2-(Diethyl)aminoethyl Methacrylate as a CO2-Switchable Comonomer for the Preparation of Readily Coagulated and Redispersed Polymer Latexes

CO2 stimuli-responsive polystyrene latexes having a solids content of 27% were prepared in a surfactant-free emulsion polymerization (SFEP) under a CO2 atmosphere, employing only commercially available chemical compounds: styrene, the initiator VA-061, and 0.54 mol % of the CO2-switchable comonomer DEAEMA. The resulting polymer particles are 230-300 nm in diameter and are monodisperse (PDI <= 0.054), as confirmed by DLS, TEM, and SEM. Although they are stable under a CO2 atmosphere, the latexes can be easily destabilized by the bubbling of air through the sample at 40 degrees C, allowing for recovery of the particles by filtration. Recovered polymer particles can be dried to powder and readily redispersed in carbonated water, yielding latexes with very similar zeta-potential and particle size as the original latexes. In addition, the bicarbonate salt of formed during the polymerization has been found to act as a CO2-switchable flocculant, thus, facilitating the coagulation of the latex without altering the properties of the latex after redispersion.