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

## TL;DR

Graphene oxide membranes can efficiently separate plastic mixtures in solvents, improving polymer recycling and depolymerization efficiency.

## Contribution

A pillared graphene oxide membrane enables stable nanofiltration of poly(styrene) in nonpolar solvents for sustainable recycling.

## Key findings

- Pillared GO membranes maintain high flux and reject high-molecular-weight poly(styrene) over 600 hours.
- Fractionation increases styrene monomer yield in depolymerization by 2-fold compared to unfractionated PS.
- Removing oligomers enhances energy transfer and promotes efficient chain scission in depolymerization.

## Abstract

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.