CO₂/N₂ triggered switchable Pickering emulsions stabilized by alumina nanoparticles in combination with a conventional anionic surfactant

Xu, Maodong; Zhang, Wanqing; Pei, Xiaomei; Jiang, Jianzhong; Cui, Zhenggang; Binks, Bernard P.

Abstract

Stable n-decane-in-water Pickering emulsions were prepared using positively charged alumina nanoparticles in combination with a trace amount of the anionic surfactant sodium dodecyl sulfate (SDS) as stabilizer. Particles were hydrophobized in situ by adsorption of surfactant enhancing their surface activity. Emulsions can be readily demulsified by addition of an equal amount of a switchable surfactant, N'-dodecyl-N,N-dimethylacetamidine (DDAA), which can be transformed between a surface-active amidinium/cationic form and a surface-inactive amidine/neutral form by bubbling CO₂ or N₂, respectively. Following addition of cationic DDAA which prefers to form ion pairs with SDS, desorption of SDS from particles surfaces occurs and alumina particles are rendered hydrophilic resulting in demulsification of the emulsion. However, by bubbling N₂ into the demulsified mixture, DDAA molecules are converted to the amidine/neutral form leading to collapse of the ion pairs and re-establishment of the in situ hydrophobization of particles. Stable Pickering emulsions can be prepared again following homogenization. This simple demulsification/re-stabilization cycle can be repeated several times. Experimental evidence including measurement of the adsorption isotherm, zeta potentials, extent of particle adsorption at droplets interfaces in emulsions and microscopy is given to support the postulated mechanisms.

Citation

Xu, M., Zhang, W., Pei, X., Jiang, J., Cui, Z., & Binks, B. P. (2017). CO₂/N₂ triggered switchable Pickering emulsions stabilized by alumina nanoparticles in combination with a conventional anionic surfactant. RSC advances, 7(47), 29742-29751. https://doi.org/10.1039/c7ra03722h

• Journal Article Type: Article
• Acceptance Date: May 29, 2017
• Online Publication Date: Jun 7, 2017
• Publication Date: Jun 7, 2017
• Deposit Date: Jun 8, 2017
• Publicly Available Date: Jun 8, 2017
• Journal: RSC advances
• Print ISSN: 2046-2069
• Electronic ISSN: 2046-2069
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 7
• Issue: 47
• Pages: 29742-29751
• DOI: https://doi.org/10.1039/c7ra03722h
• Keywords: Switchable Pickering emulsions
• Public URL: https://hull-repository.worktribe.com/output/452132
• Publisher URL: http://pubs.rsc.org/en/content/articlelanding/2017/ra/c7ra03722h#!divAbstract
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : Jianzhong Jiang (ORCID); : Zhenggang Cui (ORCID); : Bernard P. Binks (ORCID); : The Royal Society of Chemistry has an exclusive publication licence for this journal; OPEN ACCESS: This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0); : Single-blind; : Received 31 March 2017; Accepted 29 May 2017; Version of Record published 7 June 2017