Mixed shell nanoparticles via polymerization-induced self-assembly of Y-shaped ABC miktoarm star copolymers

Mixed shell polymer nanoparticles (MSPNs) have emerged as a very significant research topic in the field of macromolecular science. In this study, a robust method for efficient preparation of MSPNs with various morphologies via polymerization-induced self-assembly (PISA) of Y-shaped ABC miktoarm star copolymers was demonstrated. Poly( ε -caprolactone)- b -poly(methyl methacrylate) diblock copolymers carrying a trithiocarbonate (TTC) group at the diblock joint (PCL-TTC-PMMA) were synthesized via the sequential ring-opening polymerization of ε-caprolactone ( ε -CL) and atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) using a multifunctional initiator. Subsequently, PCL-TTC-PMMA copolymers acted as both macromolecular chain transfer agents (CTAs) and stabilizers to mediate reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of 4-vinylpyridene (4-VP) in toluene, producing MSPNs with different morphologies including spheres, short rods , worms and vesicles. The factors influencing the morphologies of MSPNs during PISA, including solid content and the chain length of stabilizers, were investigated. RAFT-based dispersion polymerizations of 4-VP monomers mediated by PCL-TTC-PMMA copolymers were also compared with those mediated by linear PMMA - TTC with approximately the same length of PCL-TTC-PMMA under the identical conditions. Their different PISA behaviors were unraveled.