The γ relaxation in polymers containing ether linkages: conformational dynamics in the amorphous phase for a series of polybibenzoates containing oxyethylene spacers

Abstract

Restricted conformational transitions in oxyethylene chains have been investigated using a molecular mechanics approach. Geometries and energies of transition pathways have been evaluated for kink inversion and formation, and for crankshaft type motions which are feasible in anisotropic 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 energy minima are significantly different. Results of the calculations are broadly consistent with dynamic mechanical measurements which indicate a γ relaxation in the amorphous phase of thermotropic liquid crystal polymers containing oxyethylene spacers. They support the hypothesis that kink formation, inversion and migration are primarily responsible for the low temperature relaxation in these polymers.