Effects Of Ionic Liquids On Organotellurium-mediated Living Radical Polymerization(TERP) And Its Kinetic Discussion

Pursuing the goal of precise synthesis of polymer, synthetic chemists have paidso many attentions to devise several controlled/living radical polymerization （CRP）methods and research them during the past decades. However, seldom technics couldbe industrialized to large-scale production like conventional radical polymerizationprocess. Organotellurium-mediated Living Radical Polymerization （TERP）, designedby Yamago and co-workers, exhibits various attractive inherent qualities, such aswider polymerizable monomer families, no need for separation, etc. Otsuka ChemicalCo., Ltd. has ultized TERP to produce polymers5tons per day. Due to theenvironmental and heathy aspects, how to reduce or avoid using dimethyl ditelluriumas cocatalyst would be a meaningful task to focus on.We applied ethyl-2-methyltellanyl-isobutyrate as chain transfer agent topolymerize methyl methacrylate （MMA）, methyl acrylate （MA） and styrene （St） withor without1-butyl-3-methylimidazolium （[Bmim]PF₆）, testifying the effects of[Bmim]PF₆. We also made a kinetic discussion about its effects by following Fukuda’sGPC resolution method.[Bmim]PF₆were perfectly served as solvent for TERP. The reaction rate ofpolymerizing MMA and MA were significantly increased as previous reported, whilethe controllability of polydispersity index （PDIs） was also improved by a great margin.TERP of MMA can now give PMMAs with PDIs less than1.1and nearly fullconversion in half an hour without the presence of dimethyl ditellerium. Kinetic studybased on GPC resolution method revealed that the improved control could be ascribedto faster degenerative chain transfer （DT） reaction which plays a key role in control ofPDI for TERP. Besides the polar effect of ILs, the existence of Lewis acid/baseinteraction between [Bmim]PF₆and Te-atom was proved by UV-Vis spectroscopy and125Te NMR results. Such positive interaction lowered the activation energy of DTprocess.Futher analysis based on kinetic equations revealed that, a) not only [Bmim]PF₆,all ILs should be compatible with TERP and good for TERP’s livingness andcontrollability; b) the livingness of other controlled/living radical polymerization（CRP） should be benefit not only from [Bmim]PF₆, but also other ILs; c) if a specificIL has no kinetic effect on a CRP’s activation-deactivation cycle, its application as solvent should be unfavorable for the controllability of CRP.