PEG Containing Thiol–Ene Network Membranes for CO₂ Separation: Effect of Cross-Linking on Thermal, Mechanical, and Gas Transport Properties

Abstract

A new family of poly(ethylene glycol) (PEG) based membranes for CO2 separation was developed using thiol–ene photopolymerization. Compared to photopolymerized PEG-containing acrylate membranes, these new thiol–ene based membranes offer improved mechanical properties and processing advantages. The starting material, a combination of a trithiol cross-linker and a PEG diene, was gradually modified with a PEG dithiol while maintaining 1:1 thiol:ene stoichiometry. This approach made it possible to decrease the network cross-link density, resulting in simultaneous increases in free volume and PEG content. Materials with high concentrations of dithiol were very stretchable, with largely, up to 500%, improved elongation at break, yet they exhibited commendable CO2/N2, O2, H2, and CH4 permeability-selectivity performance. The average molecular weight of polymer chains between cross-links, M c, was determined experimentally by fitting the classic network affine model to stress–strain data obtained via tensile testing. M c was also calculated assuming an ideal, lattice-like, network structure based on monomer stoichiometry. The effect of M c on glass transition temperature and gas permeation behavior was studied. A free volume based model was employed to describe experimental gas permeability (diffusivity) trends as a function of M c.

Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry

“…Only slight increase was obtained for the PEGDA/tetrathiol copolymers compared to the solvent‐free crosslinked PEGDA, for example, 110 barrer for the 50% SH tetrathiol, confirming the result reported in a previous study . Despite the polar nature of the thioether group, Kwisnek et al did not observe that they significantly influence the gas transport properties of the copolymers . Instead, the gas permeability increase observed presently was attributed to the siloxane chains, which are very flexible and permits higher gas diffusivity.…”

Recent Membrane Developments for CO2 Separation and Capture

“…Crosslinking agents generally applied to polyimide include benzophenone, diamino compounds, monomers pendant with carboxylic acid group, and photopolymerized thiol-ene materials [31][32][33]. Thermal treatment has also been applied extensively to improve crosslinking and CO 2 plasticization of polyimide.…”

Preparation and characterization of dithiol-modified graphene oxide nanosheets reinforced alginate nanocomposite as bone scaffold

“…Here, 2,2′-(ethylenedioxy)-diethnethiol (EDDET) was used as a cross-linker between GO nanosheets. EDDET is a biomolecular molecule containing sulfhydryl at both ends [27,39].Because the layers distance and morphology of GO changed, the pore morphology and mechanical properties of GO-based nanocomposites could be further influenced.…”