Zipping Polymers into Nanoparticles via Intrachain Alternating Radical Copolymerization

The synthesis of single-chain nanoparticles (SCNP) via the intrachain radical homopolymerization and alternating copolymerization of pendant styrene or stilbene units is reported. In the presence of a radical initiator, styrene-functionalized polymers undergo intrachain cross-linking to form SCNP; however, when an electron deficient monomer such as maleic anhydride is added, interchain coupling occurs. For the stilbene-functionalized polymer, no homopolymerization of pendant stilbene units is observed, but copolymerization initiated in the presence of maleic anhydride or N-ethyl maleimide results in nanoparticle formation. Fluorescent SCNP are synthesized using N-(1-pyrene)maleimide. Stilbene is known to undergo alternating copolymerization with these electron-deficient monomers, providing a new method for synthesizing cross-linked particles with simple alternating sequences while simultaneously installing functionality and tuning the particle size and density.