Reconsidering the relation of the JG β-relaxation to the α-relaxation and surface diffusion in ethylcyclohexane

Abstract

According to the Coupling Model (CM), secondary relaxation belonging to a special class has strong connection to the α-relaxation. These Johari-Goldstein (JG) β-relaxations are predicted to be ubiquitous, and its relaxation time is approximately equal to the primitive relaxation time and the surface diffusion time. These predictions cannot be tested directly in ethylcyclohexane (ECH) because the JG β-relaxation is unresolved and overlapping the α-relaxation to modify its dispersion. To capture the actual dispersion of the α-relaxation we considered surface diffusion data, adiabatic calorimetry data of the JG β-relaxation, and dielectric data of cyanocyclohexane (CNCH). We demonstrated the dispersion of the α-relaxation is actually narrower than known before. The primitive relaxation times calculated are now in agreement with τJG(T) and with τsurface(T), and in accord with the CM predictions.

Keywords

• Glass transition
• ethylcyclohexane
• surface diffusion
• Johari-Goldstein relaxation