ROLL-CASTING OF BLOCK-COPOLYMERS AND OF BLOCK COPOLYMER-HOMOPOLYMER BLENDS

An improved technique for casting highly oriented films of block copol ymers from solutions subjected to flow is presented. Polymer solutions were rolled between two counter-rotating adjacent cylinders while at the same time the solvent was allowed to evaporate. As the solvent eva porated, the block copolymers microphase separated into globally orien ted structures. Using this method known as 'roll-casting' we present i n this paper a study of the morphology of polystyrene-polybutadiene-po lystyrene (PS/PB/PS) triblock copolymer cast with and without addition al high molecular weight homopolymers. The pure copolymer films consis ted of polystyrene cylinders assembled on a hexagonal lattice in a pol ybutadiene matrix in a near single-crystal structure. Blends of copoly mer with high molecular weight polystyrene and/or polybutadiene, phase separated into ellipsoidal regions of homopolymer embedded in an orie nted block copolymer matrix. Annealing the films resulted in conversio n of the homopolymer regions to spheres accompanied by some misalignme nt of the copolymer microdomains. The morphology of these films as rev ealed by TEM is discussed. A brief discussion of the flow field that d evelops in the experimental system is also presented and its similarit y to the flow field of our previous work is shown. (C) 1994 John Wiley and Sons, Inc.