Ferroelectric liquid crystals containing a 2(S)-[2(S)-methylbutoxy]propionyloxy unit

A new chiral organic acid, 2(S)-[2(S)-methylbutoxy]propionic acid (2), was synthesized from ethyl lactate and (S)-1-iodo-2-methylbutane. The acid 2 containing two centres of chirality was used as a building block for preparing ferroelectric liquid crystals. Three series of chiral compounds were synthesized to study the influence of the molecular structures on the formation of liquid crystal phases. They are 4-{2(S)-[2(S)-methylbutoxy]propionyloxy}phenyl 4-(4-n-alkoxyphenyl) (series B), and 4-{2(S)-[2(S)-methylbutoxy]propionyloxy}phenyl 4-(4-n-alkoxyphenyl) benzoate (series B), and 4-{2(S)-[2(S)-methylbutoxy] propionyloxy}-4′-biphenyl 4-n-alkoxy benzoate (series C). Only one member of series A, 4-{2(S)-[2(S)-methylbutoxy]propionyloxy}phenyl 4-n-octyloxybenzoate (5c), exhibits a monotropic SA phase. The n-alkoxy chain length at the biphenyl ring of series B has a remarkable efect on the S*C phase formation. An enantiotropic S*C phase can only be observed when the n-alkoxy chain is longer than the n-octyloxy group. The n-heptyloxy and n-octyloxy homologues exhibit a monotropic S*C phase. However, all members of series C possess an enantiotropic S*C phase. The occurrence of the phase sequence C-S*C-SA-I or C-S*C-N*-I depends on the position of the biphenyl ring. The S* phase temperature range in series B and C is up to 70°C.