Synthetic Saponite Clays as Additives for Reducing Aging Effects in PIM1 Membranes
Synthetic Saponite Clays as Additives for Reducing Aging Effects in PIM1 Membranes
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DOI：
10.1021/acsapm.0c00514
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发表时间：
2020-08-01
影响因子：
5
通讯作者：
Gatti, Giorgio
中科院分区：
文献类型：
--
作者：
Begni, Federico;Paul, Geo;Gatti, Giorgio
本征微孔聚合物是气体分离领域最有前途的高分子材料之一。它们非常坚硬和扭曲的骨架导致了异常高的自由体积和高的内表面积，具有高的气体渗透率和中等的理想选择性，特别是对于O-2/N-2和CO2/N-2对，其值高于Robeson上界。然而，PIM1的高FFV往往是短暂的，很快崩溃，留下更少的运输途径和降低气体渗透性。解决这个问题的一种方法是在聚合物基体中添加填料。在这里，我们报道了使用合成粘土皂石作为填料来减缓PIM1膜的物理老化。制备了两种不同皂土样品（一种是完全无机的，另一种是表面活性剂功能化的）的混合基质膜（MMMs），并在一年的时间内研究了它们的渗透性能，以探索随时间推移的物理老化效应。在没有填料的情况下，PIM1表现出固有微孔聚合物的典型老化行为，即气体渗透率逐渐下降。与此相反，皂片在老化1周后呈现平台期，表明填充物长期减缓了PIM1膜的老化。陈化1年后，原生PIM1的CO2渗透率降低80%，而无机皂土和功能化皂土的CO2渗透率分别降低53%和59%。除了老化效应外，填料与聚合物基体之间的相互作用也通过SS-NMR谱进行了监测。C-13自旋-晶格弛豫时间（T-1）的测量表明，T-O-T片层间的PIM1链嵌入可能是PIM1延缓老化的机制之一。层状薄片之间的链约束可以在保持小的自由体积的同时降低链的致密性
Polymers of intrinsic microporosity represent one of the most promising polymeric materials for gas separation applications. Their very rigid and contorted backbone induces unusually high free volumes and high internal surface area, with high gas permeabilities and moderate ideal selectivity, especially for O-2/N-2 and CO2/N-2 pairs with values lying above Robeson's upper bound. However, the high FFV of PIM1 tends to be short-lived, soon collapsing to leave fewer transport pathways and reduce gas permeability. One way to tackle this problem is the addition of fillers within the polymeric matrix. Here we report the use of synthetic clays named saponites as fillers to slow down the physical aging of PIM1 membranes. Mixed matrix membranes (MMMs) based on two different saponite samples (one completely inorganic and one functionalized with a surfactant) have been obtained, and their permeation performances have been studied in the course of one year to explore physical aging effects over time. Without filler, PIM1 exhibits the classical aging behavior of polymers of intrinsic microporosity, namely, a progressive decline in gas permeation. On the contrary, with saponites, MMMs present a plateau after 1 week within the aging showing that the fillers slow down the aging of PIM1 membranes in the long term. After one year of aging, the total reduction for CO2 permeability for native PIM1 was 80%, whereas for the MMMs it was 53% and 59% for the inorganic and the functionalized saponite, respectively. Interactions between the fillers and the polymeric matrix in addition to aging effects have been also monitored through SS-NMR spectroscopy. The C-13 spin-lattice relaxation time (T-1) measurements reveal that PIM1 chains intercalation between T-O-T lamellar sheets could be one of the mechanisms responsible for PIM1 slowing down aging. Chains confinement between lamellar sheets could play a significant role in reducing the densification of chains, while maintaining small free volumes.yy