Thermal Properties of PMMA on Silica Using Temperature-modulated Differential Scanning Calorimetry


The behavior of an amorphous polymer, poly(methyl methacrylate) (PMMA), adsorbed on silica was studied using temperature-modulated differential scanning calorimetry (TMDSC). a two-component model, based on loosely-bound polymer with a glass transition temperature (Tg) (similar to that of the bulk polymer) and a tightly-bound polymer (with a Tg higher than that of the loosely-bound polymer) was used to interpret the thermograms. Increased sensitivity allowed the two transitions in the thermograms to be quantified much more accurately than in previous work. Linear regression analysis of the ratio of the area under two transitions with composition yielded the amount of tightly bound polymer, m″B = 1.21 +/- 0.21 mg PMMA/m 2silica. Two methods of analyzing the thermograms, fitting with a Gaussian-Lorentzian (GL) cross distribution function and perpendicular drop (PD) method, yielded similar results for the amount of tightly-bound polymer on the surfaces with the GL method having a statistically better fit to the model. the ratio of heat capacity increments of loosely bound and tightly bound polymer, ΔCpA/ΔCpB, around the glass transition, indicated the relative mobility of the two components. It was found that the ΔCpA was aboutthree times as large as that of ΔC pB suggesting that the tightly bound polymer had a much smaller change in mobility through glass transition region. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.



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