Study On Mechanism And Controlled Polymerization Of Metallic Copper Mediated Vinyl Monomers

Compared with the mechanism of atom transfer radical polymerization(ATRP),Cu(0)-mediated reversible deactivation radical polymerization(RDRP)reaction is more complicated due to the different roles and the mutual conversion of three different valence copper species(Cu~0,Cu~? and Cu~?).Supplemental activation and reducing agents(SARA)ATRP and single-electron transfer living radical polymerization(SET-LRP)are the two main contradictory mechanisms of Cu(0)-mediated RDRP,which issue is the role of different valence copper species.In this work,three different initiators i.e.EBriB(ethyl?-bromoisobutyrate),EBr P(ethyl 2-bromopropionate)and MBrP(methyl 2-bromopropionate)were used to shed a light on the origins of the induction period occurred in Cu(0)-mediated RDRP reaction.The results show that under the same reaction conditions,the system using highly active initiator EBriB has a 45 min induction period,but the systems with lower active initiators EBr P/MBrP have no such induction period.The comparative analysis shows that the existence of induction period is due to the different addition rate of initiator to monomer and the difference of relative concentration of various soluble copper species(Cu~? and Cu~?)accumulated at the early stage of the reaction.It is proved that Cu~? species is the major activator and its disproportionation is essential for establishing the equilibrium among different copper species in the reaction.Based on the understanding of Cu(0)-mediated RDRP mechanism,herein,the controllable polymerization of different vinyl monomers(methyl methacrylate(MMA),styrene(St)and acrylamide(AM))was obtained by considering the effects of different parameters(initiator,ligand,solvent and deactivator)on two equilibriums-mutual conversion of different copper species and polymerization equilibrium.Moreover,suitable polymerization parameters were also selected to investigate the homopolymerization of divinyl monomer-Tetra(ethylene glycol)diacrylate(TEGDA).The gel point was successfully delayed up to 71%(monomer conversion)and the hyperbranched polymer was obtained with a 45%branch ratio.