Dielectric Relaxations in Various Crystal Modifications of Cyclohexanol and 2,3-Dimethylbutane

Abstract

Abstract The dielectric constant and loss of crystalline cyclohexanol (CHOL) and 2,3-dimethylbutane (DMB) were measured from 4°K to the melting point, 299°K for CHOL and 145°K for DMB. The supercooled plastic crystal of CHOL above the glass temperature Tg exhibits a prominent relaxation (α) due to molecular rotation. The temperature dependence of therelaxation time was found to obey the Fogel-Tamman equation. A secondary relaxation (β) was observed below Tg , 149°K for CHOL and 76°K for DMB. The mechanism proposed for β is internal rotation; rotationof OH bond for CHOL and trans-gauche transformation for DMB. The β relaxation of DMB is well correlated with acoustic relaxation in the liquid state in the relaxation time versus timperature plot. Relaxations in the intermediate state, crystal III, of these two substances and the most stable state, crystal II of DMB were studied.