Abstract:

A single electron transfer living radical polymerization(SET-LRP) is able to rapidly achieve high molecular mass, with excellent control of molecular mass distribution, represents a robust and versatile method for the rapid synthesis of macromolecules with defined architecture. The SET-LRP of acryl amide(AM) was investigated at 40 ℃ in 1-butyl, 3-methyl tetrafluoroborate([Bmim]BF4) ionic liquid， using Cu0 power/tris(2-dimethylamin ethyl) amine(Me6-TREN) as catalyst, 2,2-dibromomethyl-1,3-dibromopropane(PEBr4) as initiator. The polymerization showed some “living” features: the conversion and ln ([M]0/[M]) increased linearly with time as well as the number-average molecular mass increased linearly with conversion. The star polyacrylamide(sPAM) prepared via SET-LRP was characterized by GPC and 1H NMR to identify its polymerization mechanism, and the results showed that the polymer had the perfect functional chain ends and relatively low molecular mass distribution Mw/Mn≈1.26(MGPCn=14.1×103， conversion rate is 43.4%), indicating a controlled polymerization. The effects of water, catalyst and initiator on polymerization were studied, and the dynamic experiments were carried out. A small amount of water added could accerlerate the polymerization, the apparent rate constants of propagation(kappp) were 0.04248 h-1 and 0.14869 h-1 for adding free water and 0.5 mL H2O respectively; the control of polymerization could be improved with the presence of catalyst and increasing the concentration of initiator. The polymerization rate of SET-LRP increased with the amount of catalyst and initiator. In addition, Mn increased with the amount of catalyst or decreasing the amount of initiator and was closed to the theoretical molecular mass. The molecular mass distribution showed a decreasing trend, the minimum was about 1.26. The [Bmim]BF4 ionic liquid was a good solvent to PEBr4 and acryl amide, and the polymers were easily separated from the catalyst.

Key words: Single electron transfer living radical polymerization, Ionic liquid, Star polymer, Acrylamide