Synthesis and solution property of acrylamide-sulfobetaine copolymers

Sulfobetaine 3-[N,N-dimethyl-N-(2-methacryloxylethyl)ammonio]-propane sulfonate (DMAPS) was used to copolymerize with acrylamide (AM) to prepare salt-sensitive copolymers. The optimal reaction conditions, such as initiator concentration, temperature, and reaction time, to achieve the largest weight averaged molecular weight (M_w) and the lowest polydispersity index (PDI) were studied. The reactivity ratios of AM and DMAPS (r₁, r₂) were calculated to be (0.45, 0.84) by the Fineman-Ross method, and (0.47, 0.91) by the Kelen-Tüdös method. The Q-e values of DMAPS were calculated to be (0.30, −0.38). DMAPS was found to be more easily to add into the copolymer than AM to form random copolymers with a slight alternating tendency. Solution rheology and molecular size of the copolymers as a function of M_w were studied in 1 M NaCl solution, a near θ-solution, by rotational rheometer and light scattering methods, respectively. Undisturbed dimension of the copolymers was evaluated according to Stockmayer-Fixman relation.