Intramolecular Flexibility of Relatively Rigid Polymers, and Intermolecular Interactions in Ordered Polymer Systems. Part II.

摘要

Conformational energy calculations were carried out on benzoxazole and benzothiazole polymers in order to determine whether or not the molecules are planar and if not, the extent of their nonplanarity. Such information is highly relevant to the nature of the chain packing in the crystalline and liquid-crystalline states. Intermolecular interactions were also investigated, both with regard to their effect on the extent to which the chains approach the desired coplanar conformations, and with regard to the origin of the high mechanical strengths of these materials and their resistance to almost all common solvents. The polarizabilities of these molecules were also estimated using a variety of theoretical methods; this information should be very useful in the interpretation of solution property studies, such as flow birefringence measurements used to obtain rheological information relevant to the processing of these materials. A series of wholly aromatic heterocyclic swivels were also characterized with regard to their flexibilities in both the unprotonated state and in protonated state present in the strongly acidic media used as solvents for these polymers. (Author)