Interfacial Energy and Glass Temperature of Polymers Confined to Nanoporous Alumina

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(phenyl methyl siloxane) (PMPS), poly(vinyl acetate) (PVAc), 1,4 polybutadiene (PB), oligostyrene (PS) and poly(dimethyl siloxane) (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 play a significant role on the segmental dynamics of polymers under confinement within AAO. There is a trend for a \textit{decreasing} glass temperature relative to the bulk with \textit{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.