Research Projects

Polyurethanes (PU) feature an extremely broad range of end-use properties (density, stiffness, hardness, etc.). They are mainly used in the form of foams (flexible, semi-rigid, rigid) in construction, transportation, furniture (bedding) and footwear. In some special applications, PUs are used as soft solid elastomers or hard solid plastics. Main materials for PUs preparation are: oligomeric polyol, isocyanate, chain extender/crosslinker. Though design properties of PUs are different, the number of components for their preparation is quite narrow. The most common (“classical”) PUs are based on polyether (PE) or polyester (PES) diols or triols and aromatic di- or poly- isocyanates. PUs prepared from polybutadiene- (PB) or polycarbonate- (PC) diols belong to the group of specialty products, due to enhanced enduse properties of PB-PUs and PC-PUs compared with “classical” PUs.
The project will be aimed on the preparation and characterization novel PUs made from polycarbonate (PC)-based macrodiols, aliphatic or aromatic diisocyanates and aliphatic chain extender/crosslinker. In some cases, inorganic nanofiller will be added. One-step and/or two-step (prepolymerization) techniques combined with solvent or solvent-free systems will be used. Multidisciplinary characterization (advanced techniques of analyses included) of PCPUs will be done in order to study relationship: material choice – preparation technique – enduse properties that will be compared with “classical” PUs, eventually PBD-based PUs.

In this project, stimuli-responsive hydrogels are devlopped, based mainly on nanocomposites of poly(N-isopropylacrylamide) with inorganic nanofiller particles. The aim is to obtain materials with very fast response to environmental changes (e.g. of T or pH) for the potential application as mechanical actuators (“artificial muscles”) in technical or biomedical devices.
The choice of the main monomer and of co-monomers determines the type and range of stimuli-responsivity, while the response rate is controlled by porosity induced in the gels and by nanofillers which support the pore system. Furthermore, the nanofillers are optimized in order to achieve a stable, long-term mechanical reinforcement of the gels, without (or with minimal possible) detriment to the amplitude of stimuli response.
In course of this project, new gels will be synthesized, and their mechanical properties, swelling behavior and force response will be investigated directly in our group. Further characterization – electron microscopy, X-ray scattering, NMR and IR analyses – will be carried out in cooperation with other departments of the Institute.

Previous published work on the topic:

B. Strachotová, A. Strachota, M. Uchman, M. Šlouf, J. Brus, J. Pleštil and L. Matějka: "Super porous organic-inorganic Poly(N-isopropylacrylamide)-based hydrogel with very fast temperature response", Polymer 48 (2007), 1471-1482

M.Lutecki, B.Strachotová, M. Uchman, J.Brus, J.Pleštil, M. Šlouf, A. Strachota L.Matějka: "Thermoresponsive PNIPA-based organic-inorganic hydrogels", Pol. Journal 38 (2006) 527-541

Most recent, not yet available (December 2008) paper: G. Huerta, K. Hishchak, B. Strachota, M. Šlouf, M. Uchman, L. Matějka and A. Strachota*: “Super porous hydrogels with fast temperature and pH response based on poly(N-isopropylacrylamide-co-sodium acrylate) filled with titanium dioxide nanoparticles”; Polymer, submitted

Polyaniline is an important conducting polymer. Tuning of reaction conditions used for the oxidation of aniline leads to the formation of various polyaniline nanostructures: nanotubes, nanowires, nano- and microspheres, and more complex systems. Acidity of reaction mixture seems to be the most important factor. The understanding of the processes controlling the polyaniline morphology is primary goal. The resulting structures can be carbonized to corresponding carbonaceous materials, serve as templates for the deposition of noble-metal nanoparticles or become a component of various composite systems.

The separation of chitilolytic enzymes will be carried out using a three-step procedure:

1. sample preparation
2. ion exchange chromatography
3. size exclusion chromatography

The participant will be involved in a project devoted to controlling structure and tailoring mechanical behaviour, degradability and lifetime of biodegradable thermoplastic materials by incorporation of the B-starch. The B-type of starch is a by-product in a starch industry and its possible applications are searched for. The project comprises both basic and applied research. It is suitable for participants with a degree in chemistry (surface modification of the starch) as well as for those with a degree in polymer physics (optimization of composite structure, structure-property interrelations).

The project will be devoted to the investigation of interactions polymer-solvent (hydration) and polymer-polymer in aqueous solutions (or gels) of stimuli-responsive polymers which show a phase transition of the coil-globule type. This transition can be induced by temperature, solvent composition etc. Multicomponent polymer systems with various architecture will be studied, e.g,, mixtures of thermoresponsive polymers, block or graft copolymers containing thermoresponsive blocks or grafts, or responsive two-component interpenetrating networks. Information how the architecture of the polymer system affects the phase-separated globular-like structures on various level should be obtained. This includes information on the fraction of monomer units in these structures, on changes in hydrogen bonding of specific functional groups and arrangement of water molecules, and in changes in dynamics of polymer segments and water due to the phase transition. The knowledge how the structure and interactions (hydration) are changed in a multicomponent system in comparison with the respective responsive homopolymer(s) should provide more information which is important to design materials with specific properties. NMR spectroscopy (including NMR relaxation measurements) will be the main method in these investigations. It can be combined with vibrational spectroscopy and other physical methods when this will be desirable.

Preparation and characterization of the complex effect of nanoclays on the structure and behaviour of polymer phase modified epoxy resin. The goal is to achieve favourable combination of clay reinforcement and influencing the dynamic phase behaviour including formation of advantageous morphology of dispersed phase. Analysis of the effect of complex inclusions structure and parameters on system behaviour.

Cellulose and its derivatives, ie., esters and ethers, contain free hydroxygroups capable of further reactions like acylation. If appropriate agent is used, namely halide of 2-haloacid, initiating centers of controlled radical polymerization (ATRP) are formed in this way, which can generate chemically various grafts. From the topological point of view, the grafts can be homopolymers as well as di- tri- or even multiblock copolymers and, therefore, wide scale of polymeric materials with various physical and mechanical properties can be synthesized. In dependence on reaction conditions, a number of active centers along the cellulose chain can be controlled in a broad range and more, due to the “living” character of ATRP, chemical structure and length of the grafts are also widely controllable. Thus, the cellulose grafting using this protocol leads to broad spectrum ov novel stil unmet materials with variable properties and application potential.

Nanomaterials are rapidly developing theme of both basic and applied research. The project involves synthesis and characterization of polymer nanocomposites based on organic-inorganic polymer systems. The inorganic phase (mainly silica structures) will be incorporated into the polymer matrix by in situ polymerization of the alkoxysilane monomers using the sol-gel process. Structure and morphology of the nanocomposites on both nano- and microscale will be controlled by the reaction conditions during the nanomaterial formation. The spectroscopy (NMR), scattering techniques (SAXS, WAXS, dynamic light scattering), microscopic techniques (TEM,SEM,AFM) and mechanical testing (dynamic mechanical analysis) will be used to characterize the polymers. The effect of size of inorganic nanodomains, their possible self-assembly within a polymer matrix and an interface interaction on mechanical and thermal properties of the nanocomposites will be studied. Determination and interpretation of processes governing the unique behaviour of polymer nanocomposites is the main goal of the project. Finally, the nanomaterial with improved mechanical and thermal properties should be prepared.

"Aplication of Electron Spin Resonance Imaging in Polymer Science; Diffusion in Polymer Gels or Profiling of Degradation in Solid Polymers". The theme comprises two projects. The first one is aimed at understanding dependence of diffusion coefficients of tracers in equilibrium swollen polymer hydrogels on the structure of the hydrogels characterized by swelling ratio, polymer volume fraction, dynamic correlation length, and concentration of elastically active chains. Coefficients of macroscopic translational diffusion of tracers carrying paramagnetic labels will be measured using electron spin resonance imaging (ESRI). Self-diffusion and mutual diffusion coefficients of some diamagnetic components of the system (diamagnetic tracers, water) will be measured by pulsed-gradient stimulated NMR spin-echo and dynamic light scattering, respectively. Better understanding to the principles controlling diffusion processes should make possible not only better description and prediction of transport properties of polymer gels in dependence on their structure but also preparation of polymer gels with transport properties required for particular applications.
The second one concerns protection of polymers against deterioration of their properties due to weathering using cooperation between various stabilizers and improving economy of protection by optimization concentration of stabilizers that requires better understanding of degradation mechanisms. This project is focused on profiling degradation process inside stabilized amorphous and semicrystalline polymers (polypropylene, polystyrene, polyethylene, poly(ethylene-co-norbornene) by measuring concentration profiles of nitroxides, key intermediates in the protection mechanism of hindered amine stabilizers (HAS), by electron spin resonance imaging (ESRI) in dependence on the duration of the accelerated weathering. In the same dependence changes in polymer transparency, changes in concentrations of carbonyl and hydroxy groups on the surface and inside the samples, and changes of integral mechanical properties of polymers will be studied.

Recently, magnetic particles find applications in different fields of bio-nanotechnology, biomedical diagnostics and bioengineering including magnetic resonance imaging, cell isolation and purification. Magnetic nanoparticles will be prepared by coprecipitation of Fe(II) and Fe(III) salts in alkaline medium and/or oxidation. The nanoparticles will be complexed with new steric stabilizers based on alternating or block copolymers. Alternatively, the nanoparticles can be obtained by the thermal decomposition of iron organic compounds using surface capping molecules to stabilize the colloids. The particles will be thoroughly characterized in terms of morphology, particle size, composition and magnetic properties by the appropriate methods, such as X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis, transmission electron microscopy, light microscopy and dynamic light scattering. Finally, polymer microspheres will be prepared by encapsulation of magnetic cores using heterogeneous polymerization methods. Effect of various reaction parameters on properties of the particles will be elucidated.

New generation of active pharmaceutical materials (APM) is based on a combination of pharmaceutical ingredients (API) and polymers forming thus solid solution or solid dispersions. Behavior of these systems: stability, pharmacokinetic activity etc. depends on the distribution of the drug within the polymer matrix, size of domains, crystallinity and segmental dynamics of polymer chains. The aim of the proposed project is development and application of the advanced solid-state NMR techniques for selective measurements of motional amplitudes and frequencies of polymer segments in order to disclose some relations between structure, molecular dynamics and stability and activity of these systems. (http://www.imc.cas.cz/nmr/cz/stud.html#4)

This project is aiming to improve understanding of gelation and micellisation processes in tri-block co-polymers Pluronics and in their modifications. Outcome of this research could be applied for biomedical purposes – e.g. for generation of hydrogels with precisely controlled properties. Raman and infrared spectroscopy are the main research methods.

Affinity biosensors use biological receptors attached to a physical transducer for binding specific analytes. For in real-time detection in biological media it is convenient to immobilize the receptors on the transducer coated with an antifouling polymer layer which prevent nonspecific deposition of biological compounds. The work will include the preparation of ultra-thin hydrogel layers from newly synthesized polymers on surface plasmon resonance (SPR) sensors. Bioreceptors, such as, antibodies and antigens, will be covalently attached to the hydrogel. The layers will be characterized by IR reflection spectroscopy and AFM, and the detection of the respective analytes in blood serum will be tested by SPR. The results will be utilized for the development of protein chips applicable in medical diagnostics.

A modern Raman confocal microscope will be used for study of the molecular structure of conducting polymers. After learning the principles of Raman spectroscopy, the mechanism of Raman effect and the selection rules of Raman scattering, near resonance and resonance Raman scattering will be used to study the molecular structure of various nanostructured polyaniline powders prepared under different conditions. Ageing of thin polyaniline films will be studied using mapping technology. Molecular structure of conducting polymers nanocomposites with nobel metals will be studied using surface enhanced Raman spectroscopy (SERS).

The topic of the research work is related to a broader project dealing with the preparation of polymer supports targeted for specific cell cultivation. The main objective will be the synthesis of hydrogels based on methacrylates in the form of 2D foils and 3D macroporous structures and their chemical modification with the aim of incorporation of desired functional groups onto the polymer surface enabling the covalent attachment of selected oligopeptide sequences or proteins. Subsequently, the biological response of thus prepared bioactive polymer supports for different types of cells will be evaluated. Skillful polymer or organic chemist with an experience in this area (particularly in oligopeptide synthesis) is welcomed.

Main idea: Titanate nanotubes (Ti-NT) represent novel type of nanoparticles with diameters around 10 nm and lengths > 1 m. Ti-NT are prepared by hydrothermal synthesis from standard TiO2 micro- and nanopowders; the preparation is relatively straightforward and cheap. Therefore, Ti-NT are suitable filler for polymer composites.

Task: Preparation of Ti-NT and their polymer composites with polyamide, polypropylene and/or epoxy resins. Characterization of morphology of Ti-NT and their compositesis by electron microscopy (SEM, TEM, SAED) and X-ray diffraction (SAXS, WAXS). Assesment of mechanical properties by dynamic mechanical analysis (DMA).

Originality: The work in this field is quite original, as the polymer composites with Ti-NT have not been reported yet. Our first results showed that Ti-NT composites exhibit higher elastic moduli than analogous composites with commercial TiO2 micro- or nanopowders, from which they had been synthesized.

Main idea: Major problem of synthetic polymer nanocomposites is to achieve a good dispersion of nanofiller in polymer matrix. That is why we developed the sandwich method, which is optimized for small samples (10mm x 10mm x 0.5mm) containing homogeneously dispersed nanoparticles. Such specimens are currently used for detailed investigation of nucleation effects and could be also employed in photovoltaic applications.

Task: Preparation of sandwich nanocomposites of polypropylene (PP) and various nucleating agents, such as gold nanoparticles (Au-NP) and commercial alpha- and beta-nucleants. The Au-NP will be prepared by both chemical way (synthesis in solution) and physical way (vacuum sputter coater). Characterization of nucleation effects by electron microscopy, differential scanning calorimetry and X-ray diffrection.

Originality: Sandwich method is our own, new technique for reproducible preparation of polymer nanocomposites, which will be published soon. By means of this method, we will be able to reliably answer the long-standing question of polymer physics: is the nucleation activity of Au-NP (and also other metallic nanoparticles) influenced by their size, shape and/or chemical purity?

Main idea: Precession electron diffraction (PED) is completely new method of electron diffraction. PED yields intensities of diffractions, which are much less influenced by dynamical effects in comparison with standard electron diffraction (ED). Therefore, PED can be used for precise analysis of synthetic polymer crystals, which has not been possible with standard ED.

Task: Preparation of polymer single crystals, characterization of their morphology and nanostructure by light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In collaboration with Physical Institute AS CR, determination of crystal structures by means of ED and PED.

Originality: PED is a new technique, which has appeared a few years ago. According to available literature, it has not been applied to study of synthetic polymer single crystals. Consequently, the PED analysis of crystalline polymers should bring quite original findings in the field of crystal structure analysis.

Main idea: Ultrahigh Molecular Weight Polyethylene (UHMWPE) is used as a key component of total joint replacements (TJR) of big human joints such as hip and knee. Life-limiting factor of TJR is wear, which is a release of tiny, microscopic particles from UHMWPE during joint movements. Wear resistance of UHMWPE and lifetime of TJR can be increased by radiation-induced crosslinking and thermal treatment.

Task: Irradiation of UHMWPE with accelerated electrons (collaboration with IPF Dresden), thermal treatment (remelting, annealing), characterization of original and modified samples by number of microscopic (SEM, TEM), diffraction (SAXS, WAXS), thermal (DSC) and spectroscopic (IR, ESR) methods. Measurement of mechanical properties (tensile testing, SPT) and wear resistance (POD; in collaboration with company Beznoska).

Originality: Modification of UHMWPE by means of irradiation has been introduced approximately ten years ago. Nevertheless, the influence of irradiation on UHMWPE structure is a complex process and research in this field still continues. We are going to compare standard (single-step) irradiation with sequentional (several-step) irradiation and publish the results in impacted journals.

Performance of polymeric gas separation membranes is often influenced by those components of the separated mixture which swell the polymer. For example membranes for biogas or biohydrogen cleaning work with mixtures saturated by water vapor. The aim of the study is to utilize the described phenomena for improvements of separation efficiency. In addition permeation of small molecules of gases through the swollen polymers brings additional information about the detailed morphology inside the polymer.

Polymeric nanoparticles have an increasing range of applications in many areas of nanotechnology and in functional systems for applications in medicine, biology and electronics. In this project we shall focus on the preparation of nanoparticles by physicochemical methods using synthesized precursors and their specific interactions with surface active materials (surfactants and block copoymers). This approach leads to the possibility of preparing nanoparticles using a wide variety of polymeric substances and therefore specifically tailored for a specific application such as targeted delivery of drugs or genetic material, or for diagnostic purposes. It is also possible to prepare nanoparticles that can be reversibly created and dissolved by action of external variables such as changes in temperature, pH, illumination, solvent composition or ionic strength. The nanoparticles and their reactions to environment will be studied by scattering of light and X-rays and by electron microscopy and atomic force microscopy.

Stimuli-responsive polymers showing a nonlinear response to an external signal have gained much interest as ‘‘smart’’ and advanced materials in the last few years. Among these, thermoresponsive polymers exhibiting lower critical solution temperature (LCST) behavior in aqueous solution represent an important class, especially for biomedical applications, and in particular to research related to tumors that exhibit a higher temperature than normal body temperature. The inverse temperature-dependent solubility leads, e.g., to association of polymers above LCST and this effect can be exploited for various biological applications.

An important family of thermoresponsive polymers that is under-researched and under-utilized is that of polyoxazolines. These polymers exhibit a number of attractive features compared to other thermosensitive polymers: 1. they are structurally closer to polypeptides than the often used N-isopropylacrylamide (NIPAM) polymers, since the amidic nitrogen is located in the main chain and not in the side group; 2. they can be synthesized in a controlled way with a narrow molecular weight; 3. they are easily copolymerized with other oxazoline monomers to create random, block, gradient and branched copolymers with adjustable LCST.

The research in this project aims at the synthesis, study of physicochemical properties and fine-tuning of structural properties of new thermoresponsive polymers based on polyoxazoline and of their micelles and nanoparticles with respect to their potential use in biological applications, in particular in the drug delivery field.

Properties of a copolymeric material are given both by molecular weight and by composition. MALDI-TOF mass spectrometry, as non-destructive method, gives only information on the molecular weight of individual components of the material; however, in principle, the information on composition can be extracted owing to the high precision of the method. In practice, this is limited due to the generally poor quality of MALDI-TOF spectra of copolymers. In the project, the ways to overcome this limitation by utilization of additional information will be pursued.

Polymers and polymer composites find an increasing use as advanced active materials in optoelectronics. The proposed work should be focused on a preparation of suitable polymer nanostructures and on the study of general relationships between the molecular and supramolecular structure and efficiency of photogeneration and transport of free charge carriers. The final aim is to optimize photoelectrical parameters for a potential application of polymers in photovoltaic solar cells. Polymers with suitable chemical structures have to be found, which yield a proper position of energy levels and extended electron delocalization. Theoretical approach based on computer modeling and, possibly, on quantum mechanical calculations, will be combined with experimental studies, mostly by steady-state and time-resolved measurements photoelectrical measurements. According to the background of a candidate either experimental or theoretical character of the work can be accented. We expect a tight collaboration activity with various laboratories in Europe.