MOLECULAR VIBRATION APPROACH TO POLARIZABILITIES OF METHYL CINNAMATE LIQUID-CRYSTAL COMPOUNDS

A new theoretical method of evaluating polarizabilities of liquid crys tals is presented and applied to the liquid crystalline compounds, nam ely n-alkyl-p-(4-ethoxy benzylidene amino)-alpha-methyl cinnamates, wh ich exhibit smectic A and nematic phases. In tile present method, vibr ational frequencies are used to evaluate force constants, mean amplitu de of vibration and hence bond polarizabilities. From mean polarizabil ities, polarizability anisotropies and mean diamagnetic susceptibiliti es are also estimated. A dose agreement is found between the values es timated from the present molecular vibration method and the reported d ata, which confirms the applicability of this method to the liquid cry stals exhibiting smectic A and nematic phases. In addition, the variat ion of the order parameter with temperature is also studied.