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/CO2. 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 CO2 atmosphere. The resulted latex particles were readily coagulated by N-2 bubbling at 60 degrees C and redispersed by CO2 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.