Synthesis of Triblock Copolymers via RAFT Polymerization and Their Application as Surfactants for Crude Oil-in-Water Emulsion

As surfactants for crude oil emulsions, poly­[N,N-(dimethylamino) ethyl methacrylate-b-poly­(ethylene glycol) methyl ether methacrylate-b-lauryl methacrylate] (PDMA-b-PPMA-b-PLMA) triblock copolymers were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization and characterized by gel permeation chromatography and proton nuclear magnetic resonance spectroscopy. The copolymers exhibited high interfacial activity which could be tuned by simply adjusting the solution pH, and remarkably reduced the dodecane/water interfacial tension from 52.8 to 2.1 mN/m, producing stable dodecane-in-water emulsions even at a low concentration of 0.5 mg·mL–1. Utilization of these copolymers in Shengli crude oil further confirmed their emulsification capacity. The apparent viscosity of crude oil reduced from 34 000 to 350 mPa·s after emulsification at 20 °C, and the formed emulsions exhibited long-term stability for above 3 months. Due to the balanced hydrophilicity and hydrophobicity, PDMA22-PPMA27-PLMA36 proved to be the most efficient surfactant, which generated stable O/W emulsion with the smallest dosage.