Core cross-linked and pH-responsive particulate emulsifiers from direct chemical preparation of divinylbenzene with P(AA-r-St) macro-CTA

In this study a type of colloidal particles with a cross-linked poly( divinylbenzene) (poly(DVB)) core and a poly( acrylic acid-r-styrene) (PAS) shell were directly prepared by reversible addition-fragmentation chain transfer (RAFT)-mediated cross-linking copolymerization. The particle size, morphology, zeta potential and pH responsibility were studied. The emulsification study showed that PAS-Poly(DVB) colloidal particles were effective particulate emulsifiers when homogenized with various oils including toluene, white oil, isooctyl palmitate, dicaprylyl carbonate, silicone oil, and propylheptyl caprylate. Additionally, the emulsification performance of PAS-Poly(DVB) colloidal particles at different pH values were investigated. Gelled white oil-in-water high internal phase emulsions (HIPEs) were formed at a high oil volume fraction of 80% when the colloidal particles were flocculated at low pH value. The addition of base can trigger the demulsification of the HIPEs, exhibiting a pH-responsive behavior. The effects of oil phase volume fraction on emulsion rheological properties were investigated. Both the emulsion viscosity and storage modulus (G') progressively increased with the increasing of oil phase volume fraction. These results suggest that our work provides a convenient and feasible way to prepare effective particulate emulsifiers via the direct chemical reaction, and the PAS-Poly(DVB) colloidal particles have promising potential application in the oil industry and preparation and exploitation of smart materials. (C) 2016 Elsevier B.V. All rights reserved.