Moisture-Permeable, Humidity-Enhanced Gas Barrier Films Based on Organic/Inorganic Multilayers

Abstract

Gas barrier films with water-vapor-permeability have exhibited broad application prospects in gas separation and dehumidification. Herein, multilayer films comprised of layered double hydroxides (LDH) nanosheets and carboxymethyl cellulose sodium (CMC) were fabricated via layer-by-layer assembly. The resulting (LDH/CMC) films show excellent gas barrier properties, which are ascribed to the significantly increased pathway for gas permeation originating from the large aspect ratio and high orientation of two-dimensional LDH nanosheets. Unlike traditional gas barrier films with nonselective blocking effect for various gases (including water vapor), the (LDH/CMC) films exhibit an unusual moisture permselective property. The moisture-permeable property was related to the hygroscopicity of CMC and hydrophilicity of LDH, which can enrich the water molecules from the surroundings and aggrandize the osmotic pressure for water vapor, resulting in an uncommon improvement of water vapor transmission. It is interesting to find that the (LDH/CMC) films exhibit enhanced gas (O, CO, CH, and N) barrier properties upon treatment in a humid environment, due to the formation of hydrogen bonds between the infiltrated water molecules and hydrophilic groups in CMC, thus padding the interstitial space of the CMC molecular chains and increasing the gas transmission path. The reduction of free volume and extension of the gas transmission path further enhance the gas barrier properties of (LDH/CMC) films. Moreover, the (LDH/CMC) films represent the water vapor permselective property in mixed gas (including O, CO, CH, N, and water vapor), while maintaining the barrier for other gases, which can be potentially applied in air dehydration and dehumidification of natural gas.

High-efficiency CO2 separation using hybrid LDH-polymer membranes

“…Monolayer LDH nanosheets were obtained by exfoliating a bulk sample in formamide. Highly crystalline, MgAl(CO 3 )-LDH platelets were first prepared by a urea-assisted hydrothermal method 32 . X-ray diffraction (XRD) pattern of the MgAl(CO 3 )-LDH (blue line in Fig.…”

“…MgAl(CO 3 )-LDH nanoplatelets were synthesised by an urea-assisted hydrothermal method 32 . Typically, Al(NO 3 ) 3 ·9H 2 O, Mg(NO 3 ) 2 ·6H 2 O and urea were dissolved in 100 mL deionized water with concentrations of 0.05, 0.1 and 0.5 M, respectively.…”

Stretchable gas barrier films achieved by hydrogen-bond self-assembly of nano-brick multilayers

“…XRD pattern of the MgAl(CO 3 )-LDH sample ( Figure 1A) shows clear diffraction peaks at 12.2°, 24.3°, 34.9°, 39.1°, 47.2°, 61.2°and 62.3°, which correspond to (003), (006), (009), (015), (018), (110) and (113) diffractions of a hydrotalcite phase. 37 To delaminate LDH into monolayer, the interlayered CO 3 2were replaced by NO 3 ions. Figure 1B displays the (003) characteristic peak shifts from 12.2deg to 10.2deg and the corresponding layer spacing expands from 0.77 nm to 0.89 nm, which confirms that the anions between the hydrotalcite layers have been exchanged from carbonate to nitrate.…”

Nano-Brick Wall Architectures Account for Super Oxygen Barrier PET Film by Quadlayer Assembly of Polyelectrolytes and α-ZrP Nanoplatelets

“…Multilayer coating can be constructed by alternating deposition of different species with negative and positive charges. Resultant multilayer coatings can increase the gas barrier properties of polymer substrate [11]. In the case of 2-dimentional inorganic nanoplatelets with negative charges, sodium montmorillonite (MMT) [8], Laponite (LATP) [9] and grapheme oxide (GO) [12] have been used to construct LbL thin coatings with positively charged polyelectrolytes.…”

“…Negatively charged 2D inorganic nanoplatelets, such as MMT, GO, and zirconium phosphate (ZrP), have been reported to construct bilayer (BL) assembly films onto the PET film with positively charged polyelectrolytes [8,9,10,11,12,13,25]. LbL transparent thin films containing inorganic components have been investigated for their high strength, anti-flammability, and oxygen barrier properties [26,27,28].…”