Segmental Motion of Surface-bound Swollen Poly(methyl Acrylate)-d

Poly(methyl acrylate)-d (PMA-d), labeled in the backbone α position, was prepared and adsorbed from toluene on silica at a coverage of 0.38 mg of PMA-d/mg of silica. This coverage was roughly that of the maximum found in the adsorption isotherm. Comparisons of deuterium NMR spin-lattice relaxation time, T1, and spin-spin relaxation time, T2, for the adsorbed, swollen polymer at different temperatures were made to obtain information about the backbone motion of the surface-bound polymer. The results were consistent with a system where the fast local motions were similar to those in solution but the longer range segmental motions were more restricted than those in solution. The log-normal distribution yielded mean correlation times which were 4-10 times slower for the surface-bound species than that in solution. The Hall-Helfand (HH) model with two correlation times yielded slow correlation times more than an order of magnitude slower for the surface species. Compared to previous studies on terminally attached polymers which formed extended brushes, liquid-like segments of randomly attached homopolymers have significantly reduced longer range segmental motions