Macro-RAFT Agent Mediated Heterogeneous Raft Polymerization: Research And Application

Free radical polymerization under heterogeneous system, such as emulsion polymerization, dispersion polymerization, seed swelling polymerization,microemulsion polymerization, soap free emulsion polymerization, miniemulsion polymerization, suspension polymerization, precipitation polymerization, is an important method for preparing functional polymer microspheres. Nowadays, the introduction of reversible addition-fragmentation chain transfer?RAFT?polymerization into heterogeneous polymerization system, especially the heterogeneous RAFT polymerization mediated by Macro-RAFT agent has received more and more attention due to their advantages of in-suit formation of block copolymer and polymerization induced self-assemble of block copolymer colloids.This dissertation is devoted to the study of RAFT polymerization in heterogeneous systems, and its application in the preparation of functional polymer colloids. The main contents are as follows:?1? Controlled synthesis of cationic PS/PMMA latexes via RAFT mediated emulsion copolymerizationAb initio batch emulsion reversible addition-fragmentation chain transfer copolymerization of styrene and methyl methacrylate is investigated by employing poly[N-?4-vinylbenzyl?-N,N-dibutylamine hydrochloride] trithiocarbonate?PVBAHTTC? as both surfactant and macromolecular reversible addition-fragmentation chain transfer?Macro-RAFT? agent. The influences of monomer component, emulsion solid content, molar ratio of macro-RAFT agent to monomer, and the molecular weight of PVBAH-TTC macro-RAFT agent on ab initio emulsion RAFT copolymerization are explored. Well-controlled polymerization with fast polymerization rate, high conversion and little coagulum can be achieved under the condition of the St monomer content above 30%, emulsion solid content below 40%, the molar ratio of macro-RAFT agent to monomer lower than 1:₆₀0, and the molecular weight of PVBAH-TTC macro-RAFT agent ranging from 4.7 to 10.5 kg/mol. The polymerization leads to formation of nano-sized colloids of the poly[N-?4-vinylbenzyl?-N,N-dibutylamine]-b-poly?styrene-co-methylmethacrylate?-bpoly[N-?4-vinylbenzyl?-N,N-dibutylamine] triblock copolymer. The colloids generally have core-shell structure, in which the hydrophilic blocks form the shell and the hydrophobic blocks form the core. The molecular weight of the triblock copolymer linearly increases with the increase in the monomer conversion, and the values are close to with the theoretical ones. The molecular weight polydispersity index of the triblock copolymer is below 1.3 at most cases of polymerization.?2? Synthesis of core-shell-corona nanopartilces through two Macro-RAFT agents co-mediated dispersion RAFT polymerizationDynamic-covalent shell corss-linkable core-shell-corona nanopartilces?DCSCNs?with boronic ester linkages were synthesized by simultaneously employing two macro-RAFT agents of poly?N,N-dimethylacrylamide?-b-poly?3-acrylamidophenyl boronic acid? trithiocarbonate?PDMA-b-PAPBA-TTC? and poly?N,N- dimethylacrylamide?-b-poly?5-ethyl-2,2-dimethyl-1,3-dioxane-5-yl?methyl acrylate trithiocarbonate?PDMA-b-PEDMA-TTC? in dispersion RAFT polymerization of styrene?St?.Polymerization leads to the formation of PDMA-b-PEDMA-b-PS/PDMA-b-PAPBAb-PS multicompartment triblock copolymer nanoparticles, in which the PDMA block forms the corona, the mixed PAPBA and PEDMA blocks form the shell and the solvophobic PS block constructs the core. Since the 1,3-dioxane ring in PEDMA segments can hydrolyze into diol group under acidic condition, DCSCNs can be prepared due to the dynamic-covalent nature of the boronic ester cross-links between the APBA and diol groups.