Jiang Chi, Zhang Liping, Li Peng, Sun Haixiang, Hou Yingfei, Niu Q Jason
State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum (East China), Qingdao 266580, China.
Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China.
ACS Appl Mater Interfaces. 2020 Jun 3;12(22):25304-25315. doi: 10.1021/acsami.0c05166. Epub 2020 May 18.
Ultrathin polyamide nanofilms are desirable as the separation layers for the highly permeable thin-film composite (TFC) membranes, and recently, their lowest thickness limits have attracted a lot of attention from researchers. Due to the interference of the underlying substrate, preparing a defect-free, ultrathin polyamide nanofilm directly on top of a membrane substrate remains a great challenge. Herein, we report a novel fabrication technique of TFC membranes, named (IFIP), where the IP reaction occurs at the uniform, free oil-water interface dozens of microns above the substrate, and then the resulting nanofilm spontaneously assembles into the TFC structure without extra manual transfer. This IFIP method not only overcomes the limitations of conventional IP, succeeding in preparing ultrathin-nanofilm composite membranes for nanofiltration and reverse osmosis application, but also enables scale membrane manufacturing that is not feasible via previously reported free-standing IP. Based on the IFIP method, the thickness of the polyamide nanofilm was successfully reduced to ca. 3-4 nm, which we believe is close to the ultrathin limit of the polyamide nanofilm for separation application. Meanwhile, the structure-performance relationship revealed that the strategy of increasing TFC membrane permeance by reducing polyamide layer thickness also had a limit. Besides, the IP mechanisms in regard to the formation of surface morphology and film growth were explored by combining experimental and molecular simulation methods. Overall, this work is expected to push forward the fundamental study and practical application of the ultrathin-film composite membrane.
超薄聚酰胺纳米膜作为高渗透性复合薄膜（TFC）膜的分离层备受青睐，近来，其最小厚度极限引起了研究人员的广泛关注。由于底层基材的干扰，直接在膜基材顶部制备无缺陷的超薄聚酰胺纳米膜仍然是一项巨大挑战。在此，我们报道了一种新型的TFC膜制备技术，名为界面自由引发聚合法（IFIP），其中界面聚合反应在距基材几十微米的均匀、自由的油水界面处发生，然后所得纳米膜会自发组装成TFC结构，无需额外的人工转移。这种IFIP方法不仅克服了传统界面聚合的局限性，成功制备出用于纳滤和反渗透应用的超薄纳米膜复合膜，还实现了规模化膜制造，而这通过先前报道的独立界面聚合是不可行的。基于IFIP方法，聚酰胺纳米膜的厚度成功降低至约3 - 4纳米，我们认为这已接近用于分离应用的聚酰胺纳米膜的超薄极限。同时，结构 - 性能关系表明，通过降低聚酰胺层厚度来提高TFC膜渗透率的策略也存在极限。此外，结合实验和分子模拟方法探索了关于表面形态形成和膜生长的界面聚合机制。总体而言，这项工作有望推动超薄复合膜的基础研究和实际应用。
