Phase Behavior of Polymer-Grafted Nanoparticles

A common strategy to control nanoparticle (NP) distribution in composites is to graft polymer chains onto the NP surfaces. Grafted polymer NPs can exhibit rich phase behavior due to complex interplays among chain conformational entropy, depletion effects, and enthalpic interactions. We use theoretically-informed Langevin dynamics (TILD) simulations to determine the structure of polymer brushes on single grafted NPs and to calculate equilibrium phase diagrams in solution. For NPs grafted with two immiscible polymers, the polymers microphase separate on the surface of the particle. A Janus structure is obtained for sufficiently small NPs, while the polymers grafted to larger NPs tend to form disordered patchy structures on the NP surface. Janus-patterned NPs self-assemble in solution into interesting aggregates such as vesicles. I will also discuss phase diagrams for NPs grafted with homopolymer and dispersed in solvent.