Several series of thermotropic polyesters were prepared by solution polymerization methods using various specially prepared diols and diacid chlorides. The effect that different flexible spacers and mesogenic units based on oxybenzoate terephthalate dyads and triads had on liquid crystallinity was studied by microscopic and thermal analysis techniques. Polymers combining triad aromatic mesogenic groups and polymethylene flexible spacers in the main chain were shown to possess a single mesophase. The transition temperatures of the homologous series were determined by polarized-light microscopy, differential scanning calorimetry (DSC), and thermal-optical analysis (TOA), and were shown to follow an even-odd relationship. Those polymers with less than seven methylene groups in the spacer possessed nematic mesophases while those polymers with seven or more methylene groups showed the optical textures of smectic mesophases. Other polymers were prepared based upon the mesogenic triad and either a poly(ethylene oxide) (PEO), or a poly(propylene oxide) (PPO) flexible spacer. Some polymers with spacers of PEO exhibited two mesophase transitions. Polymers with PPO spacers showed a single mesophase and no melt transition. More than 50 weight-% spacer led to mesophase loss. Polymers with flexible spacers and mesogenic dyads were prepared which showed either a random or alternating placement of the dyads. All of the liquid crystalline polymers containing the mesogenic dyad were nematic, and the arrangement of the dyads in the polymer chain was important, because two polymers with decamethylene spacers and differing dyad sense had different melt behaviors. A final series of polyesters was prepared by melt-transesterification that contained the mesogenic elements described above. In order to incorporate oxybenzoate groups into the polymer chain, it was necessary to use terephthalate copolymers that contained ethylene glycol in addition to a second diol. These materials were found to be more "weakly" liquid crystalline than the other polymers with mesogenic aromatic dyads and triads.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-5812 |
| Date | 01 January 1982 |
| Creators | OBER, CHRISTOPHER KEMPER |
| 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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