Li Y, Liu L, Liu X, Chen S, Fang Y. Reversibly responsive microemulsion triggered by redox reactions.
J Colloid Interface Sci 2019;
540:51-58. [PMID:
30622058 DOI:
10.1016/j.jcis.2018.12.109]
[Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 12/29/2018] [Accepted: 12/31/2018] [Indexed: 11/29/2022]
Abstract
HYPOTHESIS
Stimuli-responsive surfactants (also known as switchable surfactants) can undergo reversible conversions between active and inactive forms under particular stimuli, affecting surface and interfacial activity, aggregation structure, emulsification and solubilisation. Selenium-containing surfactants are of reversibly redox-responsive. Hence, microemulsions (MEs) stabilized by selenium-containing surfactants should reversibly respond to redox reactions.
EXPERIMENTS
The formation of MEs, consisting of sodium dodecylselanylpropyl sulfate (reduced form, SDSePS-Re) or its oxidized form (SDSePS-Ox), n-butanol, n-heptane, and water, was verified based on a pseudo-ternary phase diagram. Changes in molecular structure between SDSePS-Re and SDSePS-Ox were verified by nuclear magnetic resonance spectrometry and electrospray ionization mass spectrometry. The transition between SDSePS-Re- and SDSePS-Ox -based MEs was systematically characterized through electrical conductivity measurements, cryo-transmission electron microscopy and dynamic light-scattering.
FINDINGS
Both SDSePS-Re and SDSePS-Ox could stabilize the mixture of n-butanol-n-heptane-water to form MEs. A reversible transition between an SDSePS-Re-based ME and the corresponding SDSePS-Ox-based ME was achieved, which was realized by the oxidation of SDSePS-Re with H2O2 and then reduction with N2H4. Compared with SDSePS-Re, SDSePS-Ox has a lower surface activity, resulting in a difference in solubilization capacity of the oil between SDSePS-Re- and SDSePS-Ox -based MEs. After oxidation with H2O2, phase separation could be observed in some SDSePS-Re-based MEs; however, the SDSePS-Re-based MEs could be recovered after reduction of SDSePS-Ox-based MEs with N2H4.
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