Synthesis of Amphiphilic Copolymers and Their Effects On Rheology of Oil-in-Water Emulsion

In order to acquire stable oil-in-water (O/W) emulsion, two kinds of amphiphilic copolymers were synthesized by grafting poly(styrene-co-maleic anhydride) with 1-naphthylamine-6-sulfonic acid alone (SMANS) or together with methoxypolyethlene glycol (SMANP), and their effects on the emulsification and rheological behaviors of Shengli heavy oil emulsion were investigated. It was found that without emulsifier, it tend to form water-in-oil (W/O) emulsion, rather than O/W emulsion, with even much higher viscosity than that of the crude oil. After addition of amphiphilic copolymers, W/O emulsion converted into O/W emulsion, which remarkably reduced the viscosity and yield stress of the formed emulsion. With SMANP at the concentration of 0.2 %, stable O/W emulsion with the oil volume ratio at 70% was achieved. The electrostatic repulsion and steric hindrance generated by the copolymers are believed to play an important role on the emulsification of oil. With the presence of sulfonate groups, both kinds of copolymers can provide electrostatic repulsion among oil droplets after being adsorped on the surface of oil droplets. While for SMANP, the polyethlene glycol (PEG) pendants offer additional steric hindrance, which further stabilizes the O/W emulsion. Based on those results, the formation mechanism of O/W emulsion by amphiphilic copolymer was proposed.