Electroconductive hydrogels (ECHs) that integrate gel features and electrochemical properties are considered as promising tissue-like flexible materials important for broad applications. ...Nevertheless, realizing the synergistic features of self-healing capability, conductivity, biocompatibility, stretchability and malleability is challenging. Herein, a novel kind of versatile ECHs built on a borax-crosslinked polyvinyl alcohol (PVA) hydrogel system and conducting PANI@CNF (polyaniline-cellulose nanofiber) nanocomplexes which synergize the conductivity of PANI and the template feature of CNFs is reported. The PANI@CNF nanocomplexes are firstly prepared via in situ polymerization of anilines on CNFs, which are then evenly distributed into borax-crosslinked PVA gel system to fabricate free-standing PANI@CNF-PVA composite ECHs. Sustainable and renewable CNFs serve as flexible biotemplates and mediate the development of PANI into integrated PANI@CNF with good dispersity, enabling the establishment of an integrated conducting and reinforcing network. The dynamic multi-complexation and chain entanglements between PANI@CNF complexes, borax and PVA chains contribute to the development of a hierarchical network structure. The maximum compression stress (∼48.8 kPa) and storage modulus (∼31.5 kPa) of PANI@CNF-PVA hydrogel are about 3.5 and 400 times greater than those of pure PVA gel. These hydrogels also demonstrate appealing biocompatibility, mouldability, pH sensitivity, thermo-reversibility and fast self-healing ability within 15s. The hydrogel-based electrode with a conductivity of ∼5.2 S m−1 shows a maximum specific capacitance of 226.1 F g−1 and a capacitance retention of 74% after 3000 cycles. The integration of such remarkable features enables the promising applications of the as-prepared versatile ECHs in flexible, self-healing and implantable electronic devices.
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•Self-healable and biocompatible electro-conductive hydrogels are synthesized.•Nanostructured PANI@CNF complexes are homogeneously embedded in a viscoelastic PVA network.•Hydrogel-based electrode shows a specific capacitance of 226.1 F g−1 and a capacitance retention of 74% after 3000 cycles.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Glassy polymers are extremely difficult to self-heal below their glass transition temperature (Tg) due to the frozen molecules. Here, we fabricate a series of randomly hyperbranched polymers (RHP) ...with high density of multiple hydrogen bonds, which show Tg up to 49 °C and storage modulus up to 2.7 GPa. We reveal that the hyperbranched structure not only allows the external branch units and terminals of the molecules to have a high degree of mobility in the glassy state, but also leads to the coexistence of “free” and associated complementary moieties of hydrogen bonds. The free complementary moieties can exchange with the associated hydrogen bonds, enabling network reconfiguration in the glassy polymer. As a result, the RHP shows amazing instantaneous self-healing with recovered tensile strength up to 5.5 MPa within 1 min, and the self-healing efficiency increases with contacting time at room temperature without the intervention of external stimuli.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The rapid development of covalent adaptable networks or vitrimers shows promise for addressing the long-standing recycling issues associated with conventional, permanently cross-linked thermosets. At ...the same time, it is important to demonstrate that properties of reprocessable polymer networks can be optimized to meet the ongoing demand for high-performance materials. We have fabricated reprocessable polyhydroxyurethane (PHU) network composites reinforced with reactive polyhedral oligomeric silsesquioxanes (POSS). With functionalized POSS serving as a fraction of the cross-linkers, the PHU–POSS network nanocomposites exhibit significantly enhanced storage modulus at the rubbery plateau region relative to the neat PHU network. With up to 10 wt% POSS loading, these network composites can undergo melt-state reprocessing at 140 °C with 100% property recovery associated with cross-link density. We also show that hydroxyurethane dynamic chemistry leads to excellent creep resistance at elevated temperature up to 90 °C and is unaffected by reactive incorporation of POSS. This study demonstrates the effectiveness of POSS as nanofillers for designing high-performance, organic−inorganic dynamic PHU networks with excellent reprocessability.
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•Dynamic PHU–POSS network composites are made with up to 10 wt% reactive POSS.•PHU–POSS network composites can be melt-reprocessed with 100% recovery of cross-link density.•Improved thermal stability and rubbery plateau modulus relative to the neat PHU network.•Excellent elevated-temperature creep resistance comparable to static networks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Epoxies are widely used in many engineering applications, however, their fracture energy remains less than desired and conventional toughening agents usually lead to compromised tensile strength. In ...this study, a simple one-pot blending method was used, in which both graphene oxide and a block ionomer were blended with epoxy resin. Herein, we reported that increases of ∼200% in fracture energy (GIC), 48% in uniaxial tensile strength (σt) and 340% in tensile strain could be achieved by incorporating 1.0 wt% graphene oxide into an epoxy matrix with 20 wt% sulfonated polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene (SSEBS). In addition, the glass transition temperature (Tg) of the nanocomposite increased with increasing graphene oxide (GO) content and the storage modulus (E′) decreased when the GO content was less than 0.50 wt% owing to the introduction of the block ionomer SSEBS. Careful examination of the nano-morphology of SSEBS revealed that it improved the dispersion of the graphene oxide in and enhanced its interaction with the epoxy matrix, hence simultaneously strengthening and toughening the epoxy resin.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Thermally conductive polymer composites with satisfactory mechanical performances are highly required for practical thermal management applications as thermal interface materials. Herein, ...all-graphitized graphene aerogels with highly aligned graphene network are fabricated with graphene oxide hydrogels as the precursor by directional-freezing followed by freeze-drying and subsequent graphitization at 2800 °C, which exhibit excellent thermal and electrical conductions and superelasticity. Thanks to the vertically aligned conductance network composed by the graphitized graphene sheets, an epoxy composite with only 0.75 vol% of the high-quality graphene exhibits an excellent vertical thermal conductivity of 6.57 W/(mK), which is among the highest through-plane thermal conductivities of polymer composites at similar loading of carbon nanofillers, and more than 37 times higher than that of neat epoxy matrix. The thermally and electrically conductive composite also exhibits greatly improved storage modulus, compressive strength and compressive strain at break.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
3D printing with cementitious materials is an emerging technology and provides an active area of research. Despite this, there are only limited studies that examine the pumping behaviour of high ...yield stress fluids such as printable concrete. We present a study on the rheological behaviour of 3D printable cementitious materials with different aggregate-to-binder ratios (a/b) and analyse the pumping and printing characteristics with the measured rheological parameters. We observed that an increase in a/b resulted in a significant increase of plastic viscosity, and a nominal increase in yield stress and storage modulus. The variation in plastic viscosity and yield stress with increasing aggregate content was analysed with the Krieger-Dougherty and Chateau-Ovarlez-Trung model, respectively. Also, the rheological properties of the paste rich lubrication layer during pumping were determined with the help of a tribometer. The yield stress and viscous constant of the lubrication layer increase with the increase in a/b. The pumping pressure predictions were carried out by a suitable theoretical model by considering appropriate flow conditions for different mixtures. The variation in critical height of printed elements with an increase in a/b was correlated with the observed rheological parameters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Heating altered surface hydrophobicity, ordered structure and SS linked proteins.•Gelation time of GDL tofu was most closely related to the SS bond linked polymer.•Gel firmness and ...the decrease in protein ordered structures were closely related.•Gel viscoelasticity was found to be linked with the surface hydrophobicity.
Optimal heat treatment of the soymilks is important to the production of tofu. In this study, soymilk with protein concentration of 40 mg/mL were heated at different temperatures for the fixed 50 s and were characterized by surface hydrophobicity, disulfide linked protein species determined by non-reducing SDS-PAGE and protein structural elements determined by the circular dichroism (CD). Tofu gels were prepared by acidifying the heated soymilks at 60 ℃ and 80 ℃ respectively and gelation time, gel mechanical properties as well as gel viscoelastic properties were determined by rheological analysis. The results showed that most soymilks’ properties except surface hydrophobicity changed rapidly when heating temperature was higher than 80 ℃. Gelation time, storage modulus (G') at the end of acidifying and cooling processes as well as retardation time (λ) and recovery rate of tofu gels were affected by the heat treatments of soymilks. The distances between the standardized data describing heated soymilks and tofu gels respectively were calculated and compared. It was found that gelation time, G' and λ were most closely related to disulfide bond linked polymer, CD222 and surface hydrophobicity respectively. This study will provide useful information to the improvement of tofu processing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effects of ground granulated blast furnace slag/fly ash (GGBFS/FA) ratio, mass ratio of SiO2 to Na2O (Ms) of activator solution and sodium silicate dosage on structural build-up, flow properties ...and setting characteristics of alkali-activated cement (AAC) mixtures were investigated. The solid-like behavior becomes more dominant with increasing GGBFS/FA ratio. Ms value had significant effect on the structural build-up. Significantly higher initial storage modulus with a low increasing rate was observed for the Ms values lower than 0.8. However, for higher Ms values, a sudden increase in storage modulus was observed after negligible initial structuration. An increase in sodium silicate dosage caused a considerable delay in the abrupt increase in the structural formation. It was observed that flow curves of AAC fit the Herschel-Bulkley model with shear-thickening behavior. ICP-OES tests revealed the lower release of aluminum and calcium into the pore solution of GGBFS/FA mixtures with low Ms values.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The structures of the crosslinks in supramolecular polymer networks play an important role on their properties and functions. Herein, emissive metallacages are used as crosslinks to prepare ...metallacage‐cored polyurethanes. The mechanical properties including storage modulus, toughness, Young's modulus and breaking strength of polymers are greatly enhanced with the increase of crosslinking densities. Moreover, such polymers not only exhibit good fluorescence in the solid state, but also show self‐healing and shape memory properties owing to the dynamic reversible non‐covalent bonds in their structures. This study not only offers a convenient strategy to prepare metallacage‐crosslinked networks, but also explores their applications as self‐healing and shape memory materials, which will promote the study of metallacage‐cored supramolecular networks as smart materials.
A type of metallacage‐cored polyurethanes was prepared using emissive metallacages as crosslinks. As the content of the metallacages increases, the mechanical properties of such polymers are greatly enhanced. These polymers not only show intense emission both in solution and in the solid state, but also exhibit good self‐healing and shape memory properties, which promotes the applications of metallacage‐cored networks as elastic smart materials.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•Rotary variable stiffness device with MR fluid in pre-yield region is reported.•A unique structure is developed to provide variable damping and stiffness.•Proposed damper can provide variable ...stiffness in large angle.
A novel compact rotary magneto-rheological (MR) damper with variable damping and stiffness has been proposed and analyzed. Its variable damping is generated by tuning yield stress of MR fluid in both pre-yield and post-yield regimes. The controllable storage modulus in pre-yield region of MR fluid is used to achieve magnetic field dependent stiffness. To ensure the MR rotary damper output variable stiffness in large angle, a unique structure that contains two driven disks and an active rotary disk is proposed. The effects of current, angle and frequency on the torque–angle loops and torque-frequency loops have been investigated experimentally. Adaptive network based fuzzy inference system with learning ability is adapted to capture the non-linear behaviors of variable damping and stiffness. By comparing with the MR dampers with one driven disk and that with no driven disk, it can be found that the proposed MR rotary damper with two driven disks can provide variable stiffness in larger angle. The results made the concept of proposed damper with variable damping and stiffness become feasible.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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