| Abstract
| - Atom transfer radical polymerization (ATRP) of acrylamide has been carried out in wateror in glycerol−water (1:1 v/v) medium at 130 °C using water-soluble initiators, viz. 2-chloropropionamide(2-Cl-PA) or 2-bromopropionamide (2-Br-PA) and CuX (X = Cl, Br) bipyridine complex as catalyst.Extraneous addition of CuX2 (20 mol % of CuX) and/or excess X- ions (1 M alkali halide) in the reactionmixture helps to reduce molecular weight polydispersity (PDI). However, even under the best conditions(using both CuX2 and X- ion additives), the PDI is high, ca. 1.6−1.7. Also, the GPC traces show shoulders.The chain extension experiment, however, confirms the living nature of the polymers. Replacement ofglycerol−water with water as the medium results in sluggish polymerization. The ln M0/M vs t plots arecurved to start with but become linear after polymerization proceeds to variable extents depending onthe additives used. The molecular weights tend to agree with the theoretical values as conversion increases.A method of selecting the appropriate ligand for ATRP has been proposed on the basis of the premisethat a high rate of deactivation is one of the primary requirements for ATRP to succeed. A relative measureof the deactivation rate for various ligands has been obtained from the molecular weights (GPC) of polymersformed in a CuX2Lx deactivated polymerization initiated by an azo initiator at 90 °C. A ligand that leadsto the highest deactivation rate has been proposed to be chosen.
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