Design, synthesis and mesomorphic properties of chiral benzoates and fluorobenzoates with direct SmCA*-Iso phase transition

Abstract

Novel chiral (S)-(+)-4ʹ-(1-methylalkoxycarbonyl)biphenyl-4-yl 4-[ω-(2,2,3,3,4,4,4-heptafluoro-butoxy)alkoxy]benzoates and 4-[ω-(2,2,3,3,4,4,4-heptafluorobutoxy)alkoxy]-2-fluorobenzoates were prepared using different optically active alcohols: (S)-(+)-2-hexanol, (S)-(+)-2-heptanol, (S)-(+)-2-nonanol, (S)-(+)-2-decanol, (S)-(+)-2-undecanol and (S)-(+)-5-methylhexan-2-ol. Properties, such as the sequence of phases, transition temperatures and enthalpies, were tested by polarising optical microscopy and differential scanning calorimetry. Extremely low melting compounds were found (below 10°C) for derivatives of (S)-(+)-2-hexanol. The antiferroelectric smectic phase (SmCA*) with a direct transition from the antiferroelectric to isotropic phase (SmCA*-Iso) was observed, usually for propoxy-(CH2)3- spacing group. Initially, multicomponent mixtures with broad temperature ranges of antiferroelectric phase and direct SmCA*-Iso transition were formulated.