Thermoresponsive Pickering emulsions stabilized by silica nanoparticles in combination with alkyl polyoxyethylene ether nonionic surfactant

Zhu, Yue; Fu, Ting; Liu, Kaihong; Lin, Qi; Pei, Xiaomei; Jiang, Jianzhong; Cui, Zhenggang; Binks, Bernard P.

Abstract

We put forward a simple protocol to prepare thermo-responsive Pickering emulsions. Using hydrophilic silica nanoparticles in combination with a low concentration of alkyl polyoxyethylene monododecyl ether (C12En) nonionic surfactant as emulsifier, oil-in-water (o/w) emulsions can be obtained which are stable at room temperature but demulsified at elevated temperature. The stabilization can be restored once the separated mixture is cooled and re-homogenized, and this stabilization-destabilization behavior can be cycled many times. It is found that the adsorption of nonionic surfactant at the silica nanoparticle-water interface via hydrogen bonding between the oxygen atoms in the polyoxyethylene headgroup and the SiOH groups on particle surfaces at low temperature is responsible for the in situ hydrophobization of the particles rendering them surface-active. De-hydrophobization can be achieved at elevated temperature due to weakening or loss of this hydrogen bonding. The time required for demulsification decreases with increasing temperature and the temperature interval between stabilization and destabilization of the emulsions is affected by the surfactant headgroup length. Experimental evidence including microscopy, adsorption isotherms and three-phase contact angles is provided to support the mechanism.

Citation

Zhu, Y., Fu, T., Liu, K., Lin, Q., Pei, X., Jiang, J., Cui, Z., & Binks, B. P. (2017). Thermoresponsive Pickering emulsions stabilized by silica nanoparticles in combination with alkyl polyoxyethylene ether nonionic surfactant. Langmuir : the ACS journal of surfaces and colloids, 33(23), 5724-5733. https://doi.org/10.1021/acs.langmuir.7b00273

• Journal Article Type: Article
• Acceptance Date: May 16, 2017
• Online Publication Date: May 26, 2017
• Publication Date: Jun 13, 2017
• Deposit Date: May 22, 2017
• Publicly Available Date: May 21, 2018
• Journal: Langmuir
• Print ISSN: 0743-7463
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 33
• Issue: 23
• Pages: 5724-5733
• DOI: https://doi.org/10.1021/acs.langmuir.7b00273
• Keywords: Pickering emulsions; Nanoparticles; Nonionic surfactants
• Public URL: https://hull-repository.worktribe.com/output/451523
• Publisher URL: http://pubs.acs.org/doi/abs/10.1021/acs.langmuir.7b00273
• Additional Information: This is the accepted manuscript of an article published in Langmuir, 2017. The version of record is available at the DOI link in this record.
• Contract Date: May 21, 2018