Reorientational motion and volumetric behavior in the binary mixtures of 4-cyano-4′-pentylbiphenyl and triphenylphosphite

Reorientational relaxation times and densities of binary mixtures of 4-cyano-4′-pentylbiphenyl (5CB)-triphenylphosphite (TPP) were measured as functions of composition and temperature. The reorientational relaxation time was determined from the polarized light scattering spectra by the optical heterodyne technique. The effect of the addition of TPP molecule was discussed in terms of the effective volume of molecular reorientation, which was estimated from the extended Debye-Einstein equation. The excess volumes and partial molar volumes were calculated from the density of the mixtures. The relationship between the reorientational correlation and the partial volume was discussed from the point of view of the local structure of 5CB molecules in the mixtures.