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    Polyurethane-based nanoparticles as stabilizers for oil-in-water or water-in-oil Pickering emulsions

    Year: 2013

    Journal: Journal of Materials Chemistry, A, 1, 5353-5360, 20130926

    Authors: Chunfeng Ma, Xiaobo Bi, To Ngai, Guangzhao Zhang

    Organizations: Faculty of Materials Science and Engineering, South China University of Technology, Guangzhou, China, Department of Chemistry, The Chinese University of Hong Kong, Shatin, N. T. Hong Kong

    Well-defined polyurethane (PU)-based grafted copolymers with poly(2-(dimethylamino)ethyl methacrylate) (PDEM) side chains were prepared by a combination of radical polymerization and condensation reaction. They can self-assemble in water to form nanoparticles with PU as the core and hydrophilic PDEM chains as the shell. Tuning the pH value of the solutions allowed these nanoparticles to stabilize either oil-in-water (O/W) or water-in-oil (W/O) Pickering emulsions. Stable O/W emulsions were obtained with PU-based nanoparticles in the pH 3–5 or pH 11–12 range due to their better affinity to the aqueous phase. In contrast, changing the pH value to the range of 8–9 significantly changed the stabilizing behavior of the nanoparticles, leading to the formation of stable W/O emulsions. Additionally, the effect of oil polarity on the emulsification behavior of the PU-based nanoparticles was investigated. For highly non-polar oil like n-hexane, only O/W emulsions were generated and the resulting emulsions showed no response to pH change.