Study on molecular dynamics and phase transitions in 1,2-cyclohexanediol and 1,3-cyclohexanediol isomers by calorimetry and dielectric spectroscopy

Abstract

The results of broadband dielectric spectroscopy and differential scanning calorimetry of the trans and cis isomers of 1,2-cyclohexanediol and 1,3-cyclohexandiol are presented. Numerical analysis of the dielectric spectra points to complex dynamics of presented compounds in isotropic liquid, ordered crystalline, and orientationally disordered (plastic) crystal phases. Two relaxation processes were found in plastic crystal phases in cis-1,2-cyclohexanediol and trans-1,3-cyclohexanediol. These processes are responsible for the α-relaxation and forming/breaking hydrogen bonds between molecules forming clusters. One relaxation process was found in crystal phases and isotropic liquid phase. Temperature dependences of mean relaxation times are of the Arrhenius type, except for trans-1,3-cyclohexanediol compound for which the Vogel-Fulcher-Tammann dependence is fitted. The electric conductivity, fitted by Jonscher power law, is of similar order as for semiconducting materials. The electrode polarization effect is strong, especially in isotropic liquid and plastic crystal phases.