Hoffman John R, Phillip William A
Department of Chemical and Biomolecular Engineering, University of Notre Dame, 205 McCourtney Hall, Notre Dame, Indiana 46556, United States.
ACS Appl Mater Interfaces. 2020 Apr 29;12(17):19944-19954. doi: 10.1021/acsami.0c03075. Epub 2020 Apr 16.
Charged functional groups are often incorporated onto the surface of nanofiltration (NF) membranes to facilitate the selective rejection of multivalent ions over monovalent ions. However, since fouling-resistant surfaces tend to be electrically neutral, the incorporation of charged functionality exacerbates membrane fouling. Multifunctional Janus membrane architectures, which incorporate chemically distinct domains over their cross section, provide a strategy for balancing the competing demands associated with making fouling-resistant, ion rejecting NF membranes. Here, through the controlled exposure of poly(trifluoroethyl methacrylate--oligo-(ethylene glycol) methyl ether methacrylate--(3-azido-2-hydroxypropyl methacrylate)) copolymer substrates to a series of reactive solutions containing alkyne-terminated molecules, the process for creating dual-functional membranes by using the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction was analyzed. Under the appropriate conditions, the CuAAC reaction propagates into the copolymer substrate as a front. This phenomenon results in a process for creating layered domains of distinct functionality whereby the distribution of antifouling zwitterionic moieties and ion rejecting sulfonate moieties can be modified by manipulating the exposure time. The ion rejection and fouling propensity for a family of dual-functional membranes was examined. For short initial reaction times, which introduced a thin antifouling layer on top of an ion rejection layer, the rejection of 1 mM KSO, 87%, was comparable to the value for full charge control membranes, 90%. Moreover, when exposed to a fouling solution containing bovine serum albumin (BSA), these dual-functional membranes exhibited an 18% decline in normalized flux and recovered 99% of their flux upon rinsing with water. In comparison, the full charge membranes exhibited a 44% decline in normalized flux and recovered 65% of their flux upon washing. As such, the results demonstrate that the controlled functionalization process reported here is capable of balancing antifouling and ion rejection capabilities. Furthermore, the versatile nature of the click chemistry mechanism at the center of this process offers a means by which to design and fabricate multifunctional membranes for numerous future applications.
带电荷的官能团常被引入纳滤（NF）膜表面，以促进对多价离子的选择性截留，使其优于单价离子。然而，由于抗污染表面往往呈电中性，引入带电荷的官能团会加剧膜污染。多功能Janus膜结构在其横截面上包含化学性质不同的区域，为平衡制造抗污染、离子截留NF膜相关的相互竞争的需求提供了一种策略。在此，通过将聚（甲基丙烯酸三氟乙酯 - 聚（乙二醇）甲醚甲基丙烯酸酯 - （3 - 叠氮基 - 2 - 羟丙基甲基丙烯酸酯））共聚物基底可控地暴露于一系列含有炔基封端分子的反应溶液中，分析了利用铜（I）催化的叠氮化物 - 炔烃环加成（CuAAC）反应制备双功能膜的过程。在适当条件下，CuAAC反应以前沿的形式传播到共聚物基底中。这种现象导致了一种创建具有不同功能的分层区域的过程，通过控制暴露时间可以改变抗污染两性离子部分和离子截留磺酸根部分的分布。研究了一系列双功能膜的离子截留率和污染倾向。对于较短的初始反应时间（在离子截留层顶部引入了一层薄的抗污染层），1 mM KSO的截留率为87%，与完全电荷控制膜的值90%相当。此外，当暴露于含有牛血清白蛋白（BSA）的污染溶液中时，这些双功能膜的归一化通量下降了18%，用水冲洗后通量恢复了99%。相比之下，完全电荷膜的归一化通量下降了44%，洗涤后通量恢复了65%。因此，结果表明本文报道的可控功能化过程能够平衡抗污染和离子截留能力。此外，该过程核心的点击化学机制的通用性为设计和制造用于众多未来应用的多功能膜提供了一种方法。
