Intramolecular Cyclization Dominating Homopolymerization of Multivinyl Monomers toward Single-Chain Cyclized/Knotted Polymeric Nanoparticles

Polymerization of multifunctional monomers could produce polymers with different functionalities and novel macromolecular architectures. However, the ability to control the homopolymerization of multivinyl monomers (MVMs) has always been a challenge. Here we demonstrate that the homopolymerization of acrylate based MVMs can be kinetically controlled via Cu⁰-mediated controlled/living radical polymerization in the presence of additional Cu^II, which enables the efficient promotion of intramolecular cyclization and suppression of intermolecular cross-linking. The gelation is effectively delayed over ca. 40% monomer conversion in the concentrated polymerization system ([M] = 40.9 wt %), which is far higher than the Flory-Stockmayer theory predicts. Moreover, closer inspection of the synthesized polymers reveals that single-chain cyclized/knotted polymeric nanoparticles (SCKNPs) are formed due to the nature of one-pot in situ intramolecular reaction and self-cyclization of the propagating polymer chains. This facile method opens a new avenue to the design and synthesis of a broad range of novel single-chain cyclized/knotted polymeric materials.