Dielectric and thermodynamic study of camphor and borneol enantiomers and their binary systems

Phase behavior and dielectric relaxation of camphor and borneol enantiomers in neat phase and their binary mixtures have been studied employing dielectric spectroscopy (20 Hz-2 MHz), differential scanning calorimetry (DSC), and X-ray diffraction techniques. Camphor and borneol form a solid solution in phase SI which is an orientationally disordered phase of fcc structure and gets supercooled during cooling. For solid solutions, two α- processes and a sub-Tg process are observed. The fm values of primary relaxation processes are deviating from Arrhenius behavior. The activation energy of sub-Tg process lies in the range of 11-18 kJ/mol and is of Johari-Goldstein type indicating the intermolecular nature. Sub- Tg process is perhaps the dominant process seen at higher temperatures studied by Smyth et al. (1963) and Davies et al. (1962).