Trifunctional ambidextrous surfactants for latexes in supercritical CO2 and water

Trifunctional poly(dimethylsiloxane) (PDMS) block copolymers PDMS-b-poly(te rt-butyl acrylate (tBA)-co-acrylic acid (AA)), PDMS-b-poly(methyl methacryl ate), PMMA-b-PAA, and PDMS-b-P(MMA-co-methyacrylic acid (MA)) were synthesi zed and utilized to stabilize PMMA latexes in both nonpolar (CO2) and polar (water) solvents. Submicron PMMA particles synthesized by dispersion polym erization in supercritical CO2 have been redispersed to form up to 40 wt % stable aqueous latexes. In CO2, the PDMS block provides steric stabilizatio n. Upon transfer to water, the MA or AA groups ionize producing electrostat ic stabilization, while the acrylate group anchors to the PMMA polymer surf ace. In both media, the particle size remained constant, indicating good St abilization without agglomeration. The surfactant is "ambidextrous" in that stabilization is achieved in both CO2 and water and by different mechanism s in each medium. PMMA particles stabilized with a PDMS macromonomer could be transferred to an aqueous solution of sodium dodecyl sulfate in water to produce a stable latex.