NMR and Modulated Differential Scanning Calorimetry of Adsorbed Poly(Methyl Acrylate) on Silica
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The interaction between polymers and solid substrates can be studied by a variety of techniques. The results from different experiments can be affected by the nature of the polymer, surface, polymer-surface interactions and, also, the experiment. A great deal has been learned about the behavior of polymers at interfaces, but there is also much to be learned about the interactions and how they affect the physical properties of adsorbed polymers. In the present study, we report both deuterium nuclear magnetic resonance (NMR) and modulated differential scanning calorimetry (MDSC) of poly(methyl acrylate) (PMA) adsorbed on Cab-O-Sil silica. The focus of this study is on the dynamics of polymer segments and the interfacial glass transition temperature (Tg). In our case, very small amounts of polymer were adsorbed, and we can view behavior of polymer segments in close proximity to the silica surface. We found that both NMR and MDSC experiments provide consistent insight into the dynamics of adsorbed polymers. Both experiments show the heterogeneous nature of the adsorbed polymers, with the polymer segments closer to the solid surface being the most motionally restricted resulting in a higher Tg for those segments.