Macromolecular Rapid Communications, Vol.35, No.12, 1148-1152, 2014
pH-Induced Inversion of Water-in-Oil Emulsions to Oil-in-Water High Internal Phase Emulsions (HIPEs) Using Core Cross-Linked Star (CCS) Polymer as Interfacial Stabilizer
A pH-responsive core cross-linked star (CCS) polymer containing poly(N, N-dimethylaminoethyl methacrylate) (PDMAEMA) arms was used as an interfacial stabilizer for emulsions containing toluene (80 v%) and water (20 v%). In the pH range of 12.1-9.3, ordinary water-in-oil emulsions were formed. Intermediate multiple emulsions of oil-in-water-in-oil and water-in-oil-in-water were formed at pH 8.6 and 7.5, respectively. Further lowering the pH resulted in the formation of gelled high internal phase emulsions of oil-in-water type in the pH range of 6.4-0.6. The emulsion behavior was correlated with interfacial tension, conductivity and configuration of the CCS polymer at different pH.