A custom-made rotational coating system that can apply constant, uniform, and high force to nanosheets was made. Montmorillonite (MMT) nanosheets and polyvinyl alcohol (PVA) chains were coassembled onto a poly(ethylene terephthalate) (PET) substrate using a rotational coating process. Different concentrations and centripetal accelerations were explored to study their effects on coating properties. The nanocoating thickness was determined by a thin-film measurement system and a stylus profilometer. The turbidity of the coating layer was determined using ultraviolet–visible (UV–Vis) spectrophotometry and the Beer-Lambert law. The nanostructure of the coating was characterized by X-ray diffraction (XRD). Finally, the oxygen transmission rate was measured to determine the effects of processing conditions on permeability. Two statistical approaches were used to determine the degree to which each processing parameter has an impact on each coating property. Aside from the fundamental study on rotational coating, this coating technique can fabricate highly ordered nanocoatings with significantly improved barrier properties. Potential applications are envisioned in the fabrication of food packages, dielectric materials, and biomedical devices.

Polymer-thin films are critical dielectric materials for capacitive energy storage in power and electronic systems. The rapid development of wide bandgap semiconductors urgently calls for polymers that can attain high energy density and high charge-discharge efficiency at elevated temperatures. However, high-temperature polymers usually suffer from compromised dielectric breakdown strength and soaring conduction loss due to the intrinsic constraint between their bandgaps and thermal stability. In this work, we propose a facile and high throughput interface engineering technique utilizing nanocoatings formed by montmorillonite (MMT) nanoclays, which can serve as an out-of-the-box solution to bypass this constraint. The highly ordered MMT-based nanocoatings with layered structure can significantly block the excessive charge injection at high electric fields and dissipate the charge carriers along the in-plane direction. The MMT-coated PI films exhibit improved breakdown strength, suppressed conduction loss, and boosted charging-discharging efficiency. This work holds the promise of improving the dielectric properties of polymers through surface engineering, enabling their application at concurrent electrical and thermal extremes.

Polymer thin films operable under concurrent electric and thermal extremes represent critical building blocks of capacitive energy storage and electrical isolator for modern power and electronic systems with ever-increasing demands for power density and payload efficiency. However, polymer dielectrics are prone to fast aging under high fields due to hot electrons injected from electrodes. Especially, performance high-heat polymers such as polyimides with high aromaticity suffer fast aging induced by non-thermalized electrons even at moderate fields due to their intrinsically low bandgap and injection barrier. Herein, a facile, low-cost, and scalable interfaceengineering approach utilizing the highly ordered organic/inorganic layered nanocoatings is reported, which serve as a retrofittable solution to break this design constraint. By probing the energetic modes of transport and aging at pre-breakdown field, we demonstrate that our 2D montmorillonite (MMT) self-co-assembly nanocoatings can effectively boost the dielectric properties of substrate polyimide (PI) film by suppressing the charge injection and shifting the fast mode of hot-electron aging to a slow, ultimately thermalized process. This agingimpeding scheme imparts PI films with an exceptional endurance capability (enhanced by 100 MV/m) and a 6x improved charge-discharge efficiency at an elevated temperature of 175 degrees C. The nanostructured interface engineering disclosed in this work thus opens a new pathway of boosting the performance of a spectrum of highheat polymer dielectrics already commercially available in thin gauges of films for applications in zero-emission electric aircraft and renewable energy integration.

Polymer nanocomposites containing inorganic nanosheets have attracted high interest due to their improved stiffness and strength, enhanced barrier properties, and superior flame retardancy after properly incorporating nanosheets. alpha-Zirconium phosphate (Zr(HPO4)2) (ZrP) is a layered compound that can be well exfoliated into single-layer nanosheets by propylamine in an aqueous dispersion. A polyvinyl alcohol (PVA)/ZrP dispersion was prepared and coated on polylactic acid (PLA) films, followed with crosslinking by glutaraldehyde (GA). The morphological, optical, thermal, barrier, and mechanical properties of the PVA/ZrP nanocomposite coatings were investigated. The ZrP nanosheets were uniformly distributed and well oriented in the PVA matrix. The coated PLA films exhibited high clarity even when containing 20 wt % of ZrP nanosheets. The crosslinked coating layer containing 20 wt % of ZrP nanosheets (PVA/ZrP-20-C) had an oxygen permeability of 0.022 [10-16 cm3 (STP)cm/cm2 center dot s center dot Pa] and water vapor permeability of 0.25 [10-11 g (STP)cm/cm2 center dot s]. Compared with the neat PVA, when 20.0 wt % of ZrP nanosheets were well-aligned and properly incorporated, the Young's modulus and tensile strength of the resultant PLA nanocomposite were increased from 1.5 GPa and 29.5 MPa to 13.9 GPa and 98.3 MPa, respectively.

Polyvinyl alcohol (PVA)/laponite (LP) nanocomposite coatings were fabricated via a facile one-step coassembly process. The formed nanocoatings contain a high concentration of LP nanosheets, which can be well aligned along the substrate surface during the coassembly process. Due to the highly orientated structure, the flexible nanocoatings exhibit ultra-high transparency and superior mechanical properties, and can also act as excellent gas barriers. Such nanocoatings can be exceptional candidates for a variety of applications, such as food packaging.

Polyolefin (PO) films are commonly used for food packaging and other consumer applications. However, while polyolefins are good water vapor barriers, they are highly permeable to oxygen. To resolve this issue, montmorillonite (MMT) nanosheets were one-step coassembled with polyvinyl alcohol (PVA) chains via facile and scalable dip coating. In a one-step coassembly process, MMT nanosheets are aligned to form a nacre-like structure with PVA chains by gravity-induced shear as the aqueous coating dispersion flows and subsequently dries on the substrate surface. The surface properties of the PO substrates were modified using high-power corona discharge treatment. The resulting nanocoating layer had vastly improved barrier properties, especially against oxygen, thanks to the highly ordered nacre-like structure of the assembled MMT nanosheets creating a tortuous path for gas transport. The structure of the nanocoatings was verified via X-ray diffraction (XRD) and small angle X-ray scattering (SAXS). This nanocoating technique has unique implications for thin film vapor barrier technology such as food packaging materials, biomedical devices, and construction materials. Exfoliated montmorillonite (MMT) nanosheets were coassembled with polyvinyl alcohol (PVA) binder in a one-step dip-coating system.

Wearable electronics offer incredible benefits in mobile healthcare monitoring, sensing, portable energy harvesting and storage, human-machine interactions, etc., due to the evolution of rigid electronics structure to flexible and stretchable devices. Lately, transition metal carbides and nitrides (MXenes) are highly regarded as a group of thriving two-dimensional nanomaterials and extraordinary building blocks for emerging flexible electronics platforms because of their excellent electrical conductivity, enriched surface functionalities, and large surface area. This article reviews the most recent developments in MXene-enabled flexible electronics for wearable electronics. Several MXene-enabled electronic devices designed on a nanometric scale are highlighted by drawing attention to widely developed nonstructural attributes, including 3D configured devices, textile and planer substrates, bioinspired structures, and printed materials. Furthermore, the unique progress of these nanodevices is highlighted by representative applications in healthcare, energy, electromagnetic interference (EMI) shielding, and humanoid control of machines. The emerging prospects of MXene nanomaterials as a key frontier in next-generation wearable electronics are envisioned and the design challenges of these electronic systems are also discussed, followed by proposed solutions.

Flexible polymer dielectrics which can function well at elevated temperatures continue to be significant in harsh condition energy storage. However, state-of-the-art high-temperature polymers traditionally designed with conjugated structures for better thermal stability have compromised bandgaps and charge injection barriers. Here, we demonstrate a self-assembled polyvinyl alcohol (PVA)/montmorillonite (MMT) coating to impede charge carriers injecting into the polyimide (PI) polymer film. The anisotropic conductivity of the 2D nanolayered coating further dissipates the energy of charges through tortuous injection pathways. With the coating, high field pre-breakdown conduction measurement and space-charge profiling of PI films reveal a clear shifting of the dominant mode of conduction from the bulk-limited hopping to Schottky-injection limited conduction. The coating thus imparts PI films with a significantly suppressed electrical conduction (∼10×), and substantially improved discharge efficiency (7×) and energy density (2.7×) at 150°C. The facile and scalable flow-induced fabrication unleash enormous applications for harsh condition electrification.

Montmorillonite (MMT) nanosheets were coas-sembled with poly(vinyl alcohol) (PVA) via a spin-coating process.The resulting coating layer, consisting of a multilayered nano-composite structure, possessed an outstanding barrier propertythanks to the highly ordered structure of the MMT nanosheetscreating a tortuous path for molecular diffusion. The process ofalignment and stacking of MMT nanosheets on a solid substrate iscontrolled by an array of factors, some of which can be controlledby the coating process. To this end, the suspension concentrationand spin speed were varied to determine their impact on thefinalfilm quality. The turbidity of thefilms was quantified usingultraviolet-visible (UV-VIS) spectroscopy. The structure of thenanocoating layers was verified via X-ray diffraction (XRD).Finally, the overall performance of the coatings was tested via oxygen transmission rate (OTR) measurements, which gives anindication of the nanosheet assembly structure. The presence of high centripetal acceleration resulted in high degrees of nanosheetalignment and a high barrier to oxygen transport. This coating technique has unique implications for thin-film vapor barriertechnologies such as solar cells, dielectric materials, and biomedical devices

Polymer based dielectrics with excellent high electric field withstanding capability are of great significance for enhancing the power density and payload efficiency for both electrical and electronic systems. However, polymer-metal interface is prone to defect formation, leading to the dielectric aging and the initialization of electrical breakdown failure. A facile Montmorillonite (MMT) coating is self-co-assembled on the surface of P(VDF-HFP) high-k film to form hundreds of 2D nanosheets layers to impede the charge injection over the metal-polymer interface. The MMT coating increases the breakdown strength of the P(VDF-HFP) co-polymer film from 405 to 452 MV/m. The high field conduction study reveals a highly enhanced Schottky injection barrier that blocks the charge injection from electrodes to polymer bulk, leading to significantly suppressed charge injection and conduction loss in polymer. In addition, the introduction of MMT layered coating leads to prominent suppression of interfacial polarization loss, a phenomenon known as the blocking capacitance, which would otherwise stem from the accumulated charges of polymer-metal interface, by one order of magnitude, as demonstrated by the dielectric response analysis by using the Dissado-Hill model over a broad range of temperature and frequency. The superior charge injection and interfacial polarization suppression via the application of MMT coating impart the P(VDF-HFP) co-polymer film with higher breakdown strength, and provides an effective approach to develop high performance polymer dielectrics by interfacial engineering. This work provides insights into the understanding of the enhancement mechanism of 2D coating.

Nanocoatings In article number 2101374, Yang Cao, Luyi Sun, and co-workers present a layered nanocoating comprising hundreds of highly oriented organic/inorganic alternating nanolayers on the polymer surface to revive the Schottky barrier for effective charge-injection blocking. The superior 2D assembly leads to a flexible material architecture at the electrode–dielectric interface, thus providing a novel design strategy for high-performance dielectrics for integrated flexible electronics.

The organic insulator–metal interface is the most important junction in flexible electronics. The strong band offset of organic insulators over the Fermi level of electrodes should theoretically impart a sufficient impediment for charge injection known as the Schottky barrier. However, defect formation through Anderson localization due to topological disorder in polymers leads to reduced barriers and hence cumbersome devices. A facile nanocoating comprising hundreds of highly oriented organic/inorganic alternating nanolayers is self‐coassembled on the surface of polymer films to revive the Schottky barrier. Carrier injection over the enhanced barrier is further shunted by anisotropic 2D conduction. This new interface engineering strategy allows a significant elevation of the operating field for organic insulators by 45% and a 7× improvement in discharge efficiency for Kapton at 150 °C. This superior 2D nanocoating thus provides a defect‐tolerant approach for effective reviving of the Schottky barrier, one century after its discovery, broadly applicable for flexible electronics.

The conventional approach to exfoliate kaolinite to form aluminosilicate nanoscrolls is very time-consuming. Herein, we report a novel method to prepare aluminosilicate nanoscrolls from kaolinite by catalysis of AlCl3 under mild conditions. This method is highly efficient, environmentally friendly, and can be easily scaled up for mass production.

Leather is made from the skin of animals and possesses special micro- and nanostructures. Due to the high breathability, durability, strength, elasticity, and softness, leather is widely used in daily life, and is an ideal substrate for future multi-functional wearable smart devices. Herein, two leather-based multi-stimuli responsive chromic devices denoted as UV/thermo/electro chromic device and UV sensor are developed. The UV/thermo/electro chromic device demonstrates instantaneous and reversible chromic responses to applied UV radiation, heat, and electrical voltage with different color changing styles. The pattern design with the assistance of 3D printed molds and the broad selection of dyes/pigments endow the device with high design flexibility and wide applicability. The leather-based UV sensor exhibits a change in color gradient when exposed to UV radiation with different intensities. For more versatile color options, inactive pigments/dyes can be mixed with stimuli-responsive ones in this system. Coating the leather surface with a polyacrylic finishing agent is also conducted, which is a practical and effective method to protect the pigments and/or dyes in the leather, and improves the usability/durability of the devices. This study opens a new avenue to design and develop wearable devices and individual customization/anti-counterfeiting of leather products.

Designing photochromic systems that exhibit tunable print/erase responses is seldom studied but critical to the implementation of rewritable paper. Previous systems printed information with photocatalysts limited to specific wavelengths and light sources and rarely considered how polymers used in film formation affect erasing of information. Herein, different visible/UV light responses are achieved by engineering the formation of oxygen vacancy defects in titanium dioxide/reduced graphene oxide composite photocatalysts. Defects are manipulated during synthesis by controlling the water concentration in a mixed solvent system, which leads to tunable photochromic response of redox dyes. Furthermore, because the accessibility of ambient oxygen directly impacts the kinetics of recoloration, tailoring the oxygen barrier properties of polyvinyl alcohol via modulating inherent polymer structure as well as the external environment, the recoloration can be further tuned to meet various application purposes. The resulting insight will assist fellow researchers in tailoring defects in photocatalyst systems for superior functional design.

In this study, a calcium-aluminum-layered double hydroxide (CaAl-LDH) thin film was grown on an AA6082 aluminum alloy, for the very first time, by using a facile in situ growth method in an effort to investigate the CaAl-LDH structural geometry and corresponding corrosion resistance properties. The structure and surface morphologies of the CaAl-LDH thin film were studied using a scanning electron microscope (SEM) equipped with an EDS detector, a transmission electron microscope (TEM), an X-ray diffractometer (XRD), and a Fourier transform infrared spectrometer (FT-IR), while the electron impendence spectra (EIS) and potentiodynamic curves were recorded to understand the LDH anticorrosion behavior. The findings demonstrated that thin, well-developed CaAl-LDH coatings with different surface morphologies can be prepared with eminent corrosion resistance properties. Specifically, the CaAl-LDH thin film synthesized at 140 °C-24 h synthetic conditions showed a large impedance modulus of 7.3 Ω cm2 at 0.01 Hz (|Z|f = 0.01 Hz), along with a low corrosion current density (Icorr) of 0.0007 μA cm-2, while a vertically orientated rod like structure with a uniform surface morphology was observed.

The work presented herein focuses on simulating the compounding process via a torque rheometer, as well as the relationship between the melt viscosity and the polymer molecular weight (MW). We aim to predict the plasticization of polylactic acid (PLA) using polypropylene glycol (PPG) with different MWs. The rheological properties of the PLA/PPG composites containing PPG with different MWs were systematically studied by capillary rheometry and torque rheometry. The initial degradation of PLA/PPG composites during melt processing was monitored in real time. The results indicate that PPG can significantly reduce the melt viscosity of PLA/PPG composites, leading to obvious pseudoplastic fluid behavior. The lower the MW of PPG, the lower the viscosity of the PLA/PPG composite. The addition of PPG was favorable for the degradation of PLA during processing, and the degradation degree of the composite materials increased as the MW of PPG was decreased.

Nature not only carefully prepares ingenious raw materials but also continuously inspires and guides human beings to create a wide variety of intelligent materials. As the most abundant mineral resource on earth, clay minerals are no longer synonymous with ceramics and cements. Many natural clay minerals can be exfoliated into single- or few-layered nanosheets with exquisite physicochemical properties, which can be reassembled into functional membranes with a macroscopic controllable size and microscopic ordered structure. They are thus used in many fields including chemistry, biology, energy, and environmental science. Strategic design represents one of the key processes to enhance the value of clay minerals and broaden their applications. In this work, the three frequently used approaches of exfoliation are highlighted and the six routes of assembly including casting, dip-coating, spray coating, vacuum filtration, electrophoretic deposition, and 3D printing are compared. The corresponding principles and advantages are summarized. Representative applications of clay-based multifunctional membranes in protection, separation, responsiveness, flexible electronics, and energy conversion are presented. The challenges and future perspectives of the clay-based multifunctional membranes are discussed.