Achiral swallow-tailed materials with 'antiferroelectric-like' structure and their potential use in antiferroelectric mixtures

Achiral 'swallow-tailed' liquid crystalline materials are known to give alternating-tilt smectic C phases (S-Calt) which have structural similarities to the chiral antiferroelectric phases denoted as S*(CA). This paper describes the synthesis and characterization of three achiral branched-alkyl 4-(4'-dodecyloxybiphenyl-4-carbonyloxy)-3-fluorobenzoates. Optical microscopy and differential scanning calorimetry confirm that these materials show S-Calt and overlying S-A phases. The compounds were investigated as potential hosts which could be doped with a chiral ferroelectric liquid crystal so as to provide a viable antiferroelectric mixture. These studies (microscopy and differential scanning calorimetry), to characterize the properties of the mixtures, show that antiferroelectric phases are induced. However, switching studies show that the antiferroelectric phases are extremely stable, a property which is almost certainly a consequence of the length of the lateral branching groups (ethyl, propyl and butyl).