Bicontinuous Block Copolymer Morphologies Produced by Interfacially Active, Thermally Stable Nanoparticles
Polymeric bicontinuous morphologies were created by thermal annealing mixtures of poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) block copolymers and stabilized Au-core/Pt-shell (Au–Pt) nanoparticles. These Au–Pt nanoparticles have a cross-linked polymeric shell to promote thermal stability and are designed to adsorb strongly to the interface of the PS-b-P2VP block copolymer due to the favorable interaction between P2VP block and the exterior of the cross-linked shell of the nanoparticle. The interfacial activity of these Au–Pt nanoparticles under thermal annealing conditions leads to decrease in domain size of the lamellar diblock copolymer. As nanoparticle volume fraction p was increased, a transition from a lamellar to a bicontinuous morphology was observed. Significantly, the effect of these shell-cross-linked Au–Pt nanoparticles under thermal annealing conditions was similar to those of traditional polymer grafted Au nanoparticles under solvent annealing conditions reported previously. These results suggest a general strategy for producing bicontinuous block copolymer structures by thermal processing through judicious selection of polymeric ligands, nanoparticle core, and block copolymer.