Relaxation processes in the surface layers of polymers at the interface



The proton spin-lattice relaxation and dielectric relaxation were studied in some polymers at the solid–polymer interface was constructed from several filled polymers. A useful model of surface layer which can be considered as consisting of a great number of small solid particles covered with a polymer layer. The following systems were studied: polystyrene, poly(methyl methacrylate), their copolymers and cellulose acetate in the presence of different content of fine particles of aerosil and Teflon. It was established that the decrease of surface layer thickness shifts the minimum of spin-lattice relaxation time T1 of high temperature process to higher temperature and minimum T1 of low temperature process to lower temperature. The same was found for dielectric losses reflecting the motion of side groups and of segments. From temperature dependence of T1 and tan δ for both relaxation processes the apparent energies of activation were calculated. On the base of dielectric relaxation data the circular diagram of complex dielectric constant was constructed and by the Cole-Cole method the dispersion parameter α for polymers at the interface was calculated. These data also show the broadening of relaxation spectra in surface layers. The results are discussed in terms of the restriction of possible conformation of chains at the interface and their interaction with surface. It was established that character of molecular motion changes at the interface is dependent on the mode of molecular motion.