Atom Transfer Radical Polymerization of <i>N,N</i>-Dimethylacrylamide

Abstract

The polymerization of N,N-dimethylacrylamide (DMA) under atom transfer radical polymerization (ATRP) conditions was studied. The ligand, solvent (water, n-butanol, and toluene), initiator, and Cu halide were varied. High monomer conversions were obtained using the Me4Cyclam ligand. Polymerizations in water that were initiated at room temperature were complete within minutes. However, none of the experimental conditions produced a controlled polymerization. This conclusion is based on broad molecular weight distributions, poor agreement between theoretical and experimental Mn, incremental monomer addition experiments, and end group analysis. We believe that the Cu salts complex to the amide group of the chain ends and stabilize the radical. This stabilization retards the deactivation step in ATRP and produces an unacceptably high concentration of radicals which leads to spontaneous termination reactions. In addition, we have indirect evidence for a cyclization reaction involving nucleophilic Br displacement by the penultimate amide nitrogen; this cyclic onium intermediate undergoes hydrolysis to form a hydroxy-terminated polymer.