Directing the self-assembly of block copolymers

Recently, a new spotlight has been focused on block copolymers, thoroughly studied for nearly half a century, because of their potential use in numerous nanotechnologies. This renewed interest is a consequence of the self-assembled microdomains characteristic of these materials. The size, shape, and arrangement of these nanoscopic structures are all tunable through synthetic chemistry of the constituent molecules. Capturing the vast technological potential of block copolymers will, in many cases, require precise control over the orientation and alignment of the microdomains. This review summarizes extant applications and alignment techniques and provides an outlook toward the future. In an effort to provide a practical resource for researchers, the article is structured to identify the reported alignment approaches for a given polymer morphology rather than sorting by alignment technique. Specific materials have also been deemphasized because the alignment methods, with few exceptions, are general to a specific morphology or set of morphologies. In addition to a detailed summary of traditional methodologies, some very recent results such as optical alignment of liquid crystalline block copolymers, lithographic chemical patterning, and alignment in pores are highlighted.