Effect of atmosphere on reductions in the glass transition of thin polystyrene films

摘要

We have used nulling ellipsometry to measure the glass transition temperature, T-g, of thin films of polystyrene in ambient, dry nitrogen, and vacuum environments. For all environments, the measured T-g values decrease with decreasing film thickness in a way that is quantitatively similar to previously reported studies in ambient conditions. These results provide strong reinforcement of previous conclusions that such reduced T-g values are an intrinsic property of the confined material. Furthermore, the results are in contrast to recent reports which suggest that the T-g reductions measured by many researchers are the results of artifacts (i.e. degradation of the polymer due to annealing in ambient conditions, or moisture content).