Rheology and Changes in Structure of Thermotropic Liquid Crystalline Polymers

摘要

The objective of this thesis is to determine key features of the rheology ofthermotropic main-chain LCPs and to relate these to the underlying structural changes. Since the development of orientation and structure in these materials during flow is responsible for their rheological responses, in-situ optical (rheo-optical) experiments are necessary in addition to rheological measurements to understand their flow behavior. Until present most experimental data of the rheology and rheo-optics of liquid crystalline polymers have been obtained from solutions (lyotropes). The most widely investigated thermotropic LCP, Vectra A900, is highly turbid and, therefore, unsuitable for rheo-opical experiments. Optical investigations on this material have been performed only on quenched samples. In this thesis the results from rheological and rheo-optical experiments on a liquid crystalline copolyesteramide (Vectra B950) are reported and analyzed. Studies like these should provide a basis for further improvement of rheological models, which at present do not account for all experimental features and for the difference between melts and solutions.