Influence of length of alkyl terminal chain on mesomorphic properties of new chiral liquid crystalline homologous series of thiobenzoates

The convenient synthesis method and mesomorphic properties of novel liquid crystalline homologous series of the chiral thiobenzoate in which the chiral branched chain (S)-(1-methylheptyloxy) was attached to the biphenyl have been presented. They are liquid crystals compounds of the general formula MHOBSn (S)-(+)-4-(1-methylheptyloxy)-biphenyl-(4'-alkylphenyl)-thiobenzoate, where n denotes number of carbon atoms in the alkyl chain). DSC and polarization microscopy and X-ray diffraction measurements shoved that (S)-MHOBSn possess a rich phase polymorphism: two high ordered tilted smectic phases SmG* and SmI* as well as ferroelectric smectic C, SmC* and chiral nematic phase (N*). All compounds containing stabile enantiotropic SmC* and N* phases. The influence of chemical purity of final compound on phase behavior has been studied. The existence of weak intermolecular hydrogen bonds of (S)-MHOBSn was confirmed by FTIR method.