FORCES BETWEEN END-ADSORBED TRIBLOCK COPOLYMER CHAINS AND A BARE MICA SURFACE IN A GOOD SOLVENT

We have investigated the bridging effects of terminally adsorbed chains by directly measuring the forces between a single adsorbed layer of poly(ethylene oxide)-polystyrene-poly(ethylene oxide) (PEO-PS-PEO) triblock copolymer and a bare mica surface in a good solvent (toluene). We find, as the bare mica surface approaches, clearly detectable long-range attractive forces followed by an attractive minimum and monotonically increasing repulsion at smaller separations. Significant changes in the force-distance profiles with compression-decompression cycles are also observed, which strongly indicate rearrangement of the adsorbed macromolecular chains between the surfaces.