Fast solvent induced switchable phase-states of binary polymer-grafted nanoparticle blends*

Polymer-grafted nanoparticles (PGNPs) have potential applications in nanoelectronics, photonic devices, and as tough materials with tunable enhanced mechanical properties. However, these applications require the particles to form well-controlled structures. We hypothesize that these can be achieved through liquid-enabled phase-separation as a facile approach. To this end, we developed a method to switch the state of phase-separated structures in a binary blend film of PGNPs, poly (methyl methacrylate) silica (PMMA-SiO₂) and poly(styrene) silica (PS-SiO₂), by using a direct solvent immersion annealing (DIA) method. Our results show that by varying the solvents in the DIA solution, interchangeable phase-separated and homogeneous morphologies are formed in the PMMA-SiO₂/PS-SiO₂ blends within 1 minute. Such homopolymer matrix free PGNP only blend systems are novel, and these switchable transitions are not readily obtainable by thermal annealing due to the large masses and the athermal property of PGNPs involved.