i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, 215123, PR China.
Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN, 37235, USA.
Nat Commun. 2023 Apr 25;14(1):2373. doi: 10.1038/s41467-023-38114-3.
Polymer membranes have been used extensively for Angstrom-scale separation of solutes and molecules. However, the pore size of most polymer membranes has been considered an intrinsic membrane property that cannot be adjusted in operation by applied stimuli. In this work, we show that the pore size of an electrically conductive polyamide membrane can be modulated by an applied voltage in the presence of electrolyte via a mechanism called electrically induced osmotic swelling. Under applied voltage, the highly charged polyamide layer concentrates counter ions in the polymer network via Donnan equilibrium and creates a sizeable osmotic pressure to enlarge the free volume and the effective pore size. The relation between membrane potential and pore size can be quantitatively described using the extended Flory-Rehner theory with Donnan equilibrium. The ability to regulate pore size via applied voltage enables operando modulation of precise molecular separation in-situ. This study demonstrates the amazing capability of electro-regulation of membrane pore size at the Angstrom scale and unveils an important but previously overlooked mechanism of membrane-water-solute interactions.
聚合物膜已广泛用于亚埃尺度的溶质和分子分离。然而，大多数聚合物膜的孔径被认为是固有膜性质，不能通过施加的刺激在操作中进行调节。在这项工作中，我们通过一种称为电诱导渗透膨胀的机制表明，在电解质存在的情况下，通过施加电压可以调节导电聚酰胺膜的孔径。在施加电压下，带高电荷的聚酰胺层通过唐南平衡在聚合物网络中浓缩抗衡离子，并产生相当大的渗透压，以扩大自由体积和有效孔径。膜电位和孔径之间的关系可以使用带有唐南平衡的扩展弗洛里-雷纳理论进行定量描述。通过施加电压调节孔径的能力使精确分子分离的原位操作调节成为可能。这项研究展示了在埃尺度上电调节膜孔径的惊人能力，并揭示了一种重要但以前被忽视的膜-水-溶质相互作用的机制。
