CO2-Redispersible Polymer Latexes with Low Glass Transition Temperatures

In this work, acrylic latexes are prepared through surfactant-free emulsion polymerization of methyl methacrylate (MMA) and butyl acrylate (BA). CO2-responsive 2-(diethyl)aminoethyl methacrylate (DEAEMA) is used as a co-monomer. The resulting latexes can be easily coagulated by adding a small amount of caustic soda. Once washed, coagulated particles could be redispersed into water to prepare stable latexes with CO2 and ultrasonication. CO2-redispersibility of the latexes is examined as a function of glass transition temperature of the polymers having different MMA/BA ratios. It is found that, while high MMA content latexes are easily CO2-redispersed, it is challenging to re-disperse high BA content latexes. For latex particles with T-g below ambient conditions, coagulation with caustic soda leads to the fusion of individual particles, and the particles are no longer redispersible. This work provides a mechanistic insight and practical guidance for the applicability of CO2-responsive amine-containing molecules (employed as comonomer, initiator, surfactant, and so on) in developing CO2-redispersible latex products.