Effect of orientational stretching and the conditions of imidization on the supramolecular structure of films of poly(4,4′-oxydiphenylene) pyromellitimide subjected to high temperature treatment

X-ray, IR spectroscopy and dilatometric methods have been used to investigate the effect of preliminary cold stretching and the regime of imidization of polyamido acid films of poly(4,4′-oxydiphenylene)pyromellitimide on the supramolecular structure formed after high temperature thermal treatment. These films on orientation behave like monophase systems and become uniaxially oriented for high degrees of stretching. Increase in the rate of heating on imidization permits thermal treatment in the softened state making it possible to remove the stresses appearing during preparation of the films and to obtain both completely isotropic and highly oriented samples on heating under load. On high temperature heating increase in the rate of rise in temperature, as in the case of the non-oriented samples, leads to the formation of a more refined structure than on slow heating.