THE GAMMA-RELAXATION IN POLYMERS CONTAINING ETHER LINKAGES - CONFORMATIONAL DYNAMICS IN THE AMORPHOUS PHASE FOR A SERIES OF POLYBIBENZOATESCONTAINING OXYETHYLENE SPACERS

Restricted conformational transitions in oxyethylene chains have been investigated using a molecular mechanics approach. Geometries and ener gies of transition pathways have been evaluated for kink inversion and formation, and for crankshaft type motions which are feasible in anis otropic glassy matrices. Barrier heights for these processes are found to be similar to those determined for the corresponding processes in polyethylene chains although geometries of the conformations at the en ergy minima are significantly different. Results of the calculations a re broadly consistent with dynamic mechanical measurements which indic ate a gamma relaxation in the amorphous phase of thermotropic liquid c rystal polymers containing oxyethylene spacers. They support the hypot hesis that kink formation, inversion and migration are primarily respo nsible for the low temperature relaxation in these polymers. Copyright (C) 1996 Elsevier Science Ltd.