An unconventional route to hierarchically ordered block copolymers on a gradient patterned surface through controlled evaporative self-assembly

A chemically patterned surface was formed by controlled evaporative self-assembly of concentric polymer stripes, followed by the removal of weakly deposited polymer, giving ultrathin polymer stripes with a width gradient on the Si substrate (see picture). A thin film of diblock copolymer hierarchically self-assembled on the ultrathin polymer stripes, giving arrays of nanocylinders perpendicular to the surface of the film.