Abstract
By the methods of IR spectroscopy, the characteristics of molecular structure and the glass temperature T g were determined in the surface layers of PMMA films. It was found that near to the interphase boundary, the PMMA macromolecules exhibit an enhanced content of the high-energy tg-conformers, at the expense of the energetically more favoured tt conformers. The concentration of tg-conformers increases monotonously with decreasing thickness d of the polymer film, starting from d = 10 μm. Moreover, at d < 4 μm, the interactions between side chains are enhanced. T g was found to change in a complex (nonmonotonous) manner with decreasing film thickness, starting from d = 10 μm decreases, attaining a minimum at d = 3.5 μm, and begins to grow further on. The observed behaviour of T g could be fully explained in terms of the Gibbs-DiMarzio theory, relating T g to the rotational-isomeric characteristics of the polymer chain.
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