Working Group of Photonics and Paramagnetic Phenomena

Head: Jan Pilař, DSc (phone +420-296 809 395, e-mail pilar@imc.cas.cz)

Research

Activities of the Group cover studies of structure and dynamic properties of polymer systems using common experimental techniques available in the Institute (dynamic light scattering, pulse NMR) and in particular the electron spin resonance (ESR) spin label technique. The group is equipped with Bruker ELEXSYS E-540 spectrometer with ESR imaging (ESRI) accessories.

Detailed analysis of ESR spectra of suitable paramagnetic compounds (such as sterically hindered nitroxides) chemically attached to polymers as spin labels makes it possible to obtain information on segmental dynamics of polymers. The systems studied comprise dilute and concentrated polymer solutions and polymer gels and, also solid polymers near or above the glass transition temperature.

ESR imaging enables the determination of space distribution of paramagnetic compounds in the sample. By analyzing the time dependence of concentration profiles of paramagnetic tracers (low-molecular-weight, oligomers and polymers), macroscopic translational diffusion coefficients of these tracers in polymer gels and in concentrated solutions can be determined, depending on molecular mass of the tracer, gel structure and polymer concentration.

By measuring and analyzing concentration profiles of paramagnetic intermediates in transformation of hindered amine stabilizers (HAS), which are generated in photo- and thermodegradation in stabilized solid polymers, we try to contribute to more detailed description of polymer degradation processes and to elucidation of mechanisms of various stabilization systems.

Spectral - space distribution of paramagnetic nitroxides formed as transformation intermediates from HAS stabilizer Tinuvin 770 after long-term weathering of polypropylene and polystyrene sheets in an Atlas Xenon Ci3000+ weatherometer measured with a Bruker ELEXSYS E-540 ESRI spectrometer

Send your comments to:
pilar@imc.cas.cz