Segmental Dynamics of Bulk and Adsorbed Poly(methyl Acrylate)-d₃ by Deuterium NMR: Effect of Molecular Weight

Deuterium solid-state quadrupole-echo NMR was used to study the effect of molecular weight on the segmental dynamics of bulk and adsorbed poly(methyl acrylate)-d3 (PMA-d3). It was found that the bulk PMA-d3 with lower molecular weight was more mobile and more heterogeneous in motion than the high molecular weight species. Surface samples with coverages up to saturation coverage in toluene, adsorption maximum in toluene (Am), were prepared by adsorption of PMA-d3 with two different molecular weights onto silica from different solvent systems. After drying, the spectra were collected from the surface species at the solid−air interface. For the adsorbed polymers, the low molecular weight PMA-d3 segments on silica were more rigid than those of the high molecular weight PMA-d3. For both molecular weights, the surface polymers exhibited a wider range of mobilities than the bulk polymers