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Equilibrium and Non-Equilibrium Type β-Relaxations: d -Sorbitol versus o -Terphenyl

1999; American Chemical Society; Volume: 103; Issue: 20 Linguagem: Inglês

10.1021/jp9838947

1520-6106

Hermann Wagner, Ranko Richert,

Ionic liquids properties and applications

A previous observation, which indicated that the β-relaxation intensity of o-terphenyl is sensitive to the thermal history, is substantiated by dielectric relaxation experiments. Unlike the β-processes of other materials, only the quenched glassy state of o-terphenyl displays this secondary relaxation feature. The β-intensity is observed to decay gradually upon annealing and disappears altogether in the equilibrium liquid state at T > Tg. We compare the case of o-terphenyl with the concomitant signatures of d-sorbitol, which represents the more typical case of a glass-former which exhibits the slow β-process also in the liquid state including the α−β-merging scenario. We also present data of this α−β-merging for d-sorbitol confined to pores of 5 nm diameter, indicating that no longer-ranged correlations are involved in the secondary process.