Switchable Block Copolymer Surfactants for Preparation of Reversibly Coagulatable and Redispersible Poly(methyl methacrylate) Latexes

Poly(2-(dimethylamino)ethyl methacrylate)-block-poly(methyl methacrylate) (PDMAEMA-b-PMMA) has been used as a surfactant in the preparation of PMMA latexes that can be coagulated and redispersed reversibly. In this work, we investigated in detail the effects of the block copolymer composition on the coagulation/redispersion performance of the latexes. A series of well-defined PDMAEMA-b-PMMA samples that have 10–30 DMAEMA units and 5–45 MMA units were synthesized through a two-step solution RAFT polymerization process and were used as the surfactant in the emulsion polymerization of MMA. PMMA latexes obtained with surfactants having MMA weight fraction (F MMA) < 58.5% were stable. The particle size of the resulting PMMA latexes decreased gradually with the increase of F MMA. The latex particles initially coagulated with a small amount of caustic soda could be repeatedly redispersed into fresh water through CO2 bubbling with ultrasonication and coagulated through N2 bubbling with some heating. The coagulation/redispersion process was repeatable through the CO2/N2 bubbling. The latexes showed excellent redispersibility with the surfactants of F MMA < 46%. With FMMA > 46%, the latex particle sizes could increase over 20% after the coagulation/redispersion process.