THE FAST RELAXATION PROCESS NEAR THE GLASS-TRANSITION IN AMORPHOUS POLYMERS WITH DIFFERENT MICROSTRUCTURE

Inelastic neutron scattering results on polymers with different microstructure and fragility (polybutadiene, polyisoprene, poly(ethylene-propylene) and polyisobutylene) are presented. The experimental results from polybutadiene are briefly reviewed and new data for the fast relaxation process which appears near the glass transition temperature in polyisoprene and poly(ethylene-propylene) are presented. The recent observation that the fast relaxation process is of inelastic nature in polyisobutylene, a weakly fragile glass former, is discussed, and also a correlation between the Boson peak position in the glass and the monomeric friction coefficient in the melt is pointed out. Finally the results in connection with the mode coupling theory and the soft potential model are discussed.