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Electron microscopy images of silica nanoparticles in inorganic/organic NC ion gel with SiO2/PDMAAm weight ratio = 0.32. (a) Over view, (b) magnified view, and (c–f) ring-like silica nanoparticle aggregates. The white arrows in the (c) mean primary particles with ca. 3 nm diameter
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We have previously reported tough inorganic/organic nanocomposite (NC) ion gels composed of silica particles and poly(N,N-dimethylacrylamide) (PDMAAm) networks and a large amount of ionic liquid. In this study, the network structure and toughening mechanism of NC ion gels were investigated. The NC ion gels showed characteristic mechanical propertie...
Citations
... However, the IL content of the earliest DN ion gel membranes was limited to~80 wt% because the ILs were impregnated in a DN hydrogel [28], which was used as a template for the preparation of the DN ion gel membrane. In contrast, we recently developed a new class of DN ion gels with an interpenetrating inorganic/organic network, termed inorganic/organic DN ion gels (hereafter simply denoted as DN ion gels) [22,23,[29][30][31], which have the potential to support an increased IL content because of the in situ double-network formation in the IL. ...
To examine the potential of ion gels as materials for CO2 separation membranes, inorganic/organic double-network ion gel (DN ion gel) membranes with different ionic liquid (IL) contents were fabricated. The composition of the inorganic and organic networks was optimized to maximize the mechanical strength of the DN ion gel. The DN ion gel with an inorganic/organic network composition of 0.35 mol/mol showed the maximum mechanical strength because the inorganic and organic networks sufficiently acted as sacrificial bonds and hidden lengths, respectively. Using DN ion gel membranes with different IL contents prepared with the optimized precursor solution, the relationship between the CO2 permeability and IL content of the DN ion gel membranes was examined. The DN ion gel membrane with 95.2 wt% IL had a CO2 permeability of 1380 barrer, which was ~67% of the theoretical maximum predicted for the pure IL membrane. The CO2 permeability of the DN ion gel membrane exponentially increased with increasing IL content and approached the theoretical maximum. DN ion gels with high strength can be used to develop maximum-performance IL-based CO2 separation membranes by giving the membrane the maximum IL potential. The effect of the ionic liquid content in tough inorganic/organic double-network (DN) ion gel membrane on the CO2 permeability was investigated. By optimizing the composition of the inorganic and organic networks, the mechanical strength of the DN ion gel was significantly increased, and the DN ion gel membrane with more than 95 wt% of an ionic liquid was successfully prepared. With the increase in the ionic liquid content, the CO2 permeability of the DN ion gel membrane exponentially increased up to ~67% of the theoretical maximum CO2 permeability.
Ion gels have the potential to be used in a broad range of applications, such as in carbon dioxide separation membranes and soft electronics. However, their low mechanical strength limits their practical applications. In this study, we developed double-network (DN) ion gels composed of TEMPO-oxidized cellulose nanofibers with hydrophobic groups (TOCNF) and cross-linked poly(1-ethyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide (PC 2im-TFSI) networks. The mechanical strength of the gel increased as the amount of TOCNF in the gels increased up to 6 wt%. Moreover, the fracture energy of the DN ion gels with 6 wt% TOCNF was found to be 19 times higher than that of the PC 2im-TFSI single network (SN) ion gels. Cyclic stress-strain measurements of the DN gels showed that the loading energy on the gels dissipates owing to the destruction of the physically cross-linked TOCNF network in the gels. The DN ion gels also exhibited a high decomposition temperature of approximately 400 °C because of the thermal stability of all components. Additionally, 2 the fracture energy of the TOCNF/poly(ionic liquid) (PIL) DN ion gel was two times higher than that of the silica nanoparticles/PIL DN ion gel developed in our previous study [Watanabe et al., Soft Matter 2020, 16, 1572-1581]. This suggests that fiber-shaped nanomaterials are more effective than spherical nanomaterials in enhancing the mechanical properties of ion gels. These results show that TOCNF can be used to toughen PIL-based ion gels and hence broaden their applications.
Compared with conventional polymer gels, nanocomposite gels have significant advantages in strength and temperature resistance. They can adapt to more severe reservoir environments and achieve the purpose of controlling water and increasing oil or temporarily plugging and diverting. Based on nanoparticles used in nanocomposite gels, nanocomposite gels can be divided into silica-based nanocomposite gels, nano-montmorillonite-based nanocomposite gels, layered silicate nanocomposite gels, laponite-based nanocomposite gels, CFA (coal fly ash)-based nanocomposite gels, and other nanocomposite gels. The researcher summarized the materials used in various nanocomposite gels (nanomaterials, main polymers, and crosslinking agents), mechanisms, excellent performance, and analyzed the shortcomings of various nanocomposite gels and current development trends. The results show that the research of nanocomposite gels needs to deal with the high temperature and high salinity oil and gas reservoir environment, and it is necessary to adopt environmentally friendly, easy-to-prepare and cheap materials. At the same time, more numerical simulation studies are needed for theoretical guidance.
Double-network (DN) hydrogel is consist of two intertwined crosslinked networks, with a balanced mechanical performance combining high strength and toughness. In addition to the excellent mechanical properties brought about by the double-network structure, it can also possess good anti-swelling and self-healing properties, laying a good foundation for the application of hydrogels in the environment. Recently, research on the application of double-network hydrogels in the environment has gradually increased. We classify this type of hydrogel in terms of composition and crosslinking methods, and discuss its adsorption mechanism for different environmental pollutants (metal ions, dyes, antibiotics). Finally put forward prospects for the preparation, environmental pollutant removal, and practical application of double-network hydrogels.
