ARGET ATRP of methyl acrylate with inexpensive ligands and ppm concentrations of catalyst

摘要

A simple and versatile polymerization technique via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) of methyl acrylate (MA) with inexpensive commercially available ligands, including diethylenetriamine (DETA), N,N,N′,N′′,N′′- pentamethyldiethylenetriamine (PMDETA), and tris(2-aminoethyl)amine (TREN), is reported. Catalytic amounts of catalyst were utilized achieving ppm levels of Cu~(II)Br_2/L in the presence of a zerovalent copper metal (i.e., copper powder or wire) at 25 °. High molecular weight poly(methyl acrylate) (PMA) could also be obtained with M_n > 1.5 million and M_w/M_n ～ 1.25. A "map" was generated, illustrating minimal catalyst concentrations (i.e., copper and ligand) required over a range of targeted degrees of polymerization with various ligands. Several conclusions were made: (1) lower catalyst concentrations require higher targeted degrees of polymerization to produce equally controlled polymerizations, (2) higher catalyst concentrations are necessary for lower targeted degrees of polymerization, to ensure every activation-deactivation cycle adds fewer monomer units, (3) catalyst performance decreased from Me _6TREN > TREN > PMDETA > DETA, and (4) degrees of polymerization ≥1000 exhibited a catalyst concentration boundary, which required higher Cu~(II)Br_2/L catalyst concentrations to produce similarly controlled polymerizations. Successful chain extension of a PMA macroinitiator demonstrated excellent chain-end functionality and living character.