Crystallization in block copolymer melts: Small soft structures that template larger hard structures

The crystallization of shear oriented oxyethylene/oxybutylene (E/B) diblock copolymers has been studied by simultaneous small and wide angle x-ray sca ttering. Crystallization of ordered melts can be accompanied by a change in length scale and retention of the melt orientation. Lamellar melts crystal lize with an increase in length scale with multiply folded E blocks and the B blocks slightly stretched from their melt conformation. Crystallization from oriented gyroid melts leads to an increase in length scale with prefer red melt directions being selected. The retention of layer planes on crysta llization from an ordered melt is caused by the local stretching of chains and the locally one-dimensional structure, despite the relative strength of the structural process. We demonstrate that an interfacial preordering eff ect can cause crystallographic register to jump length scales in a soft mat ter system showing epitaxial crystallization. (C) 2001 American Institute o f Physics.