The phase behaviors of cylindrical diblock copolymers and rigid nanorods' mixtures

Mixtures of cylindrical forming diblock copolymers (DBCPs) and mobile nanorods (NRs) are systematically investigated via dissipative particle dynamics (DPD) simulations. Final morphology of such composites depends not only on the characteristics of the copolymers, but also on the physical or chemical features of NRs, such as NR number, length, and surface adsorption (neutral, A and B attractive). A consideration of enthalpic and entropic interactions is necessary when physically or chemically distinct NRs are introduced into the copolymer/nanorod composites. For the short NRs, the phase behavior is similar to that of spherical nanoparticles (NPs). For the long NRs, the self-assembly of NRs can influence both the orientation and morphology of diblock/nanorod mixtures. If more NRs are incorporated, under stronger confinement from the host phase separated domains, the long NRs will aggregate and self-assemble into a certain spatial organization, inducing the morphological transitions of the composites from one phase to another. This behavior is not encountered for a similar system doped with spherical particles, emphasizing the role of particle shape in the interaction between doping particles and the host phase. (C) 2009 Elsevier Ltd. All rights reserved.