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.
