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

工业能源生产过程会产生二氧化碳等气体产品，必须从废气中去除这些产品才能达到监管排放标准。从巨大体积的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。需要高能效的分离技术，如膜，以保护利润并将对环境的影响降至最低。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高效节能气体分离技术，其应用范围从天然气预处理到碳减排。然而，聚合物/离子液体复合膜由于不稳定和性能限制，不适合在高压下使用，阻碍了这些系统的工业化应用。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来扩大聚合物/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产生在工业相关压力下具有增强的机械稳定性和竞争分离性能的膜。研究人员将专注于聚合物/离子液体复合膜的合成和演示，以选择性地从也含有甲烷的气流中去除二氧化碳。计算机模拟将阐明膜性能背后的基本机制，可用于进一步优化设计。除了对社会的技术益处外，该项目还将通过动手的本科生研究项目，扩大代表不足的群体在STEM的参与。密西西比大学的本科生还将通过为聚合物科学、膜科学和模拟课程开发的教学模块来了解膜科学领域。该项目旨在通过利用嵌段共聚平台中离子液体纳米限制导致的富离子液体相性质的有益变化，设计具有最佳气体分离性能的两相聚合物/离子液体复合膜。通过综合的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受限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。具体地说，通过将实验设计方法与分子动力学模拟相结合来指导实验，将实现可调嵌段共聚物平台的设计。研究人员假设，离子液体中化学渗透性和选择性的极大值是由于分子内有序引起的尺度相关限制效应而存在的。实验设计详细介绍了两种共聚物的用途：聚苯乙烯-嵌段-聚(N，N-二甲氨基甲基丙烯酸乙酯)(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：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]。在基线实验期间，DMAEMA和聚苯乙烯的均聚物将作为嵌段共聚物的亲水(极性)和疏水(非极性)组分的模型。将测量二氧化碳和甲烷的纯气体渗透，以评估最佳两相膜的气体分离性能。还将进行混合渗透研究。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度量来量化纳米限制对二氧化碳和甲烷吸收的影响。研究人员将致力于通过为聚合物科学、膜科学和分子模拟的本科生课程开发研究集成模块来提高学生对膜领域的认识。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.