Macroscopically oriented lamellar microdomains created by cold zone-heating method involving OOT

The zone-heating method, which involves ordering of materials under moving temperature gradient del T, has been widely used as a technique to create Macroscopically oriented ordered structures of various kinds of materials. We applied this method to a large molecular weight symmetric polystyrene-block-polyisoprene diblock copolymer (dibcp) at a temperature where the del T field exists below its order-disorder transition temperature T-ODT of the dibcp. In this method we first prepared the solvent-cast bulk films of the dibcp having a nonequilibrium morphology of hexagonally packed cylindrical microdomains (hex-cyl) by using a solvent selectively good for polyisoprene blocks. Then the zone-heating method was applied to the order-order transition process from the nonequilibrium hex-cyl to equilibrium lamellae. The cold zone-heating method, cold in the sense of the del T field existing below T-ODT, successfully created macroscopically oriented lamellae with their normals preferentially oriented parallel to the del T axis and their edges preferentially standing with respect to the bulk film surfaces. It was also found that the initial orientation of the (100) plane of hex-cyl normal to the del T axis prefers to that parallel to the del T axis for a better macroscopic alignment of lamellae. A possible model for the cold zone-heating-induced lamellar orientation will be discussed in the text. (C) 2008 Elsevier Ltd. All rights reserved.