This research was motivated by theoretical and experimental objectives regarding blends of thermotropic liquid crystalline polymers and flexible coil polymers with specific application to in situ fiber-reinforced composites. The primary aim has been the prediction of the phase behavior of blends and diblock copolymers containing rigid (liquid crystalline) species. The objective was to first derive a free energy expression that went beyond the mean field theories by taking composition fluctuations into account. Computational procedures were then developed for the evaluation of the free energy. The analytical derivation and the computational procedures provide the means for predicting the phase behavior of blends and diblocks as a function of molecular weight. The connectivity of the diblock molecule is shown to be responsible for a shifting of the isotropic-nematic transition in composition and a lowering of the critical $\chi$ value. A critical examination of the theory is difficult due to the lack of experimental data required for comparison. A secondary aim was to resolve some specific questions about a novel blend system that shows good prospects as an in situ composite. Investigation concerned the effect of blend composition on crystallization, the nucleating properties of the liquid crystalline component relative to those of more common nucleating agents, and the degree of miscibility between the blend components. The liquid crystalline component was shown to decrease crystallinity with increasing concentration. Its nucleation properties were similar to those of more common nucleating agents. No evidence of immiscibility was found in the blend system.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-8537 |
| Date | 01 January 1992 |
| Creators | Graff, Michael Scott |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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