Glass transition temperature of freely-standing films of atactic poly(methyl methacrylate)
Department of Physics and the Guelph-Waterloo Physics Institute, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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Published online: 5 November 2003
We have used ellipsometry to measure the glass transition temperature T g of high molecular weight (M w =790 × 103), freely-standing films of atactic poly(methyl methacrylate) (a-PMMA), as well as films of the same polymer supported on two different substrates: the native oxide layer of silicon (Si) and gold-covered Si. We observe linear reductions in T g with decreasing film thickness h for the freely-standing PMMA films with 30 nm <h<100 nm, which is qualitatively similar to previous results obtained for freely-standing polystyrene (PS) films. However the magnitude of the T g reductions for PMMA is much less than for freely-standing films of PS of comparable molecular weight and thickness. We also find that for films supported on either substrate, with thicknesses as small as 30 nm, the T g values do not deviate substantially from the value measured for thick films.
PACS: codes. – 36.20.-r - Macromolecules and polymer molecules / codes. – 64.70.Pf - Glass transitions / codes. – 68.60.Bs - Mechanical and acoustic properties of thin films
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003