Porous hydrogels templated from soy-protein-stabilized high internal phase emulsions
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Porous hydrogels templated from soy-proteinstabilized high internal phase emulsions Xuehui Gong1, Kristen Rohm2, Zihang Su1, Boran Zhao1, Julie Renner1, Ica Manas-Zloczower2, and Donald L. Feke1,* 1
Department of Chemical and Biomolecular Engineering, Case Western Reserve University, A.W. Smith Building, 2102 Adelbert Rd, Cleveland, OH 44106, USA 2 Department of Macromolecular Science and Engineering, Case Western Reserve University, Kent Hale Smith Building, 2100 Adelbert Rd, Cleveland, OH 44106, USA
Received: 31 May 2020
ABSTRACT
Accepted: 23 August 2020
Porous hydrogels with controlled morphology were successfully prepared from polymerizing soy-protein-isolate (SPI)-stabilized high internal phase emulsions (HIPEs). The ability of SPI to act as a surfactant in an oil-in-water HIPE containing acrylic acid or acrylamide monomer was investigated. The void and window sizes in the polyHIPEs were tailored by adjusting SPI and/or monomer concentration. Ultrasonication treatment was applied to vary the physical properties of the SPI. Although this treatment weakens the emulsifying efficiency of SPI, the HIPEs were stable enough to create polyHIPEs with larger pores and windows than polyHIPEs from untreated counterparts. The formation of polyHIPEs with interconnected, open-cell morphologies indicated that SPI is not a typical Pickering emulsifier. The performance of the hydrogels to capture heavy metal (e.g. lead (II)) ions was also explored. The highly interconnected polyHIPE structure with large voids revealed an enhanced absorption behavior compared with non-porous hydrogels.
Published online: 16 September 2020
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
Handling Editor: Catalin Croitoru.
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10853-020-05261-7
17285
J Mater Sci (2020) 55:17284–17301
GRAPHIC ABSTRACT
Introduction Hydrogels are materials with significant importance for energy storage [1], transportation [2], tissue engineering [3] and adsorption [4] applications. Hydrophilic functional groups on the polymer backbone lend hydrogels the ability to absorb and retain a large amount of water [5]. Introducing porosity to hydrogels increases the amount of retainable water per volume of material, which enables porous hydrogels to be widely used for drug delivery [6] as well as sorbents for contaminants like heavy-metal removal from water [7, 8]. Freeze-drying [9], self-assembly [10, 11] and emulsion formation [12, 13] have been explored as effective approaches to produce porous hydrogels. Templating a highly porous solid via oil-in-water high internal phase emulsion (HIPE) polymerization [14–16] has been shown as an easy and scalable way to generate hydrogels with very high porosity. HIPEs are colloids formed by the mixing of two immiscible phases. An internal phase with a volume fraction higher than 74% [17] is dispersed as droplets
in the continuous phase. Typically, the emulsion requires surfactants to stabilize the high surface area between th
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