PEG Containing Thiol-ene Network Membranes For CO2 Separation: Effect of Cross-Linking On Thermal, Mechanical, and Gas Transport Properties

Document Type

Article

Publication Date

5-9-2014

School

Polymer Science and Engineering

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, Mc, was determined experimentally by fitting the classic network affine model to stress–strain data obtained via tensile testing. Mc was also calculated assuming an ideal, lattice-like, network structure based on monomer stoichiometry. The effect of Mc 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 Mc.

Publication Title

Macromolecules

Volume

47

Issue

10

First Page

3243

Last Page

3253

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