Structure Regulation of Ionic Copolymers: Unlocking Ionic Clusters through Solvent Shear Adaptation, a Computational-Experimental Insight

非技术概述：该项目重点研究离子共聚物，这是一种由离子传输片段组成的大分子家族，与可以增强机械稳定性的片段相连。这种聚合物材料有望作为膜应用于创新技术，例如，轻质清洁能源的产生和储存、水净化和生物医学应用。然而，科学家们还不能控制这些聚合物在加工成膜的过程中形成的结构。这提出了一个重要的障碍，因为这些结构决定了聚合物薄膜的性质，从而控制了它们在器件中的潜在用途。膜结构是由聚合物块之间的相互作用以及每个块与溶剂之间的相互作用以及加工条件决定的。控制结构的障碍源于离子段聚集的趋势，并形成在膜形成过程中仍然被捕获和“锁定”聚合物的区域。利用实验研究支持的计算工具，该项目将确定离子共聚物在伸长流动和溶剂蒸发时的结构演变。工作假设是，通过流动下的溶剂调节，“解锁”离子簇而不“锁定”其余的块，将使离子共聚物形成可控的、定义良好的结构膜。利用先进的计算工具，再加上结构测定技术，该项目将为聚合物加工提供基本的见解。这些知识将直接促进科学技术的进步，而科学技术的进步将促进国家的经济健康和繁荣。技术总结：随着在动态条件下理解离子聚合物的巨大挑战，该研究将努力捕捉离子嵌段共聚物在拉长流动和溶剂蒸发溶液中的结构的时间演变。该研究将利用非平衡分子动力学模拟，在选择性中子研究的支持下，捕捉聚合物加工的基本原理。提出的研究的工作假设是，“解锁”离子簇而不“锁定”疏水块将使离子共聚物膜中形成受控的定义良好的结构。这一过程可以通过操纵溶剂流动歧管来实现，该歧管将控制离子共聚物的结构，从而控制它们的性质。一组定义明确的二嵌段和三嵌段，包含聚苯乙烯磺酸电离嵌段，在选择性溶剂的溶液中，每个嵌段和所有嵌段的theta-溶剂，将在伸长流动和溶剂蒸发中进行研究。该研究将解析动态条件下导致所有区块处于“未锁定-未锁定”状态的参数，以及其对整齐电离相整体结构的影响。在静态条件和流场下，理解几种高度不相容的块体及其与溶剂相互作用的微妙平衡是实验和计算上的挑战。然而，随着离子共聚物溶剂流动响应的结构演变，计算研究和实验努力的融合将提供所需的多时间长度尺度的洞察力，这对驱动可电离共聚物的结构至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARY:This project focuses on ionic copolymers, a family of macromolecules comprised of segments that enable ionic transport, tethered to ones that can enhance mechanical stability. Such polymer materials show promise as membranes for use in innovative technologies, for example, light-weight clean energy generation and storage, water purification, and biomedical applications. However, scientists cannot yet control the structures these polymers form during their processing into membranes. This presents a significant roadblock since these structures determine the properties of the polymer films, and hence control their potential use for devices. The membrane structure is governed by interactions among the polymer blocks and between each of the blocks with the solvent, as well as processing conditions. The barrier to controlling the structure stems from the tendency of the ionic segments to aggregate and form regions that remain trapped and "lock" the polymers during membrane formation. Using computational tools supported by experimental studies, the project will determine the structure evolution of ionic co-polymers in elongational flow and as the solvents evaporate. The working hypothesis is that "unlocking" the ionic clusters without "locking" the rest of the blocks, through solvent tuning under flow, will enable the formation of controlled, well-defined structured membranes of ionic co-polymers. With advanced computational tools, coupled with structure determination techniques, the project will provide fundamental insights into polymer processing. This knowledge will directly promote the progress of science and technologies that will advance the economic health and prosperity of the nation. TECHNICAL SUMMARY: With the grand challenge of understanding ionic polymers under dynamic conditions, the research will strive to capture the time evolution of the structure of ionic block co-polymers in solutions in elongational flow and as solvents evaporate. The study will capture polymer processing fundamentals, using non-equilibrium molecular dynamics simulations, supported by selective neutron studies. The working hypothesis of the proposed research is that "unlocking" the ionic clusters without "locking" the hydrophobic blocks will enable the formation of controlled well-defined structures in ionic copolymer membranes. This process is achievable by manipulating a solvent-flow manifold that will control the structure of ionic copolymers and consequently their properties. A set of well-defined diblocks and triblocks that contain polystyrene sulfonate ionizable blocks, in solutions of selective solvents for each of the blocks and theta-solvents for all blocks, will be studied in elongational flow and as the solvents evaporate. The study will resolve the parameters that lead to the "unlocked-unlocked" state for all blocks under dynamic conditions, and its effect on the overall structure of the neat ionizable phases. Understanding the delicate balance of several highly incompatible blocks and their interactions with solvents under quiescent conditions and under flow fields presents experimental and computational challenges. However, the convergence of computational studies and experimental efforts following the structure evolution of ionic co-polymers solvent-flow response will provide the required multi-time-length-scale insight essential to drive the structure of ionizable copolymers..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.