Tg-Confinement Effects in Polymer Thin Films, Nanotubes, and Nanospheres as Measured by DSC, Ellipsometry and Fluorescence

The effect of nanoscale confinement on the glass transition temperature (Tg) of supported and free-standing polymer films has been studied for two decades by various techniques. However, conventional DSC, which is the most common method for measuring Tg of bulk polymers, is not well suited for such measurements. Here, we demonstrate that Tg-confinement effects measured by conventional DSC in nanotubes of polymer supported in anodic aluminum oxide (AAO) templates compare well with with Tg-confinement effects measured in supported polymer films by ellipsometry and fluorescence. We further show that Tg-confinement effect data for nanotubes obtained by fluorescence agree well with data obtained by DSC. Finally, we draw comparisons between the Tg-confinement behavior of nanoprecipitated polymer nanospheres as measured by fluorescence to Tg-confinement effects for both supported and free-standing polymer films. The roles, if any, of confinement dimensionality (1-D vs 2-D vs 3-D) and measurement technique on the observed Tg-confinement effect will be discussed.