Title : Controlled Fabrication and Morphological Transformation of Polymeric Bowl-shaped Nanoparticles
Bowl-shaped nanoparticles are asymmetric hollow structures with a single large opening on the surface. As a classical kind of asymmetric nanoparticle, bowl-shaped nanoparticles have shown advantages in loading and delivery of large sized cargoes, catalysis and energy storage. However, also due to the asymmetric structure, the controlled fabrication of bowl-shaped nanoparticles is still challenging. The self-assembly of amphiphilic polymers is powerful tool to prepare functional soft nanomaterials. Herein, we demonstrate a versatile strategy for preparing nanobowls with precisely controlled openings and interior holes based on the synergy of hydrogen bonding and π–π interaction of amphiphilic homopolymers. A series of azobenzene pendants containing amphiphilic homopolymers were synthesized via RAFT polymerization. Upon adding water to the solution of the homopolymers, the high local viscosity of the preformed large compound spheres provided by non-covalent interactions hinders the homogeneous shrinkage of the spheres, leading to the formation of bowl-shaped nanoparticles. The intermediates of bowl-shaped nanoparticles were tracked by investigation into the kinetic process of assembly, and we also proposed a formation mechanism of the bowl-shaped nanoparticles. In addition, the sizes of the openings and interior holes can be well controlled by molecular weight, initial concentration and concentration of ions. Based on the aforementioned design principle of amphiphilic polymers to prepare bowl-shaped nanoparticles, we also induced amphiphilic homopolymers that only form nanospheres by adding π–π interaction donors. Taking advantage of the UV-induced isomerization of azobenzene group, we also investigated the controlled transformation of amorphous bowl-shaped nanoparticles to crystalline ellipsoids, which opens new avenue for the transformation of amorphous nanomaterials to crystalline ones. Overall, we proposed the strategy to prepare bowl-shaped nanoparticles via the self-assembly of amphiphilic homopolymers via the introduction of non-covalent interactions and realized the controlled shape transformation of bowl-shaped nanoparticles.
- The structure and functions of bowl-shaped nanoparticles.
- The design principle of amphiphilic polymers to prepare bowl-shaped nanoparticles and the formation mechanism.
- How to control the sizes of openings and interior holes of bowl-shaped nanoparticles?
- The controlled dis-assembly and re-assembly of bowl-shaped nanoparticles induced by UV light.