Graphene Oxide Membranes for Sustainable Recycling: Poly(styrene) Fractionation by Organic Solvent Nanofiltration

Efficient separation and purification of polymeric mixtures is an important challenge in plastic recycling. Here we demonstrate a robust graphene oxide (GO) membrane platform capable of separating low- and high-molecular-weight poly-(styrene) (PS) in nonpolar solvents. By tuning GO membrane properties through pillaring with a polyconjugated aromatic compound (PAC) and controlled reduction, we obtain the efficient nanofiltration of poly-(styrene) in a hydrocarbon solvent, enabling the removal of monomers and low-molecular-weight oligomers. Over 600 h of continuous operation, the pillared membrane maintains a stable high flux of 8 ± 1 L m^-2 h^-1 and total rejection of high-MW polymer. Postfractionation, the enriched high-MW retentate has a 2-fold higher yield of styrene monomers in mechanocatalytic ball-milling depolymerization compared to unfractionated PS. Removing oligomeric diluents improves energy transfer, suppresses chain transfer, and promotes chain scission followed by chain-end depropagation. Thus, fractionation by organic solvent nanofiltration with GO membranes can enable scalable and efficient routes to mechanochemical polymer recycling.