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pH-Responsive Poly(dimethylsiloxane) Copolymer Decorated Magnetic Nanoparticles for Remotely Controlled Oil-in-Water
Jing Yang1, Xian Jun Loh1, Beng Hoon Tan1
1Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore, 138634, Singapore.
Abstract:
A smart and recyclable oil absorber based on pH-responsive block copolymer modified magnetic nanoparticles is constructed for effective separation of oil-in-water emulsions. Superparamagnetic iron(III) oxide (Fe3 O4 ) nanoparticles are designed as the core materials for providing the separation force, and surface modification with poly(4-vinylpyridine-b-dimethyl siloxane-b-4-vinylpyridine) (P4VP-PDMS-P4VP) block copolymer is performed to supply switchable oil wettability. The mean hydrodynamic radius of the nanoparticles increases from 43.8 ± 3.6 to 75.2 ± 5.3 nm when the neutral pH is reduced to 3, due to the protonation and subsequent swelling of P4VP segments at lower pH. The nanoparticles show excellent separation performance and can absorb octadecene up to 78.2 times of their own weight, simply by switching the pH of the oil-in-water emulsion treated with the nanoparticles and using a magnetic field. The different dipole of P4VP-PDMS-P4VP and protonated P4VP-PDMS-P4VP, as confirmed by density functional theory calculations, is responsible for the different oil miscibility and wettability of the nanoparticles.
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