Theoretical Studies of Relatively Rigid Polymer Chains

摘要

Various theoretical approaches were applied to elucidate the structure and properties of rigid rodlike polymer chains which are of interest as high-performance polymeric materials. First, semi-empirical molecular mechanics methods were used to calculate the intramolecular and intermolecular energies pertinent to conformational flexibility and chain packing effects, and to characterize the rotational flexibility of various molecular swivels which could be inserted into these rodlike chains to facilitate their processing. Second, geometry optimized CND0/2 molecular orbital calculations were carried out to investigate the structure and conformational characteristics of the rodlike polymers and of wholly aromatic swivels, in both the unprotonated and protonated states. Third, several theoretical approaches were used to calculate the molecular polarizabilities of the; rodlike chains and of several analogous aliphatic and aromatic hydrocarbons. Fourth, electronic band gap calculations within the extended Huckel approximation were carried out in both the axial and perpendicular directions to elucidate the packing and electronic properties of these chains in the crystalline state. Some of these same methods were also used to investigate a variety of molecular species possessing structural features similar to those of the rodlike polymers. (Author)