title: Iron oxide nanoparticles grafted with sulfonated copolymers are stable in concentrated brine at elevated temperatures and weakly adsorb on silica.
abstract: Magnetic nanoparticles that can be transported in subsurface reservoirs at high salinities and temperatures are expected to have a major impact on enhanced oil recovery, carbon dioxide sequestration, and electromagnetic imaging. Herein we report a rare example of steric stabilization of iron oxide (IO) nanoparticles (NPs) grafted with poly(2-acrylamido-2-methylpropanesulfonate-co-acrylic acid) (poly(AMPS-co-AA)) that not only display colloidal stability in standard American Petroleum Institute (API) brine (8% NaCl + 2% CaCl2 by weight) at 90 °C for 1 month but also resist undesirable adsorption on silica surfaces (0.4% monolayer NPs). Because the AMPS groups interacted weakly with Ca(2+), they were sufficiently well solvated to provide steric stabilization. The PAA groups, in contrast, enabled covalent grafting of the poly(AMPS-co-AA) chains to amine-functionalized IO NPs via formation of amide bonds and prevented polymer desorption even after a 40,000-fold dilution. The aforementioned methodology may be readily adapted to stabilize a variety of other functional inorganic and organic NPs at high salinities and temperatures.
authors.affiliation: Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Hitesh G
authors.initials: HG
authors.lastname: Bagaria
authors.forename: Zheng
authors.initials: Z
authors.lastname: Xue
authors.forename: Bethany M
authors.initials: BM
authors.lastname: Neilson
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Worthen
authors.forename: Ki Youl
authors.initials: KY
authors.lastname: Yoon
authors.forename: Susheela
authors.initials: S
authors.lastname: Nayak
authors.forename: Victoria
authors.initials: V
authors.lastname: Cheng
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Bielawski
authors.forename: Keith P
authors.initials: KP
authors.lastname: Johnston