DYNAMICS OF ADSORBED, SWOLLEN BLOCK-COPOLYMERS

Deuterium NMR relaxation times of specifically deuterated block terpol ymers of 2-vinyIpyridine (VP), styrene (S), and deuteriostyrene (DS) w ere measured for the polymers in solution and on silica as a function of temperature and solvent. The block polymers were attached to the si lica through the VP segments; the S and DS segments were extended into the solution. In a thermodynamically poor solvent, such as carbon tet rachloride, the relaxation times were consistent with the S segments o n the surface-bound polymer being less mobile than their counterparts in solution. This is in contrast with their behavior in toluene (previ ously reported), where the styrene segments of the surface-bound polym er appeared to be more mobile than in solution. The results demonstrat e that the solvent quality may have a dramatic effect on the dynamics of the chain segments of the surface-bound polymer. In a mixture of so lvents, namely, carbon tetrachloride and methanol, there was evidence for more mobile S segments in the surface-bound polymer; however, the VP units also had additional mobility due to the presence of the metha nol. The relaxation times were also used, along with the model of Hall and Helfand, to determine the motional parameters and spectral densit ies for the polymers in the different systems.