Segmental Dynamics of Bulk and Adsorbed Poly(methyl Acrylate)-d3 by Deuterium NMR: Effect of Adsorbed Amount
Deuterium solid-state quadrupole-echo NMR techniques were used to probe the dynamics of bulk and silica-adsorbed methyl-labeled poly(methyl acrylate)-d3 (PMA-d3). For bulk PMA-d3, collapse of the 2H NMR powder pattern indicated a sudden increase in segmental motion at about 50 °C. This temperature was 40 °C above the reported glass transition temperature (Tg) of bulk PMA and was due to the higher frequencies to which the “NMR” Tg was sensitive. Surface samples with different adsorbed amounts exhibited different behavior at the silica-polymer-air interface and consisted of superpositions from different components. At lower temperatures, a mobile component not found in the bulk PMA-d3 was observed while, at higher temperatures, a rigid component still existed. The mobile component was attributed to polymer segments near the polymer-air interface and the rigid component to segments nearer to the polymer-silica interface. As the adsorbed amount increased, the relative amounts of mobile components increased. The results were consistent with an interface graded in mobility with a broad distribution in the adsorbed layer. The mobilities were generally reduced at lower adsorbed amounts.
W. Lin and F. D. Blum, "Segmental Dynamics of Bulk and Adsorbed Poly(methyl Acrylate)-d3 by Deuterium NMR: Effect of Adsorbed Amount," Macromolecules, American Chemical Society (ACS), Jan 1997.
The definitive version is available at https://doi.org/10.1021/ma9700587
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