene dimethacrylate (EDMA) by suspension radical polymerization in aqueous medium.

The swelling of the gel particles in several solvents was determined by the volume swelling ratio, q_v (q_v = V_swolen/V_dry). Since the networks show low swelling as a consequence of high crosslinking densities (q_v 1.0-1.2 for water and alcohols and 1.3-1.8 for DMF), the solvent uptake by porous particles relates mainly to the filling-up of the pores. This fact was proved by the determination of the sorption-expansion balance H (H = q_w/q_v; q_w is a weight analogy of q_v). High values of H (for porous polymers H @ 2), would be a sign of high solvent regain, which is the ideal condition for rigid-network particles.

On the basis of q_v and H values and other structure parameters such as density, specific surface area, pore size distribution of porous particles and considering the amount of hydrophilic groups, nonporous copolymer poly(DEGMA-co-EDMA) and porous terpolymer poly(GMA-co-DEGMA-co-EDMA) with particle diameters 20-50 mm and 100-350 µm, respectively, seem to be suitable supports for immobilized metal affinity chromatography. Chelating groupings of either iminodiacetic acid or quinolin-8-ol were covalently bonded onto polymer gel particles and then treated with NiCl₂ to form immobilized Ni²⁺ complexes. Due to appropriate structure parameters of the solid supports, immobilized Ni²⁺ complexes were accessible for interaction with immunoglobulins.

PC80

Styrene-Butadiene Rubber Compounds containing liquid polybutadiene curable at Low Temperatures

Z. Hrdlička, A. Kuta, E. Landová, V. Ducháček

This paper deals with styrene-butadiene rubber (SBR) compounds containing liquid polybutadiene (LB) and cured at low temperatures (below 100 °C). Processing of rubber consumes a lot of energy in two steps: in mixing of rubber with additives and in cure (vulcanization). LB was used for decreasing the mixing energy. It decreases the viscosity of the rubber compound, which improves its mouldability. To decrease also curing energy vulcanizing system with ultra-fast accelerator was used, which enables cure at low temperature. Active role of LB in curing reactions is assumed.

Various curing systems were tested. Cure characteristics was measured and cure rate was evaluated. The common ultra-fast accelerators (e.g. carbamates or xanthates) usually used for vulcanization of NR at temperatures below 100 °C failed in the SBR compounds. The curing system based on tetramethylthiuram disulfide and thiourea without elementary sulfur was acceptable.

A particular attention was paid to the constitution of vulcanizate network. Crosslink density and sol content were determined by extraction tests with various solvents. Active role of LB at network formation was proved by the comparison of the sol content of compounds with LB and those without LB. It was calculated that 1/4 to 1/3 of the liquid polybutadiene contained in a rubber compound is bound in the matrix of styrene-butadiene rubber after vulcanization.

PC81

PC82

NEW TYPES OF AMPHIPHILIC CO-NETWORKS: SYNTHESIS AND CHARACTERIZATION OF POLY(N,N-DIMETHYL ACRYLAMIDE)-POLY(DIMETHYLSILOXANE)S

S. SZABÓ L.^a, B. IVÁN^a, J. SCHERBLE^b, R. MÜLHAUPT^b

Amphiphilic conetworks (APCN) are crosslinked polymer structures consisting of covalently bonded hydrophilic and hydrophobic polymer chains, and thus they swell in both hydrophilic and hydrophobic solvents. Due to the advantageous properties which are the result of their unique structure, APCNs may be applied in a variety of advanced technologies and fields, and they have been widely investigated worldwide in recent years. Among other polymers, various modified polysiloxanes, polyisobutylenes, polybutadienes etc. have been used as hydrophobic segments in APCNs until now.

In this presentation, we report on the synthesis of poly(N,N-dimethyl acrylamide)-l-poly(dimethylsiloxane) (PDMAAm-l-PDMS) amphipilic conetworks, in which the hydrophilic poly(N,N-dimethyl acrylamide) chains are linked by hydrophobic poly(dimethylsiloxane) chains. The synthesis of the conetworks was carried out by free radical copolymerization of N,N-dimethyl acrylamide and methacrylate-telechelic poly(dimethylsiloxane) macromonomer (crosslinker) initiated by 2,2'-azobisisobutyronitrile (AIBN) in THF common solvent at 60 °C. After 3 days reaction time, the conetworks were purified, and then analyzed by elemental analysis, DSC and AFM.

We prepared several types of PDMAAm-l-PDMS amphipilic conetworks with different hydrophilic/hydrophobic polymer content, hydrophobic macromonomer chain length, and also with added small molecular weight crosslinker (ethylene glycol dimethacrylate). The amphiphilic nature of these new materials was investigated by swelling in various hydrophilic and hydrophobic solvents. Both the DSC and AFM and the swelling experiments indicate the unique nano phase separated morphology of the prepared APCNs.

PC83

SWELLING RESPONSE OF AMPHIPHILIC CO-NETWORKS TO SALT CONCENTRATION

G. KALI, B. IVÁN

In recent years amphiphilic conetworks (APCNs) have recived significant attention. APCNs are build up from hydrophilic and hydrophobic polymer chains connected with covalent bonds (Fig. 1). These types of conetworks have a variety of special properties.

Swelling behaviour of homopolymer polyelectrolyte hydrogels in salt solutions have been widely investigated but such studies cannot be found for APCNs in the literature. In our recent work we prepared and characterized methacrylate-telechelic-polyisobutylene based amphiphilic conetworks. The swelling behaviour of poly(methacrylic-acid)-l-polyisobutylene conetworks was studied in CaCl₂ salt solutions, and the data were compared with the measurements found in the literature for homopolymer hydrogels. APCNs do not show the same behavior in the salt solution like the homopolymer hydrogels, ie. the APCNs did not suffer rapid gel collapse, the change in the swelling degree is continuous. This means that in the presence of hydrophobic polymer segments, the swelling behavior of APCNs is substantially different from homopolymer polyelectrolyte gels.

Fig. 1: The general structure of amphiphilic conetworks

PC84

MORPHOLOGY STUDIES AND POTENTIAL APPLICATIONS OF POLY(N,N-DIMETHYLACRYLAMIDE) - AMPHIPHILIC POLYMER CO-NETWORKS

P. MEZEY^a, A. DOMJÁN^a, B. IVÁN^a, R. THOMANN^b, R. MÜLHAUPT^b

Poly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB) amphiphilic conetworks were synthesized in a wide range of composition (38-80 m/m % PIB). Swelling experiments were carried out in both hydrophilic (water) and hydrophobic (n-hexane) solvents to determine the equilibrium swelling ratios which are in unambiguous correlation with the composition of the investigated conetworks.

Thermal analysis (DSC) of the PDMAAm-l-PIB amphiphilic conetworks was performed, and it was found that the glass transition temperatures of both PIB and PDMAAm exist. It can be concluded that these type of materials possess phase separated morphology. For the better understanding of this phenomenon small angle X-ray scattering (SAXS) measurements were performed. The results show that a short range order can be observed in these amphiphilic conetworks , and the size of the phases are in the 8-15 nm interval depending on the composition. As a conclusion, these materials possess a unique nanophase separated morphology. Furthermore, it can be seen from the atomic force microscopy (AFM) pictures that the conetworks have different spatial arrangement, where the size of the phases are in the nanometer range in all cases.

The separate nanophases can be utilized as nanoreactors in several chemical reactions. Swelling the hydrophilic phase with aqueous silver nitrate solution and a subsequent reduction with N,N-dimethylformamide resulted in silver nanoparticles in the PDMAAm-l-PIB amphiphilic conetworks.

PC85

COMPUTER SIMULATION OF MODEL PROTEIN DENATURATION, AGGREGATION AND GELATION

G. COSTELLO, S.R. EUSTON

Globular proteins are valued by food manufacturers for their ability to form gels when heated. The structure of gels lies between that of a liquid and a solid. They are too concentrated to be studied using diffraction techniques, and are not crystalline, thus ruling out x-ray diffraction. Computer simulation offers a way of probing gelation at a molecular level. Current computer simulation models of aggregation and gelation assume that the constituent particles are spherical. Whereas this may be a good approximation in many circumstances for some protein gels this may be an oversimplification. Globular proteins denature and gel on heating. Denaturation is characterised by large structural changes in the molecule. This aspect of protein gelation is not accounted for in models that treat particles as spheres.

We will introduce a new form of aggregation model that treats globular proteins as an assembly of inter-linked spheres. The "proteins" are simulated on a 3-D lattice using Monte Carlo simulation techniques. Each "protein" consists of a core of "hydrophobic" subunits that have a strong attractive interaction for each other, and an outer layer of weakly or non-interacting subunits. This deformable globule model allows us to simulate not only the aggregation behaviour of model proteins, but also the temperature induced denaturation. This allows us to generate simulated state diagram (temperature-composition diagrams) that define regions where the model proteins are either non-denatured, denatured and aggregated but not gelled, or gelled.

We will present results for the simulated state diagrams that show the model system is able to exist in a number of different states depending on the temperature, "protein" volume fraction, and fraction of "hydrophobic" subunits. The fractal dimension and pair radial distribution function will be used a measure of gel or solution structure.

PC86

PREPARATION OF POLY(N,N‑DIMETHYLACRYLAMIDE)‑BASED MICROSPHERES BY A HETEROGENEOUS POLYMERYIZATION TECHNIQUES

M. BABIČ^{a, b}, D. HORÁK^a, P. SÁHA^b

In recent years, hydrophilic polymer microspheres based on substituted acrylamides have been increasingly used in diverse applications, such as improved oil recovery, controlled drug release, biotechnology, homogeneous and heterogeneous catalysis, gene engineering and separation processes. Polymers based on substituted acrylamides attract attention due to their stimuli-responsive behavior, in particular the presence of lower critical solution temperature in water in the range 0‑100°C. Development of poly(N,N‑dimethylacrylamide) microspheres with low nonspecific adsorption of biomolecules is therefore desirable.

We report two new routes for preparation of hydrophilic poly(N,N‑dimethylacrylamide) microspheres. The first method was the inverse emulsion polymerization, the other the dispersion polymerization. The inverse emulsion polymerization proceeded in trichloroethylene/toluene/water system; 2,2'‑azobisisobutyronitrile (AIBN) and cellulose acetate butyrate were the initiator and emulsifier, respectively. The dispersion polymerization was performed in toluene/heptane and stabilized by polystyrene‑block‑hydrogenated polybutadiene‑block‑polystyrene (Kraton G 1650); AIBN was the initiator. Resulting microspheres were characterized by scanning electron microscopy in terms of particle morphology, size and size distribution. The effect of various polymerization reaction conditions, such as crosslinking, solvent ratio, and concentration of stabilizer and/or initiator, on the properties of resulting microspheres was elucidated. While the inverse emulsion polymerization yielded cca 300 nm microspheres, the dispersion polymerization produced particles in the micrometers range.

Financial support of the Grant Agency of the Czech Republic (grant No. 203/05/0241) is gratefully acknowledged.

PC87

ISOCYANATE-MULTIFUNCTIONALIZED POLYISOBUTYLENES AS NOVEL CROSSLINKING AGENTS FOR PREPARATION OF POLYMER GELS AND NETWORKS

L. TOMAN*, M. JANATA, J. SPĚVÁČEK, A. SIKORA, P. VLČEK, P. LÁTALOVÁ, J. DYBAL, J. MICHÁLEK, M. PEKÁREK, P. HOLLER, B. MASAŘ

Rapid advances in the field of fundamental research of cationic polymerization of isobutylene (IB) have led to the synthesis of numerous new (co)polymers, polymer gels and networks. Amphiphilic networks (APN), i.e., polymer networks composed of covalently bonded hydrophobic (PIB) and hydrophilic segment, represent a novel class of specialty hydrogels.^1-4 Generally, hydroxy, isocyanate, and methacrylate end-functionalized PIBs, e.g., OH-PIB-OH, OCN-PIB-NCO, MA-PIB-MA have been used successfully for the synthesis of APNs. Most of the hydrophilic segments are well-known for their high biocompatibility, such as poly(2-hydroxyethyl methacrylate) (PHEMA) or poly(ethylene glycol) (PEG). However, PIB-based APNs have been prepared only via sequential synthesis using the site-transformation techniques, e.g., Cl-PIB-Cl → CH₂=CH-PIB-CH=CH₂ → HO-PIB-OH → MA-PIB-MA or OCN-PIB-NCO → APNs.⁴ Recently, a novel method of one-pot synthesis of multifunctionalized PIB bearing pendant methacrylate groups along the chain (PIB(MA)_n, where n ~ 3-12) was developed.⁵ Cationic copolymerization of IB and 3-isopropenyl-α,α-dimethylbenzyl isocyanate gives rise to the multifunctionalized PIB bearing pendant isocyanate groups along the chain (PIB(NCO)_n).⁶ The isocyanate groups were subsequently transformed to methacrylate groups by the dibutyltin dilaurate-catalyzed reaction with HEMA giving PIB(MA)_n.⁵

In the present work, we prepared PIB(MA)_n (M_n = 8 200 with an average functionality F_n ~ 5 per chain) in a one-pot synthesis. The PIB(MA)_n is then used as a polymeric crosslinking agent in radical copolymerization of HEMA, glyceryl methacrylate (GMA; 2,3-dihydroxypropyl methacrylate) and poly(ethylene glycol) methacrylate (PEGMA; M_n ~ 360 and 526) giving rise to a rubbery PHEMA-PIB, PGMA-PIB and PEGMA-PIB networks containing 50-60 wt % isobutylene. The amphiphilic nature of the networks has been demonstrated by swelling in both n-heptane and water. We have characterized PIB(NCO)_n, PIB(MA)_n by SEC, IR, ¹H NMR and APNs by solid state ¹³C NMR and DSC analysis.

Acknowledgement: Financial funding of this research provided by the Grant Agency of the Czech Republic (Grant 203/04/1050) is greatly appreciated.

References

1. B. Iván, J. P. Kennedy, P.W. Mackey, Polym. Prepr. 31(2), 215 (1990).

2. B. Iván, J. Feldthusen, A.H.E. Müller, Macromol.Symp. 102, 81 (1996).

3. B. Iván, J. P. Kennedy, P.W. Mackey, Polym. Prepr. 31(2), 217 (1990).

4. J. P. Kennedy, M. Hiza, J. Polym. Sci., Polym. Chem. Ed. 21, 1033 (1983).

5. L.Toman, P. Vlček, J. Vacík, J. Michálek, Czech Patent 290817 (2002).

6. L. Toman, P. Vlček, Czech Patent 291062 (2003); 290909 (2002).

PC88

EVIDENCE OF THE PRESENCE OF CHEMICAL CLUSTERS IN END-LINKED MULTIMODAL POLYURETHANE NETWORKS BY THERMOMECHANICAL AND SOLID-STATE ¹H NMR ANALYSIS

R. REGISSER, F. MECHIN, J.-P. PASCAULT

The concept of chemical clusters has been used in end-linked polyurethanes (PU) in order to explain dynamic mechanical relaxation, equilibrium moduli, and glass temperature transition. Two groups of polyurethane samples were synthesized, based on isophorone diisocyanate and i) a monomodal distribution of poly(oxypropylene) (PPO) triol, with six different PPO of average number molecular weight ranging from 450 to 4700 g.mol^-1 and ii) bi- or tri-modal distributions of respectively one or two short PPO monomers and a long macrotriol (4700 g.mol^-1). Hence, a total of ten networks were studied.

The aim of this study was to illustrate the presence of chemical clusters, using the thermomechanical and rubber behaviour of these polymers. Thus, the front factor A, used in affine and phantom theories for rubber elasticity, has been exploited to characterize the structure of such multimodal networks, which were showed to contain clusters having a high functionality. Moreover, a new parameter has been introduced: a threshold of theoretical molecular weight between two crosslinks under which clusters can be formed, even in monomodal samples. Indeed, according to the rubber elasticity and to the glass temperature transition predictions, these PU were found to behave like multimodal networks containing chemical clusters.

The model used to explain ¹H Solid-State NMR results considers clusters as perfect spheres homogeneously distributed in a matrix. Preliminary NMR results are in agreement with mechanical data.

PC89

SWELLING AND MECHANICAL BEHAVIOR OF CHARGED POLY (N-ISOPROPYLMETHACRYLAMIDE) AND POLY(N-ISOPROPYLACRYL AMIDE) NETWORKS IN WATER/ETHANOL MIXTURES

I. ALENICHEV^a, Z.SEDLÁKOVÁ^b, M. Ilavský^a,b

Swelling and mechanical behavior of negatively (ionic comonomer-sodium methacrylate) and positively (ionic comonomer-(2-acrylamidoethyl)trimethyl ammonium chloride) charged networks of poly(N-isopropylmethacrylamide) (PIPMAm) and poly(N-isopropylacrylamide) (PIPAAm) was investigated in water/ethanol mixtures at room temperature. Strong cononsolvency effect was observed for both uncharged gels; while for neat solvents high degree of swelling was observed, for solvent mixtures pronounced minimum in swelling was found. This swelling minimum is connected with coil-to-globule transition of network chains and its characteristic parameters-concentration of ethanol at the minimum, c_e,m, and corresponding swelling degree, Q_m, were determined. It was found that c_e,m values of both networks roughly correspond to water/ethanol composition at which maximum of the mixing enthalpy of solvents was found (c_e = 35 vol.%). With increasing ionization the swelling degree Q in mixtures increases for all four systems. Negatively charged networks of both systems exhibit also cononsolvency effect; with increasing amount of ionic comonomer the minimum in swelling shifts to higher acetone concentration c_e,m and Q_m increases. Generally it was observed that changes in c_e,m and Q_m with increasing amount of sodium methacrylate are more pronounced for PIPAAm gels than those found for PIPMAm gels. On the other hand, positively charged networks of both systems exhibit roughly constant Q values practically independent of solvent mixtures compositions. For all four systems it was found that mechanical behavior is predominantly determined by the degree of swelling regardless of charge concentration.

*Work was supported by the Ministry of Education of the Czech Republic (project MSM0021620835)

PC90

DYNAMIC MECHANICAL BEHAVIOR OF REINFORCED ELASTOMERS BASED ON NR, SBR, BR AND BR/SBR RUBBERS

O. Truněček^a, h. VALENTOVÁ^a, J.Budinski-Simendić^b, M. PLAVŠIĆ^c, M. Ilavský^a,d

(helena.valentova / mff.cuni.cz, jarka / uns.ns.ac.yu, ilavsky / kmf.troja.mff.cuni.cz)

Networks based on NR, SBR, NR/SBR and BR/SBR rubbers crosslinked by sulfur and BR/SBR elastomers reinforced by silica were prepared and their dynamic mechanical behavior was examined in a broad frequency and temperature regions. While for neat NR and SBR one glass transition was observed, for NR/SBR two separated transitions were found. Frequency measurements clearly indicate that even for neat NR and SBR elastomers the width of the main transition region on temperature increases with increasing frequency; at the same time storage modulus in rubbery region is lower and losses in rubbery region are higher for NR sample in comparison with SBR one. For NR/SBR network two transitions can be detected from frequency measurements and equilibrium storage modulus roughly correspond to that of neat SBR elastomer.

Reinforced elastomers based on BR/SBR (from 30/70 to 70/30 wt. %) filled by constant amount of filler - silica (40 wt. %) exhibit roughly one order of magnitude higher equilibrium moduli than neat elastomers. As expected, increasing BR content shifts the main transition region to lower temperatures. The width of transition on temperature increases with increasing BR content; for 50BR/50SBR two transitions start to occur and for 70BR/30SBR two transitions are clearly detected. For reinforced networks the temperature width of transitions is roughly independent of frequency so that frequency-temperature superposition could be applied to mechanical functions.

Work was supported by the Ministry of Education of the Czech Republic (project MSM0021620835)

PC91

Dielectric, Dynamic Mechanical and Thermal Behavior of Ordered Polyurethane networks

H. Valentová^a, J. Nedbal^a, Z. Sedláková^b, M. Ilavský^{a, b}

The relations between formation, structure and dielectric, dynamic mechanical and thermal behaviour of ordered three-component polyurethane networks based on a mesogenic diol, 6,6¢-[ethylenebis(1,4phenyleneoxy)] dihexanol (D)

2(4)-methyl-1,3-phenylene diisocyanate (DI), and poly(oxypropylene)triol (T) were investigated. The stoichiometric networks were prepared at various initial molar ratios of hydroxy (OH) groups from D and T together with off-stoichiometric ones (prepared in excess of triols OH groups); all networks were prepared to full conversion isocyanate (NCO) groups. Mechanical (G' andG'') and dielectric (e' and e'') functions were measured at various constant temperatures and frequencies. Thermal properties were investigated using a Perkin-Elmer DSC calorimeter.

Dynamic mechanical and dielectric measurements on stoichiometric and off-stoichiometric LC polyurethane networks showed thermorheologically complex behavior due to on going of various liquid-crystalline (LC) structures formation (smectic, nematic) with temperature. Introduction of chemical crosslinks into networks reduces the flexibility of the elastically active network chains (EANC's) and inhibits conformational rearrangement required for LC ordering. With increasing content of LC diol in EANC's the complexity of the dielectric, mechanical and thermal behavior grows and beside the glass transition from glassy to rubbery state (located at the lowest temperature - α-transition) two LC transitions at higher temperatures (characterised by temperatures T₁ and T₂) were observed. The transition at the highest temperature T_m is connected with the transition from nematic to the isotropic state.

Acknowledgement: This work was supported by the Grant Agency of the Academy of Sciences of the Czech Republic (grant No. IAA4112401), by the Ministry of Education, Youths and Sports of the Czech Republic (project ME 691 and MSM 0021620835) and Greek Ministry for Development (General Secretariat of Research and Technology).

PC92

COIL/GLOBULE TRANSITION IN POLY(VINYL METHYL ETHER) WATER/ETHANOL SOLUTIONS STUDIED BY NMR SPECTROSCOPY

L. HANYKOVÁ^a, J. LABUTA^a, J. SPĚVÁČEK^b, J. LANG^a, M. ILAVSKÝ^a,b

The dimensions of linear or crosslinked polymer chains in mixed-solvent medium are dependent not only on polymer segments-solvents molecules interactions but are influenced by the interactions between the solvents themselves. Investigation of polymer solutions in mixed solvents on molecular level can contribute to understanding of collapse phenomenon in polymer networks. Poly(vinyl methyl ether) (PVME) exhibits phase separation in water above 308 K as a consequence of a lower critical solution temperature (LCST); such separation is manifestation of a coil-globule transition associated with competition between hydrogen bonding and hydrophobic interactions. We applied NMR spectroscopy to investigate the temperature-induced phase transition of linear PVME in water/ethanol (D₂O/EtOH) mixtures. For this purpose, PVME solutions were prepared in a broad concentration range of polymer (0.1 - 20 wt.-%) and of ethanol (1 - 20 vol.-%), respectively. From the methodical point of view, we combined the measurements of ¹H and ¹³C NMR spectra (mainly integrated intensities) and measurements of ¹H and ¹³C relaxation times of solvent molecules in a broad range of temperatures (290 - 340 K).

In the temperature range 310 - 325 K (above the LCST), a marked reduction in the absolute integrated intensities was observed for PVME lines in high-resolution spectra, due to a decrease of the PVME chain mobility. The effect of the hydrogen bonding stabilization in presence of ethanol in solution was manifested by marked shift of the transition region to higher temperature and by the decrease of the transition extent with increasing ethanol concentration.

¹H and ¹³C relaxation experiments were employed to study a dynamics of the solvent molecules (water and ethanol) during the phase separation. The appearance of two different state of ethanol molecules above the transition in solutions with the highest polymer concentration (c = 20 wt.%) was manifested by two distinguished NMR signals in ¹³C spectra. Analysis of ¹³C relaxation experiments, using the model of a rigid body isotropic rotation, permitted to determine correlation times correponding to the motional dynamics of ethanol in these two different states.

Work was supported by the Ministry of Education of the Czech Republic (project MSM0021620835) and Grant Agency of the Charles University (project 294/2004/B).

PC93

thermotropic phase transitions in aqueous solutions of polymer mixtures STUDIED BY NMR SPECTROSCOPY

L. Starovoytova^a,b, J. Spěváček^a,b, L. Hanyková^b, M. Ilavský^a,b

Mixtures of two polymers with a lower critical solution temperatures (LCST's) as well as block copolymers or interpenetrating polymer networks of such type exhibit two coil/globule transitions on heating in water. The thermosensitivity makes these systems interesting for many technological and biomedical applications. LCST behavior of such two-phase systems will depend not only on polymer segments-water interactions of individual components but also on interphase interactions. Investigation of aqueous polymer mixtures on molecular level can thus contribute to understanding of collapse phenomenon in polymer networks. In this study NMR and partly also FTIR spectroscopy were applied to investigate changes during phase separation in D₂O solutions of poly(N-isopropylmethacrylamide) (PIPMAm)/poly(N-isopropylacrylamide) (PIPAAm) and poly(vinyl methyl ether) (PVME)/PIPMAm mixtures. In both investigated mixtures, the LCST behavior of the PIPAAm and PVME components (appears at lower temperatures) not affected by the presence of the PIPMAm in mixtures was found. On the other hand, the phase transition of the PIPMAm component (appears at higher temperatures) is affected by the phase separation of the other polymer component in the mixtures and depends on polymer concentration. From measurements of spin-spin relaxation times T₂ of water (HDO) it was found that a certain portion of water molecules is bound at elevated temperatures in globular structures and that with time the originally bound water is slowly released from these structures. This process significantly depends on flexibility of polymer chains; it is fastest for flexible PVME. The slowest release of the bound water was found for PIPAAm/D₂O solutions. Time dependence of the transition temperature of the PIPMAm component in mixtures is probably a direct consequence of the time dependence of water reorganization.

Acknowledgement: This work was supported by the Academy of Sciences of the Czech Republic (project No. AVOZ 40500505) and Grant Agency of the Charles University (project No. 294/2004/B).

PC94

THERMAL STABILITY AND STRUCTURAL STUDIES OF POLYURETHANE NETWORKS CONTAINING ISOCYANURIC ACID (HEXAHYDRO-1,3,5-TRIAZIN-2,4,6-TRIONE) RINGS AS A CROSSLINK

J. BUDINSKI-SIMENDIC*^a, M. SPIRKOVA^b, K. DUSEK^b, T. DIKIC^a, M. PLAVSIC^c, I. POPOVIC^c, L. KATSIKAS^c, M. ILAVSKY^b,d

Polyurethanes are used in a wide range of industrial applications such as foams, coatings, adhesives, and elastomers. Although such materials provide good mechanical properties, they are not generally suitable for the applications that require heat resistance because of the low thermal stability of the urethane group. In order to increase its stability polyurethanes could be modified by substituting some of the urethane groups with more heat-resistant heterocyclic groups. The polyurethane networks crosslinked with isocyanurate linkages exhibited a much higher heat resistance, their thermal stability are increasing with the higher content of isocyanurate(hexahidro-1,3,5-triazin-2,4,6-trion) junction points. The aim of this study was to correlate the structure and thermal stability of model networks prepared by catalytic cyclotrimerization of telechelic diisocyanate. Five types of network precursors based on 2.4-tolylenediisocyanate and a,w-dihydroxypoly oxypropylene (PPD725, PPD1200, PPD 2000, PPD 3000, PPD4000) were synthesized in the undiluted state. The network properties were determined by swelling, multiple extractions, differential scanning calorimetry, and photoelastical measurements. The theory of branching processes was used for the network structure estimation. The amount of isocyanurate rings was calculated from the gel content. Decomposition of networks in nitrogen or air was studied by means of thermogravimetry. A Perkin Elmer TGS-2 instrument was used for the measurements (performed at heating rates 2.5; 10; 20 and 40°/min). The decomposition was monitoring by the weight loss of the samples as a function of temperature (in the range from 30 to 500°C).

PC95

WATER STRUCTURE IN SWELLED/DESWELLED HYDROGELS SYSTEM STUDIED BY RAMAN SPECTROSCOPY

M. PASTORCZAK¹, M. KOZANECKI¹, S. KADŁUBOWSKI², J. M. ROSIAK², J. ULAŃSKI¹

One of the most important factors determining physical properties of hydrogels and simultaneously deciding of their applicability is the structure of water. Three described states of water called: freezable free water, freezable band water and nonfreezing water, are a result of intermolecular hydrogen bonds formed between water molecules themselves as well as between water molecules and polymer network [1]. Raman spectroscopy is a powerful technique for characterization of the systems containing hydrogen bonds. It is well known that the high frequency range (2900-3600 cm^-1) is sensitive to the supramolecular structure of water. Band c.a. 3200cm^-1 is connected with a quasi-crystalline phase (rigidly H-bonded dimmers and tetramers), while band c.a. 3400 cm^-1 is connected with a solid-like amorphous phase. Consequently, the ratio of the integral intensity of 3400 cm^-1 and 3200cm^-1 peaks can be used as an indicator of a water structure [2,3].

In this work Raman studies of water structure in linear and crosslinked poly(vinyl methyl ether) (PVME - water soluble polymer with phase transition temperature ca. 37 °C) will be presented. Moreover the relation between water content in hydrogel and its structure will be shown.

Hydrogel of PVME was prepared by means of gamma irradiation of 10% w/w water solution saturated with N₂O. In order to remove uncrosslinked part of the polymer after irradiation hydrogel was swelled until equilibrium swelling degree has been obtained. Liophilization technique has been used for drying of the hydrogel.

References:

[1] F. Muller-Plathe, Macromolecules 31 (19) , 6721-6723

[2] Y. Maeda, H. Kitano Spectrochim. Acta, Part A, 51 (1995) 2433-2446

[3] D.V. Luu, L. Cambon J. Mol. Struct., 237 (1990) 411

PC96

PHYSICAL NETWORK OF POLYMERS IN PARTIALLY MISCIBLE SOLVENTS: LIGHT SCATTERING STUDY

Z. TUZAR^a, P. ŠTĚPÁNEK^a, J. KŘÍŽ^a, P. KADLEC^a, F. NALLET^b

Mixtures of cyclohexane (CX) and dimethylformamide (DMF) form one-phase or two-phase systems, depending on temperature and composition. The borderline between the two regimes is called the coexistence curve or the binodal. When a homopolymer or a copolymer is added, the coexistence curve of the three-component system is modified and new structures and dynamics can be observed. In semidilute polystyrene solutions, fluctuations in correlation length and light scattering intensity increase critically when the system approaches the macrophase separation. A qualitative model for such a system is proposed.

In presence of a diblock copolymer, e.g. polystyrene-polyisoprene or polystyrene-poly(ethylene propylene), where DMF is a selectively good solvent for the first block and CX for the second, solutions fail to separate macroscopically. Instead, the system is macroscopically homogeneous and solvents are microphase-segregated to DMF-rich and CX-rich domains, separated by interfaces covered with a diblock copolymer. Various temperature-dependent dynamic modes of the physical polymer network belonging to the cooperative diffusion, selfdifusion of the copolymer molecules, and large-scale heterogeneities can be observed by light scattering. The structural features become regular at temperatures well below the coexistence curve of the solvents and give rise to characteristic patterns in small angle neutron scattering.

We acknowledge support by the Grant Agency of the Czech Republic (SON/03/E001) within the EUROCORES Programme SONS of the European Science Foundation, which is also supported by the European Commission, Sixth Framework Programme.

PC97

SMALL-ANGLE NEUTRON SCATTERING STUDY OF TRANSIENT NETWORKS OF BLOCK COPOLYMERS IN A MIXTURE OF IMMISCIBLE SOLVENTS.

P. ŠTĚPÁNEK^a, V. RYUKHTIN^b, K. PRANZAS^c, Z. TUZAR^a, F. NALLET^d

Cyclohexane (CX) and dimethylformamide (DMF) are fully miscible above 48°C. At lower temperatures the phase behavior is governed by the coexistence curve. When a homopolymer or a copolymer is added, the coexistence curve of the three-component system is modified and new structures and dynamics can be observed. In presence of a diblock copolymer, e.g. polystyrene-polyisoprene or polystyrene-poly(ethylene propylene), where DMF is a selectively good solvent for the first block and CX for the second, solutions do not separate macroscopically. Instead, the system is macroscopically homogeneous and solvents are microphase-segregated to DMF-rich and CX-rich domains, separated by interfaces covered with a diblock copolymer.

Small-angle neutron scattering shows that the low-temperature ordered phases have in all cases examined a hexagonal or cubic symmetry. Typical diameter of the structure building blocks (cylinders or spheres) is 15 nm, their typical distance is 80 nm. On cooling, the ordered phase does not appear at a particular temperature but progressively grows from the disordered phase in a temperature interval that begins about 15^oC above the phase separation temperature of the neat solvents.

The macroscopic morphology of the phase separated solutions consists of a large number of grains each exhibiting long-range order. We have shown by ultra small-angle neutron scattering that the typical size of these grains is 2 mm.

We acknowledge support by the Grant Agency of the Academy of Sciences of the Czech Republic (A4050403) and by the Grant Agency of the Czech Republic (SON/03/E001) within the EUROCORES Programme SONS of the European Science Foundation, which is also supported by the European Commission, Sixth Framework Programme

PC98

HYPERBRANCHED POLYMERS BASED ON 4,4-BIS(4'-HYDROXYPHE­NYL)PENTANOIC ACID

M. WALCZAK, J. B. LECHOWICZ, H. GALINA

Hyperbranched polymers prepared from AB₂ (or AB_f) type monomers where A and B are functional groups reacting with each other exhibit a very broad molecular size distribution. There exist several ways of narrowing the broad molecular size distribution of hyperbranched macromolecules. The simplest way is to introduce a 'core' monomer, usually multifunctional one sharing with AB_f monomer (f = 2, 3,…) the same type of B groups. It has also been found, mostly experimentally, that gradual or slow monomer addition to the 'core' monomer yields a product of relatively limited distribution of polymer molecular sizes.

We present a comparison of results from chemical experiments with theoretical model of hyperbranched polymerization. Both, in real and model systems, AB₂ monomer is added to the condensation reactor containing multifunctional 'core' monomer B_f in three or five portions. The parameters changed are the: number and relative size of portions as well as conversions at which new portions are added.

The majority of hyperbranched polymers are synthesized by polycondensation of AB₂ monomers. The method however has several synthetic limitations, which include difficulties in precise control of conversion and the presence of products of degradation particularly at high polymerization temperature. Therefore we propose the alternative approach of room temperature polycondensation using carbodiimide-coupling reagents in the presence of a suitable catalyst. In this way, we synthesized aliphatic-aromatic polyesters from 4,4-bis(4'-hydroxyphenyl)pentanoic acid with the following 'core' molecules: resorcinol, bisphenol-A, 1,4-butanediol (B₂), 1,1,1-tris­(hydroxymethyl)propan (B₃), and pentaerytrytol (B₄). Chemical modification of hyperbranched polyesters has been carried out by reacting them with p-nitrophenyl chloroformate. The products were characterized by chemical and spectral analysis, gel permeation chromatography and differential scanning calorimetry.

PC99

USE OF POLYMER NETWORKS AS CHIRAL STATIONARY PHASES FOR HPLC

J. ŠIRC^1,2), J. MICHÁLEK¹⁾, Z. BOSÁKOVÁ²⁾, V. GURYČA^1,2)

Molecularly imprinted polymers have recieved much attention in various fields because of their high selectivity for target molecules. It has been recognized as a promising technique, where the molecule to be detected is added to a reaction mixture of a cross-linker, a solvent, an initiator and a functional monomer that possesses a functional groups capable of interacting with the target molecule. Binding sites in the resultant polymers involve functional groups, which are constructed according to the shape and chemical properties of the target molecules. After removal of the target molecules, these specific binding sites exhibit high selectivity and affinity for the template molecules.

Monolithic HPLC stationary phases based on molecular imprinting were prepared by in situ polymerization. The template compound (L-tosylphenylalanine), the functional monomer (methacrylic acid), the cross-linker (ethylene glycol dimethacrylate), the initiator (azobisisobutyronitrile or hydroxydimethylacetophenone) and a porogen mixture (dodecanol with cyclohexanol or toluene) were placed in glass columns (150 x 3 mm i.d.) and heated or irradiated to induce polymerization.

Newly prepared monolithic columns were tested on HPLC separations of enantiomer pairs of derivatized amino acids and a standard mixture of hydrophobic solutes. The structure of the monoliths was investigated by scanning electron microscopy and nitrogen/mercury porosimetry. The dependences of the polymer morphology and the chromatographic behavior on the composition of the polymerization mixture and on the polymerization conditions were also investigated.

Ackowledgements:

We would like to thank the Ministry of Education, Youth and Physical Training of the Czech Republic, Grant No. 908/2005/G6 and Academy of Sciences of the Czech Republic, project AVOZ 40500505 for financial support.

PC100

Hybrid Inorganic / Organic EPOXY networks containing Stannoxane and Siloxane clusters

Hybrid Inorganic / Organic Epoxy networks containing Stannoxane and Siloxane Clusters

A. Strachota¹, F. Ribot², P. Whelan¹, J. Brus¹, M. Steinhart¹, L. Matějka¹

¹ Department of Polymer Networks and Mechanical Properties, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic,

Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic (strachota / imc.cas.cz)

² Institute Laboratoire de Chimie de la Matière Condensée, UMR CNRS 7574, Tour 54, 5e étage, Université Pierre et Marie Curie, 4 Place Jussieu, F-75252 Paris

Cedex 05, France (fri / ccr.jussieu.fr)

In this contribution we present our results concerning the preparation, the kinetics of formation and the mechanical properties of DGEBA-based Epoxy resins reinforced by the incorporation of nano-sized inorganic building blocks, i.e. of siloxane (POSS) and stannoxane clusters (see Fig. 1).

The thermomechanical properties and the thermal stability of both groups of reinforced resins will be compared. Especially, the irreversible post-curing in the stannoxane-reinforced resins and the reversible aggregation of siloxane units in the POSS-reinforced materials will be discussed.

Finally, we will present kinetic data concerning the formation of both groups of reinforced resins.

Fig. 1: Stannoxane (left) and POSS (right) clusters used in this work

PC101

Dynamic Rheology Characterization of SBR crosslinking in Organic solutions.

I. Fernández ^a, O.Vernáez ^a, G.Navarro ^b

For some oil industry application it is important to develop gels in non-aqueous environments and be able to control the gelification process throughout he compound formulation. Crosslinking kinetics for a Styrene-Butadiene Rubber (SBR) compound in solution with organic solvents was studied by dynamic rheology as a quantitative characterization method of the gelling reaction. The crosslinking reaction was performed using peroxide as curing agent. The relationship between the storage (G') and loss (G'') shear modulus (tan d =G''/G') was used to characterize the viscoelastic behavior of the system during the gelling process. Both storage and loss modulus were measured periodically during the reaction. The results obtained by this method were compared with the qualitative observation and they were in good agreement. It was also obtained that it is possible to quantify both induction and curing periods using some characteristic points from the modulus against gelling time curves. The reactions kinetics could be studied through the determination of the rate of increment of consistency (dG'/dt) varying the initial polymer and peroxide concentration. This procedure allowed approaching the kinetic constants and exponents for an empirical kinetic model in order to simulate mathematically the curing sequence for these elastomers solutions. The aim of this kind of work is to be able of predicting the progress of crosslinking reaction in organic solvents and therefore to provide a possible way to relate process condition and properties directly to de compound formulation with the minimum amount of laboratory tests.

PC102

Effect of Reaction Parameters on Properties of Thermosensitive Poly(N-isopropylacrylamide) Microspheres

H. MACKOVÁ, D. HORÁK

With continuously growing number of applications of responsive hydrogels in temperature-controlled drug delivery systems and separation processes, the demand for monodisperse poly(N-isopropylacrylamide) still increases microspheres (PNIPAAm). The microspheres possess improved and reproducible response rates when compared with conventional bulky PNIPAAm hydrogels.

Two methods of preparation of PNIPAAm-based microspheres, precipitation and dispersion polymerization were compared. While the first method proceeds in water and the polymerization was initiated with ammonium persulfate, the other one runs in a toluene/heptane, the polymerization was stabilized with polystyrene-block-hydrogenated polyisoprene (Shellvis 50) and initiated with 2,2´-azobisisobutyronitrile. The effect of several reaction parameters, such as type and concentration of crosslinker (N,N´-methylenebisacrylamide or ethylene dimethacrylate), addition of ethanol, concentrations of monomer and initiator and polymerization temperature, on their properties were examined. The hydrogel microspheres were characterized by of their chemical structure, size and its distribution and morphological and temperature-induced swelling properties. A decrease in the particle size was observed with increasing polarity of the reaction medium or increasing concentration of steric stabilizer in the dispersion polymerization. It was found that the higher the content of the crosslinking agent, the lower the swelling ratio. High amounts of crosslinker gave unstable dispersions. The solvent power of the reaction mixture controlled the PNIPAAm microsphere size in the range 0.2-1 µm for the precipitation polymerization and in micrometer range for the Shellvis 50-stabilized dispersion polymerization in toluene/heptane. Particles had fairly narrow size distributions. Copolymerization with the functional monomer glycidyl methacrylate (GMA) afforded the reactive oxirane groups in the microspheres.

Financial support of the Grant Agency of the Czech Republic (grant No. 203/05/2256) is gratefully acknowledged.

PC103

SAXS, Photoelastic and Dynamic Mechanical Behavior of THREE component polyurethane Networks Prepared BY One‑stage and Two-Stage Process

J. ŠOMVÁRSKY^a, Z. SEDLÁKOVÁ^b, J. PLEŠTIL^b, M. ILAVSKÝ^a,b

The effect of the initial ratio of components and of one- or two-stage process of formation of polyurethane networks prepared from poly(oxypropylene)diol (PD), 4,4'-diisocyanatodiphenylmethane (MDI) and trimethylolpropane (TMP) on their extraction, swelling, SAXS, photoelastic and dynamic mechanical behavior was investigated. The networks were prepared at various ratios of hydroxy (OH) to isocyanate (NCO) groups, r_HT = [OH]_TMP/(0.5[NCO]) = 1 - 1.5, by a one- or two-stage process (in the first step [OH]_PD/[NCO] = 1/2) up to the full conversion of NCO groups. Due to decreasing reactivity of OH groups on TMP non-uniform distribution of hard (TMP-MDI-TMP) segments (chemical clusters) was developed in both network series. SAXS experiments proved that one-stage networks exhibit more heterogeneous structure than two-stage ones. It was found that the weight fraction of the gel w_g, equilibrium modulus G_e, stress-optical coefficient C_e and dynamic mechanical behavior depend on r_HT and formation process. The results are compared with prediction of theory of branching processes in which substitution effect on TMP is accounted for.

Work was supported by the Ministry of Education of the Czech Republic (project MSM0021620835).

PC104

Mixed systems of hydrophobically modified polyelectrolytes: Controlling rheology by charge and hydrophobe stoichiometry and interaction strength

F.E. Antunes^1,2*, B. Lindman^1,2, M.G. Miguel¹

Rheology and phase separation were investigated for aqueous mixtures of two oppositely charged hydrophobically modified polyelectrolytes. The typical phase separation, normally seen for oppositely charged polymer mixtures, is dramatically reduced by the presence of hydrophobic modification and phase separation is only detected close to the point of charge neutralization. While the two polyelectrolytes separately can give high viscosities and a gel-like behaviour, a pronounced maximum in viscosity and storage modulus with the mixing ratio of the polyelectrolytes is observed; the maximum is located between the points of charge and hydrophobe stoichiometry and reflects a combination of hydrophobic and electrostatic association. Lowering the charge density of the anionic polymer leads to a strengthened association at first but at lower charge densities there is a weakened association due to the onset of phase separation. The strength of the electrostatic interaction was modified by adding salt. Increased ionic strength can lead to phase separation and to increased or decreased viscosity depending on the polyelectrolyte mixing ratio.

Fig. 1

PC105

HOW DOES A POLYELECTROLYTE RESHAPE AN OPPOSITELY CHARGED CATANIONIC VESICLE? A RHEOLOGICAL AND MICRO-CALORIMETRIC STUDY

F.E. ANTUNES^a, R. BRITO^b, E.F. MARQUES^b, B. LINDMAN^a,c, M. MIGUEL^a

Catanionic SDS/DDAB vesicles are spontaneously formed by mixing the two surfactant solutions with the appropriate mixing ratio. These vesicles show long term stability and are suitable models for biomembranes and drug delivery systems. Polymer addition induces an interesting effect in the vesicle structure, changing the aggregate shape from spherical to faceted¹. This phenomenon was observed with two different oppositely charged polyelectrolytes, with different charge densities, one being hydrophobically modified.

Phase behavior maps previously investigated show the presence of solution and gel regions². The experimental results obtained by micro-DSC and rheology for the polymer-vesicle gels clearly show different mechanisms for the interaction, depending on the polymer used. For the lower charged hydrophobically modified polyelectrolyte, the vesicle faceting is associated with surfactant alkyl chains crystallization. For the higher charged non-modified polycation, the faceting is attributed to surfactant segregation within the vesicles, with formation of SDS-rich and DDAB-rich domains.

¹ Antunes, F.E. et al., Langmuir 2004, 20, 4647-4656

² Marques, E. F. et al, Macromolecules 1999, 32, 6626.

PC106

Thermal and Dielectric Behaviour of Organic/inorganic interpenetrating networks

J. Nedbal^a, L. Matějka^b, V. Velychko^a, I. Kroutilová^b

Two types of organic-inorganic networks were studied; the systems containing (a) polybutadiene (PB) or (b) epoxy-amine network as soft organic matrices. The hard inorganic phase of the interpenetrating networks was formed in situ by the sol-gel process of alkoxysilane derivatives, or the well defined polyhedral oligomeric silsesquioxanes (POSS) were used.

Complex dielectric permitivity (e' and e'') was measured at various constant temperatures and frequencies in temperature region from - 100°C up to 230°C and in frequency region from 5Hz up 10MHz. The dielectric measurement was also performed by method of thermally stimulated depolarization currents. Thermal properties were investigated using a Perkin-Elmer DSC calorimeter.

From thermal DSC and TSDC measurements we can determine the temperatures of observed absorptions. From frequency dependence of dielectric permitivity then the temperature dependence of maxima of e'', the shape and the magnitude of this absorption.

All measured samples show heterogeneous structure with both soft (low temperatures) and hard (higher temperatures) phases. Temperature dependence of e'' in soft part behaves according the WLF equation contrary to hard one which has Arrhenius like temperature dependence in measured region. Samples with high concetration of POSS show crystalization of POSS.

Acknowledgement: This work was supported by the Ministry of Education, Youths and Sports of the Czech Republic (project ME 691) and by the Grant Agency of the Czech Republic (project 203/05/2252).

PC107

HYDROXY-FUNCTIONAL HYPERBRANCHED PRECURSORS OF POLYURETHANE NETWORKS

E. PAVLOVA ^a, M. DUŠKOVÁ-SMRČKOVÁ ^a, K. DUŠEK ^a, B. VOIT ^b

Hyperbranched polyesters (HBP) based on 4,4-bis-(4'-hydroxyphenyl) pentatonic acid (a monomer of AB₂ type), bearing hydroxyl groups, were synthesized by melt polycondensation. The molecular structure and distribution were varied by adding of different core molecules with 3, 4, or 6 OH-groups, respectively. The average functionalities of products were respectively 8, 12 and 14 hydroxy groups per molecule whereas the number average molecular weights ranged from 1880 to 3300 g/mol.

The hyperbranched polyesters were further used as precursors of polyurethane networks prepared with either trimer of 1,6-diisocyanatohexane (tri-HDI) or 1,6-diisocyanatohexane (HDI). The concentration of elastically active network chains (EANC) in samples (containing 40 % of diluent at network formation) was calculated from equilibrium shear modulus determined in the swollen state and also predicted using the Theory of branching processes. The measured concentrations of EANC were about one half of the predicted values that ranged from 4.0´10^-3 to 4.3 ´ 10^-3 mol/cm³ in samples with tri-HDI. The EANC's in samples with HDI, measured and calculated, were similar but shifted to somewhat lower values. One reason for differences between calculated and measured values is the intramolecular reaction, (cyclization). The extent of cyclization was determined as the shift of the critical (gel) conversions with dilution. The fractions of bonds forming cycles at 40%-wt. dilution at the gel point were between 0.25 - 0.50. The intensity of cyclization was more significant for samples containing core molecules. The networks prepared from HBP precursors had T_g from 120° - 150°C and they showed excellent film-forming properties in solvent - born high solids systems.

PC108

Latex microgel particles as reactive fillers

J. Mísařová, L. Svoboda, L. Prokůpek, J. Šňupárek

Latex microgel particles were prepared by emulsion polymerization of methyl methacrylate (MMA), butyl methacrylate (BMA), 2-hydroxyethyl methacrylate (HEMA) or glycidyl methacrylate (GMA), methacrylic acid (MAA) and allyl methacrylate (AMA) crosslinker. The latex particles were studied as reactive polymer fillers for epoxy resins and water acrylic dispersions.

Reactive fillers for epoxy resins were prepared by copolymerization of MMA, BMA, GMA, MAA and AMA. Epoxy groups of the filler reacted with polyamine and made crosslinked structure within epoxy matrix. The main problem was homogenization, because the particles were apt to form agglomerates in the matrix. The structure of the epoxy composites with acrylic copolymers were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM), the mechanical properties were studied by dynamical mechanical and thermo-mechanical analysis (DMA, TMA).

Reactive fillers for water acrylic dispersions were prepared by copolymerization of MMA, BMA, HEMA and AMA. Properties of films cast from mixtures of the film-forming water acrylic dispersion and the water dispersion of hard hydroxy-functionalised microgel particles were investigated by AFM and tensile measurements. The film properties were studied in relation to the component ratio and the addition of an isocyanate curing agent.

PC109

PC110

SMART CHITIN/CHITOSAN-BASED HYDROGELS

F. M. GOYCOOLEA^A*, W.M. ARGÜELLES-MONAL^B, I. HIGUERA-CIAPARA^B, C. PENICHE^C, J. HERNÁNDEZ ^a, J. LIZARDI ^a, A. HERAS^D, L. FÉLIX^A and E.I. DÍAZ^A

Gelation of chitin, chitosan and chitosan derivatives, has been the subject of active collaborative research in our group over the past years. Chitin is known to fully dissolve in cold aqueous alkali to form a true macromolecular solution (alkali chitin). On heating, alkali chitin undergoes phase separation describing a characteristic "U"-shaped cloud point curve with a lower critical solution temperature (LCST) centered at ~ 30°C. The process is accompanied by gelation of the polymer-rich phase. A different strategy to induce alkali chitin phase separation/gelation is by leaving alkali chitin standing at room temperature under vacuum, whereby chitin is deacetylated (i.e. it forms chitosan). Changes in the thermal and mechanical properties of chitosan hydrogels thus obtained and washed to neutrality evidenced a phase transition centered at ~ 22°C. Whereas swelling properties are closely dependent on pH and become more pronounced in the vicinity of pH ~7.6. In turn, chitosan hydrogels were chemically cross-linked with glutaraldehyde. Variation in swelling response as a result of stepwise changes in temperature between 40 and 2 °C at pH values of 7.0, 7.6 and 8.0, revealed that the system responds in markedly different manner in dependence of pH. This behavior is consistent with the existence of a fine balance between hydrophobic and electrostatic intreractions at varying temperature and pH, thus effectively controlling the entropy-driven collapse of the gel network. The third system under study was the derivative obtained by N-acylation of chitosan with isobutyric anhydride whereby a functional group analogous to that present in polyNIPA is attached to chitosan. The gel formation process of these gels seems follow closely the kinetics of the reaction and it proceeds predominantly under second order. These hydrogels also show negative thermal sensitivity driven by hydrophobic association of the N-isobutyryl groups.

PC111

RHEOLOGICAL BEHAVIOUR OF LAYERED SILICATES AND SEPIOLITE IN EPOXY RESIN

L. SOLAR, A. NOHALES, CM. GOMEZ

In the last years inorganic fillers such as clay, mica, alumina trihydrate, silice... have been mixed with thermosets in order to improve toughness without detriment in thermal stability. The degree of the initial dispersion of the fillers before the cure process starts determines the usefullness of the selected filler. In this paper we present the rheological behaviour of binary mixtures epoxy/sepiolite and epoxy/layered silicates to assess the extent of the dispersion attained (with or without aggregate formation).

A diglycidyl ether of bisphenol A (DGEBA) GY250 was used as epoxy resin. Organic modified and not modified layered silicates and sepiolites at different weight per cent were employed as fillers. They were dried for 24 h at 100 C before use. Steady state flow and oscillatory measurements were performed using a TA AR-1000 rheometer. The steady-state viscosity measurements were carried out in the shear rate range from 0.1 to 1000 s^-1 using parallel plate geometry. For every viscosity measurement, the filler-epoxy compounds were presheared at a shear rate of 1000 s^-1 for 3 min to maintain the same initial conditions.

Whereas the neat epoxy system exhibited Newtonian flow, the dispersions of the fillers in the epoxy prepolymer showed pseudoplastic flow behaviour that increase with the percentage of filler, typical of polymeric fluids such as gels. The dispersions also present yield stress. The flow curves of organophilic layered silicates fit the Carreau model while the corresponding to the organophilic sepiolite fit the Cross model. The strain sweep dynamic tests show a linear viscoleastic region that widens with decreasing filler concentration. The storage (G') and loss (G") moduli as a function of angular frequency show different trends as a function of the type of filler and its concentration. Scaling laws have been established for the changes in rheometrical parameters with the volume fraction Φ, revealing a pronounced increase in the degree of particles interactions as Φ is increased. Fractal dimension was estimated from the storage modulus and Φ dependence. This suggests that the suspensions structure is dominated by diffusion limited aggregation, mostly due to the attractions involving the interparticle potentials.

Acknowledgements: Financial support from projects MAT2002-03485 and GV04B133 is gratefully acknowledged.

PC112

SYNTHESIS AND CHARACTERIZATON OF POLY(METHACRYLIC ACID)-l-POLYISOBUTYLENE POLYELECTROLYTE AMPHIPHILIC CONETWORKS

MÁRTON HARASZTI, BÉLA IVÁN

Combinations of polymer chains of different character into one material composition hold very promising aspects. Such materials may possess several novel unique properties and thus be apt for unprecedented functions. One form of creating new composites is combining hydrophilic and hydrophobic chains in one polymer network [2-6]. Polymers obtained from linking strongly hydrophilic (meth)acrylic acid and hydrophobic polymer chain segments by covalent bonds to form a variety of block copolymers has been intensively investigated in recent years [1].

By using a special two-step procedure we have recently been able to prepare poly(methacrylic acid)-l-polyisobutylene (PMMA-l-PIB) amphiphilic conetworks with a wide range of compositions (~ 20-85 w/w % PIB content). The synthesis is based on the utilizaton of methacrylate-telechelic polyisobutylene (MA-PIB-MA) obtained via quasiliving carbocationic polymerization as macromolecular crosslinking agent. The resulting conetworks exhibit unique physical, physicochemical and swelling behavior. This presentation will provide the details of the synthesis method, characterization and major properties of these new unique bicomponent polyelectolyte amphiphilic conetworks.

REFERENCES

[1] H. Mori, A. H. E. Müller, Prog. Polym. Sci., 28, 1403-1439 (2003)

[2] B. Iván, J. P. Kennedy, P. W. Mackey, ACS Symp. Ser., 469, 194-212 (1991)

[3] B. Iván, J. P. Kennedy, P. W. Mackey, US Patent, 5,073,381 (1991)

[4] B. Iván, K. Almdal, K. Mortensen, I. Johannsen, J. Kops, Macromolecules, 34, 1579-1585 (2001)

[5 A. Domján, G. Erdődi, M. Wilhelm, M. Neidhöfer, K. Landfester, B. Iván, H. W. Spiess, Macromolecules, 36, 9107-9114 (2003)

[6] G. Erdődi, B. Iván, Chem. Mater., 16, 959-962 (2004)