Comparison of differential scanning calorimetry, FTIR, and NMR to measurements of adsorbed polymers

Temperature modulated differential scanning calorimetry (TMDSC) measurements on samples with very small amounts of polymers adsorbed on silica particles have been contrasted with spectroscopic techniques (FTIR and NMR) on the same or similar systems. The results are consistent in that the hydrogen bonding of the polymers to surface silanols reduces the mobility of some of the adsorbed polymer segments and results in higher glass transition temperatures for those polymer segments. These experiments reinforce the notion of an interface that is graded in terms of mobility. In contrast to bulk polymers, where the glass transition process can be considered spatially homogeneous, interfacial polymers can be considered heterogeneous on the scale of the interface. The results also suggest that the heterogeneous nature of the interfacial polymers and various sensitivities of the different techniques may result in apparently different conclusions about the surface effect and its reach.