A model of supermolecular structure of stiff-chain polyimide copolymers and composites

Microstructure and molecular packing in stiff-chain polyimide copolymers and composites of various composition was studied by PMR, X-ray diffraction, and also by calculating the diffraction patterns for model systems. Copolymers of different microheterogeneity were synthesized; it is shown how to characterize the microheterogeneity in the stage of poly(amic acid) by means of PMR and in the polyimide stage by means of X-ray diffraction measurements. A generalized model has been proposed for the domain structure of polyimide copolymers and composites, which shows the latter to be molecular composites and elucidates the reasons underlying the improvement of physico-mechanical over those of homopolymers.