(4bm) Phase Behavior of Polymer/Nanoparticle Blends near a Substrate

We use both fluids density functional theory (DFT) with mean-field attractions and molecular dynamics (MD) simulations to investigate the phase behavior of polymer/nanoparticle blends near a substrate. Earlier studies have shown that for an athermal system, with freely jointed chains, there is a first order transition, where the nanoparticles expel the polymer from the surface to form a monolayer at a certain nanoparticle concentration. This transition has been justified by nanoparticle segregation to the substrate observed in experiments. In the presence of attractions, the first order transition moves to higher nanoparticle concentrations as the strength of attraction is increased. Chains with limited flexibility show nematic ordering at higher densities in the bulk. Upon reducing the temperature, the system undergoes a sol-gel transition resulting in a nematic gel. We intend to study the phase behavior of blends with semiflexible polymer chains and nanoparticles in presence of a substrate. The primary objective of this work is to model the experimental system with PCBM in P3HT thin films used in solar cells. By modeling the experimental results, we can identify the stiffness of P3HT, which is currently unknown.