Specific Ion Separations by Controlling the Molecular Environment of Hydrated Polymers

研究人员的目标是解决从具有相同电荷，相似大小和相似化学性质的混合离子类型溶液中按类型分离离子（带电原子或分子）的困难挑战。研究人员建议使用一种称为极化率的特性来实现这种具有挑战性的分离。极化率是电子在分子周围移动和转移的能力。这些电子带负电荷，导致分子中具有更多电子的区域带更多的负电荷，留下分子中具有较少电子的区域带正电荷。这种转移分子周围电荷的能力，或极化率，是影响离子如何与其他分子相互作用的关键属性。通过改变分离膜中可极化分子的数量和类型，研究人员将了解这种性质对从混合物中分离离子的基本影响。设计具有精确分离性能的膜的能力，特别是对于类似离子的这些具有挑战性的分离，将有助于改善废水处理，减少环境污染，以及核电工业中的再循环和回收过程。研究人员计划通过开放日活动期间提供的互动模块分享他们的研究成果，该模块将向广大观众介绍与食品，水和能源需求相关的问题。该提案旨在研究聚合物膜中可极化官能团驱动的离子吸附。研究人员假设，增加聚合物主链上官能团的极化率将有利于吸附极化程度较低的离子。为了验证这一假设，研究人员将合成两个系列的聚砜膜，一个具有固定数量的日益极化的官能团，另一个具有不同的氢键供体官能团。研究人员还将通过比较侧链官能化聚合物与嵌段共聚物（其中只有一个嵌段含有可极化官能团），来测试水合聚合物的极化率可以通过将聚合物主链上的官能团更紧密地聚集在一起而增加的假设。嵌段共聚物结构允许可极化的官能团被定位到材料的隔离区域中。可极化官能化的程度将通过核磁共振光谱和滴定来确认。所得膜将表征介电常数，其测量介电常数，以及它们的离子吸附和选择性性质。拟议活动的结果将是对尺寸驱动分离过程的基本理解，与尺寸或扩散驱动过程相比，这一过程的研究不够彻底。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

The investigators aim to tackle the difficult challenge of separating ions (charged atoms or molecules) by type from a solution of mixed ion types that have the same charge, similar size and similar chemistry. The investigators propose to use a property called polarizability to achieve this challenging separation. Polarizability is the capacity for electrons to move and shift around a molecule. These electrons are negatively charged, causing areas of a molecule with a greater number of electrons to be more negatively charged, leaving areas of the molecule with fewer electrons positively charged. This capacity for shifting charges around a molecule, or polarizability, is a key property that influences how ions interact with other molecules. By changing the number and type of polarizable molecules within the separation membrane, the investigators will learn what fundamental effects this property has on separating ions from a mixture. The ability to design membranes with precise separation performance, especially for these challenging separations of similar ions, will contribute to improving waste-water treatment, reducing environmental contamination, and recycling and recovery processes in the nuclear power industry. The investigators plan to share their research results through an interactive module, offered during the Open House event, which will introduce a wide audience to issues related to food, water, and energy resource needs.This proposal aims to investigate ion sorption driven by polarizable functional groups in a polymer membrane. The investigators hypothesize that increasing the polarizability of the functional groups on the polymer backbone will favor sorption of less polarizable ions. To test this hypothesis the investigators will synthesize two series polysulfone-based membranes, one with a fixed number of increasingly polarizable functional groups and the other with varying hydrogen bond-donating functional groups. The investigators will also test the hypothesis that the polarizability of a hydrated polymer can be increased by clustering functional groups closer together on the polymer backbone, by comparing the side-chain functionalized polymers with block copolymers, where only one block contains the polarizable functionality. The block copolymer architecture allows the polarizable functionality to be localized into segregated regions of the material. The degree of polarizable functionalization will be confirmed via nuclear magnetic resonance spectroscopy and titration. The resulting membranes will be characterized for the dielectric permittivity, which measures the dielectric constant, and their ion sorption and selectivity properties. The outcome of the proposed activities will be a fundamental understanding of thermodynamically-driven separation processes, which are less thoroughly investigated when compared to size- or diffusivity-driven processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.