Single-chain tethered nanoparticles with tunable softness: scalable synthesis and unique self-assembly behavior†
A general and scalable strategy for the preparation of single-chain tethered nanoparticles (SCTNPs) with tunable size and softness is reported. The SCTNPs composed of a poly(ethylene glycol) (PEG) chain anchored on a star polymer with 20 poly(tert-butyl acrylate) (PtBA) arms were synthesized by successive click coupling reaction and controlled radical polymerization at high concentrations, enabling large-scale preparation. As predicted by theoretical analysis, the 20-arm star polymer can be considered as a spherical NP with tunable size and softness, which has been confirmed by TEM characterization in this research. Hence the obtained systems are named as single-chain tethered sea urchin-like nanoparticles (SCTSUNPs). The self-assembly of the synthesized SCTSUNPs was induced by slowly pumping water into their DMF solutions. Toroidal nanostructures, a mixture of bicontinuous worms and spherical micelles, interdigitated vesicles, and bilayer vesicles were successively obtained with increasing arm length, which significantly differs from their linear counterparts (PEG-b-PtBA block copolymers, also investigated in this research). The low deformability of the sea urchin-like nanoparticles is believed to be the key factor that determines the formation of the special nanostructures, e.g. toroids and interdigitated vesicles. This report provides a new platform for the preparation of SCTNPs with tunable size and softness on a large scale.