IN SEARCH OF SMECTIC-C PHASES AT MESOGENS WITH A PHENYL RING CONTAINING LATERAL BRANCH

Generally, substituents laterally attached at calamitic molecules prev ent the existence of tilted smectic phases. However, mesogens with a b ulky phenyl ring containing lateral branch are subjected to other rela tionships. The following constitutional parameters should be realized to prepare liquid crystals exhibiting smectic C phases: the lateral a romatic ring is linked by an odd-numbered spacer to a four-ring basic molecule bearing the chiral group. The lateral phenyl ring should be s ubstituted in 4-position with substituents having a suitable shape and defined electron-withdrawing properties. Biphenyl units within the ba sic mesogen are of advantage. Measurements of the spontaneous polariza tion were performed. Therefore, by the existence of one chloro or nitr o substituent in ortho-position to the chiral 1-methylheptyloxy group the values of P-s are increased. However, the bulky lateral segment is of few influence on the spontaneous polarization.