CRYSTAL-STRUCTURES OF FERROELECTRIC AND ANTIFERROELECTRIC MESOGENS WITH A 1-METHYLALKOXYCARBONYL GROUP

Crystal structures have been determined for 4-[(S)-1-methylpentyloxyca rbonyl]phenyl, 4-([S)-1-methylhexyloxycarbonyl]phenyl 4'-octyloxybiphe nyl-4-carboxylates (1 and 2, respectively) and (R)-1-methylheptyl 4-(4 '-octyloxybiphenyl-4-yloxymethylene)benzoate (3), which have S-CA, S- C and S-CA* phases, respectively. All the crystals have a common pack ing mode with the previously determined structure of 4-(1-methylheptyl oxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC). Each cr ystal forms a smectic-like layer structure composed of largely bent mo lecules with the long alkyl chain of the chiral group almost perpendic ular to the core moiety. Differential scanning calorimetry showed that the crystals of 1, 2, and MHPOBC, which have a carbonyloxy group as t he central linkage between the biphenyl and phenylene moieties, transf orm to higher temperature solid phases in a similar temperature range (around 60 degrees C). For 3, which has an oxymethylene linkage betwee n the biphenyl and phenylene moieties, three kinds of solids were dist inguished.