Ultrafast SET-LRP of hydrophobic acrylates in multiphase alcohol–water mixtures

Abstract

A solution of a hydrophobic nonpolar acrylate such as n-butyl acrylate (BA) in a large diversity of alcohols is immiscible with a solution containing tris(2-dimethylaminoethyl)amine (Me₆-TREN) and Cu(II)Br₂ in water. Addition of NaBH₄ to this biphasic mixture reduces instantaneously the Cu(II)Br₂ to red Cu(0). When a biphasic mixture containing an alcohol, Me₆-TREN, methyl 2-bromopropanoate (MBP), Cu(II)Br₂ and water was combined with NaBH₄ in an inexpensive test tube at 25 °C under a blanket of N₂, an ultrafast single electron transfer-living radical polymerization (SET-LRP) of the hydrophobic monomer in a two- or three-phase reaction mixture took place. First order kinetics up to 100% monomer conversion in less than 20 min with narrow molecular weight distribution of the resulting polyacrylate were observed regardless of the rate of the polymerization. The rate of this SET-LRP can be mediated both by the ratio between alcohol and water and by the ratio between Cu(II)Br₂ and NaBH₄. At the end of the polymerization all Cu(II)X₂ is available only in the water phase that can be isolated leading to colorless polymers that are virtually free of any copper. This new multiphase polymerization methodology provides access to the synthesis of hydrophobic nonpolar polyacrylates by SET-LRP.