Carbon fiber (CF)‐reinforced polymers (CFRPs) demonstrate potential for use in personal protective equipment. However, existing CFRPs are typically rigid, nonrecyclable, and lack of tearing ...resistance. In this study, flexible, recyclable, and tearing resistant polyurethane (PU)‐CF composites are fabricated through complexation of reversibly cross‐linked PU elastomer binders with CF fabrics. The PU‐CF composites possess a high strength of 767 MPa and a record‐high fracture energy of 2012 kJ m−2. The high performance of the PU‐CF composites originates from the well‐engineered PU elastomer binders that are obtained by cross‐linking polytetrahydrofuran chains with in situ‐formed nanodomains composed of hierarchical supramolecular interactions of hydrogen and coordination bonds. When subjected to tearing, the force concentrated on the damaged regions of the PU‐CF composites can be effectively distributed to a wider area through the PU binders, leading to a significantly enhanced tearing resistance of the composites. The strong interfacial adhesion between PU binders and the CF fabrics enables the fracture of the CF in bundles, thereby significantly enhancing the strength and fracture energy of the composites. Because of the dynamic nature of the PU elastomer binders, the PU‐CF composites can be recycled through the dissociation of the PU elastomer binders.
Flexible elastomer/carbon fiber (CF) composites with extraordinary tearing resistance are fabricated through complexation of CF fabrics and reversibly cross‐linked polyurethane (PU) elastomer binders that are dynamically cross‐linked with hierarchical supramolecular interactions with high binding energy. The PU‐CF composites with a record‐high fracture energy of 2012 kJ m−2 are recyclable through the dynamic dissociation of the PU binders.
It is challenging to fabricate degradable poly(vinyl alcohol) (PVA)‐based plastics that can be used in watery environments because PVA is soluble in water. In this study, PVA‐based supramolecular ...plastics with excellent degradability in soil and high mechanical strength in watery environments are fabricated by the complexation of vanillin‐grafted PVA (VPVA), hydrophobic humic acid (HA), and Fe3+ ions (hereafter denoted as VPVA–HA–Fe complexes). Large‐area PVA‐based plastics can be easily prepared from a solution of VPVA–HA–Fe complexes using a blade‐coating method. The high‐density of hydrogen bonds and coordination interactions, as well as the reinforcement of self‐assembled Fe3+‐chelated HA nanoparticles, facilitate the fabrication of PVA‐based plastics with a breaking strength of ≈85.0 MPa. After immersion in water at room temperature for 7 d, the PVA‐based plastics exhibit a breaking strength of ≈26.2 MPa, which is similar to that of polyethylene in its dry state. Furthermore, owing to the reversibility of the hydrogen bonds and coordination interactions, the VPVA–HA–Fe plastics are recyclable and can be conveniently processed into plastic products with desired shapes. After being placed under soil for ≈108 d, the PVA‐based plastics are completely degraded into nontoxic species without requiring manual interference.
Completely degradable and easily processable poly(vinyl alcohol) (PVA)‐based supramolecular plastics are fabricated by complexation of vanillin‐grafted PVA, hydrophobic humic acid, and Fe3+ ions. In watery environments, the plastics have a mechanical strength similar to that of polyethylene in its dry state. The PVA‐based plastics can completely degrade into nontoxic species after being placed under soil for approximately 108 d.
Fabricating electrical double-layer capacitors (EDLCs) with high energy density for various applications has been of great interest in recent years. However, activated carbon (AC) electrodes are ...restricted to a lower operating voltage because they suffer from instability above a threshold potential window. Thus, they are limited in their energy storage. The deposition of inorganic compounds’ atomic layer deposition (ALD) aiming to enhance cycling performance of supercapacitors and battery electrodes can be applied to the AC electrode materials. Here, we report on the investigation of zinc oxide (ZnO) coating strategy in terms of different pulse times of precursors, ALD cycles, and deposition temperatures to ensure high electrical conductivity and capacitance retention without blocking the micropores of the AC electrode. Crystalline ZnO phase with its optimal forming condition is obtained preferably using a longer precursor pulse time. Supercapacitors comprising AC electrodes coated with 20 cycles of ALD ZnO at 70 °C and operated in TEABF4/acetonitrile organic electrolyte show a specific capacitance of 23.13 F g−1 at 5 mA cm−2 and enhanced capacitance retention at 3.2 V, which well exceeds the normal working voltage of a commercial EDLC product (2.7 V). This work delivers an additional feasible approach of using ZnO ALD modification of AC materials, enhancing and promoting stable EDLC cells under high working voltages.
Excellent self-recovery is critically important for soft materials such as hydrogels and shape memory polymers. In this work, weak-polyelectrolyte-based hydrogels with high mechanical strength, ...toughness, healability, and excellent self-recovery are fabricated by one-step polymerization of acrylic acid and poly(ethylene glycol) methacrylate in the presence of oppositely charged branched polyethylenimine. The synergy of electrostatic and hydrogen-bonding interactions and the in situ formed polyelectrolyte complex nanoparticles endow the hydrogels with a tensile strength of ∼4.7 MPa, strain at break of ∼1200%, and toughness of ∼32.6 MJ m–3. The hydrogels can recover from an ∼300% strain to their initial state within 10 min at room temperature without any external assistance. Moreover, the hydrogels can heal from physical cut at room temperature and exhibit a prominent shape-memory performance with rapid shape recovery speed and high shape-fixing and shape-recovery ratios.
It remains a challenge to fabricate sacrificial films that are stable in most of solvents and can be readily decomposed on demand. Here we report the fabrication of a near-infrared (NIR) light ...decomposable sacrificial film by layer-by-layer (LbL) assembly of UV-light-decomposable poly((4-(2-bromoethoxy)-5-methoxy-2-nitrobenzyl acrylate) triethylammonium bromide) (PNBA-TEA), poly(sodium 4-styrene-sulfonate) (PSS), branched polyethyleimine (bPEI), and lanthanide-doped upconversion nanoparticles (UCNPs). The (PNBA-TEA/PSS)*2/(bPEI/UCNPs)*3*2 films are stable in deposition solutions of various materials and decompose upon NIR light irradiation. In the (PNBA-TEA/PSS)*2/(bPEI/UCNPs)*3*2 films, UCNPs can convert NIR light into UV light, which can decompose PNBA-TEA. After immersing the NIR light-irradiated (PNBA-TEA/PSS)*2/(bPEI/UCNPs)*3*2 films in 0.1 M aqueous NaHCO3 solution, the disintegration of the entire films occurs because of the repulsive force between the negatively charged photoproduct of PNBA-TEA and PSS. LbL-assembled (PAH/PAA)*50 films deposited on top of the NIR-light-decomposable (PNBA-TEA/PSS)*2/(bPEI/UCNPs)*3*2 films can be conveniently released to produce large-area and defect-free (PAH/PAA)*50 free-standing films after NIR light irradiation and subsequent immersion in 0.1 M aqueous NaHCO3 solution. Because of the satisfactory stability and on-demand decomposable property, the (PNBA-TEA/PSS)*2/(bPEI/UCNPs)*3*2 films are promising as sacrificial layers for the fabrication of various free-standing films.
Water-based adhesives which have strong adhesion and can simplify the adhesion process, endow the adhesives with desired functions are important for various applications. In this work, water-based ...highly adhesive films with drug delivery ability are fabricated by layer-by-layer (LbL) assembly of chemically cross-linked poly(allylamine hydrochloride)-dextran (PAH-D) microgels and hyaluronic acid (HA). Strong adhesion as high as 6.95 ± 0.92 MPa can be achieved when glass substrates deposited with LbL assembled PAH-D/HA films are slightly pressed together. Confocal laser scanning microscope (CLSM) measurements disclose that the strong adhesion originates from the intermixing of HA with PAH-D microgels at the interface of two contacted PAH-D/HA films. Free-standing PAH-D/HA films are released from substrate under assistance of a sacrificial layer for direct use as adhesives because PAH-D microgels have strong interactions with various surfaces. PAH-D/HA adhesive films can load negatively charged drugs such as ibuprofen based on electrostatic interaction between PAH-D microgels and ibuprofen molecules and release them in physiological conditions. Ibuprofen-loaded PAH-D/HA free-standing films can strongly glue periostea, promising their potential application as bioadhesives capable of accelerating the healing of damaged tissues or organs.
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Thermochromic smart windows have gained increasing popularity in light modulation and energy management in buildings. However, the fabrication of flexible thermochromic smart windows with high ...luminous transmittance (Tlum), tailorable critical temperature (τc), strong solar modulation ability (ΔTsol), and long‐term durability remains a huge challenge. In this study, hydrogel‐based thermochromic smart windows are fabricated by sandwiching thermochromic hydrogels of polyallylamine hydrochloride, polyacrylic acid, and carbonized polymer dots (CPDs) complexes between two pieces of transparent substrates. Benefiting from the incorporation of nanosized CPDs, the thermochromic hydrogel has an ultrahigh Tlum of ~98.7%, a desirable τc of ~24.2 °C, a ΔTsol of ~89.3% and a rapid transition time of ~3 s from opaque state to transparent state. Moreover, the thermochromic hydrogel exhibits excellent anti‐freezing ability, tight adhesion toward various substrates, and excellent self‐healing capability. The self‐healing capability enables the fabrication of large‐area smart windows by welding multiple hydrogel pieces. The smart windows retain their original thermochromic properties after being stored under ambient conditions for at least 147 days or undergoing 10,000 uninterrupted heating/cooling cycles. The model houses with smart windows can achieve a temperature reduction of 9.2 °C, demonstrating the excellent indoor temperature modulation performance of the smart windows.
Thermochromic hydrogels for the construction of high‐performance thermochromic smart windows are conveniently fabricated by complexation of polyallylamine hydrochloride, polyacrylic acid, and carbonized polymer dots (CPDs). Because of the employment of polyelectrolyte complexes and CPDs, the resultant smart window exhibits high luminous transmittance, strong solar modulation ability, quick transition time, and long‐term durability and can work reliably under subzero temperatures.
Robust and flexible free-standing polymer films for unidirectional drug delivery are fabricated by sandwiching drug-containing polyelectrolyte multilayer films between poly(lactic-co-glycolic acid) ...(PLGA) barrier and capping layers. The drug-containing films are fabricated by layer-by-layer (LbL) assembly of chemically cross-linked poly(allylamine hydrochloride)–dextran (PAH-D) microgel and hyaluronic acid (HA), which can load negatively charged cancer-inhibiting drug, methotrexate (MTX). Because the PLGA barrier layer effectively blocks MTX release, MTX can be predominantly released from the PLGA capping layer of the free-standing film. This increases the efficacy of released MTX to cancer cells while minimizing its side effects on the normal tissues. We believe that the unidirectional drug delivery free-standing films can open a new avenue to design of highly efficient drug delivery systems for biomedical application.
Intrinsically stretchable organic electrochemical transistors (OECTs) are being pursued as the next‐generation tissue‐like bioelectronic technologies to improve the interfacing with the soft human ...body. However, the performance of current intrinsically stretchable OECTs is far inferior to their rigid counterparts. In this work, for the first time, the authors report intrinsically stretchable OECTs with overall performance benchmarkable to conventional rigid devices. In particular, oxygen level in the stretchable substrate is revealed to have a significant impact on the on/off ratio. By employing stretchable substrates with low oxygen permeabilities, the on/off ratio is elevated from ≈10 to a record‐high value of ≈104, which is on par with a rigid OECT. The device remained functional after cyclic stretching tests. This work demonstrates that intrinsically stretchable OECTs have the potential to serve as a new building block for emerging soft bioelectronic applications such as electronic skin, soft implantables, and soft neuromorphic computing.
It is observed that the poor electrical performance of stretchable organic electrochemical transistors (OECTs) can be significantly improved by controlling the oxygen permeability of the elastic substrate. The overall performance of the optimized device is verified benchmarkable to a conventional rigid OECT.
In this work, self‐healing polyampholyte hydrogels with high mechanical strength in megapascal order, good resilience, improved toughness, and satisfactory conductivity are fabricated via one‐step ...polymerization of positively charged imidazolium‐based ionic liquid monomers containing urea groups and negatively charged 3‐sulfopropyl methacrylate potassium salt monomers followed by subsequent dialysis in water. Dialysis can remove partial counter ions in the original hydrogels to strengthen electrostatic interactions between imidazolium and sulfonate groups and improve mechanical strength of the hydrogels. After dialysis for 3 d, the originally soft hydrogels become mechanically robust with a tensile strength of ≈1.3 MPa, strain at break of ≈720%, and toughness of ≈6.7 MJ m−3. Hydrogen‐bonding interactions between urea groups, which act as sacrificial bonds to dissipate energy, are important to improve the mechanical strength and toughness of the hydrogels. More importantly, the hydrogel can automatically heal from physical cut at room temperature with a healing efficiency of ≈91% because of the reversibility of the electrostatic and hydrogen‐bonding interactions. Because of the undialyzed salts in the hydrogels, the mechanically robust hydrogels possess a satisfactory ionic conductivity of ≈3 S m−1 at room temperature and can serve as highly flexible and stretchable conductors with self‐healing capacity.
Self‐healing polyampholyte hydrogels with high mechanical strength, good resilience, improved toughness, and satisfactory conductivity are fabricated via copolymerization of imidazolium‐based ionic liquid monomers and sulfonate‐containing methacrylate monomers, followed by dialysis in water to partially remove salts. The hydrogels, which are cross linked by reversible electrostatic and hydrogen‐bonding interactions, can automatically heal from physical cut at room temperature to restore mechanical strength and conductivity.
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