Thermal Analysis of Adsorbed Poly(Vinyl Acetate) on Silica

Boonta Hetayothin
Frank D. Blum, Missouri University of Science and Technology

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The physical properties of polymers at interfaces can be quite different from those in bulk due to the interaction between the absorbed polymer and the surface. This phenomenon can be probed through the dynamic behavior of the polymer chains at the interface which can be experimentally probed by techniques such as nuclear magnetic resonance spectroscopy (NMR),1 viscoelasticity, and calorimetry. At the polymer-air interface, polymer chains have more flexibility than those at the polymer-substrate interface. On the other hand, at the silica-polymer interface, where chains are more restricted on the surface, a higher glass transition temperature (Tg) results as compared with that for the bulk polymer. Absorbed polymers like poly(methyl acrylate) (PMA) with different absorbed amounts behave differently at the silicapolymer- air interface.2 It was found that at low adsorbed amounts, the adsorbed polymer deviates significantly from the behavior of the bulk polymer. This behavior can be observed through measurement of the Tg. In this paper, we report preliminary studies of the interfacial interaction of silica-polymer-air system through the glass transition from the thermal analysis point of view. Modulated differential scanning calorimetry (MDSC) is a widely used technique for identifying the Tg of polymers. Recently, we have reported the thermal behavior of poly(methyl methacrylate) (PMMA) and PMA adsorbed on Cab-O-Sil silica.3,4 in this work, we extend the observation to poly(vinyl acetate) (PVAc), an important polymer used in paints and adhesives applications where surface interactions are crucial to the performance of PVAc-containing system