Abstract Incorporation of nanoplatelets is known to be effectively in the reduction of gas permeation of polymer membranes, which has been typically attributed to the torturous path effect. However, the measured water vapor transmission rates (WVTR) from the poly(vinyl alcohol) (PVA)/graphene oxide (GO) nanocomposite membranes are found to be smaller than the theoretical values calculated by the Bharadwaj model based on the torturous path effect. This discrepancy is indicative of the existence of other structural factors responsible for the WVTR that are rarely discussed in literature. In this work, the positron annihilation lifetime spectroscopy (PALS), a widely recognized method for characterization of the atomic-scale microstructure of polymers, is employed herein to study the free volume of the PVA/GO composite membranes. The free volume size of the composite membrane decreases with increasing GO contents, and the fractional free volume (FFV) decreases with the increase of annealing temperature. Strong dependence of the WVTR of PVA/GO on the FFV and crystallinity has been revealed, indicating that, along with the nanoplatelets-induced torturous path effect, they are important factors affecting the water vapor permeation of polymer nanocomposite membranes.

中文翻译：

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正电子湮没寿命光谱研究聚合物纳米复合膜中水蒸气渗透的结构依赖性

摘要 已知纳米血小板的掺入可有效减少聚合物膜的气体渗透，这通常归因于曲折路径效应。然而，发现从聚乙烯醇 (PVA)/氧化石墨烯 (GO) 纳米复合膜测得的水蒸气透过率 (WVTR) 小于 Bharadwaj 模型基于曲折路径效应计算的理论值。这种差异表明存在导致 WVTR 的其他结构因素，这些因素在文献中很少讨论。在这项工作中，正电子湮没寿命光谱 (PALS) 是一种广泛认可的表征聚合物原子级微观结构的方法，用于研究 PVA/GO 复合膜的自由体积。复合膜的自由体积尺寸随着GO含量的增加而减小，而自由体积分数（FFV）随着退火温度的升高而减小。已揭示 PVA/GO 的 WVTR 对 FFV 和结晶度的强烈依赖性，表明除了纳米血小板诱导的曲折路径效应外，它们是影响聚合物纳米复合膜水蒸气渗透的重要因素。