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

Abstract

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 (S_I) 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-T_g 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 T_g found in the DSC experiments.