Macromolecules, Vol.52, No.10, 3612-3624, 2019
Radical Ring-Opening Copolymerization-Induced Self-Assembly (rROPISA)
Radical ring-opening copolymerization-induced self-assembly (rROPISA) was performed by copolymerizing benzyl methacrylate and cyclic ketene acetals (CKA), such as 2-methylene-4-phenyl-1,3-dioxolane or 5,6-benzo-2-methylene-1,3-dioxepane, in heptane at 90 degrees C by reversible addition-fragmentation chain transfer (RAFT) polymerization from a poly(lauryl methacrylate) macro-RAFT agent. The chain lengths of both the solvophilic macro-RAFT agent and the solvophobic block, together with the initial amount of CKA, were independently varied to achieve various compositions. The amount of CKA in the copolymers ranged from 4 to similar to 40 mol % by adjusting the monomer stoichiometry, leading to nearly complete degradation for CKA contents above similar to 15 mol %. rROPISA led to stable nanoparticles in all cases, ranging from 40 to 500 nm in diameter, depending on the experimental conditions, as assessed by dynamic light scattering and transmission electron microscopy. Low average diameters and very narrow particle size distributions were obtained for CKA contents below 20 mol %, except for a targeted solvophobic chain length of 300 that gave narrow particle size distributions up to 50 mol % in CKA. Morphological investigation revealed the formation of spheres for all copolymer compositions, which was assigned to both the nature of the RAFT agent used and insertion of CKA in the solvophobic block, which prevent the formation of other morphologies.