Abstract
PCILO conformational calculations have been carried out on several model compounds of thermotropic liquid crystalline polyesters [—OC—φ—φ—φ—CO—Os—R—O—] where R = (—CH2—)2; (—CHCH3—)2; (—CHCH3—CH2—). Several conformations corresponding to the trans and gauche states of the C-C single bonds are preferred, the TGT form being of lower energy than the TTT form. The replacement of—CH2—group by—CH(CH3) group results in a decrease of the number of the energy minima, an increase in the energy of the molecule in all the preferred conformations, compared to that of the TGT form, a sharpening of the potential energy wells and an increase in the energy barriers. The presence of a methyl group also shifts the aliphatic chain away from the ideal trans and gauche positions.