Conformational Characteristics of Some Liquid Crystalline Aromatic Heterocyclic Polymers Usable as High-Performance Materials

摘要

The review on a new type of para-catenated aromatic polymer being used in the preparation of high-performance films and fibers of exceptional strength, thermal stability, and environmental resistance, including inertness to essentially all common solvents. Polymers of this type include the cis- and trans-poly(p-phenylene benzobisoxazole) (PBO), the cis- and trans-forms of the corresponding poly-(p-phenylene benzobisthiazole) (PBT), and the structurally similar poly(5,5' -bibenzoxazole-2,2' -diyl-1,3-phenylene) (AAPBO) and poly(2,5-benzoxazole) (ABPBO) and their sulfur-containing analogues. Because of their rigidity, these polymers become highly oriented in solution and some display liquid crystalline behavior. The purpose of this paper is to summarize the authors' theoretical work on the structures, conformational energies and intermolecular interactions for these chains, including, in some cases, the so-called articulated forms and the protonated forms known to exist in strong acids. The emphasis is on how such studies provide a molecular understanding of the unusual properties and processing characteristics of this new class of materials.