Tailoring branching and helicoidal morphologies on cylindrical nanoparticles via grafted amphiphilic macromolecules: Computer modelling

The article presents computer experiments on the self-organization of polymer layers from macromolecules with A- graft -B monomer units, that are grafted onto an infinitely long cylindrical nanoparticle (nanorod) and immersed in selective solvent. Mirror-symmetric solvents with the same pair of energy interaction parameters corresponding to the effective attraction (poor solvent) and repulsion (good solvent) between groups assigned at different solvent to different groups of the monomer unit were considered. In a selectively good solvent for side chains, macromolecules assemble into fibrillar aggregates that deviate from the surface of the nanoparticles and are capable of branching into narrower fibrils and merging with neighboring aggregates. In the opposite case, when the solvent is selectively good for the main chain and poor for the side chains, the macromolecules self-assemble into thin membrane-like layers that wrap around nanoparticles and at higher grafting densities form ordered helicoidal morphologies. In both cases, the morphological states depend on the grafting density and the macromolecular length, and are also very sensitive to the mobility of the grafting points. The results are in qualitative correspondence with literature experimental data. This work demonstrates the diversity of possible morphological states of comb-shaped macromolecules grafted onto a cylindrical nanoparticle, highlights the importance of the relative positions of different groups for structure formation, and opens avenues for the targeted design of complex patterned surfaces on cylindrical particles.