Adsorption of polystyrene–poly(ethylene oxide) block copolymers on quartz using a parallel-plate surface-force apparatus and simultaneous neutron reflection

Abstract

Block copolymers of polystyrene and poly(ethylene oxide) adsorbed on quartz plates under compression have been studied using neutron reflectometry. Adsorption from a good solvent (toluene) leads to the preferential adsorption of the ethylene oxide chains, but because of the very high asymmetry of the polymers and the favourable adsorption energy, the polystyrene is also adsorbed. The extent of the polystyrene adsorbed layer is less than the radius of gyration for both samples studied. On the approach of a second coated plate, the polystyrene volume fraction increases near the interface, indicative of a strong interlayer repulsion. On changing the solvent to octane the profiles indicate collapse of the polymer layer and there is a dramatic decrease in the pressure required to hold the quartz plates at the same separation.