Sequence-defined Gas Sorption and Permeation in a Copolymer Membrane

Polymers have been routinely used as membrane materials due to their high selectivity, ease of processing, and scalability. However, their inherent low permeability and plasticization remain a bottleneck for improving efficiency and durability of polymeric membranes. Here, we combine molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations to investigate the influence of the monomer sequence on the selectivity, permeability, and plasticization of a polystyrene (PS)-poly(methyl methacrylate) (PMMA) copolymer membrane. Our results show strong correlations between sequence, selectivity, permeability, and plasticity of the membrane. The data indicate that permeability and plasticity can be tuned to a large extent via monomer-to-monomer sequence control. Interestingly, the optimal membrane performance is found in an irregular non-intuitive sequence for CO₂ separation from a mixture of CO₂ and CH₄. The work demonstrates that the sequence of monomers in a copolymer membrane can serve as an important design parameter for targeted gas separation applications.