(204b) Synthesis, Gas Permeation and Selectivity of Highly Elastic Poly(dimethylsiloxane)/Graphene Oxide Composite Elastomer Membranes

Recently, polymer membranes have been considered ideal materials for large-scale industrial processes and they are currently being used for air separation to produce N₂-enriched air, natural gas treatment to remove acid gas, H₂ separation from hydrocarbons, and many other applications. However, polymer-based membranes still require additional improvements in gas separation performance, which is typically linked to the so-called permeability-selectivity trade-off. In addition, polymers are generally vulnerable to high temperature and harsh chemical environments. Therefore, understanding and enhancing mechanical and chemical stability of polymer-based membranes in industrial environments is crucial.

This study illustrates that amine functional groups on the ends of telechelic poly(dimethylsiloxane) (PDMS) can undergo post-processing reactions with surface epoxy groups on graphene oxide (GO) to form a robust elastomer during simple heating. In these materials, GO acts both as a nanofiller which reinforces the mechanical properties and participates as a multifunctional crosslinker, thereby promoting elastic properties. Experiments indicate that the telechelic PDMS/GO elastomer is highly crosslinked (e.g., more than 75 wt % is a non-dissolving crosslinked gel) but highly flexible such that it can be stretched up to 300% of its original length.

Using the same material, permeability for some common gases was studied as a function of GO concentration. Incorporating only 3.55 vol % GO into the PDMS matrix resulted in a more than 99.9% reduction in gas permeation for various gases, such as H₂, O₂, N₂, CH₄ and CO₂. Moreover, factor of two enhancements in gas selectivities were observed for CO₂/N₂ and CO₂/CH₄ compared to neat PDMS membranes. As a supplement to experimental data from scanning-electron and atomic-force microscopy and x-ray diffraction, theoretical models such as the Nielsen and Cussler models were applied to comprehend the dispersion and alignment of GO in the polymer. Considering the expected thermal and chemical tolerance of the PDMS/GO composite membrane detailed in this work suggests these membranes could be useful in applications such as post-combustion CO₂ capture, CO₂ removal from natural gas and in other industries that use or process CO₂.