Issue 24, 2015

Phase inversion of ionomer-stabilized emulsions to form high internal phase emulsions (HIPEs)

Abstract

Herein, we report the phase inversion of ionomer-stabilized emulsions to form high internal phase emulsions (HIPEs) induced by salt concentration and pH changes. The ionomers are sulfonated polystyrenes (SPSs) with different sulfonation degrees. The emulsion types were determined by conductivity measurements, confocal microscopy and optical microscopy, and the formation of HIPE organogels was verified by the tube-inversion method and rheological measurements. SPSs with high sulfonation degrees (water-soluble) and low sulfonation degrees (water-insoluble) can stabilize oil-in-water emulsions; these emulsions were transformed into water-in-oil HIPEs by varying salt concentrations and/or changing the pH. SPS, with a sulfonation degree of 11.6%, is the most efficient, and as low as 0.2 (w/v)% of the organic phase is enough to stabilize the HIPEs. Phase inversion of the oil-in-water emulsions occurred to form water-in-oil HIPEs by increasing the salt concentration in the aqueous phase. Two phase inversion points from oil-in-water emulsions to water-in-oil HIPEs were observed at pH 1 and 13. Moreover, synergetic effects between the salt concentration and pH changes occurred upon the inversion of the emulsion type. The organic phase can be a variety of organic solvents, including toluene, xylene, chloroform, dichloroethane, dichloromethane and anisole, as well as monomers such as styrene, butyl acrylate, methyl methacrylate and ethylene glycol dimethacrylate. Poly(HIPEs) were successfully prepared by the polymerization of monomers as the continuous phase in the ionomer-stabilized HIPEs.

Graphical abstract: Phase inversion of ionomer-stabilized emulsions to form high internal phase emulsions (HIPEs)

Article information

Article type
Paper
Submitted
26 Feb 2015
Accepted
08 May 2015
First published
18 May 2015

Phys. Chem. Chem. Phys., 2015,17, 16033-16039

Author version available

Phase inversion of ionomer-stabilized emulsions to form high internal phase emulsions (HIPEs)

T. Zhang, Z. Xu, Z. Cai and Q. Guo, Phys. Chem. Chem. Phys., 2015, 17, 16033 DOI: 10.1039/C5CP01157D

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