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.