Preparation of N2/CO2 triggered reversibly coagulatable and redispersible latexes by emulsion polymerization of styrene with a reactive switchable surfactant.

This work reports the development of a reversibly coagulatable and redispersible polystyrene latex system that can be triggered by N(2)/CO(2). The coagulatability and redispersibility of the latexes were achieved by employing 0.9-5.6 wt % (N-amidino)dodecyl acrylamide (DAm), a reactive switchable surfactant, in an emulsion polymerization of styrene under CO(2) atmosphere. The resulted latex particles were readily coagulated by N(2) bubbling at 60 °C and redispersed by CO(2) bubbling and ultrasonication, which switched amidine moieties between neutral and ionic states. The coagulation/redispersion processes were repeatable. The prepared latexes showed good stabilities against electrolytes, especially with higher charges.