Polyesters with Mesogenic Elements and Flexible Spacers in the Main Chain: A Further Investigation by Conformational Energy Calculations

PCILO conformational calculations have been carried out on several model compounds of thermotropic liquid crystalline polyesters [- OC-R1 -CO-O-R2]- where R1 = biphenyl, terphenyl and R2 = (-CH2-)3, -CH2-C(CH3)2-CH2–CH2-C(C2H5-) CH2-. The calculated structures can be compared to the X-ray crystallographic data. The conformational characteristics of the carboxyl groups are independent of the number of phenyl rings. The introduction of substituents into the flexible spacer results in a sharpening of the potential energy wells and an increase in the energy barriers.