MESOMORPHIC BEHAVIOR IN POLYDIPHENYLSILOXANE - 3 - AN EXAMINATION OF HIGH-MOLECULAR-WEIGHT POLYDIPHENYLSILOXANE

Polydiphenylsiloxane (PDPhS) has been prepared by solution ring openin g polymerization of hexaphenylcyclotrisiloxane and characterized by Si -29 solid-state NMR spectroscopy. The thermal characteristics of the p olymer have been examined by DSC, dynamic mechanical thermal analysis, linear expansion and X-ray diffraction analysis, and polarized optica l microscopy in an attempt to elucidate the nature of the high-tempera ture mesomorphic phase and understand the high-temperature processing difficulties associated with the material. The results were indicative of a partially ordered molecular structure in the mesomorphic region that is not capable of viscous flow and cannot be ordered by shear. Th e absence of purely crystalline or purely Liquid crystalline behavior is suggestive of a type of intermediate structure for mesomorphic PDPh S.