Surface orientation of amphiphilic block copolymers via thermal annealing

The surface aggregation states of the amphiphilic diblock copolymer films, which are consistent with polyacrylates and polystyrene, were examined. The hydrophilic polyacrylates presented a lower surface free energy (γ) at room temperature, resulting in surface segregation. A perpendicular microdomain orientation was achieved after thermal annealing above the glass transition temperature of both components. As the annealing temperature increased, the surface became hydrophobic while maintaining this orientation due to polystyrene segregation. The key to this process is appropriate thermal annealing, considering the entropic contribution to γ from differences in molecular motion between the two components.