(587i) Experimentally Validated Simulation of Self-Assembled Morphologies and Gas Transport Properties in PS-b-Pdmaema / [EMIM][SCN] Membranes

Ionic liquid (IL)/diblock copolymers with tunable self-assembled morphologies have emerged as suitable membranes for gas separation applications. Depending on the copolymer block size, IL loading, and film casting temperature, different morphologies, such as spherical micelles, lamellar, and IL microphases, can arise in these systems. However, not all morphologies will yield stable membranes at elevated gas pressures. Moreover, complex phenomena, such as ion segregation may affect the gas separation performance in these membranes. In this work, we utilized a combined experimental and computational approach to investigate the self-assembled morphologies of polystyrene-block-poly[2-(dimethylamino)ethyl methacrylate] (PS-b-PDMAEMA)/1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]) membrane materials for three PS:PDMAEMA block ratios of 80:20, 50:50, and 20:80 and two IL loadings of 10 and 40 wt.% at room temperature. Using the mesoscopic dynamics method, we simulated the IL/diblock copolymer morphologies in BIOVIA® Materials Studio® software package. For this purpose, we determined the Flory-Huggins interaction parameters for the coarse-grained bead models of PS, PDMAEMA, EMIM cation, and SCN anion using the COMPASS III force field. We then performed mesoscopic simulations with explicit electrostatics at 298 K with a time step of 50 ns for a total simulation time of 5 ms. We are currently analyzing and validating our preliminary computational results, i.e., the fully equilibrated self-assembled morphologies of the IL/diblock copolymers, with the scanning electron micrographs of the cast PS-b-PDMAEMA/[EMIM][SCN] films. Moreover, we are comparing the computationally observed ion segregation behavior with the elemental maps of the IL obtained by energy-dispersive x-ray spectroscopy. Based on these results, we are currently in the process of determining the characteristic confinement length of the IL in the membranes for the different morphologies. In a follow-up Grand Canonical Monte Carlo Molecular Dynamics (GCMC-MD) simulation study, we are calculating the transport properties, i.e., diffusivity, selectivity, density profiles, and mean square displacement (MSD) of CO₂ and CH₄ gases in the confined IL phase. The outcomes of this research provide a fundamental understanding of the molecular mechanisms underlying the gas transport properties of IL/diblock copolymers, which can contribute to the development of next-generation gas separation membranes with enhanced separation efficiencies.