Acrylamide homopolymers and acrylamide- n -isopropylacrylamide block copolymers by atomic transfer radical polymerization in water

摘要

Atomic transfer radical polymerization (ATRP) of acrylamide has been accomplished in aqueous media at room temperature. By using methyl 2-chloropropionate (MeClPr) as the initiator and tris[2-(dimethylamino)ethyl] amine (Me _6TREN)/copper halogenide (CuX) as the catalyst system, different linear polyacrylamides with apparent molecular weights up to <150 000 g/mol were synthesized with dispersities as low as 1.39. The molecular weights agreed well with the theoretical ones at relatively low-medium monomer/initiator ratios (>700:1). Initial chain extension experiments (isolated macroinitiator) resulted in a polymer with bimodal distribution. However, in situ chain extension experiments, carried out by addition of a second fresh batch of monomer to the reaction mixture, confirmed the living nature of the polymerization. By adding a fresh batch of monomer to a linear macroinitiator (M _n = 22-780 g/mol, PDI = 1.42) in solution, an increase in the molecular weight up to 30-220 g/mol (PDI = 1.64) was observed. In addition, linear polyacrylamides were used as macroinitiators for the synthesis of block copolymers polyacrylamide-b-poly(N-isopropylacrylamide).