Design Of A Novel Active/controlled Radical Polymerization System

Ionic liquids(ILs)are organic salts with liquid state at or near room temperature.They have good solubility to transition-metal catalysts and considered to be an environmentally friendly solvent due to the nonvolatile and nonflammable properties.Atom transfer radical polymerization(ATRP)has received much attention for preparing polymers with predictable molecular weights and low polydispersity index values in the last twenty years.In normal ATRP,a dynamic equilibrium is established by the oxidation-reduction reaction between activator and dormant species.However,the transition-metal complexes in their lower oxidation states are air sensitive and particularly easy oxidized in the presence of even traces of oxygen in normal ATRP systems.Therefore,various ILs are designed as reaction medium or even as ligands by varying the structures of cation and anion for ATRP,especially for reverse ATRP.Firstly,most of ILs are used as solvent in Fe(III)-catalyzed reverse ATRP.However,the facile,simple and inexpensive ILs,1-alkyl-3-methylimidazole chloride([Rmim][Cl])has rarely been employed as ligand for in Fe(III)-catalyzed reverse ATRP.Therefore,the purpose of this study is to demonstrate the feasibility of Fe(III)-catalyzed reverse ATRP of MMA using AIBN as initiator,FeCl3 as catalyst,and[Rmim][Cl]as the ligand.The living/controlled characteristics was studied including the polymerization whether in accord with first-order kinetics,the relation of polymer molecular weight and monomer conversion,and polydispersity index values.Effects of various experimental parameters including different alkyl chain length of ILs,the concentration of ILs,solvent,catalyst,reaction temperature,and the molar ratio of FeCl3/[Rmim][Cl]on the polymerization were investigated in detail.Furthermore,1H NMR and gel permeation chromatography(GPC)analyses confirmed FeCl3/[Rmim][Cl]catalyzed reverse ATRP of MMA belongs to living/controlled radical polymerization principle,and high chain-end functionality of the resultant polymer.Subsequently,the selectivity of copper catalyst for ligand is very high.It is difficult to employ ILs as ligand,the controllability can be loss even some the polymerization is reported.The aim of this work is to confirm the feasibility of Cu(II)-catalyzed reverse ATRP of MMA using AIBN as initiator,CuBr2 as catalyst,and 1-phenyl-3-methylimidazole diphenyl phosphate([Phmim][Ph2PO4])as the ligand.The results indicated that the polymerization belongs to first-order kinetics,polymer molecular weight increased with monomer conversion,and polydispersity index values remained in a narrow range.Meanwhile,effects of various experimental parameters on the living of polymerization were investigated in detail.Furthermore,1H NMR and GPC analyses confirmed CuBr2-[Phmim][Ph2PO4]catalyzed reverse ATRP of MMA proceed in a living/controlled radical polymerization,and high chain-end functionality of the resultant polymer.