Nanosheets of copolymerized ionic liquid-based polyelectrolyte complexes regulated at oil–water interface and their emulsification capability

• Published in: Journal of industrial and engineering chemistry (Seoul, Korea) Vol. 97; pp. 173 - 179
• Main Authors: Zhang, He, Zhang, Jun Bo, Meng, Qing Bo, Guo, Wei, Yang, Ming, Wu, Shuyao, Wu, Qiong, Liu, Daliang, Song, Xi-Ming
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25-05-2021; 한국공업화학회
• Subjects: Complex; Copolymer; Ionic liquid; Pickering emulsions; Polyelectrolyte; 화학공학; Polyelectrolyte; Pickering emulsions; Copolymer; Complex; Ionic liquid
• ISSN: 1226-086X; 1876-794X
• DOI: 10.1016/j.jiec.2021.02.015

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•An efficient PEC emulsifier is formed by two oppositely charged hydrophilic polyions.•The emulsification capability can be easily adjusted, and the emulsion can be stable for two mouths.•The uncharged comonomer plays an important role for the high emulsification capability of PECs.•Ultrathin PECs nanosheet (10 nm) is formed at the oil–water interface.•Functional groups including ionic liquid can be simply immobilized to the oil–water interface.
The emulsification by polyelectrolyte complexes is easy to handle, and could be considered as an effective strategy for introducing functional materials to liquid–liquid interfaces, but the related studies are still insufficient. Herein, a kind of copolymerized ionic liquid (PIL-co-PVIm) which is synthesized from 1-vinyl-3-ethylimidazolium bromide and 1-vinylimidazole, are used as polycation to form polyelectrolyte complexes type Pickering emulsifiers with sodium alginate, poly(sodium 4-styrenesulfonate) and poly (acrylic acid) sodium salt respectively as polyanion. For toluene-water emulsion systems and hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm]PF6)-water system, the polyelectrolyte complexes formed by PIL-co-PVIm and sodium alginate or poly (sodium 4-styrenesulfonate) showed best emulsification capability. The emulsions stabilized by the polyelectrolyte complexes at stoichiometric ratio are relatively less stable compared to non-stoichiometric complexes, while PIL-co-PVIm without complexation has no emulsification capability. The polyelectrolyte complexes based on homopolymerized PIL give an unsatisfied emulsification capability, while the emulsification performance could be remarkably improved by copolymerizing ionic liquids with the uncharged comonomer, but excessive contents of the uncharged unit make the polyelectrolyte complexes less interface active. The sheet-like PECs are formed in aqueous dispersions, and their thickness is remarkably reduced at oil–water interface after emulsification, approximately ranging from 200 nm to 10 nm by manipulating the polyanion.