Construction of Metallacycle-Linked Heteroarm Star Polymers via Orthogonal Post-Assembly Polymerization and Their Intriguing Self-Assembly into Large-Area and Regular Nanocubes^†

In recent years, synthesis of hybrid heteroarm star polymer with precisely defined arms has evolved to be one of the most attractive topics within polymer chemistry. In this study, we present the successful synthesis of metallacycle-linked heteroarm star polymers (HASPs) composed of crystalline poly(ε-caprolactone) (PCL) and polyacrylate (poly (N-isopropylacrylamide) (PNIPAM) segments via combination of ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization. Firstly, a hexagonal metallacycle containing three hydroxy groups and three chain transfer agent moieties at the alternative vertexes was designed and synthesized based on the general principle of coordination-driven self-assembly. Subsequently, upon combination of two orthogonal post-assembly polymerizations, a new family of HASPs containing a well-defined hexagonal metallacycle with precisely controlled position of polymer arms was facilely prepared. Interestingly, the obtained HASPs could spontaneously self-assemble into large-area and regular cubic nanoparticles in tetrahydrofuran (THF)/methanol (MeOH) mixed solvents under specific conditions as confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). This study provides a simple route to the controllable preparation of HASPs, and opens up a new way for further study on self-assembly of different HASPs systems.