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) and polystyrene has been studied as a function of solvency. Both neutron reflectometry and surface force measurements have been used to study the structure of the adsorbed layer. The results show that the adsorbed polymer is highly extended in good solvency conditions for the polystyrene but collapses when the solvent worsens. The results are compared with the self-consistent mean-field theory of Evers-Scheutjens-Fleer for the adsorption of block copolymers. Both the extended length of the polymer and the amount of polymer adsorbed on mica have been measured independently. For this small polymer it is found that both the extended length and the amount adsorbed are about twice as large as would be expected from theoretical predictions based on the size of the blocks but are consistent both with each other and with the neutron data.