ADSORBED BLOCK-COPOLYMER OF POLY(2-VINYLPYRIDINE) AND POLYSTYRENE STUDIED BY NEUTRON REFLECTIVITY AND SURFACE FORCE TECHNIQUES

The adsorption of a small block copolymer of poly-(2-vinylypyridine) a nd polystyrene has been studied as a function of solvency. Both neutro n reflectometry and surface force measurements have been used to study the structure of the adsorbed layer. The results show that the adsorb ed polymer is highly extended in good solvency conditions for the poly styrene but collapses when the solvent worsens. The results are compar ed with the self-consistent mean-field theory of Evers-Scheutjens-Flee r for the adsorption of block copolymers. Both the extended length of the polymer and the amount of polymer adsorbed on mica have been measu red independently. For this small polymer it is found that both the ex tended length and the amount adsorbed are about twice as large as woul d be expected from theoretical predictions based on the size of the bl ocks but are consistent both with each other and with the neutron data .