Structure and particle aggregation in block copolymer-binary nanoparticle composites

The aggregation behavior and location of binary nanoparticles in a block copolymer-nanoparticle composite are investigated by employing three-dimensional dissipative particle dynamics (DPD) simulations. The dependence of the morphology of the composites and of the composition of the nanoparticle aggregates on the pair interactions between the same and different kinds of nanoparticles or segments, as well as between each kind of nanoparticles and each kind of segments of the block copolymer, is examined. The natures of the two kinds of nanoparticles employed constitute an important factor in the phase behavior of these composites. When the change of the state of some particles from individually distributed to aggregated is induced particularly by the interactions between particles, the configuration of the block copolymer is changed from lamellar to a complex one. In contrast, when the above change in the configuration of the particles (aggregated or nonaggregated) is induced particularly by the interactions between the particles and the segments of the block copolymer, the configuration of the block copolymer remains lamellar. DPD simulations imply repulsive pair interactions between all pairs of particles, segments and particles, as well as segments of the block copolymers. The aggregation observed in simulations, is caused by the collective behavior of the system which transforms the pair repulsive interactions (which are the only ones that are considered in DPD) in a collective attraction.