Abstract
The orientation of different segments of 4'-cyanophenyl 4-heptylbenzoate (7CPB) has been investigated using 13C NMR. The method of proton-encoded local field (PELF) spectroscopy in combination with off-magic-angle spinning (OMAS) of the sample was used. High resolution 2D spectra were obtained, from which the order parameters were calculated. Linear relations between the obtained order parameters and anisotropic chemical shifts determined by 1D 13C NMR were established and semi-empirical parameters were achieved. A 1:2 mixture of 7CPB and its chain-perfluorinated analogue (7PFCPB) showed interesting phase behaviour with the change of temperature. It was studied by the use of 13C NMR and polarizing optical microscopy. The order parameters of 7CPB in the smectic A phase of the mixture were calculated using the semi-empirical parameters obtained from the 2D NMR method.