DEVELOPMENT OF CRYSTALLINITY IN A POLYURETHANE CONTAINING MESOGENIC UNITS .1. MORPHOLOGY AND MECHANISM

This work extends prior studies of a polyurethane containing mesogenic moieties. Optical and thermal methods reveal that this polyurethane exhibits monotropic mesomorphic behavior. Two distinct crystallization mechanisms and crystal morphologies are identified, one arising from the isotropic melt and producing a spherulitic texture and the other arising from the mesophase and producing a threaded texture. A combination of thermal analysis, X-ray diffraction, and dynamic rheological studies reveals that crystals grown from the mesophase are readily perfected to a higher melting form by annealing whereas spherulitic crystals are less amenable to perfection. The development and perfection of the crystalline state were also found to be dependent on polyurethane molecular weight. © 1990, American Chemical Society. All rights reserved.