Glass Transition Behavior of PMMA Thin Films
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In the last decade there has been an increased interest in the study of the properties of supported thin polymer films. This has been prompted by the incorporation of thin films into device applications and many other technologies. Although not without controversy, a large body of experimental work indicates departures from bulk behavior by thin films. Strong evidence from both theoretical and experimental work shows that the interaction of polymer with a substrate alters the polymer conformation and mobility. A variety of techniques has been employed to probe the mobility of thin supported polymer films. Some of these techniques indirectly measured chain mobility by inference from the glass transition temperature, Tg. We report here the results of the study of the glass transition behavior of PMMA thin films supported on silica. by varying the adsorbed amount of PMMA samples of different molecular weights we are able to simultaneously test the effect of molecular weight and adsorbed amount on the Tg. The use of modulated differential scanning calorimetry (MDSC) allows us to probe these very thin films.