Radical Coupling Polymerization And Its Application

Although the radical addition reaction to carbon-carbon double bonds is widely applied in chain polymerization of vinyl monomer, the coupling reaction of a radical, another extremely rapid reaction of radicals, is scarcely used in polymerization. Radical coupling reaction was applied to preparation of polymer and systematic research was carried out.Self coupling reaction benzyl-type diradcial was eliminated by choosing proper ligand and polymerization condition in radical addition-coupling polymerization (RACP). Various sequence controlled polymers with repeating units such as [AX], [AAX] and [ABAX] using a, a’-dibromo benzyl-type compound as monomers were prepared. Effect of substisuents on the molecular weight was discussed.Polymer with different molecular weight can be prepared by radical coupling polymerization (RCP), which involves a consecutive direct radical coupling reaction of in situ formed benzyl-type biradicals from dibromide in the presence of a Cu(0)/ligand. The RCP of 1,4-bis(bromomethyl) was monitored at various polymerization times. The evolution of molecular weight distribution clearly demonstrated that the polymerization follows the step-growth mechanism. Effect of reaction conditions such as monomer concentration and polymerization temperature on the polymerization results were discussed. Polyarene, polyester, polyether and polysulfone can be prepared under mild conditions and within a short time.Radical coupling copolymerization (RCCP) of several pairs of benzyl-type biradicals were investigated. The composition of monomers and diad sequence distributions of copolymers can be determined by 1H NMR. Effect of substisuents on the molecular weight and composition of copolymer was discussed. Polymerization of asymmetrical monomers with two different functional groups was also studied.Multisegmented polystyrene was prepared by polymerization of styrene initiated by α, ω-dibromo compound in the presence of Cu(0)/ligand. The polymer chain was constructed by radical multiple addition-coupling polymerization (RMACP) in which addition and coupling reaction proceed simultaneously in one pot. Effects of solvent and polymerization temperature on RMACP was investigated. Multisegmented polymer with relatively narrow molecular weight distribution of chain segment can be prepared in specific condition. Molecular weight of chain segment and number of segment can be regulated by adjusting the ratio of initiator/styrene, amount of copper powder and other factors.