BLOCK-COPOLYMER SELF-ASSEMBLY IN 2 DIMENSIONS - NANOSCALE EMULSIONS AND FOAMS

The interfacial properties of diblock copolymers are of particular imp ortance to their application as solution-based surfactants. We have st udied the ultrathin film or monolayer properties of a series of AB dib lock copolymers using Langmuir film balance, Langmuir-Blodgett and mic roscopy (transmission electron and atomic force techniques). Previous studies have established that AB diblocks spontaneously self-assemble at the air/water interface to yield highly defined, nanometre-sized ag gregates which we refer to as surface micelles. We report two new aspe cts of 2D self assembly. (i) A highly ordered two-dimensional foam or honeycomb is observed in the Langmuir-Blodgett films of polystyrene-b- poly(sodium acrylate) (PS-b-PANa) and polystrene-b-poly(sodium methacr ylate) (PS-b-PMANa) block copolymers. The cell areas of these nanofoam s are remarkably small, ranging from 100 to 5000 nm(2). (ii) Changes i n the morphology of a surface micelle (circle, ribbon, plane) can be e ffected by adding homoPS to the diblock him. Transitions, paralleling those seen in the melt, occur as the homoPS partitions into the surfac e micelle.