(637d) Influence of Block Size and Ionic Liquid Loading within PS-b-Pdmaema and PS-b-Peg Biphasic Block Copolymer Thin Films for Gas Separation Applications.

For two decades, gas separation membranes for carbon capture have been of significant interest as scientists develop robust and efficient carbon capture technologies to address the current climate crisis. Supported Ionic Liquid Membranes (SILMs) are studied due to their high CO₂/CH₄ selectivities for carbon capture technologies. However, stability at high pressures has limited SILM adoption in industrial systems. Novel polymers are needed to enhance SILM performance and selectivity, including ensuring high-pressure stability. One approach to address the current limitation is to encapsulate the ionic liquid of interest within a polymer matrix; however, the morphologies and molecular interactions of ionic liquids within diblock and triblock polymer systems are still poorly understood. In this study, we investigated the various morphologies and characteristics of polymer biphasic thin films. Specifically, we synthesized PS-b-PDMAEMA and PS-b-PEG block copolymer thin films with varying loadings of 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TF2N], and 1-Ethyl-3-methylimidazolium thiocyanate, [EMIM][SCN]. Relative block size ratios (20-80 wt.%, 50-50 wt%, 80-20 wt.%) and IL loading (10-40 wt.%) were varied to identify the relative morphologies of resultant thin films. Films were characterized via SEM, AFM, TGA, and XRD to determine the resulting morphology. Further, we sought to quantify the confinement degree of encapsulated ionic liquids through synergistic molecular dynamics simulations. Ionic liquid confinement also correlated with enhanced CO₂/CH₄ selectivity for gas separation applications. Results indicate the block size ratio significantly influences the resulting film morphology with high percentages of PS, resulting in spherical morphologies of the secondary phase (PDMAEMA or PEG). Further, high loadings of ionic liquid within the thin films resulted in the microphase separation of ionic liquid, shifting the ionic liquid confinement from dispersed in the polymer matrix to a non-disbursed ionic liquid encapsulated by the block copolymer. The resultant microphases formed at high loadings have reduced the ionic liquid confinement degree within the polymer matrix, diminishing confinement effects within the resultant thin films.