Dual Dynamic Covalent Gemini Surfactant for Intensified Release of Drag Reducer via pH Stimulation

The introduction of stimuli-responsive surfactants effectively avoids the contradiction between the stability of the emulsion and the rapid release of the drag reducer, but the single-tailed chain structure limits the storage stability and the release rate of the switching emulsion drag reducer. Adding response sites on gemini surfactants to enhance the release rate of drag reducers and strengthen the storage efficiency of the emulsions is an effective strategy. Herein, a dual dynamic covalently bonded-based gemini surfactant (DF-PEG200/OAC) was synthesized by poly(ethylene glycol) 200 (PEG200), 4-carboxybenzaldehyde (DF), and oleylamine (OAC). The two tails of DF-PEG200/OAC enhanced the stability of the switching emulsion drag reducer and provided sufficient response sites, thereby intensifying the release of the drag reducer. The reorganization and decomposition of the imine bond on DF-PEG200/OAC was realized at different pH, thus endowing the DF-PEG200/OAC-stabilized monomer emulsion with controllable stability. Using the monomer emulsion as the inverse emulsion polymerization template, a switching emulsion drag reducer was obtained without delamination or demulsification within 30 days. When the pH of deionized water is 4.7, the switching emulsion drag reducer was completely dissolved in 30 s. At a concentration of 0.05 wt % of the switching emulsion drag reducer, the drag reduction rate reached 69.64%. We believe that the construction of a switching emulsion is expected to provide a new option for the development of drag reducers.