Interfacial Energy and Glass Temperature of Polymers Confined to Nanoporous Alumina

Abstract

We report on the effect of interfacial energy on the glass temperature, T-g, of several amorphous polymers with various glass temperatures and polymer/substrate interactions confined within self-ordered nanoporous alumina (AAO). The polymers studied include poly(phenylmethylsiloxane) (PMPS), poly(vinyl acetate) (PVAc), 1,4-polybutadiene (PB), oligostyrene (PS), and poly(dimethylsiloxane) (PDMS). The segmental dynamics and associated T-g's are studied by means of dielectric spectroscopy. The interfacial energy for the polymer/substrate interface, gamma(SL), is calculated with Young's equation whereas the AAO membrane surface energy is obtained by measuring contact angles for several reference liquids. We find that interfacial energy plays a significant role in the segmental dynamics of polymers under confinement within AAO. There is a trend for a decreasing glass temperature relative to the bulk with increasing interfacial energy. PDMS exhibits the highest interfacial energy and the highest reduction in glass temperature within AAO. Other effects that may also contribute to changes in T-g are discussed.