Temperature-Dependent Swelling of Brodie Graphite Oxide in Liquid Primary Amides

Swelling in polar solvents is a fundamental property of graphite oxide (GO). Using in situ synchrotron X-ray diffraction (XRD), Brodie graphite oxide (BGO) swelling was studied in a series of primary amides with the number of carbon atoms in the alkyl chain ranging from one (acetamide) to ten (decanamide) and compared to GO swelling in primary alcohols of equivalent chain lengths. The uptake of solvent due to swelling was determined via Differential Scanning Calorimetry (DSC). Swelling of BGO in acetamide, propionamide, and butyramide was found to expand the interlayer distance d(001) by ∼3.5-3.7 Å, consistent with the intercalation of a single molecular layer with an orientation parallel to the GO sheets. Swelling in longer molten amides produced larger c-lattice expansions correlating with the c-unit cell parameter of the pure amides, suggesting two-layer intercalation in a tilted "stand-up" orientation. Reversible swelling transition was found in the BGO-formamide system. This transition corresponds to the change between BGO structures with one-layer and two-layer formamide intercalation and has an enthalpy of 0.01 kJ g^-1 (BGO). No temperature-driven swelling transitions were observed for the other studied amides, acetamide through decanamide, in contrast to previously reported transitions in BGO-alcohol systems. These results demonstrate the wide tunability of interlayer spacing in BGO-amide systems and highlight the potential of controlled intercalation for applications such as molecular separation and sorption.