Truncated Wedge-Shaped Nanostructures Formed from Lateral Microphase Separation of Mixed Homopolymer Brushes Grafted on 67 nm Silica Nanoparticles: Evidence of the Effect of Substrate Curvature

Mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes with controlled molecular weights and narrow polydispersities were synthesized from asymmetric difunctional initiator (Y-initiator)-functionalized 67 nm silica nanoparticles by sequential surface-initiated atom transfer radical polymerization of tBA at 75 degrees C and nitroxide-mediated radical polymerization of styrene at 120 degrees C in the presence of a free initiator in each polymerization. The Y-initiator-functionalized nanoparticles were prepared by the immobilization of a triethoxysilane-terminated Y-initiator onto the surface of 67 nm silica particles via an ammonia catalyzed hydrolysis and condensation process. Transmission electron microscopy studies showed that mixed PtBA/PS brushes grafted on 67 nm silica nanoparticles with comparable with comparable molecular weights for the two polymers underwent lateral microphase separation after being cast from CHCl3 and annealed with CHCl3 vapor producing distinct truncated wedge-shaped nanostrudures. In contrast, under the same Conditions, Mixed PtBA/PS brushes grafted on 160 nm silica particles self assembled into nanodomains with a more uniform width. This suggests that the truncated wedge-shaped nanostructures formed by mixed brushes on 67 nm silica nanoparticles originated from a higher substrate curvature.