Dielectric and calorimetric investigation of an unusual two-component plastic crystal: cyclohexanol-neopentylglycol

In the present article, investigations of an unusual two-component (H-) bonded pair, i.e. the cyclohexanol–neopentylglycol system, are reported. The phase I of cyclohexanol (CHXOL) forms a continuous solid solution with the phase I of neopentylglycol (NPGOL). This binary solid solution (SI) has been investigated at low temperatures and several concentrations, by means of dielectric spectroscopy and differential scanning calorimetry (DSC). Depending upon the concentration, this phase reveals a glass transition in the temperature range 150–180 K and a pronounced relaxation process identifiable with the so-called primary relaxation process, or α-process. The analysis of the various parameters obtained shows an isomorphic relationship between the face-centered cubic phases of both the pure components through a continuous change of parameters. In addition, two sub-Tg processes (designated as β-and γ-) are found. The present observation suggests that the β-process is probably a Johari–Goldstein relaxation process and the γ-process is intramolecular in nature. The kinetic freezing of the various dielectric processes has been examined in relation to the Tg found in the DSC experiments.