Living radical polymerization. II. Improved atom transfer radical polymerization of acrylamide in aqueous glycerol media with a novel pentamethyldiethylenetriamine-based soluble copper(I) complex catalyst system

An improved atom transfer radical polymerization (ATRP) of acrylamide was achieved in a glycerol/water (1:1 v/v) medium with 2-halopropionamide initiators, CuX (X = Cl or Br) as catalysts, pentamethyldiethylenetriamine (PMDETA) as a ligand, and CuX2 ( greater than or equal to20 mol % CuX) and excess alkali halide (ca. 1 mol/dm(3)) as additives. The first-order kinetic plots for the disappearance of the monomer at 130 degreesC were linear; this was a significant improvement over the results obtained earlier with the bipyridine ligand. However, even under such improved situations, about 7 mol % of the polymer chains were estimated to be formed dead. The polydispersity index was approximately 1.5. At a lower temperature (ca. 90 degreesC), a lower polydispersity index (1.24) was obtained for the bromide-based initiating system. Chain-extension experiments proved the living nature of the polymers. The presence of both extra halide ions and the monomer was necessary to take the CuX-PMDETA complex into solution. It was suggested that the soluble Cu(I) complex was formed with one PMDETA molecule acting as a monodentate ligand and with two halide ions and one acrylamide molecule occupying the other three coordination sites. Some support for the involvement of all three ligands (X-, PMDETA, and acrylamide) in the complex formation was obtained from ultraviolet-visible spectroscopy studies. The better ATRP with the PMDETA ligand was attributed to the better stability and lesser hydrolysis of the 1:1 Cu+2/ PMDETA complex with respect the corresponding bipyridine complex. (C) 2004 Wiley Periodicals, Inc.