Differential scanning calorimetric and Fourier transform infrared spectrometric investigations of the influence of silica on the liquid crystalline properties of 4′-cyano-4-biphenyl[4-(4-pentenyloxy) ]benzoate

The influence of surface effects on the thermotropic and microscopic properties of the liquid crystal, 4′-cyano-4-biphenyl[4-(4-pentenyloxy)]benzoate (CBPB), have been studied by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Multiple endothermic events were observed for CBPB coated silica, which demonstrate that the liquid crystal exists as several different microstructures on the surface. This was further confirmed by infrared studies which show that the nitrile stretching band is made up of four spectral components that correspond to hydrogen bonded, randomized, surface crystalline and bulk crystalline species. A redistribution of the physically coated liquid crystal occurs on the surface as the result of thermal preconditioning, which is reflected in the shapes of both the DSC curves and infrared spectra.