Slow Dynamics and the Glass Transition in Confining Systems

Abstract

ABSTRACTThe slow dynamics associated with the structural relaxation of glass forming materials near the glass transition is very sensitive to the effects of small confining geometries. Based upon the experimental results of triplet state solvation dynamics, we explore the extent to which confinement effects can be rationalized solely in terms of interfacial dynamics which are modified relative to the bulk situation. The importance of the interfacial conditions is emphasized by observing the changes due to the surface chemistry, by comparing relaxation times at and further away from the surface, and by studying the effects of ‘soft’ versus ‘hard’ confining materials. While ‘hard’ confinement by porous solids is observed to result in slower dynamics and an increased glass transition temperature Tg for propylene glycol, our 4.6 nm nanodroplets suspended in a more fluid environment display faster structural relaxation, equivalent to a reduction of Tg as observed in free standing polymer films.