MORPHOLOGY OF THERMOTROPIC LIQUID CRYSTALLINE POLYMERS.

Recent liquid crystalline polymer (LCP) research has focused on understanding the process-structure-property relationships of these novel materials. Overall, the process history of thermotropic LCP's is related to the microstructure frozen into the solid state, i. e. , the high mechanical anisotropy of the molecules favors formation of complex skin core and layered structures. The fundamental structures observed in thermotropic LCP's are; 'domains', regions of local order, observed by optical techniques; and microfibrils, elongated structures observed by optical and electron microscope (EM) techniques. Fibrillar and domain structures have been observed by optical, scanning, and transmission EM techniques, in materials prepared by microtomy, etching, fracture and sonication methods. Importantly, the morphology observed for highly oriented LCP fibers, thick extrudates and molded articles is described by a single structural model which shows the fibrillar units to be organized in a hierarchial structure ranging from micrometers to nanometers in size. Specifically, the structures observed are: microfibrils, on the order of 50 nm; fibrils on the order of 500 nm; and macrofibrils about 5 micrometers in size. Evidence presented suggests this fibrillar structure exists in the materials prior to specimen preparation for microscopy.