PCILO conformational calculations have been carried out on several model compounds of mesogenic cores of liquid crystalline aromatic polyesters

-CO-O--O-CO-

-CO -O-CO-O- and -O-CO-CO-O-.The calculated structures can be compared to the X-ray crystallographic data. In addition

bond orders of the model compounds were also obtained by using CNDO. It has been found that the three phenylene rings statistically take orientations perpendicular to each other

and that when the carbonyl group turns into plane of the phenylene ring which is not the immediate neighbor but the one through the ether-oxygen

the best conjugation reached is not accompanied by the lowest conformational ener-gy.