Novel Pickering Emulsifiers Based on pH-Responsive Poly(2-(diethylamino)ethyl methacrylate) Latexes

Abstract

Emulsion copolymerization of 2-(tert-butylamino)ethyl methacrylate in the presence of divinylbenzene (DVB) cross-linker and monomethoxy-capped poly(ethylene glycol) methacrylate (PEGMA) macromonomer at 70 °C afforded sterically-stabilized latexes at approximately 10% solids at pH 9. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) confirmed that relatively narrow size distributions were obtained. SEM confirmed the formation of spherical particles in the absence of any DVB cross-linker using a simple batch protocol, but in the presence of DVB it was necessary to use seeded emulsion polymerization under monomer-starved conditions to prevent the formation of latexes with ill-defined non-spherical morphologies. Lightly cross-linked latexes acquired cationic microgel character upon lowering the solution pH, as expected. Increasing the degree of cross-linking led to a progressively lower effective pK a of the copolymer chains from 8.0 to 7.3, which implies a gradual reduction in their basicity. Poly(tert-butylamino)ethyl methacrylate latex proved to be an effective Pickering emulsifier at pH 10, forming stable oilin-water emulsions when homogenized with either n-dodecane or sunflower oil at 12 000 rpm for 2 min. These Pickering emulsions exhibited pH-responsive behavior: lowering the solution pH to pH 3 resulted in immediate demulsification due to spontaneous desorption of the cationic microgels from the oil/water interface. With subsequent rehomogenization at high pH, four successive demulsification/emulsification pH cycles could be achieved without discernible loss in performance. However, no demulsification occurred on acidification of the fifth cycle.

CO2-responsive polymeric materials: synthesis, self-assembly, and functional applications

“…193 The particles were zwitterionic in nature because of the presence of oppositely charged DEAEMA and SMA. 17 Instead, when CO 2 was performed for the switching on process and N 2 for the switching off process, no significant reduction in the size of the particles was detected even after 10 cycles. Switching on and off cycles were performed at room temperature with relatively fast response to the triggers.…”

“…11 The initiator-derived endgroups on each polymer chain, bearing an imidazole moiety, were protonated by CO 2 and provided stabilization of the latex particles. 17,193 DEAEMA and DMAEMA are both prone to hydrolysis, specifically at high temperatures and high pH. Therefore, the total amount of charge available for particle stabilization was limited, with the result being the solid content could not be increased to more than B7%.…”

“…193 The crosslinked polymer particles were prepared via surfactant-free emulsion polymerization (SFEP) of DEAEMA and sodium methacrylate (SMA) as a stabilizer in the presence of N,N-methylenebis(acrylamide) (MBA) crosslinker. 17 Polymerization was performed at 70 1C using monomethoxy-capped poly(ethylene glycol) methacrylate (PEGMA) as a reactive stabilizer. Bubbling CO 2 led to the dissolution of particles while bubbling N 2 induced their precipitation.…”

pH‐Responsive Non‐Ionic Diblock Copolymers: Ionization of Carboxylic Acid End‐Groups Induces an Order–Order Morphological Transition

“…This may be important if repeated pH cycling is required, as the otherwise problematic accumulation of background salt is minimized. [11] It is also shown that a pH switch can induce an irreversible vesicle-to-worm morphological transition. This work represents an important new paradigm for pH-induced morphological transitions exhibited by block copolymer nano-objects.…”

Mineralization and drug release of hydroxyapatite/poly( l -lactic acid) nanocomposite scaffolds prepared by Pickering emulsion templating

“…The fabrication procedure involves first preparing a Pickering emulsion and then solidifying the emulsion continuous phase. Pickering emulsion is a solid particle-stabilized emulsion [26][27][28][29][30][31][32], where solid particles are nearly irreversibly adsorbed at liquid-liquid interfaces and act as a barrier against coalescence making the resulted emulsions extremely stable [33][34][35][36]. Thus, Pickering emulsion templates are stable enough to maintain the designed porous structures in the fabrication procedure.…”