title: 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 by1H 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.
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Shandong University , Jinan, Shandong 250100, People's Republic of China.
authors.forename: Gaihuan
authors.initials: G
authors.lastname: Ren
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Shandong University , Jinan, Shandong 250100, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Shandong University , Jinan, Shandong 250100, People's Republic of China.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Department of Chemical and Materials Engineering, University of Alberta , Edmonton, Alberta T6G 2 V4, Canada.|Institute of Nuclear and New Energy Technology, Tsinghua University , Beijing 1000084, People's Republic of China.
authors.forename: Zhenghe
authors.identifier: 0000-0001-8118-1920
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Shandong University , Jinan, Shandong 250100, People's Republic of China.
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Shandong University , Jinan, Shandong 250100, People's Republic of China.
authors.forename: Dejun
authors.identifier: 0000-0003-0841-1501
authors.initials: D
authors.lastname: Sun