3-RING PHENYL BIPHENYLPYRIMIDINE ESTERS - DEPENDENCE OF LIQUID-CRYSTAL TRANSITION-TEMPERATURES AND OTHER PHYSICAL-PROPERTIES ON THE POSITION OF THE NITROGEN-ATOMS AND THE DOUBLE-BOND CONFIGURATION

We have introduced a carbon-carbon double bond into four series of thr ee-ring phenyl/biphenylpyrimidinyl octanoates to produce the correspon ding octenoates. The position of the two nitrogen atoms in each series is different. For each of the four separate isomeric series the posit ion and nature (E/Z) of the double bond have been varied systematicall y and the effect on the liquid-crystal transition temperatures studied . The new octenoates exhibit nematic (N) and (sometimes highly ordered ) smectic phases. A smectic C (S-c) phase is observed for most isomers . Four homologous series of alkenoates with a trans double bond in the 2-position [(E)-2] were prepared. Three series of the (E)-alk-2-enoat es possess broad S-c and N phases at elevated temperatures. One homolo gous series is purely N. In an admixture with a chiral smectic C (S-c ) base mixture, some of the (E)-alk-2-enoates can induce a substantial increase in the S-c and N transition temperatures. The temperature o f crystallization is not affected adversely. Thus, the temperature ran ge of the S-c mesophase can be significantly increased without increa sing the viscosity (and thus response times) excessively. The (E)-alk- 2-enoates can also be used to induce a chiral nematic (N) phase in S- c mixtures (which do not possess one), while at the same time increas ing the temperature range of the S-c phase.