Regulation of the nanostructures self-assembled from an amphiphilic azobenzene homopolymer: influence of initial concentration and solvent solubility parameter.

The control over the morphology and nanostructure of soft nanomaterials self-assembled from amphiphilic polymers is of high interest, but is still challenging. Herein, we manipulate the morphology of bowl-shaped nanoparticles by changing initial polymer concentrations, and prepare nanotubes and nanowires, both twisted and not, by using solvents with different solubility parameters. An amphiphilic azobenzene homopolymer (poly(4-(phenyldiazenyl)phenyl methacrylamide), PAzoMAA) is designed and synthesized reversible addition fragmentation chain transfer (RAFT) polymerization, which can self-assemble into bowl-shaped nanoparticles promoted by the synergy of hydrogen bonding and π-π interaction. More significantly, the opening size of the bowl-shaped nanoparticles can be controlled by changing initial polymer concentrations. Nanotubes and nanowires, both twisted and not, are also obtained using a solvothermal method in alcohols. The relationship between the structure of the nanomaterials and the solubility parameters of the alcohols is investigated, revealing the molecular arrangement patterns of PAzoMAA in different nanostructures. Overall, we propose a facile strategy to manipulate the microstructure of bowl-shaped nanoparticles and one-dimensional nanomaterials by adjusting initial polymer concentration and solvent solubility parameters. Our study may bring new avenues for controlling the nanostructures of soft nanomaterials.