Leonorina G. Cada
Institute of Chemistry, University of the Philippines Diliman
doi.org/10.57043/transnastphl.1998.5841
Abstract
Low molar mass liquid-crystalline cholesteryl esters and epoxy-based polymeric liquid crystals were synthesized in the laboratory. Fatty acids obtained from coconut oil were esterified with cholesterol, and the resulting esters were added to commercial nematic E7 to yield cholesteric low molar mass liquid crystals (LCs ). These are presently being utilized in researches involving liquid crystals dispersions and thennochromic mixtures. Epoxy-based side-chain polymeric LCs were also synthesized for possible use as matrices in LC/polymer composites. Ring opening reaction of a commercially available epon resin, ethyleneglycol diglicidyl ether (EGDE) with the nematic 4-o) aminohexyloxy)-4′-cyanobiphenyl and the twisted nematic cholesteryl 4-aminobutyrate was carried out in bulk at l00°C for 10 hours. The side-chain copolymers obtained were found to be mesomorphic as obsetved under the polarizing micoscope. No trend was observed in the transition temperatures of these polymeric systems based on the differential scanning calorimetric (DSC) study. A liquid-crystalline epoxy prepolymer exhibiting monotropic mesomorphism was also prepared by functionalization of the dihydroxyl terminated groups of 4,4′-dihydroxybiphenol with the glycidyl groups of epichlorohydrin. The effect on its mesomorphic propenies with the addition of sidechain mesogenic pendant group, 4-(ro-aminohexyloxy)-4′-cyanobiphenyl and varying concentrations of a diamine crosslinker were compared. FTIR and DSC were used to monitor the isothermal cure of the thermosets at different temperatures. Liquid crystallinity of the thermosets were sustained for a 3 wt % cross linker whereas a highly crosslinked network resulted in the loss in mesomorphic properties.