CO₂-Responsive Latexes Coagulated by Electric Potential: A Fast and Green Methodology for Emulsion Breaking

In recent years, coagulatable and redispersible polymeric latexes have received increasing attention. This method could provide energy and cost savings when transporting polymeric dispersions or resins. We report two methods to prepare CO2-responsive latexes that are able to be aggregated/broken by passing electric potential (EP) through latex medium (water). In this work, miniemulsion polymerization of methyl methacrylate (MMA) was conducted by using the poly(N,N-dimethylaminoethylmethacrylate)-block-poly(methyl methacrylate) (PDMAEMA-b-PMMA or PDM) copolymer as a CO2-responsive surfactant. The effect of different numbers of DMAEMA in PDMAEMA as a hydrophilic block of PDM on latex particle size and conductivity was studied. By increasing PDMAEMA block length, the average particle size and conductivity of the produced latexes increased. Moreover, polystyrene latex which is prepared by surfactant-free emulsion polymerization, in the presence of low levels of MMA (5 mol %) and 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (VA-061) as the CO2-switchable initiator, yields a narrow particle size distribution. The results showed that EP and CO2 triggers could be successfully used to coagulate and redisperse the synthesized latexes, respectively.