Controlled evaporative self-assembly of hierarchically structured bottlebrush block copolymer with nanochannels

The toluene solution of a bottlebrush block copolymer, polystyrene- polylactide (PS-PLA), was confined in a cylinder-on-flat geometry, from which the consecutive "stick-slip" motion of the three-phase contact line of the PS-PLA solution was effectively regulated as toluene evaporated, thereby yielding gradient stripes at the microscopic scale. Subsequent selective solvent vapor annealing led to the formation of hierarchically structured PS-PLA in which the lamellar nanodomains of PS-PLA normal to the substrate were obtained within the microscopic stripes. After the selective removal of the PLA block by enzymatic degradation, nanochannels were yielded within the stripes. This facile approach of combining the controlled evaporative self-assembly with subsequent solvent vapor annealing opens up a new avenue to rationally organize and engineer self-assembling building blocks into functional materials and devices in a simple, cost-effective and controllable manner.