Experimental study of relaxation dynamics in solid solutions of benzene, hexa-substituted benzenes. II

Abstract

In continuation with Part I of current study, we present here the orientationally disordered materials pentachloroaniline (PCA), bromopentamethylbenzene (BPMB), and their solid solutions with hexachlorobenzene (HCB) and hexamethylbenzene (HMB), respectively, encompassing the entire concentration range, studied employing dielectric spectroscopy, differential scanning calorimetry, and powder X-ray spectroscopy. The α- relaxation in these systems gets closer to Debye behaviour on non-polar rich side and is analyzed employing Havriliak-Negami equation, whereas the β- relaxation is found to be symmetric everywhere and follows Cole–Cole equation. In both the systems studied here, the temperature dependence of relaxation rates could be described by Arrhenius equation. The β- relaxation evidenced in these two binary systems appears to originate from the different microscopic mechanism that is discussed based on their spectral behaviour. Further, we probe the liquid glasses of very dilute concentrations of dipolar HSB solutes in OTP matrix, and compare it with the spectral features of the dilute dipolar solid solutions of HSBs.