We designed and synthesized a colorless transparent glassy polyurethane assembled using low‐molecular‐weight oligomers carrying a large number of loosely packed weak hydrogen bonds (H‐bonds), which ...has a glass transition temperature (Tg) up to 36.8 °C and behaves unprecedentedly robust stiffness with a tensile Young's modulus of 1.56±0.03 GPa. Fast room‐temperature self‐healing was observed in this polymer network: the broken glassy polyurethane (GPU) specimen can recover to a tensile strength up 7.74±0.76 MPa after healing for as little as 10 min, which is prominent compared to reported room‐temperature self‐healing polymers. The high density of loose‐packed hydrogen bonds can reversibly dissociate/associate below Tg of GPU (that is secondary relaxation), which enables the reconfiguration of the damaged network in the fractured interfaces, despite the extremely slow diffusion dynamics of molecular chains under room temperature. This GPU shows potential application as an optical lens.
A glassy polyurethane (GPU) assembled by linear oligomers carrying abundant weak hydrogen bonds is presented. It is not only colorless, transparent, and stiff, but also shows fast room‐temperature self‐healing owing to the high mobility of the loosely packed hydrogen bonds in the glassy state. Molecular‐level events that occur in this process are established.
The design and synthesis of supramolecular self‐healing polymers with high healing efficiency and excellent integrated mechanical properties is challenging due to conflicting attributes of dynamic ...self‐healing and mechanical properties. Herein, this study introduces a design concept, that is, “dynamic hard domains,” to balance self‐healing performance, mechanical strength, elastic recovery, and at the same time obtain extreme toughness. The essential features of the dynamic hard domains include: (i) a noncrystallized and loose structure, (ii) low binding energy and high mobility, and (iii) sequential dissociation and rapid rearrangement. Based on this strategy, a simple one‐step polycondensation route is reported to synthesize a transparent polyurethane‐urea supramolecular elastomer (PPGTD‐IDA), which successfully combines decent mechanical strength, extreme toughness, outstanding notch‐sensitiveness, self‐recoverability, and room‐temperature self‐healing. Upon rupture, the PPGTD‐IDA completely restores the mechanical properties within 48 h. Furthermore, the results demonstrate repeatable healing of mechanical properties and prominent antiaging healability. Taking advantages of merits of PPGTD‐IDA, it can be utilized for fabricating impact‐resistant materials for protection of aluminum alloys as well as stretchable and self‐healing conductors, which exhibits unique characteristics such as stable conductivity during stretching (even after healing or with notch), and automatic elimination of the notch during stretching/releasing cycles.
A transparent supramolecular elastomer, combining relatively high mechanical strength, extreme toughness, outstanding notch‐insensitiveness, self‐recoverability, and room‐temperature self‐healing properties with complete recovery of mechanical properties is facilely synthesized via the design conception of dynamic hard domains. These well‐balanced properties enable its immediate use in impact‐resistant and energy‐absorbing protective materials as well as stretchable and self‐healing conductors.
Benefiting from the development of nanotechnology, drug delivery systems (DDSs) with stimuli-responsive controlled release function show great potential in clinical anti-tumor applications. By using ...a DDS, the harsh side effects of traditional anti-cancer drug treatments and damage to normal tissues and organs can be avoided to the greatest extent. An ideal DDS must firstly meet bio-safety standards and secondarily the efficiency-related demands of a large drug payload and controlled release function. This review highlights recent research progress on DDSs with stimuli-responsive characteristics. The first section briefly reviews the nanoscale scaffolds of DDSs, including mesoporous nanoparticles, polymers, metal-organic frameworks (MOFs), quantum dots (QDs) and carbon nanotubes (CNTs). The second section presents the main types of stimuli-responsive mechanisms and classifies these into two categories: intrinsic (pH, redox state, biomolecules) and extrinsic (temperature, light irradiation, magnetic field and ultrasound) ones. Clinical applications of DDS, future challenges and perspectives are also mentioned.
The present paper introduces an intelligent anticorrosion coating, based on the mechanized hollow mesoporous silica nanoparticles (HMSs) as smart nanocontainers implanted into the self-assembled ...nanophase particles (SNAP) coating. As the key component, smart nanocontainers assembled by installing supramolecular nanovalves in the form of the bistable pseudorotaxanes on the external surface of HMSs realize pH-responsive controlled release for corrosion inhibitor, caffeine molecules. The smart nanocontainers encapsulate caffeine molecules at neutral pH, and release the molecules either under acidic or alkaline conditions, which make them spontaneously experience the pH excursions arisen from corrosion process and respond quickly. The intelligent anticorrosion coating was deposited on the surface of aluminum alloy AA2024 and investigated by electrochemical impedance spectroscopy and scanning vibrating electrode technique (SVET). Compared with the pure SNAP coating, the well-dispersed smart nanocontainers not only delay the penetration rate of corrosive species but also repair damaged aluminum oxide layer to maintain the long term anticorrosion behavior. From the experimental results of SVET, the smart nanocontainers with the acid and alkaline dual stimuli-responsive characteristics can simultaneously suppress corrosion activities on microanodic and microcathodic regions, demonstrating an excellent self-healing functionality.
We constructed a novel stimuli-responsive system, MSNPs 1, based on mechanized silica nanoparticles, in which mesoporous silica nanoparticles (MSNs) acted as nanocontainers to load cargo, and ...supramolecular switches consisting of hydrazone bond, azobenzene and α-cyclodextrin (α-CD) realized the controlled release of cargo molecules from MSNPs 1. In neutral solution and without UV light irradiation, the azobenzene component on functional stalks was in
trans
form, and combined with α-CD to block the mesoporous channels and prevent the cargo from escaping. Upon adjusting the solution pH to acid range, the acid-sensitive hydrazone bonds rapidly hydrolyzed, resulting in the disconnection between pseudorotaxanes and MSNs. The encapsulated cargo molecules were released simultaneously from MSNPs 1 due to the removal of supramolecular switches. On the other hand, when the neutral solution was irradiated with UV light at 365 nm,
trans
-azobenzene converted to
cis
, disassociating with α-CD to activate the switches and release the cargo. The unique acid- and light-triggered controlled release properties of MSNPs 1 have potential application in various fields. In this manuscript, doxorubicin (DOX) was selected to be stored in MSNPs 1, due to the anticancer property. MCF-7 human breast cancer cells could phagocytose DOX-loaded MSNPs 1 easily, and the released DOX showed the killing effect.
Catastrophically mechanical failure of soft self-healing materials is unavoidable due to their inherently poor resistance to crack propagation. Here, with a model system, i.e., soft self-healing ...polyurea, we present a biomimetic strategy of surpassing trade-off between soft self-healing and high fracture toughness, enabling the conversion of soft and weak into soft yet tough self-healing material. Such an achievement is inspired by vascular smooth muscles, where core-shell structured Galinstan micro-droplets are introduced through molecularly interfacial metal-coordinated assembly, resulting in an increased crack-resistant strain and fracture toughness of 12.2 and 34.9 times without sacrificing softness. The obtained fracture toughness is up to 111.16 ± 8.76 kJ/m
, even higher than that of Al and Zn alloys. Moreover, the resultant composite delivers fast self-healing kinetics (1 min) upon local near-infrared irradiation, and possesses ultra-high dielectric constants (~14.57), thus being able to be fabricated into sensitive and self-healing capacitive strain-sensors tolerant towards cracks potentially evolved in service.
The Mesozoic strata, within the Bangong-Nujiang suture zone in central Tibet, recorded critical information about the subduction-accretion processes of the Bangong-Nujiang Ocean prior to the ...Lhasa-Qiangtang collision. This paper reports detailed field observations, petrographic descriptions, sandstone detrital zircon U-Pb ages and Hf isotopic analyses from an accretionary complex (preserved as Mugagangri Group) and the unconformably overlying Shamuluo Formation near Gaize. The youngest detrital zircon ages, together with other age constraints from literature, suggest that the Mugagangri Group was deposited during late Triassic-early Jurassic, while the Shamuluo Formation was deposited during late Jurassic-early Cretaceous. Based on the differences in lithology, age and provenance, the Mugagangri Group is subdivided into the upper, middle and lower subunits. These units are younging structurally downward/southward, consistent with models of progressive off-scrapping and accretion in a southward-facing subduction complex. The upper subunit, comprising mainly quartz-sandstone and siliceous mud/shale, was deposited in abyssal plain environment close to the Qiangtang passive margin during late Triassic, with sediments derived from the southern Qiangtang block. The middle and lower subunits comprise mainly lithic-quartz-sandstone and mud/shale, containing abundant ultramafic/ophiolitic fragments. The middle subunit, of late Triassic-early Jurassic age, records a transition in tectono-depositional setting from abyssal plain to trench-wedge basin, with sudden influx of sediments sourced from the central Qiangtang metamorphic belt and northern Qiangtang magmatic belt. The appearance of ultramafic/ophiolitic fragments in the middle subunit reflects the subduction initiation. The lower subunit was deposited in a trench-wedge basin during early Jurassic, with influx of Jurassic-aged zircons originating from the newly active southern Qiangtang magmatic arc. The lower subunit records the onset of arc magmatism related to the northward subduction of the Bangong-Nujiang Ocean. The Shamuluo Formation, comprising mainly lithic-feldspar-sandstone with limestone interlayers, was deposited in a post-collisional residual-sea or pre-collisional trench-slope basin, with sediments derived entirely from the Qiangtang block.
•The Mugagangri Group is explained as a southward-facing accretionary complex.•The Shamuluo Formation was deposited in a residual-sea or trench-slope basin.•The northward subduction of the Bangong-Nujiang Ocean began at ~195–190Ma.•The associated arc-magmatism in southern Qiangtang block initiated at ~185Ma.
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•The RGB-switchable orthogonal UCNPs were constructed based on selective photon capture.•The UCNPs could reinforce mechanical properties of the self-healing copolymer.•The ...self-healing luminescent composites possessed the room-temperature healing efficiency of 90.8%.•They could be used to fabricate various patterns on substrate by screen-printing method.•They were available for flexible multicolor displays, and high-security-level anti-counterfeiting.
The luminescent self-healing materials have a significant prospect in optical device applications such as biosensing, multicolor displays, and high-level anti-counterfeiting. Herein, a novel printable, room-temperature self-healing and full-color-tunable luminescent composites were developed through the noncovalent binding of physically cross-linked p(HFBM-co-SBMA)/EMITFSI and excitation-orthogonalized RGB-switchable UCNPs. According to a strategy of Selective photon capture (SPC), the RGB-switchable core-sextuple-shell UCNPs were first established for red/green/blue-switchable luminescence under three different excitations (980/808/1550 nm) and even full-color output through the combination of 980/808/1550 nm light. The copolymer p(HFBM-co-SBMA), pre-synthesized via free radical polymerization, was incorporated with ionic liquid EMITFSI to formulate room-temperature self-healing material owing to ion–dipole interactions between EMITFSI and p(HFBM-co-SBMA). Afterward, the integration of 30 wt% EMITFSI copolymer and fluothane-modified UCNPs resulted in the formation of the final full-color-tunable luminescent self-healing composites, which not only exhibited superior Young’s modulus and healing efficiency than some previously reported room-temperature self-healing materials, but also realized full-color-tunable emissions under ternary 980/808/1550 nm excitations. Significantly, the luminescent self-healing composites, which also exhibited colorless character and high transmittance, could be employed as printable inks for making various luminescent patterns (including clock, flower, and QR code) on flexible substrates via convenient and cost-effective screen-printing technique. As the results of proofs of concept, these luminescent patterns displayed fantastic viewing capability and highly secured property, which showed enormous potential of the proposed luminescent self-healing composites in flexible panchromatic display and high-security-level anti-counterfeiting. To our knowledge, this work provides the strategy for constructing full-color-tunable self-healing luminescent composites for the first time. Undoubtedly, the well-designed luminescent self-healing materials will provide new insights and guidance for exploiting the new generation of flexible optical devices, especially multicolor displays and anti-counterfeiting devices.
The inhibition of mild steel corrosion in 1.0 M HCl solution by quinoxaline and its derivatives were evaluated at 25 °C using weight loss measurement and Tafel polarization technique. These ...measurements reveal that the inhibition efficiency increased with increase in the concentrations of inhibitors, and the inhibition efficiencies decrease in the order 4-(quinoxalin-2-yl)phenol (PHQX) > 2-quinoxalinethiol (THQX) > 2-chloroquinoxaline (CHQX) > quinoxaline (QX). Tafel polarization curves show that all the investigated inhibitors act as mixed-type inhibitors. Quantum chemical calculation was applied to correlate electronic structure parameters of quinoxaline and its derivatives with their inhibition performances. Molecular dynamics simulations were also used to optimize the equilibrium configurations of the inhibitor molecules on the iron surface. The efficiency order of the studied inhibitors obtained by experimental results was verified by theoretical calculations.
► A series of chromium-doped TiO2 coatings has been prepared and characterized. ► Cr(III) improves photogenerated cathodic protection properties of TiO2 coatings. ► Cr(III) and Cr(VI) provide ...self-healing properties for the TiO2 coated metal.
A series of chromium-doped TiO2 coatings was prepared for corrosion protection of 316L stainless steel substrates. The morphology, crystalline phase and composition of the coatings were systematically investigated. The corrosion protection performances of the coatings in the presence and absence of simulated sunlight illumination were evaluated through electrochemical measurements. The chromium-doped TiO2 coatings showed a remarkable improvement in photogenerated cathodic protection properties under illumination. In addition, during a long-time dark immersion process, the chromium-doped TiO2 coatings could provide an active corrosion protection for metal substrates due to the self-healing property of chromium ions.
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