Chiral smectic C phases exhibited by biphenyl resorcylate and vanillate derivatives

We report the synthesis and mesomorphic behaviour of alkoxybiphenyl resorcylate and vanillate derivatives with a chiral moiety obtained from chloro analogues of L-leucine, L-valine and L-isoleucine. The compounds have been characterized by NMR spectroscopy and the mesophases studied by DSC and optical microscopy. In the synthesized compounds, an enantiotropic chiral smectic C phase over a wide temperature range has been observed. Changes in the phase behaviour caused by structural variations in the core and the optically active alkyl chain are also discussed.