Polymeric Bottle‐Shaped Nanoparticles With Controlled Cavity and Neck

ABSTRACT Bottle‐shaped nanoparticles, comprising a long neck and a large single interior cavity, have been drawing extensive attention due to their unique structural characteristics, exhibiting significant potential in catalysis, drug delivery and nanomotors. In this study, a polymer self‐assembly strategy is proposed to prepare bottle‐shaped nanoparticles with controlled cavity and neck dimensions based on a triphenylamine‐functionalized amphiphilic alternating copolymer of poly(amic acid) (PAA). By adjusting the initial concentration and water dropping rate during self‐assembly, the cavity diameter and neck length of the bottle‐shaped nanoparticles can be well controlled. Once the PAA is annealed at 160, 180 and 220°C, respectively, hydrophobic and rigid polyimide segments are generated in the backbone of the polymer, leading to a shape transformation from bottle‐shaped nanoparticles to porous capsules and pod‐shaped nanoparticles, as well as a significant red shift and enhancement of the fluorescence. Exploring the formation mechanism of bottle‐shaped nanoparticles, a protrusion is formed at the early stage of the self‐assembly due to the build‐up of osmotic pressure, which extends with the addition of water to afford bottle‐shaped nanoparticles. Overall, the controlled preparation of bottle‐shaped nanoparticles with adjustable cavity and neck is achieved, opening up new avenues for the controlled construction of highly anisotropic nanostructures.