Abstract Porous MXene-polymer composites have gained attention due to their low density, large surface area, and high electrical conductivity, which can be used in applications such as electromagnetic interference shielding, sensing, energy storage, and catalysis. High internal phase emulsions (HIPEs) can be used to template the synthesis of porous polymer structures, and when solid particles are used as the interfacial agent, composites with pores lined with the particles can be realized. Here, we report a simple and scalable method to prepare conductive porous MXene/polyacrylamide structures via polymerization of the continuous phase in oil/water HIPEs. The HIPEs are stabilized by salt flocculated Ti 3 C 2 T x nanosheets, without the use of a co-surfactant. After polymerization, the polyHIPE structure consists of porous polymer struts and pores lined with Ti 3 C 2 T x nanosheets, as confirmed by scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. The pore size can be tuned by varying the Ti 3 C 2 T x concentration, and the interconnected Ti 3 C 2 T x network allows for electrical percolation at low Ti 3 C 2 T x loading; further, the electrical conductivity is stable for months indicating that in these composites, the nanosheets are stable to oxidation at ambient conditions. The polyHIPEs also exhibit rapid radio frequency heating at low power (10 °C s −1 at 1 W). This work demonstrates a simple approach to accessing electrically conductive porous MXene/polymer composites with tunable pore morphology and good oxidation stability of the nanosheets.
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Polymer particles armored with cobalt oxide nanosheets for the catalytic degradation of bisphenol A
2D particle surfactants are attractive for the formation of highly stable emulsions and use as templates to prepare composite structures with performance properties dependent on the composition. Cobalt oxide nanosheets (CONs) are a relatively understudied class of 2D particle surfactants that can be produced by the chemical exfoliation of lithium cobalt oxide, a transition metal oxide known for excellent gas-sensing, catalytic, and electrochemical properties. Here, we report a simple method to access CONs stabilized oil-in-water Pickering emulsions and use these as templates to prepare particles with a core of polymer and shell of CONs. Salt-flocculated CONs produce emulsions with droplets of hydrophobic monomer ( e.g. , styrene) in water that are stable for at least 24 hours, and suspension free radical polymerization is used to produce CON-armored particles. Characterization by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) confirmed the presence of CONs on the surface of the polymer core. We then demonstrated the CON-armored polymer particles can activate the oxidant peroxymonosulfate (PMS) for the degradation of bisphenol A (BPA). Freshly prepared and artificially aged CON-armored particles showed full degradation of BPA in less than an hour and no decrease in activity was observed after two uses. CON-armored particles combine high surface area of the nanosheets with the ease of recoverability of the particles.
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- Award ID(s):
- 1808406
- NSF-PAR ID:
- 10350414
- Date Published:
- Journal Name:
- Materials Advances
- Volume:
- 3
- Issue:
- 5
- ISSN:
- 2633-5409
- Page Range / eLocation ID:
- 2354 to 2363
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Stable poly(styrene-co-2-ethylhexyl acrylate) latex particles with diameter less than 600 nm were prepared by the miniemulsion polymerization of Pickering emulsions stabilized with hexyl-functionalized cellulose nanocrystals (CNC-hexyl-COOHs). Polymer nanocomposites were fabricated by casting of the CNC-stabilized latex particles, and the thermomechanical properties and microstructures of the films were studied and related to the type and amount of stabilizer as well as the processing conditions. Compared to the latex films stabilized with low-molecular-weight sodium dodecyl sulfate (SDS) surfactant, or using a combination of SDS and carboxylic acid CNC-COOHs, films stabilized solely with the alkyl-functionalized CNC-hexyl-COOHs showed much higher storage moduli in the rubbery regime and lower water uptake. Scanning electron microscopy (SEM) revealed a CNC network structure that is formed by excluded volume effects of the latex particles, which concentrates the CNC-hexyl-COOHs into the interstitial space during solvent evaporation. This effect results in the formation of a percolation network at a lower CNC concentration within the latex composite films. The network can be further reinforced by increasing the concentration of CNCs through an “ex situ” process where CNC-hexyl-COOH-stabilized latex particles were mixed with CNC-COOH aqueous dispersions before film casting. The ability to replace low-molecular-weight surfactants in water-based latexes with alkyl-functionalized CNCs that are not only biosourced but also act as reinforcing agents offers an opportunity to expand the property profile of a variety of commercial products such as paints, coatings, and adhesives.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1MA00832C
