Experimental and simulation study of single-matrix, all-polymeric thin-film composite membranes for CO2 capture: Block vs random copolymers

High-performance, additive-free, all-polymeric thin-film composite (TFC) membranes were developed for COQ capture, focusing on a comparison between block and random copolymers (referred to as PTF) composed of hydrophobic poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) and CO2-philic polar poly(oxyethylene methacrylate) (POEM) chains. The PTF random copolymer, synthesized via free-radical polymerization (FRP), exhibited a disordered morphology. In contrast, the PTF block copolymer, synthesized via reversible additionfragmentation chain transfer (RAFT) polymerization, formed a well-ordered hexagonally packed cylindrical structure, creating an amphiphilic, microphase-separated nanostructure. Molecular dynamics (MD) simulations revealed that in both copolymers, there was minimal interaction between the gases (COQ and NQ) and the hydrophobic PTFEMA segments, while COQ showed strong affinity for the hydrophilic POEM segments. The block and random copolymers demonstrated similar COQ permeance, which can be attributed to their comparable COQ diffusivity and solubility. However, the block copolymer exhibited significantly lower NQ permeance than the random copolymer, resulting in nearly quadruple the COQ/NQ selectivity. This increase in selectivity was supported by the lower NQ mean squared displacement (indicating reduced diffusivity) observed in the block copolymer. The PTF block copolymer outperformed the commercial Pebax block copolymer, achieving COQ capture efficiencies that surpass industrial standards for COQ separation and capture. This positions the singlematrix PTF block copolymer as a promising alternative to mixed-matrix membranes for practical applications in gas separation technologies.