Study Of Fluoroalcohol Effects On SET-LRP

Controlled/"living"radical polymerization (LRP) witnessed vast developments for the synthesis of well-defined polymer with predetermined molecular weights, tailored architectures and functionalities. Meanwhile, the precise control of the chain microstructure during radical polymerization is one of the important issues in the field of LRP. Some novel LRP methods have been invented, such as iodine transfer polymerization, Te-, Sb-, and Bi-mediated radical polymerizations, quinone transfer radical polymerization, reversible chain transfer catalyzed polymerization, and single electron-transfer living radical polymerization (SET-LRP). Among them, SET-LRP has shown distinct advantages over other LRPs since its emergence in 2006 by Percec et al., including mild reaction conditions (room temperature or below), a catalytic amount of catalyst, ultrafast polymerization and resultant of high molecular weight polymers with low polydispersity. The article was based on the study of the mechamism of SET-LRP, including: the solvent effect of fluoroalcohol on polymerization behaviors; the effect of initiator structure and halogen species on the polymerizations with fluoroalcohol as solvent; and the SET-LRP of progargyl methacrylate (PgMA) in fluoroalcohol.The detailed works were summarized as the following:(1) The Cu(0)-mediated single electron-transfer living radical polymerization (SET-LRP) of methyl methacrylate (MMA) using ethyl 2-bromoisobutyrate (EBiB) as an initiator with Cu(0)/N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) as a catalyst system in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was studied. The polymerization showed some living features: the measured number-average molecular weight (Mn,GPC) increased with monomer conversion and produced polymers with relatively low polydispersities, the resultant polymer was end-capped by EBiB species. The increase of HFIP concentration improved the controllability over the polymerization with increased initiation efficiency and lowered polydisperisties values. HFIP also facilitated the polymerization with control over stereoregularity of the polymers. Higher concentration of HFIP and lower reaction temperature produced higher syndiotactic ratio.(2) SET-LRP of MMA was investigated initiated with benzyl halide in HFIP, with Cu(0)/N, N, N', N", N"-pentamethyldiethylenetriamine (PMDETA) as a catalyst system. Since HFIP complies with the rules of solvent selection in SET-LRP, it can be expected to improve the controllability the polymerization. The polymerization showed some living features: the measured number-average molecular weight (Mn,GPC) increased with monomer conversion and produced polymers with relatively low polydispersities. Spontaneously, the effect of the nature of halogen in initiators on polymerization was researched.(3) An alkyne monomer, progargyl methacrylate (PgMA), was successfully polymerized in a well-controlled manner via SET-LRP initiated with 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) in the presence of HFIP. The living nature of the polymerization was confirmed by the first-order kinetic plots, the linear relationships between molecular weights and the monomer conversions while keeping relatively narrow molecular weight distributions under 50% of conversion.