Smart Emulsions Stabilized by a Multi‐headgroup Surfactant Tolerant to High Concentrations of Acids and Salts
Wanqing Zhang, Bernard P. Binks, Jianzhong Jiang, Zhenggang Cui
Abstract
Abstract Retaining emulsions stable at high acidity and salinity is still a great challenge. Here, we report a novel multi‐headgroup surfactant (C 3 H 7 −NH + (C 10 COOH) 2 , di‐UAPAc) which can be reversibly transformed among cationic, anionic and zwitterionic forms upon pH variation. Stable oil‐in‐dispersion (OID) emulsions in strong acidity (pH=2) can be co‐stabilized by low concentrations of di‐UAPAc and silica nanoparticles. High salinity at pH=2 improves the adsorption of di‐UAPAc on silica particles through hydrogen bonding, resulting in the transformation of OID emulsions into Pickering emulsions. Moreover, emulsification/demulsification and interconversion between OID and Pickering emulsions together with control of the viscosity and droplet size can be triggered by pH. The present work provides a new protocol for designing surfactants for various applications in harsh aqueous media, such as strong acidity and high salinity, involved in oil recovery and sewerage treatments.