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