Structure and Dynamics of Terminally Attached, Swollen Block Copolymers

摘要

The dynamics of block copolymers of poly(strene-co-2-vinylpyridine) have beenprobed when adsorbed on silica, and swollen with solvent. The block copolymers are labelled on half of the styrene segments with deuterons in the methine positions. The polymers adsorb with the vinylpyridine attached to the surface and the styrene segments further away from the surface. The addition of solvent to the polymers cause the styrene segments to become extended away from the surface in a extent which depends on the thermodynamic quality of the solvent. The use of deuterium NMR relaxation times allow comparison of molecular motion of the surface-bound polymers with the solution polymers. The use of the Hall-Helfand model for the autocorrelation functions for the reorientation of the C-D bond vectors allow a numerical comparison of the molecular motion. It is found that in toluene, a good solvent for polystyrene, more isotropic (or faster) motion than in solution for the styrene segments occurs. As the solvent quality decreases, so does the mobility of the styrene segments. (TTL)