Swelling Pressures of Graphite Oxide and Graphene Oxide Membranes in Water and Ethanol

Swelling of graphene oxide (GO) membranes and bulk graphite oxide under confinement conditions is found to produce pressures up to approximate to 220 bar. Swelling pressure is important to take into account in many applications of GO membranes, but it has not been previously reported. Swelling pressures are typically measured only for bulk materials. However, it is demonstrated that even mu m thick GO membranes develop pressures 3-25 bar due to the volume expansion caused by swelling in water. A rather strong difference in kinetics of pressure increase is found for both graphite oxide and GO membranes in water and ethanol despite similar lattice expansion due to swelling. This effect is attributed to slower penetration of ethanol into GO interlayers. Significantly faster saturation of swelling pressure is found for GO membranes (few hours) as compared to bulk graphite oxides (weeks) due to a higher degree of compaction. Swelling pressure is an important factor in applications, which require confinement, encapsulation of GO membranes or using external pressure to limit the lattice expansion. Finally, the swelling pressure can be used as an estimation for the suction pressure developed in pervaporation or vapor permeation applications, which is suggested as a driving force in rapid water permeation across GO membranes.