Hoffman John R, Phillip William A
205 McCourtney Hall, Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States.
ACS Macro Lett. 2020 Sep 15;9(9):1267-1279. doi: 10.1021/acsmacrolett.0c00482. Epub 2020 Aug 18.
Membranes fabricated from self-assembled materials are one recent example of how polymer science has been leveraged to advance membrane technology. Due to their well-defined nanostructures, the performance of membranes made from these materials is pushing the boundaries of size-selective filtration. Still, there remains a need for higher performance and more selective membranes. The advent of functional membrane platforms that rely on mechanisms beyond steric hindrance (e.g., charge-selective membranes and membrane sorbents) is one approach to realize improved solute-solute selectivity and further advance membrane technology. To date, the lab-scale demonstration of these platforms has often relied on fabrication schemes that require extended processing times. However, in order to translate lab-scale demonstrations to larger-scale implementation, it is critical that the rate of the functionalization scheme is reconciled with membrane manufacturing rates. In this viewpoint, it is postulated that substrates lined by reactive moieties that are amenable to postfabrication modification would enable the production of membranes with controlled nanostructures while providing access to a diverse array of pore wall chemistries. A comparison of reaction and manufacturing rates suggests that mechanisms that exhibit second-order reaction rate constants of at least 1 M s are needed for roll-to-roll processing. Furthermore, for mechanisms that exhibit rate constants greater than 300 M s, it may be possible to integrate multiple functional domains over the membrane surface such that useful properties emerge. These multifunctional systems can expand the capabilities of membranes when the patterned chemistries interact at the heterojunctions between domains (e.g., Janus and charge-patterned mosaic membranes) or if they exhibit cooperative responses to external operating conditions (e.g., membrane pumps).
由自组装材料制成的膜是聚合物科学如何被用于推动膜技术发展的一个最新例子。由于其明确的纳米结构，由这些材料制成的膜的性能正在突破尺寸选择性过滤的界限。然而，仍然需要更高性能和更具选择性的膜。依赖于空间位阻以外机制的功能性膜平台（例如，电荷选择性膜和膜吸附剂）的出现是实现改善溶质-溶质选择性并进一步推动膜技术发展的一种方法。迄今为止，这些平台在实验室规模的演示通常依赖于需要较长加工时间的制造方案。然而，为了将实验室规模的演示转化为更大规模的实施，使功能化方案的速率与膜制造速率相匹配至关重要。在这个观点中，假设由易于进行后加工改性的反应性部分排列的基材将能够生产具有可控纳米结构的膜，同时提供多种孔壁化学性质。反应速率和制造速率的比较表明，对于卷对卷加工，需要具有至少1 M s二级反应速率常数的机制。此外，对于表现出大于300 M s速率常数的机制，有可能在膜表面整合多个功能域，从而产生有用的性质。当图案化的化学物质在域之间的异质结处相互作用时（例如，Janus膜和电荷图案化镶嵌膜），或者如果它们对外部操作条件表现出协同响应时（例如，膜泵），这些多功能系统可以扩展膜的功能。
