Temperature Dependence of the Activation Volume of Secondary Relaxation in Glass Formers

Soheil Sharifi

doi:10.5402/2011/460751

Abstract

We study a nonmonotonic behavior with temperature of the activation volume ΔVβ of secondary relaxation in PPGE [Poly[(phenyl glycidyl ether)-co-formaldehyde]] and PVAc [Poly(vinyl acetate)] glass formers. Our results show that the non-monotonic behaviour of secondary relaxation does not depend on the type of the secondary relaxation. Moreover, the study of secondary relaxation under pressure at isothermal paths shows two different behaviours of ΔVβ in the glassy state (which describe two different types of glasses); for temperatures higher than the glass transition temperature (Tg), ΔVβ increases with a decrease of the temperature while at temperatures lower than Tg, ΔVβ decreases with a decrease of the temperature.

Highlights

The glassy state is a nonequilibrium state of materials [1]
Glass formers are characterized by a complex relaxation pattern, which evolves over several decades
We focused on the slower secondary process of PPGE (JG relaxation) and on the one observed in PVAc whose microscopic origin is not clear

Summary

Introduction

The observed thermodynamic and relaxation properties slowly evolve with time because of the evolution of the molecular configuration towards a state with a lower energy [2] Another consequence of the none-quilibrium condition of glasses is that the thermodynamic and relaxation properties show different values when measured in the glassy state at a fixed thermodynamic condition as a consequence of different vitrification histories [3,4,5]. It has been suggested that the connection or the similarity of dynamic properties (dependence of relaxation time on temperature, pressure, thermodynamic history of glass formation) of the secondary relaxation with those of the structural one, can be used as a criterium to distinguish JG and non-JG relaxations [12]. We study the temperature dependence of the activation volume of one observed secondary relaxation in PVAc and compare

Results

Discussion

Conclusion