Conformational calculation of the conditions of internal rotation and torsional vibrations of cyclic groups in poly(4,4′-oxydiphenylene)pyromellitimide☆

For PI on the basis of pyromellitic acid dianhydride and 4,4′-diaminodiphenyl ether, the potential surface for the motion of cyclic chain fragments was calculated in the atom-atom approximation. The amplitudes of thermal vibrations and energy barriers to rotation of pyromellitimide and phenylene rings were calculated for a defect-free crystalline lattice and for defective fragments resulting from point defects and from local density fluctuations in the polymer. Types of motions of cyclic fragments which can be manifested as local relaxation processes are proposed.