Synthesis and properties of hydrophobically modified acrylamide-based polysulfobetaines

Acrylamide-based, hydrophobically modified polysulfobetaines containing 3-[N-(2-methacroyloylethyl)-N,N-dimethylammonio]-propane sulfonate (DMAPS) and varying amounts of the hydrophobic monomer stearyl methylacrylate (SMA) were synthesized by micellar copolymerization. The basic physico-chemical properties of the synthesized copolymers were studied by means of surface tension, dynamic laser light scattering, and rheological measurements. All the copolymers showed surface activity when the copolymer concentration was above 0.07 wt%. The dynamic laser light scattering measurement revealed that both zwitterionic and hydrophobic associations were important in copolymer aggregation. The rheological properties of the copolymers in aqueous solution depended on the content of hydrophobic monomer, the copolymer concentration and the addition of salt, which were characteristic of hydrophobically modified polyacrylamide and acrylamide-based polyzwitterions. The critical aggregation concentration of the copolymers was in the range of 0.07–0.1 wt%.