Polymeric Bottle-Shaped Nanoparticles With Controlled Cavity and Neck

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.