pH Switchable Emulsions Based on Dynamic Covalent Surfactants

Abstract

Dynamic covalent surfactants were designed to prepare pH switchable emulsions. A dynamic covalent bond between nonamphiphilic building blocks (polyethylenimine (PEI) and benzaldehyde (B)) was introduced to form the dynamic covalent surfactant PEI-B. The dynamic nature of covalent bond in PEI-B was confirmed by H NMR and fluorescence probe analysis. Stable emulsions were successfully prepared with interfacial active PEI-B at pH 7.8 with various water/paraffin oil ratios under sonication. When lowering the pH to 3.5, a complete phase separation was observed as a result of breaking dynamic covalent bond in the interfacial active PEI-B. After tuning the pH back to 7.8, stable emulsion was obtained again due to the reformation of the dynamic covalent bond and hence interfacial active PEI-B. The emulsification and demulsification were dependent on the formation and breaking of dynamic covalent bond in PEI-B. Such pH-triggered emulsification and demulsification can be switched at least three times. Application of dynamic covalent surfactants will open up a novel route for preparing responsive emulsions.

Responsive drop method: quantitativein situdetermination of surfactant effectiveness using reconfigurable Janus emulsions

“…changes in droplet size or stability. [12][13][14] In contrast, Janus emulsions, i.e. droplets comprised of two dispersed fluids, have the intrinsic advantage that interfacial tension variations transduce into a change in the internal shape of the droplets whereas the overall emulsion stability remains intact.…”

Temperature‐induced self‐assembly and metal‐ion stabilization of histidine functional block copolymers

“…In some applications, it is acceptable to lock the polymer self‐assemblies permanently; however, the ability to manipulate the self‐assemblies based on external stimuli is a highly attractive reason to instead employ dynamic crosslinking strategies. The use of responsive and highly functional building blocks to make block copolymers allows for their assembly and disassembly, in addition to their changing shapes or sizes based on external stimuli . It has been demonstrated that polymer micelles are more readily uptaken into cells than their unimers, and as a result, acid‐degradable polymers have been a focus in polymer cancer therapy developments .…”

“…The use of responsive and highly functional building blocks to make block copolymers allows for their assembly and disassembly, 18 in addition to their changing shapes or sizes based on external stimuli. 11,19,20 It has been demonstrated that polymer micelles are more readily uptaken into cells than their unimers, 21 and as a result, aciddegradable polymers have been a focus in polymer cancer therapy developments. 15,22 In addition to pH as a stimulus, polyelectrolytes have been used to reversibly lock micelles using electrostatic interactions and electrolytes as stimuli.…”

pH-Responsive Nanoemulsions Based on a Dynamic Covalent Surfactant

“…Responsive emulsifiers have emerged as a class of smart surfactants that permit regulating the emulsion stability under external stimuli [4][5][6][7][8]. The external stimuli include pH [9][10][11][12][13][14][15], CO 2 [6,16], temperature [17], magnetism [8], light [18,19], and redox [7,20]. Among these external stimulation types, pH has attracted particular interest because it has the advantage of being simple to regulate [11,21].…”