Large area orientation of block copolymer microdomains in thin films via directional crystallization of a solvent

A fast method for inducing alignment of microdomains in noncrystalline bloc k copolymers is presented. The method is based on the use of crystalline or ganic materials, which are solvents for the block copolymers above their me lting temperatures, and, when cooled and directionally crystallized, act as a substrate on which thin films of the block copolymers are formed. Both l amellar and cylindrical type microdomains in a symmetric polystyrene-block- poly( methyl methacrylate) diblock copolymer and in an asymmetric polystyre ne-block-polyisoprene respectively are globally aligned using either benzoi c acid (BA) or anthracene (AN) as the crystallizable solvent. The fast dire ctional solidification during the phase separation leads to alignment of th e intermaterial dividing surface (IMDS) of both types of microdomains paral lel to the fast growth direction of BA and AN crystals (b axis direction in both cases). Depending on film thicknesses, the block copolymers show vari ous microdomain orientations such as vertical lamellae and parallel and per pendicular cylinders to the substrate. With respect to the processing metho ds currently used to induce orientation in block copolymers, our method all ows attainment of ordered patterns over regions larger than 50 mum(2) withi n a few seconds without annealing.