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

Inelastic neutron scattering results on polymers with different micros tructure and fragility (polybutadiene, polyisoprene, poly(ethylene-pro pylene) and polyisobutylene) are presented. The experimental results f rom polybutadiene are briefly reviewed and new data for the fast relax ation process which appears near the glass transition temperature in p olyisoprene and poly(ethylene-propylene) are presented. The recent obs ervation that the fast relaxation process is of inelastic nature in po lyisobutylene, a weakly fragile glass former, is discussed, and also a correlation between the Boson peak position in the glass and the mono meric friction coefficient in the melt is pointed out. Finally the res ults in connection with the mode coupling theory and the soft potentia l model are discussed.