CAREER:SusChEM: Design and Discovery of Polymers with Pendant Rings for Membrane Gas Separations

CAREER 1554236-Lin Membrane technology has emerged as an important gas separation technology due to simplicity of operation, compactness, modularity, and high energy efficiency. However, the available membranes for important applications such as CO2/CH4 and C3H6/C3H8 separations are restricted by their deteriorated separation performance when made into industrial thin films operating in the presence of strongly plasticizing components of CO2 and heavy hydrocarbons. These polymers may have superior pure-gas separation performance in thick films of 20 µm or more. However, in the thin films of ~100 nm for industrial composite membranes, these polymers show gas permeability rapidly decreasing with time (i.e., aging). The CO2 and hydrocarbons swell the polymer matrix (i.e., plasticization), leading to weaker size sieving ability and reduced gas selectivity. This project will address these issues by developing a molecular-based mechanistic understanding of the relationship between the polymer structure and thin film properties including permeability, selectivity, aging and plasticization. The integrated educational activities are expected to achieve the following benefits: (a) an educational module for teachers and their students in middle school and high school in the Buffalo Public Schools (a district with a large fraction of students whose background is underrepresented in STEM fields) on membrane technology to solve global climate change; (b) an ongoing polymer workshop to promote the interdisciplinary collaboration on the Buffalo campus and in the Western New York area; (c) improvement in the core courses of Heat and Mass Transfer and Materials Characterization to stimulate students? interests in membrane research; and (d) interdisciplinary training opportunities in polymer synthesis, characterization, membrane separation and modeling for students at the undergraduate and graduate level. The research project will elucidate the effect of polymer pendant rings and crosslinking in the advanced polymeric materials on membrane gas separation properties, including gas permeability and selectivity, thin film stability against aging, and stability against hydrocarbon induced plasticization. These bulky pendent rings disrupt the polymer chain packing, leading to high free volume and permeability, and they are also expected to slow the chain motion, reducing densification or physical aging. The size of the rings will be conveniently tuned during the chemical synthesis, and substituents will be introduced to rationally design the structure. A bottom-up design of crosslinking networks will be generated, which are expected to be resistant to plasticization. A modified free volume model will be used to elucidate the effect of aging and plasticization on membrane separation properties. This interdisciplinary research program integrating materials discovery, synthesis, characterization, modeling and applications will enrich the fundamental understanding of polymer structure/property correlation for membrane gas separation. It is anticipated that the technical approach and materials design guidelines derived from this project will be directly applied to the development of industrial membranes for energy-efficient gas separation. This CAREER project is also expected to enhance students? awareness of materials design and discovery to solve important practical problems.