| This work incorporates three studies on the influence of molecular architecture on liquid crystalline phase transitions, physical transformations, and thermal stability for acetylene functionalized liquid crystalline thermosets (LCTs). The first study focuses on synthesis and liquid crystalline phase characterization of acetylene functionalized LCTs. The second examines architecture's influence on liquid crystalline phase transitions and physical transformations that occur during isothermal curing of LCTs. The third deals with architecture and the thermal stability of the uncured and fully cured thermosets.;Two homologous series of LCT monomers, differing in mesogen length, were synthesized: with monomers composed of an aromatic mesogen based on either hydroquinone (nHQ) or biphenol (nBP), end-capped with acetylene functional groups, and terminated with flexible alkyl chains of 3 to 8 carbons in length. The nHQ monomers melt and clear at lower temperatures than the nBP series. The monomers were characterized with differential scanning calorimetry (DSC), dynamic thermogravimetric analysis (TGA), and cross-polarized optical microscopy (POM). The monomers displayed liquid crystalline behavior similar to that of a related small molecule liquid crystal series. A related fully aromatic monomer was also synthesized (PEBP). It possesses higher melting and clearing temperatures, displays only a nematic phase, and has higher thermal stability.;The monomers of the two series were isothermally cured in a rheometer. Gelation times were determined from the shear moduli crossover point. Both series display an odd-even effect for gel times, even though the entire nHQ series is isotropic during the isothermal cure. This is the first time such behavior has been seen for an unordered system. From POM, the monomers lose their molecular ordering during initial chain extension, but may regain some order at later extents of curing if at low enough temperatures.;TGA and isothermal thermogravimetric analysis data were collected for cured PEBP in air and nitrogen atmospheres, from which activation energies were calculated. The data indicate independence with respect to atmosphere and thermal path taken to reach the first few percent of weight loss. The network is very stable, and shows 5% degradation at 491°C and 507°C, when tested at 10°C/min in air and nitrogen respectively. |
