Effect of silicate layer anisotropy on cylindrical and spherical microdomain ordering in block copolymer nanocomposites

The influence of the addition of small quantities of anisotropic layered si licates on the ordering of block copolymers is studied by a combination of linear viscoelasticity and small angle neutron scattering. Specifically, we examine the influence of varying the lateral dimensions of thermodynamical ly roughly equivalent layered silicates on the development of cylindrical a nd spherical microdomain order in a blend of a matched diblock and triblock copolymer. The kinetics for the development of spheres arranged on a bcc l attice from an initial disordered state are dramatically accelerated by the two larger layered silicates with equivalent diameters of similar to1 and 10 mum, while the incorporation of an organically modified laponite, with a n equivalent diameter of similar to 30 nm, has no influence on these kineti cs. On the other hand, the addition of layered silicates, irrespective of l ayer dimensions, has no influence on the development of cylindrical ordered microdomains and the epitaxial transformation of shear-aligned cylindrical microdomains to spherical microdomains. (C) 2001 American Institute of Phy sics.