Gas Barrier Films Research Articles

Innovating a EVOH composite coating towards outstanding H2 barrier and anti-corrosion properties

Concerning the mitigating leakage and hydrogen-induced embrittlement during the conveyance of hydrogen (H2), we have developed an innovative dual-layer composite coating that exhibits exceptional hydrogen gas barrier properties and good resistance to corrosion. Using a bottom-top approach combining hot pressing with spin-coating techniques, the bottom Ethylene-vinyl alcohol copolymer (EVOH) layer with glass flakes (GF) serves as an effective hydrogen gas barrier and the top fluorosilicone resin (FSR) layer with composite nanofiller possesses good corrosion resistance, ensuring the functional integrity of the EVOH layer. The composite coating shows an exemplary low hydrogen gas transmission rate (H2 GTR) value of 2.858 cm3/(m2·24 h·0.1 MPa), representing a substantial decrease of 99.98 % compared to the FSR coating and 15 times more effective than commercial gas barrier films. Moreover, even after a 90-day immersion in 3.5 wt% NaCl solution, the coating maintains an impressive impedance at 0.01 Hz (|Z|0.01 Hz) of 1.0 × 1011 Ω·cm2. The composite coating is exposed to 2 MPa hydrogen for 7 days, and we find that it still sustains outstanding hydrogen gas barrier and anti-corrosion properties.

Room temperature self-healing and high gas barrier properties of elastomer composites incorporated with liquid metal

Flexible electronic devices require stretchable packaging materials that provide a hermetic seal. However, conventional soft materials often exhibit strong gas permeability, making it difficult to achieve stable operation, which requires films with high deformability, self-healing capability, and gas barrier functionality. In this study, a layer by layer (LBL) method was employed to uniformly coat a controllable thickness of liquid metal (LM) onto a designed and synthesized self-healing thermoplastic polyurethane (TPU) film, successfully developing a stretchable gas barrier film (TPU/LM) with high gas barrier properties. The designed polyurethane film significantly enhanced the adhesion of the liquid metal, effectively preventing leakage. The experimental results show that the water vapor transmission rate (WVTR) of the TPU/LM composite film with a thickness of 40 μm is 4.04g/(m2·day). Compared to the film without LM, the gas barrier performance has been improved by approximately 16 times. Additionally, there is a significant enhancement in nitrogen (N2) barrier, with a permeation rate reaching 4.0*10−17 cm3 cm/(cm2·s·Pa), effectively blocking the N2 permeation. This demonstrates the universality of the TPU/LM in gas barrier applications. Furthermore, the TPU/LM film also demonstrated excellent electromagnetic shielding effectiveness. The self-healing capability of the stretchable gas barrier film allows it to recover its initial gas barrier performance after mechanical damage. Humidity-sensitive resistors encapsulated with TPU/LM exhibited stable operation in both air and 90 % humidity environments, confirming the superior barrier properties of the TPU/LM. Generally, the developed TPU/LM is suitable for packaging applications in the next generation of flexible electronic devices.

Transparent, thermal stable, water resistant and high gas barrier films from cellulose nanocrystals prepared by reactive deep eutectic solvents

Nanocellulose-based film, as a novel new type of film mainly made of nanosized cellulose, has demonstrated an ideal combination of renewability and enhanced or novel properties. Considerable efforts have been made to enhance its intrinsic properties or create new functions to expand its applications, such as in food packaging, water treatment or flexible electronics. In this paper, two different types of deep eutectic solvents (guanidine sulfamate-glycerol and guanidine sulfamate-choline chloride) were formulated and applied to prepare cellulose nanocrystals with dialdehyde cellulose (DAC). The effects of reaction conditions including time, temperature and cellulose-DES ratio on the grafting degree and yield were studied. After ultrasonication, two types of CNCs, with an average diameter of 3–5 nm and an average length of 140.7–204.2 nm, were obtained. The synthesized CNCs displayed an enhanced thermal stability compared to pristine cellulose. Moreover, highly transparent (light transmittance higher than 90 %) and water stable nanocellulose based films (a wet tensile strength of higher than 30 MPa after immersing in water for 24 h) were fabricated. Besides, the obtained films exhibited low oxygen transmission rate, showing a good potential application in food packaging.

Study on ultrasound-assisted preparation of sphere-like high-purity alumina

Spherical alumina with a purity greater than 99.999% is calcined by the precursor obtained from the reaction of high-purity aluminum with ultrapure water, which is of great interest for grinding in semiconductor processing and other fields. In this study, tetramethylammonium hydroxide is introduced to the aluminum-water (Al-H2O) reaction, and the crystal growth of the HPA precursor is adjusted by ultrasonication. The ultrasound can break the gas barrier film at the early stage of the reaction, then increase the reaction potential energy on the aluminum surface, accelerate the reaction rate, and inhibit the preferential growth of Al(OH)3 crystals along (110), (111), (131), and (202) faces. It increases the dissociation rate of crystals in the corresponding crystal faces and promotes the formation of the Al-O bond in Al(OH)3 and Al2O3 to obtain fine HPA precursors with uniform size distribution. Then, the ultrafine and sphere-like α-Al2O3 powders with a particle size D50 of 370 nm are prepared after calcination at 1250 °C.

Polymer Nanocomposites

In the last 20 years, there has been a strong emphasis on the development of polymer nanocomposites, where at least one of the dimensions of the filler material is of the order of a nanometer. Polymer nanocomposites are fundamentally different from traditional filled polymers because of the immense internal interfacial area and the nanoscopic nature of the nanomaterials. The new multifunctional properties derived from the nano-structure of nanocomposites provide an opportunity to circumvent the traditional properties associated with traditional composites. Numerous examples can be found in the literature that show significant improvements in multifunctional properties of the nanocomposites and this new class materials now being introduced in structural applications, such as gas barrier film, flame retardant product, and other load-bearing applications. This review offers a comprehensive review on the basic concept, technology and application for polymer nanocomposites.

Efficient preparation of hydrogen barrier films by ultrasonic‐assisted layer‐by‐layer assembly

AbstractGraphene oxide (GO) can be self‐assembled with various polymer materials layer by layer to prepare composite materials with excellent barrier properties. However, the process is cumbersome and time‐consuming. In this article, GO/polyethyleneimine(PEI) hydrogen barrier films were successfully prepared by ultrasonic‐assisted layer‐by‐layer self‐assembly technology. Results show that the ultrasonic‐assisted method not only reduced the immersion time from several minutes to 10 s, but also increased the density of the material packing to reduce the channels through which hydrogen molecules can diffuse while improving the horizontal orientation of the GO sheet to prolong the diffusion paths of gas molecules. Finally, the hydrogen transmission rate of 20‐bilayer films assembled under ultrasonic conditions is equivalent to that of 30‐bilayer films assembled without ultrasonic conditions, which greatly shortens the film‐making period. Therefore, the ultrasonic‐assisted method has a good prospect in the preparation of gas barrier films.

Experimental investigation of methods to reduce outgassing from core materials in the fabrication process of transparent vacuum insulation panels

The notion that modern buildings should strive to be net-zero energy buildings (NZEBs) is widely accepted. In order to improve window’s insulation in existing buildings, structured-core transparent vacuum insulation panels (TVIPs) are proposed. TVIPs mainly consist of the structured core material, the low-emissivity film, and the transparent gas barrier envelope. TVIPs have high insulation performance and are inexpensive to manufacture and can be easily installed. However, it is necessary to overcome the issue of preventing the pressure rise inside TVIP after vacuum sealing. The authors constructed an experimental setup by applying the pressure-rate-of-rise-method to establish the fabrication process for TVIPs that prevents the pressure rise. In this experiment, a gas barrier film with a straw was used as the vacuum chamber. This could reproduce the pressure increase in the TVIP after sealing and the gas flow rate in the TVIP is evaluated. The experimental results showed that the internal pressure of TVIP could be reduced to about 1 Pa after vacuuming while heating for 8 hours, coating the core material, and sealing the getter material.

Investigation on Longer Service Life of Vacuum Insulation Panels by Applying Double Envelopes

The conversion of existing buildings to ZEB requires high thermal insulation. Vacuum insulation panels (VIPs) have a potential to be used for retrofitting thermal insulation of existing buildings from the viewpoint of low thermal conductivity, small thickness, and light weight. However, in order to realize vacuum insulation panels applicable to building insulation, it is necessary to overcome the challenge of maintaining the low pressure at which the high insulation performance can be achieved for several decades. The authors applied the double envelopes to VIPs and investigated longer service life of VIPs. The double envelope VIP is fabricated by fabricating a normal VIP, then wrapping the VIP with core materials, and then inserting it into the envelope for vacuum sealing. By applying the double envelopes, the pressure difference and the permeation of gas in inner VIP can be drastically reduced, resulting in a longer VIP lifetime. In this paper, the gas permeabilities of the gas barrier envelopes were experimentally estimated. Then, the pressure ageing in the double envelope VIP is calculated. The inner pressure after 25 years was 1.6 Pa for the envelope of aluminium composite film and 59.3 Pa for the envelope of transparent gas barrier film, indicating that long-term insulation performance could be improved. Next, the authors carried out acceleration test, in which the double envelope VIPs were put in a chamber at 80oC and remove once a month to measure the thermal conductivity. Even after 136 weeks, one sample showed only a 9.1% decrease in thermal resistance. From this result, it was confirmed that long-term insulation performance can be greatly improved by fabricating double envelope VIPs with the getter agent inside and the desiccant agent outside.

Experimental analysis of vacuum pressure and gas flow rate in structured-core transparent vacuum insulation panels

The notion that modern buildings should strive to be net-zero energy buildings (NZEBs) is widely accepted. One of the causes leading to high energy usage for space heating, resulting in avoidable carbon emissions, is heat loss via building windows. In order to improve window’s insulation in existing buildings, structured-core transparent vacuum insulation panels (TVIPs) are proposed. TVIPs mainly consist of the structured core material, the low-emissivity film, and the transparent gas barrier envelope. TVIPs have high insulation performance and are inexpensive to manufacture and can be easily installed. Therefore, TVIPs have the potential to improve window’s insulation in existing buildings at a low cost. However, it is necessary to overcome the issue of preventing the pressure rise inside TVIP after vacuum sealing. The authors constructed an experimental setup to quantify the effect of reduction of gas flow rate in TVIP after evacuation by applying the pressure-rate-of-rise-method. In this experiment, a gas barrier film with a straw was used as the vacuum chamber. This could reproduce the pressure increase in the TVIP after sealing and the gas flow rate in the TVIP is evaluated. The experimental result shows that the coated core material and the enclosing getter agent lowered the pressure rise and gas flow rate in TVIP by combining concurrent evacuation and heating. Furthermore, after extending the simultaneous vacuuming and heating period to 8 h and applying the coated core material, and enclosing the getter agent, the internal pressure in TVIP may be lowered to around 1 Pa after 30 min after halting vacuuming. It was confirmed that this pressure satisfied the performance required for TVIPs, and the result was much closer to the realization of TVIPs.

Transparent, Stretchable, and Self‐Healable Gas Barrier Films with 2D Nanoplatelets for Flexible Electronic Device Packaging Applications

AbstractSelf‐healable elastomeric materials (PUAxPU10–x‐PDMS, x = 4, 6, or 8) have been synthesized and utilized as substrates or encapsulation films on the top of barrier films (deposited on polyethylene terephthalate (PET) substrates) to improve their gas barrier properties for packaging applications. Hexa‐layer (HL) assembly consisting of two inorganic 2D nanoplatelets, including Mg‐Al layered double hydroxide (LDH) and hexagonal boron nitride (hBN), and two oppositely charged polyelectrolytes, that is, polyethyleneimine (PEI) and poly(sodium styrene‐4‐sulfonate) (PSS), have been developed by alternative depositions of HL (i.e., PSS/LDH/PSS/PEI/hBN/PEI) sequentially. Then, a layer‐by‐layer technique is applied to produce multiple assemblies of hexa‐layer (HL)n and reduce water vapor transmission rate (WVTR) values of elastomeric PUA8PU2‐PDMS and PET substrates. The optimum WVTR values of 7.1 × 10−3 and 8.0 × 10−3 g m−2 day−1 are achieved using barrier PET/(HL)8/PUA8PU2‐PDMS (125/3/1 µm) and PUA8PU2‐PDMS/(HL)8 (125/3 µm) films, respectively. The self‐healable barrier PUA8PU2‐PDMS and PUA8PU2‐PDMS/(HL)8 films recover their initial WVTR values after self‐healing of mechanically damaged films. Organic light‐emitting diodes (OLEDs) encapsulated with PET/(HL)8/PUA8PU2‐PDMS and PUA8PU2‐PDMS/(HL)8 have 9–10 times longer half‐lifetime values than bare OLEDs. Accordingly, this report develops transparent, stretchable, and self‐healable gas barrier films for next‐generation flexible electronic device packaging applications.

Health Effects Caused by Soil Fumigant Chloropicrin, Reduction of Exposure to Chloropicrin, and Alternative Technology of Soil Fumigants

Pesticides are essentially toxic to living things and are used openly, so it is necessary to monitor them to prevent their adverse effects. We have studied farmers'exposure to pesticides during soil fumigation operations with chloropicrin, and have noted a danger to the farmers in the form of dyspnea. We examined accidents/symptoms of residents from chloropicrin reported by the Ministry of Agriculture, Forestry, and Fishery from 2010 to 2019. Eighty percent of the cause of these manifestations was the failure to cover fumigated soil with plastic film. Symptoms shown by residents included eye pain (91%), sore throat (35%), and headache (14%). The most common film used for covering fumigated soil in Japan is polyethylene. The agricultural technology centers in Japan have studied the use of gas barrier films, and found it possible to decrease the amount of chloropicrin used to 1/3, and leakage into the atmosphere to less than 1/10. This technology has become popular in the production of sweet potatoes in Tokushima Prefecture. Soil disinfection by solar heat has also been studied in Japan. These studies have shown positive advancements in the fertilization of soil and in the control of microbes. Chloropicrin has caused occupational exposure to farmers and environmental exposure to local residents. It is advisable that the technologies mentioned above become common practice.

Nacre-inspired biodegradable nanocellulose/MXene/AgNPs films with high strength and superior gas barrier properties

Super strength and high barrier properties are the bottleneck of the application of cellulose film materials. Herein, it is reported a flexible gas barrier film with nacre-like layered structure, in which 1D TEMPO-oxidized nanocellulose (TNF) and 2D MXene self-assembled to form an interwoven stack structure with 0D AgNPs filling the void space. The strong interaction and dense structure endowed TNF/MX/AgNPs film with mechanical properties far superior to PE films and acid-base stability. Importantly, the film presented ultra-low oxygen permeability confirmed by molecular dynamics simulations and better barrier properties to volatile organic gases than PE films. It is here considered the tortuous path diffusion mechanism of the composite film responsible for the enhanced gas barrier performance. The TNF/MX/AgNPs film also possessed antibacterial properties, biocompatibility and degradability (completely degraded after 150 days in soil). Collectively, the TNF/MX/AgNPs film brings innovative insights into the design and fabrication of high-performance materials.

Stretchable Gas Barrier Films Using Liquid Metal toward a Highly Deformable Battery.

Highly deformable batteries that are flexible and stretchable are important for the next-generation wearable devices. Several studies have focused on the stable operation and life span of batteries. On the other hand, there has been less focus on the packaging of highly deformable batteries. In wearable devices, solid-state or pouch lithium-ion batteries (LIBs) packaged in aluminum (Al)-laminated films, which protect against moisture and gas permeation, are used. Stretchable elastomer materials are used as the packaging films of highly deformable batteries; however, they are extremely permeable to gas and moisture. Therefore, a packaging film that provides high deformability along with gas and moisture barrier functionalities is required for the stable operation of highly deformable batteries used in ambient conditions. In this study, a stretchable packaging film with high gas barrier functionality is developed successfully by coating a thin layer of liquid metal onto a gold (Au)-deposited thermoplastic polyurethane film using the layer-by-layer method. The film exhibits excellent oxygen gas impermeability under mechanical strain and extremely low moisture permeability. It shows high impermeability along with high mechanical robustness. Using the proposed stretchable gas barrier film, a highly deformable LIB is assembled, which offers reliable operation in air. The operation of the highly deformable battery is analyzed by powering LEDs under mechanical deformations in ambient conditions. The proposed stretchable packaging film can potentially be used for the development of packaging films in advanced wearable electronic devices.

Analysis of volatile organic compounds produced during incineration of non-degradable and biodegradable plastics

As plastic consumption has increased, environmental problems associated with the accumulation of plastic wastes have started to emerge. These include the non-degradability of plastic and its disintegration into sub-micron particles. Although some biodegradable plastic products have been developed to relieve the landfill and leakage burden, a significant portion of discarded plastics are inevitably still incinerated. The concern here is that incinerating plastics may result in the emission of toxic volatile organic compounds (VOCs). Moreover, lack of policy and the limited market share contributes to the indiscriminate discarding of biodegradable plastics, whereby it is mixed and subsequently incinerated with non-degradable plastics. The aim of this study was therefore to qualitatively and quantitatively analyze the VOCs emitted from both non-degradable and biodegradable plastics during combustion employing gas chromatography mass spectrometry. Here, non-degradable poly(vinyl chloride) and poly(ethylene terephthalate) emitted 10-115 and 6-22 ppmv of VOCs, respectively. These emission levels were more than 100 times higher than the VOC concentrations of 0.1-0.5 and 0.1-1.8 ppmv obtained for biodegradable polyhydroxyalkanoate and polylactic acid, respectively. Notably, due to the presence of a repeating butylene group in both non-degradable and biodegradable plastics, 1,3-butadiene accounted for the highest concentration among the VOCs identified, with concentrations of 6-116 ppmv and 0.5-558 ppmv obtained, respectively. During the evaluation of gas barrier films employed for food packaging purposes, non-degradable aluminum-coated multilayered films emitted 9-515 ppmv of VOCs, compared to the 2-41 ppmv VOCs emitted by biodegradable nanocellulose/nanochitin-coated films. Despite the significantly lower levels of VOCs emitted during the incineration of biodegradable plastics, this does not represent suitable waste treatment solution because VOCs are still emitted during incomplete combustion. This study aims to encourage further research into diverse combustion conditions for plastics and stimulate discussions on the fate of discarded plastics.

Achieving a Superhydrophobic, Moisture, Oil and Gas Barrier Film Using a Regenerated Cellulose–Calcium Carbonate Composite Derived from Paper Components or Waste

It has been a persistent challenge to develop eco-friendly packaging cellulose film providing the required multiple barrier properties whilst simultaneously contributing to a circular economy. Typically, a cellulosic film made from nanocellulose materials presents severe limitations, such as poor water/moisture resistance and lacking water vapour barrier properties, related primarily to the hydrophilic and hygroscopic nature of cellulose. In this work, alkyl ketene dimer (AKD) and starch, both eco-friendly, non-toxic, cost-effective materials, were used to achieve barrier properties of novel cellulose–calcium carbonate composite films regenerated from paper components, including paper waste, using ionic liquid as solvent. AKD and starch were applied first into the ionic cellulose solution dope mix, and secondly, AKD alone was coated from hot aqueous suspension onto the film surface using a substrate surface precooling technique. The interactions between the AKD and cellulose film were characterised by Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) showing the formation of a ketone ester structure between AKD and the hydroxyl groups of cellulose. The presence of calcium carbonate particles in the composite was seen to enhance the cellulose crystallinity. The initial high-water vapour and oxygen transmission rates of the untreated base films could be decreased significantly from 2.00 to 0.14 g m−2 d−1, and 3.85 × 102 to 0.45 × 102 cm3 m−2 d−1, respectively. In addition, by applying subsequent heat treatment to the AKD coating, the water contact angle was markedly increased to reach levels of superhydrophobicity (>150°, and roll-off angle < 5°). The resistance to water absorption, grease-permeation, and tensile strength properties were ultimately improved by 41.52%, 95.33%, and 127.33%, respectively, compared with those of an untreated pure cellulose film. The resulting regenerated cellulose–calcium carbonate composite-based film and coating formulation can be considered to provide a future bio-based circular economy barrier film, for example, for the packaging, construction and agriculture industries, to complement or replace oil-based plastics.

A novel dual-functional epoxy-based composite coating with exceptional anti-corrosion and enhanced hydrogen gas barrier properties

Traditional hydrogen gas (H2) barrier polymer composite coatings or films suffered from poor corrosion resistance performance and low adhesion level, both of which could cause high risk of equipment failure and barrier property deficiency. Herein, a unique composite filler fabricated by hydrothermally in-situ grown hydrophobic CeO2 on glass flakes (GFs) was incorporated into epoxy resin (EP), followed by blade coating on different substrate, which facilitated orientation of GFs generated by shear force. The permeation of H2 and corrosive media could be dramatically decreased because of orientation-strengthened barrier and oxygen vacancies absorption effects. Additionally, interfacial interactions were also improved by means of covalent and hydrogen bonds between filler and polymer, reducing the free volume in EP and thereby further lowering gas diffusion. The CeO2 inhibition film and hydrophobicity property of composite filler prevent further penetration of corrosive media. Under the explicit and elaborate division of strengthening and inhibitive effects, the optimum sample demonstrated high impedance value 2 × 1010 ohm cm2 for 60d saltwater immersion and can tolerate 14d incessant harsh salt-spray test. It also exhibited 65.6% in H2 permeability coefficient reduction compared to pure EP coating and high adhesion strength of 6.35 MPa, which exhibits widespread industrial application prospect.

High-performance cellulose acetate-based gas barrier films via tailoring reduced graphene oxide nanosheets

Improving the gas molecule barrier performance and structural stability of bio-plastic films dramatically contribute to packaging and protective fields. Herein, we proposed a novel nanocomposite film consisting of cellulose acetate (CA)/polyethyleneimine (PEI)/reduced graphene oxide (rGO)-NiCoFeOx) with high gas barrier property by applying “molecular glue” and “nano-patching” strategies. Systematical investigations demonstrated that the CA/rGO interfacial interaction was effectively enhanced due to the “molecular glue” role of PEI chains via physical/chemical bonds and the defective regions in rGO plane were nano-patched through hydrophilic interactions between edged oxygen-containing functional groups and ultrafine NiCoFeOx nanoparticles (~3 nm). As a result, the oxygen and moisture transmission rates of the prepared CA/PEI/rGO-NPs hybrid film were significantly reduced to 0.31 cm3 ∗ μm/(m2 ∗ d ∗ kPa) and 314.23 g/m2 ∗ 24 h, respectively, which were 99.60% and 54.69% lower than pristine CA films. Meanwhile, the tensile strength of hybrid film was increased from 25.90 MPa to 40.67 MPa. More importantly, the designed nanocomposite film possesses excellent structural stability without obvious GO layer shedding and hydrophobicity attenuation after persistent bending at least 100 times. The exceptional robust and high gas barrier film displays great promising application in food, agriculture, pharmaceuticals and electronic instruments packaging industry.

Experimental Analysis of Evacuation Pressure and Gas Flow Rate in Structured-Core Transparent Vacuum Insulation Panels

The notion that modern buildings should strive to be net zero energy buildings (NZEBs) is widely accepted. One of the causes leading to high energy usage for space heating, resulting in avoidable carbon emissions, is heat loss via building windows. In order to improve window’s insulation in existing buildings, structured-core transparent vacuum insulation panels (TVIPs) are proposed. TVIPs mainly consist of the structured core material, the low-emissivity film, and the transparent gas barrier envelope. TVIPs have high insulation performance and are inexpensive to manufacture and can be easily installed. Therefore, TVIPs have potential to improve window’s insulation in existing buildings with low cost. However, it is necessary to overcome the issue of preventing the pressure rise inside TVIP after vacuum sealing. The authors constructed an experimental setup to quantify the effect of reduction of gas flow rate in TVIP after evacuation by applying pressure-rate-of-rise-method. In this experiment, a gas barrier film with a straw was used as the vacuum chamber. This could reproduce the pressure increase in the TVIP after sealing and the gas flow rate in the TVIP is evaluated. The experimental result show that the coated core material and the enclosing getter agentlowered the pressure rise and gas flow rate in TVIP by combining concurrent evacuation and heating. Furthermore, after extending the simultaneous vacuuming and heating period to 8 hours and applying the coated core material and enclosing the gettering agent, the internal pressure in TVIP may be lowered to around 1 Pa after 30 minutes after halting vacuuming. It was confirmed that this pressure satisfied the performance required for TVIPs, and the result was much closer to the realization of TVIPs.

New Structural Insights into Densely Assembled Reduced Graphene Oxide Membranes

AbstractDensely assembled graphene‐based membranes have attracted substantial interest for their widespread applications, such as compact capacitive energy storage, ion/molecular separation, gas barrier films, and flexible electronics. However, the multiscale structure of densely packed graphene membranes remains ambiguously understood. This article combines X‐ray and light scattering techniques as well as dynamic electrosorption analysis to uncover the stacking structure of the densely stacked reduced graphene oxide (rGO) membranes. The membranes are produced by reducing graphene oxide (GO) membranes with hydrazine, during which the colloidal interactions between GO sheets are modulated by the electrolyte solution. In contrast to the common notion that direct reduction of densely assembled GO sheets in parallel tends to result in significant “graphitization”, this article unexpectedly discovers that the resultant densely packed rGO membrane can still retain the interconnected network nanochannels and show good capacitive performances. This inspires the development of a hierarchical structural model to describe the densely packed rGO membranes. This article further shows that the nanochannel network can be fine‐tuned at the sub‐nanometer level by tailoring the salt concentration and the reduction temperature to render exceptional volumetric capacitance and good rate performance for rGO membranes even with increased packing density.

Two-Dimensional Stacked Composites of Self-Assembled Alkane Layers and Graphene for Transparent Gas Barrier Films with Low Permeability

Self-assembled alkane layers are introduced between graphene layers to physically block nanometer size defects in graphene and lateral gas pathways between graphene layers. A well-defined hexatriacontane (HTC) monolayer on graphene could cover nanometer-size defects because of the flexible nature and strong intermolecular van der Waals interactions of alkane, despite the roughness of graphene. In addition, HTC multilayers between graphene layers greatly improve their adhesion. This indicates that HTC multilayers between graphene layers can effectively block the lateral pathway between graphene layers by filling open space with close-packed self-assembled alkanes. By these mechanisms, alternately stacked composites of graphene and self-assembled alkane layers greatly increase the gas-barrier property to a water vapor transmission rate (WVTR) as low as 1.2 × 10-3 g/(m2 day), whereas stacked graphene layers generally show a WVTR < 0.5 g/(m2 day). Furthermore, the self-assembled alkane layers have superior crystallinity and wide bandgap, so they have little effect on the transmittance.