due to their mechanical flexibility in volume and shape requirement, high power density, rapid charge/discharge rate, long cycle lifetimes, and remarkable stitchability. [1][2][3][4][5][6][7][8] However, one of the key challenges of the FSCs in the light of their practical applications is to increase their volumetric energy density to the value approaching to or even exceeding those of microbatteries without sacrificing the power density, cycle life, and other performance para meters. [9][10][11][12][13][14][15] Both the energy and power density of a SC is strongly dependent on the operating voltage, that is, V 2 (E = 1/2 CV 2 and P = V 2 /4R ESR , where C is the capacitance of the device, V is the operating voltage, and R ESR is the equivalent series resistance). [16][17][18][19][20][21][22][23][24][25] Therefore, increasing the voltage window would be an effective approach to achieve highefficiency FSCs.To this end, enormous efforts have been devoted to the fabrication of asymmetric FSCs (AFSCs) which make full utilization of the operational windows of both the positive and negative electrode materials. [25][26][27][28][29][30][31][32] Nevertheless, the intrinsic characteristic voltage of water splitting (1.23 V) means that an aqueous electrolyte is limited to a potential domain of around 1 V, thus constraining the operating voltage to a maxi mum of 1.8-2.0 V, [28][29][30][31][32][33] which is indeed lower than that of Fiber supercapacitors (FSCs) represent a promising class of energy storage devices that can complement or even replace microbatteries in miniaturized portable and wearable electronics. One of their main limitations, however, is the low volumetric energy density when compared with those of rechargeable batteries. Considering the energy density of FSC is proportional to CV 2 (E = 1/2 CV 2 , where C is the capacitance and V is the operating voltage), one would explore high operating voltage as an effective strategy to promote the volumetric energy density. In the present work, an all-solid-state asymmetric FSC (AFSC) with a maximum operating voltage of 3.5 V is successfully achieved, by employing an ionic liquid (IL) incorporated gel-polymer as the electrolyte (EMIMTFSI/PVDF-HFP). The optimized AFSC is based on MnO x @TiN nanowires@carbon nanotube (NWs@CNT) fiber as the positive electrode and C@TiN NWs@CNT fiber as the negative electrode, which gives rise to an ultrahigh stack volumetric energy density of 61.2 mW h cm −3 , being even comparable to those of commercially planar lead-acid batteries (50-90 mW h cm −3 ), and an excellent flexibility of 92.7% retention after 1000 blending cycles at 90°. The demonstration of employing the ILs-based electrolyte opens up new opportunities to fabricate high-performance flexible AFSC for future portable and wearable electronic devices.
The supramolecular polymer hydrogels feature self-healability, adjustable mechanical strength, and thermoplasticity, which are derived from the formation of supramolecular physical interactions in the hydrogel networks, such as H-bonding interactions, [6] host-guest interactions, [7] metal-ligand coordination interactions, [8] hydrophobic interactions, [9] multiple combined interactions. [10] Among them, H-bonds are generally weak noncovalent bonds, ubiquitous in biomolecules, but their synergistic interactions can reach a strength of the covalent bond; thus it is commonly utilized in designing supramolecular tough hydrogels. [11] Our previous study suggested that supramolecular polymer hydrogels based on single amide H-bonding interaction were unstable in water, [12] because the competitive solvation of H-bond donor and acceptor in polar solvents weakens its strengthening effect. [13] Inspired by the hydrogen-bonded clusters in the secondary structure of proteins, we constructed a supramolecular poly(N-acryloyl glycinamide) (PNAGA) hydrogel whose dual amide motifs in the side chain contributed to high strengths and outstanding antiswelling ability due to strong shielding of the hydrogen-bonded microdomains from water molecule attack. [12] By utilizing Type II photoinitiated self-condensing vinyl polymerization of N-acryloyl glycinamide (NAGA), the resultant hyperbranched PNAGA hydrogels demonstrated superior mechanical performances to those of linear PNAGA counterparts owing to the higher cross-linking density of H-bonds. [14] In addition, the H-bonding interactions of dual amide motifs could also be modulated by copolymerizing other monomers, [15][16][17][18] thus achieving the versatile hydrogels with mechanical properties spanning from high strength to soft injectability, which show promising applications as 3D printed osteochondral regeneration scaffold, [16] artificial vitreous body, [17] and postoperative antiadhesion barrier. [18] Our recent study revealed that only introducing one methyl group to the double bond of NAGA could lead to a considerable decrease in mechanical strengths and an increase in room temperature autonomous self-healability of the poly(N-methacryloyl glycinamide) hydrogels (MNAGA), which was resulted from the perturbation of one methyl substitution to H-bonds. [19] The intermolecular H-bonding density heavily influences the gelation and rheological behavior of hydrogen-bonded supramolecular polymer hydrogels, thus offering a delicate pathway to tailor their physicochemical properties for meeting a specific biomedical application. Herein, one methylene spacer between two amides in the side chain of N-acryloyl glycinamide (NAGA) is introduced to generate a variant monomer, N-acryloyl alaninamide (NAAA). Polymerization of NAAA in aqueous solution affords an unprecedented ultrasoft and highly swollen supramolecular polymer hydrogel due to weakened H-bonds caused by an extra methylene spacer, which is verified by variabletemperature Fourier transform infrared (FTIR) spectroscopy and s...
We hereby report a strategy to synthesize sequence-regulated substituted polyacetylenes using living anionic polymerization of designed monomers, that is, 2,4-disubstituted butadienes. It is found that proper substituents, such as 2-isopropyl-4-phenyl, lead to nearly 100% 1,4-addition during the polymerization, thus, giving product with high regioregularity, precise molecular weight, and narrow molecular weight distribution. The product is convertible into sequence-regulated substituted polyacetylene by oxidative dehydrogenation using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Block copolymers containing polyacetylene segment are also prepared. Owing to the versatility of the anionic reactions, the present strategy can serve as a powerful tool of precise control on polymer chain microstructure, architecture, and functionalities in the same time.
Substituted polyacetylenes with alkylphenyl side groups and head-to-head regioregularity were prepared through anionic living polymerization of template monomers and subsequent dehydrogenation process. The template monomers have the structure of 2,3-disubstituted-1,3butadienes prepared by palladium-catalyzed Kumada coupling of the corresponding vinyl bromides. Anionic polymerizations of the template monomers produced narrow disperse substituted polybutadiene precursors with exclusive 1,4-enchainment. The precursors were converted into soluble polyacetylene derivatives via two methods, e.g., bromination followed by elimination of HBr, and direct dehydrogenation by 2,3-dichloro-5,6dicyano-1,4-benzoquinone (DDQ), both resulting in dark colored products with significant red shift in UV spectra. The obtained head-to-head polyacetylene derivatives exhibited highly thermal stability, possibly due to trans-rich and/or head-to-head chain configurations. The microstructures of the poly(2,3-dialkylphenyl butadiene) precursors were analyzed in detail using NMR spectroscopy with regard to the solvent effect during polymerization. Block copolymers containing substituted polyacetylene segments were prepared through sequential anionic polymerization of different monomers, followed by dehydrogenation transformation. The present synthesis may serve as a new strategy for tailoring molecular structures of polyacetylene-based polymers by virtue of anionic living polymerization techniques.
underway to construct hydrogel materials into different shapes such as 3D, [5] 2D, [6] or fiber-like configurations, [7] wherein hydrogel fibers as a novel type of materials cast great impact on our daily life, ranging from smart textile, [8] conductor to functional reinforcements. [9] Compared with 3D and 2D hydrogels, fiber-like hydrogel, also known as 1D hydrogel fiber, always possess smaller cross-sectional areas, [10] which means such thin hydrogel fibers would bear more significant tensile force under the same load, leading to a higher standard on the mechanical properties for engineering 1D hydrogel fibers.With the synergistic effect of covalent and reversible bonds including hydrogen bonds, [11] hydrophobic interactions, [12] ionic bonds, and host-guest interactions, [13] a variety of hydrogel fibers with great mechanical properties have been developed, such as artificial spider silk with twisted core-sheath hydrogel fibers (tensile strength of 895 MPa and strain of 44.3%), [14] ultrastretchable fibers (tensile strength of 5.6 MPa and strain of 1180%), [9] and supramolecular fibers (tensile strength of 193 MPa and strain of 36%). [15] Despite their excellent mechanical properties, those hydrogel fibers are fabricated by manual drawing from the hydrogel, limiting their practical applications where scaled-up manufacture of fibers is required.To satisfy the demand of scaled-up production, the eligible hydrogel fibers are anticipated to be manufactured on a large scale via spinning process, including electrospinning, [16] extrusion spinning, [17] microfluidic or draw-spinning process. [18] For example, Ju et al. developed a hydrogel microfiber based on a continuous draw-spinning process, and the resulting fibers exhibited tensile stress of 1.4 MPa. [19] Song et al. spun a transparent hydrogel fiber possessing tensile stress of 200 kPa. [20] It should be noted that, as for spinning those hydrogel fibers, relatively low crosslinking density is often essential to a spinning solution due to the large deformation required during the spinning process and the requirements for spinning long and uniform hydrogel fibers, [19] which, in turn, leads to unsatisfied mechanical properties of the final spun hydrogel fibers.
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