(251b) Manipulating Structures of Block Copolymers with Functionalized Layered Silicates

Polystyrene (PS) functionalized layered silicates are preferentially dispersed in the PS domain of a symmetric polystyrene-polyisoprene diblock copolymer. PS is polymerized from individual layered silicates so as to provide neutral enthalpic interactions (i.e. close matching of molecular weights) between the PS chains on the layered silicates and the PS block in the block copolymer The layered silicates are exfoliated and serve as directing agents for the ordering of the lamellar domains particularly under application of large amplitude oscillatory shear due to their large lateral dimensions, thus reducing polydomain structures with random orientations usually associated with self-assembly exhibited by the copolymer melts. In particular, the order-disorder transition is suppressed in the presence of randomly dispersed layered silicates. On the other hand, copolymer hybrids after shear alignment exhibit longer coherent length than that of the pure copolymer. The results have been elucidated in terms of dynamic oscillatory shear rheology, small angle X-ray scattering and transmission electron microscopy.