CYCLIC VERSUS LINEAR SILOXANE LIQUID-CRYSTALS - PHASE-BEHAVIOR AND X-RAY-DIFFRACTION RESULTS

The phase behavior of cyclic and linear polysiloxanes containing biphenyl-4-allyloxybenzoate and cholesteryl-4-allyloxybenzoate mesogens is reported. The presence of the cholesterol-based mesogen was observed to induce layered packing structures for both linear and cyclic siloxane backbones. Differences in the mesophase behavior are discussed with respect to composition and type of siloxane. Small differences in the thermal transitions of cyclic and linear compounds containing the same composition of mesogens were observed. X-ray diffraction results are used to confirm the effect of composition on previously proposed packing models. Differences in the reflection spacings and intensity are discussed with regard to composition, temperature, and type of siloxane. Orientational differences between backbone type observed in aligned fibers are also discussed.