Synthesis and transition temperatures of host materials for ferroelectric mixtures

Abstract

Two types of trans-4-alkylcyclohexyl-substituted 2,3-difluorobiphenyls that exhibit quite high smectic C (S_c) phase stability are reported. In addition, the analogous trans-4-alkyl-2,2-difluorocyclohexyl-substituted 2,3-difluorobiphenyls are reported and these materials have much lower S_c character. A useful alternative synthesis of trans-1,4-disubstituted cyclohexane intermediates is discussed. Palladium-catalysed cross-coupling reactions involving arylboronic acids with both aryl bromides and phenolic trifluoromethanesulfonates (triflates) have been used in the synthesis of the final materials. The mesomorphic behaviour of these novel materials is discussed in terms of their molecular structure and the structure–property relationships are compared with those of the wholly aromatic analogues and other significant materials.