Critical phase separation concentration of acrylamide and 2-acrylamido-2-methylpropanesulfonate copolymers in ammonium sulfate aqueous solution and its influence factors

Copolymers of acrylamide (AM) and sodium 2-acrylamido-2-methylpropanesulfonate (AMPSNa) with different compositions and molecular weights were prepared by aqueous RAFT polymerization using S , S '-bis(α,α'-dimethyl-α"-acetic acid) trithiocarbonate (BDMAT) as a RAFT agent. The critical phase separation concentrations (C p *) of these copolymers, termed P(AM-AMPSNa)s, in ammonium sulfate ((NH 4 ) 2 SO 4 ) solution were determined by a turbidimetric method. The effects of molecular weight and monomer composition of P(AM-AMPSNa)s, (NH 4 ) 2 SO 4 concentration, and temperature on C p * were studied in detail. Based on these phase separation characters of P(AM-AMPSNa)s, the mechanism of aqueous RAFT dispersion polymerization of AM/AMPSNa in (NH 4 ) 2 SO 4 aqueous solution was discussed.