CONFORMATIONS OF BLOCK COPOLYMERS TERMINALLY ADSORBED AT THE SOLID-LIQUID INTERFACE

The conformations of end-adsorbed diblock and triblock copolymers of polystyrene (PS) and polyethylene oxide (PEO) adsorbed onto mica from toluene have been studied by the surface force method. The PS-PEO diblock copolymer system forms a semi-dilute brush with the non-adsorbing PS chains adopting an extended configuration away from the surface. Neutron reflectometry indicates that the volume fraction profile of such a system has a broadly parabolic shape, in agreement with theory. In contrast to PS-PEO diblock copolymers which adsorb only in a "tail" conformation, PEO-PS-PEO triblock chains form "loops" as well as "tails" on the mica substrate. Attractive forces are observed when an adsorbed layer of PEO-PS-PEO triblock copolymer is allowed to interact with a bare mica wall, due to the formation of polymer bridges between the two opposing surfaces.