(610b) Effect of Graphene Oxide on Gas Transport and Sorption in Poly(dimethylsiloxane)-Based Membranes

We report the gas transport properties of poly(dimethylsiloxane)/graphene oxide (PDMS/GO) thermoset composites synthesized from graphite and amine-terminated telechelic PDMS. The material was prepared by a simple method using a thermally-activated reaction between the amine terminal end groups of the telechelic PDMS and epoxides on the surface of GO. A systematic reduction in pure gas permeability was observed for various gases, such as N₂, O₂, CH₄, and CO₂, by adding different amounts of GO into the PDMS matrix. At 3.55 vol. % (8 wt. %) GO loading, the composites resulted in a more than 99.9% reduction in gas permeability for all gases. Moreover, with increasing GO concentration, the composites showed a systematic increase in gas permselectivity for several pairs of gases. For instance, the permselectivity of CO₂/N_2, and CO₂/CH₄ at the maximum GO loading of 3.55 vol. % (8 wt. %) increased by approximately a factor of 2 and 3, respectively, compared to the neat PDMS membrane. The solubility of N₂, O₂, CH₄, and CO­₂ were measured for neat PDMS and PDMS containing varying amounts of GO to better understand the effect of GO filler on gas transport, specifically in terms of the individual effects on the gas solubility and diffusivity. In general, the gas solubilities in PDMS/GO composites were not affected by the addition of GO at concentrations of up to 3.55 vol. % (8 wt. %). In this regard, these results suggest that the reduction of gas permeabilities in PDMS/GO composites is mainly attributed to the dispersed phase of impermeable GO, which provides longer tortuous paths for gas diffusion. The permselectivity of PDMS/GO composites is controlled by the diffusivity selectivity, and both appear to increase with increasing GO concentration, which clearly illustrates that increasing the concentration of GO in the PDMS matrix enhances the size-sieving capability. Theoretical models for predicting the tortuosity of mixed matrix membranes (MMM) are discussed in detail to provide further understanding of the correlation between gas diffusion and morphology in PDMS/GO composites.