Rationally Designed Biphasic Block Co-Polymer/Ionic Liquid Transport Platforms through Manipulation of Physical Chemistry and Nano-Confinement

工业能源生产过程产生的气体产品，如二氧化碳，必须从废气流中去除，以满足监管排放标准。从大量高温高压气体中选择性地去除二氧化碳等单个分子是一个具有挑战性的问题。节能分离技术，如膜，需要保持利润和尽量减少对环境的影响。由聚合物和离子液体复合而成的一种特殊类型的膜是一种很有前途的节能气体分离技术，其应用范围从天然气预处理到碳减排。然而，由于不稳定性和性能限制，聚合物/离子液体复合膜不适合在高压下使用，阻碍了这些系统的工业部署。该项目旨在通过一种将离子液体限制在聚合物平台内的替代设计，扩大聚合物/离子液体复合材料作为气体分离膜的有效性。由此产生的化学和物理特性有望使膜在工业相关压力下具有增强的机械稳定性和具有竞争力的分离性能。研究人员将专注于聚合物/离子液体复合膜的合成和演示，以选择性地从含有甲烷的气流中去除二氧化碳。计算机模拟将说明膜性能背后的基本机制，可用于进一步优化设计。除了为社会带来技术效益外，该项目还将通过亲身实践的本科生研究项目，扩大代表性不足的群体对STEM的参与。密西西比大学的本科生也将通过为聚合物科学、膜科学和模拟课程开发的教学模块获得对膜科学领域的认识。该项目旨在设计一种具有最佳气体分离性能的双相聚合物/离子液体复合膜，通过利用嵌段共聚物平台内离子液体纳米约束导致的富离子液体相特性的有益变化。通过综合实验和计算研究方法，研究人员将阐明嵌段共聚物尺寸和结构与纳米限制离子液体结构之间的结构/性能/性能关系，以开发具有工业意义的稳定气体分离膜。具体而言，通过将实验设计方法与分子动力学模拟相结合来实现可调嵌段共聚物平台的设计。研究人员假设离子液体中存在最大的化学渗透性和选择性，这是由于分子内有序引起的尺度依赖的限制效应。实验设计详细介绍了两种共聚物的使用：聚苯乙烯-嵌段聚（N， N-二甲氨基乙基甲基丙烯酸酯）（PS-b-DMAEMA）和聚苯乙烯-嵌段聚乙二醇（PS-b-PEG）。选择了两种离子液体进行研究：1-乙基-3-甲基咪唑双（三氟甲基磺酰基）亚胺[EMIM][Tf2N]和1-乙基-3-甲基咪唑硫氰酸盐[EMIM][SCN]。在基线实验中，DMAEMA和聚苯乙烯的均聚物将作为嵌段共聚物的亲水性（极性）和疏水性（非极性）组分的模型。将测量二氧化碳和甲烷的纯气体渗透率，以评估最佳双相膜的气体分离性能。混合渗透研究也将进行。通过模拟，研究人员将预测聚合物/离子液体的相互作用，并通过适当的能量和结构指标量化纳米限制对二氧化碳和甲烷吸收的影响。研究人员将通过开发高分子科学、膜科学和分子模拟等本科课程的研究集成模块，努力提高学生对膜领域的认识。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

Industrial energy production processes generate gaseous products such as carbon dioxide that must be removed from the exhaust streams to meet regulatory emissions standards. The selective removal of individual molecules like carbon dioxide from enormous volumes of hot, high-pressure gas is a challenging problem. Energy-efficient separation technologies, such as membranes, are required to preserve profits and minimize environmental impacts. A special class of membranes formed from a composite of polymer and ionic liquid is a promising energy-efficient gas separation technology with demonstrated applications ranging from natural gas pretreatment to carbon emission reduction. However, polymer/ionic liquid composite membranes are not suitable for use at high pressures due to instability and performance limitations, preventing industrial deployment of these systems. This project seeks to expand the effectiveness of polymer/ionic liquid composites as gas separation membranes through an alternative design that confines the ionic liquid within a polymer platform. The resulting chemical and physical characteristics are expected to yield membranes with enhanced mechanical stability at industrially-relevant pressures and with competitive separation performance. The investigators will focus on synthesis and demonstration of polymer/ionic liquid composite membranes for selectively removing carbon dioxide from a gas stream also containing methane. Computer simulations will illustrate the fundamental mechanisms behind membrane performance, which can be used to further optimize the design. In addition to the technological benefit to society, the project will broaden the participation of underrepresented groups in STEM through hands-on undergraduate research projects. Undergraduates at the University of Mississippi will also gain awareness of the membrane science field through instructional modules developed for polymer science, membrane science, and simulation courses.This project seeks to design a biphasic polymer/ionic liquid composite membrane with optimal gas separation properties by exploiting the beneficial changes in the ionic liquid-rich phase properties resulting from ionic liquid nano-confinement within a block copolymer platform. Through an integrated experimental and computational research approach, the investigators will elucidate the structure/property/performance relationships between block copolymer size and structure and nano-confined ionic liquid structure to develop stable gas separation membranes of industrial interest. Specifically, the design of a tunable block copolymer platform will be achieved by combining design-of-experiments methods with molecular dynamics simulations to inform experiments. The investigators hypothesize that maxima in chemical permeability and selectivity in ionic liquids exist due to scale-dependent confinement effects resulting from intramolecular ordering. The design of experiments details the use of two copolymers: polystyrene-block-poly(N, N-dimethylaminoethyl methacrylate) (PS-b-DMAEMA) and polystyrene-block-polyethylene glycol (PS-b-PEG). Two ionic liquids have been selected for study: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide [EMIM][Tf2N] and 1-ethyl-3-methylimidazolium thiocyanate [EMIM][SCN]. During the baseline experiments, the homopolymers of DMAEMA and polystyrene will serve as models of the hydrophilic (polar) and hydrophobic (non-polar) components of the block copolymers. Pure gas permeation of carbon dioxide and methane will be measured to assess gas separation performance of optimal biphasic membranes. Mixed permeation studies will also be conducted. Using simulations, the investigators will predict the polymer/ionic liquid interactions and quantify the nano-confinement effect on carbon dioxide and methane absorption through proper energetic and structural metrics. The investigators will work to increase student awareness of the membrane field by developing research-integrated modules for undergraduate courses in polymer science, membrane science, and molecular simulation.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.