Electric-field-induced alignment of block copolymer/nanoparticle blends

External electric fields readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-field-induced alignment of a lamellae-forming polystyrene-block-poly(2- vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-field-assisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such films under benign experimental conditions. Similar to neat block copolymers, nanocomposites composed of polystyrene-block-poly(2-vinyl pyridine) and gold nanoparticles can be aligned in electric fields, which leads to a striped and aligned structure of nanoparticles after removal of the polymer. The onset of domain alignment in the presence of nanosized gold particles occurs at a substantially lower field than for corresponding films in the absence of particles, and decreases with increasing nanoparticle concentration.