Comprehensive Summary With the rapid growth of soft electronic and ionotronic devices such as artificial tissues, soft luminescent devices, soft robotics, and human‐machine interfaces, there is a demanding need to accelerate the development of soft ionic conductive materials. To date, the first‐generation ionotronic devices are mainly based on hydrogels or ionogels. However, due to their intrinsic drawbacks, such as freezing or volatilization at extreme temperatures, and the leakage problem under external mechanical forces, the reliability of ionotronic devices under harsh conditions remains a great challenge. The advent of liquid‐free ionic conductive elastomers (ICEs) has the potentials to solve the issues related to the gel‐type soft conductive materials. The free ions shuttling within the ion‐dissolvable polymer network enable liquid‐free ICEs to exhibit unparalleled ionic conductivity and elasticity. Moreover, by tuning the composition and structure of the polymeric network, it is also feasible to integrate other desirable properties, such as self‐healing ability, transparency, biocompatibility, and stimulus responsiveness, into liquid‐free ICE materials. In this review, we summarize the design strategies of recently reported liquid‐free ICEs, and further explore the methods to introduce multifunctionality, which originate from the rational molecular design and/or the synergy with other materials. Moreover, we highlight the representative applications of liquid‐free ICEs in soft ionotronics. It is believed that liquid‐free ICEs might provide a unique material platform for the next‐generation ionotronics.
In article number 1807173, Yu Shrike Zhang and co-workers report the development of an improved tumor-on-a-chip model consisting of a bioprinted hollow, perfusable blood vessel for liquid delivery and a hollow, single end-blinded lymphatic vessel for interstitial fluid draining, hosted in a 3D tumor microenvironment-like hydrogel matrix. This model featuring the biomimetic local microcirculation exhibits well-controlled transport of biomolecules and anti-cancer drugs.
Abstract Harvesting low‐grade waste heat into electrical energy is recognized as a promising solution for sustainable energy supply. In parallel, thermotropic smart windows have emerged as an efficient way to reduce building energy consumption. It is posit that thermotropic smart windows with inherent thermoelectric property may offer unique advantages for practical applications. Herein, the preparation and characterization of a series of ionic hydrogels that exhibit temperature‐sensitive phase transition behavior is reported, which are suitable for both thermotropic smart windows and thermoelectric generators. Notably, the lower critical solution temperature (LCST) of this ionic hydrogels can be feasibly modulated, and the thermoteopic phase transition also induces a sharp increase in their Seebeck coefficient, reaching up to 39.03 mV K −1 with a power factor (PF i ) value up to 0.838 mW m −1 K −2 . A prototype dual functional thermotropic smart window that simultaneously works as an ionic thermoelectric generator is further demonstrated, achieving both efficient phase transition driven by solar heat at ≈26 °C and an energy density up to 250 mJ m −2 . This study offers new opportunity for the development of smart materials that can bridge the gap between thermal comfort and energy sustainability for energy harvesting and smart building applicat.
A series of triangular, shape-persistent arylene–ethynylene macrocycles (AEMs) of related structures were synthesized and studied, with a focus on their mesomorphic behavior in correlation with their chemical structure. Generally, these discotic molecules decorated with flexible side chains demonstrated a propensity to form thermotropic liquid-crystalline (LC) phases. Characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction (XRD), four of the eight investigated macrocycles manifested thermodynamically stable mesophases, featuring discotic nematic or columnar structures. Longer alkyl side chains were found more conducive to mesophases, and the alkoxycarbonyl functionality was a more effective side-chain linkage at inducing and stabilizing the LC states than the alkoxy side group. The size and structure of the cyclic aromatic backbone influenced both the occurrence and type of mesophase exhibited.
A new approach has been developed for the preparation of well-defined, eight-arm star polymers via the addition of poly(styryl)lithium to octavinylPOSS in benzene. The reaction proceeds rapidly to completion (within 5 min for molecular weight of each arm up to 33 kg/mol), forming predominantly eight-arm star polymers. The products were purified by fractionation and fully characterized by 1H NMR, 13C NMR, 29Si NMR, FT-IR, MALDI-TOF mass spectrometry, and size exclusion chromatography. Compared to conventional coupling approaches, this process is found to be less sensitive to the stoichiometry of the reactants and the molecular weight of each arm. A mechanism based on cross-association and intra-aggregate addition is invoked to account for this unusual observation. As evidence, when a polar solvent, tetrahydrofuran, or a strongly coordinating and disassociating Lewis base, tetramethylethylenediamine, was used to dissociate the living polymer chains, star polymers with lower average arm numbers than those of the products synthesized in pure benzene were formed at the same stoichiometry of the reactants. The method has general implications in the understanding of the reactive nature of the living anionic polymerization and may find practical application in the synthesis of functional star polymers of diverse compositions and architectures.
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