State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering , Beijing University of Chemical Technology , Beijing 100029 , P. R. China.
ACS Appl Mater Interfaces. 2018 Aug 22;10(33):28130-28138. doi: 10.1021/acsami.8b09740. Epub 2018 Aug 9.
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.
具有水蒸气透过性的气体阻隔膜在气体分离和除湿方面具有广阔的应用前景。本文通过层层组装的方法制备了由层状双氢氧化物（LDH）纳米片和羧甲基纤维素钠（CMC）组成的多层膜。所得的（LDH/CMC）膜表现出优异的气体阻隔性能，这归因于二维 LDH 纳米片的大纵横比和高取向性，显著增加了气体渗透的途径。与传统的对各种气体（包括水蒸气）具有非选择性阻隔效果的气体阻隔膜不同，（LDH/CMC）膜表现出异常的水分选择渗透性。透湿性与 CMC 的吸湿性和 LDH 的亲水性有关，这可以从周围环境中富集水分子并增大水蒸气的渗透压，从而导致水蒸气传输的异常改善。有趣的是，发现（LDH/CMC）膜在潮湿环境中的处理会增强气体（O、CO、CH 和 N）阻隔性能，这是由于渗透水分子和 CMC 中亲水性基团之间形成氢键，从而填充了 CMC 分子链的间隙空间并增加了气体传输路径。自由体积的减少和气体传输路径的延长进一步增强了（LDH/CMC）膜的气体阻隔性能。此外，（LDH/CMC）膜在混合气体（包括 O、CO、CH、N 和水蒸气）中表现出水蒸气选择渗透性，同时保持对其他气体的阻隔性，这可能在空气脱水和天然气除湿方面有潜在应用。
