Co-assembly behaviour of Janus nanoparticles and amphiphilic block copolymers in dilute solution.

Nanoparticles can co-assemble with amphiphilic block copolymers (ABPs) in solution to generate nanoaggregates with unique properties, yet the mechanism of such a co-assembly behaviour for Janus nanoparticles (JPs) and ABPs remains unclear. Here, the self-assembly behaviour of JP/ABP mixtures in dilute solution was studied via theoretical simulations. Two kinds of ABPs with different volume fractions fA of hydrophilic blocks were considered: one is symmetric copolymers with fA = 0.5, and the other is asymmetric ABPs with fA = 0.3. In the first case, mixtures of spheres and rods, connected networks and vesicles were formed sequentially as the volume fraction cJP of nanoparticles increases. In the second case, vesicles were constantly formed. For both cases, at lower cJP values, the nanoparticles were located at the core-corona interfaces. By contrast, at higher particle loadings, a large number of particles were involved in clusters embedded in the vesicle walls. Based on the simulation results, a morphological diagram in the space of cJP and fA was constructed to indicate the stability regions of different nanostructures. Specifically, it was found that the vesicles formed by JPs and ABPs with short hydrophilic blocks are stimuli-responsive. By changing the interaction parameters between hydrophobic blocks, controllable pores in the vesicle walls could be created. Our findings not only provide insights into the co-assembly behaviour of Janus nanoparticles and amphiphilic block copolymers in solution, but also offer a novel strategy to prepare nanoreactors with permeable membranes.