Phase Transitions in Graphite Oxide Solvates at Temperatures Near Ambient

Abstract

It is demonstrated that solvent-saturated graphite oxide can be considered to be solid solvate, and two phases with distinctly different solvent composition are found near room temperature. Phase transitions between these two solvated phases were observed using synchrotron powder X-ray diffraction and DSC for methanol, ethanol, acetone, and dimethylformamide (DMF) solvents. Solvate A, formed at room temperature, undergoes a reversible phase transition into expanded Solvate L at temperatures slightly below ambient due to insertion of one monolayer of solvent molecules between the GO planes. The phase transition is reversible upon heating, whereas the low-temperature expanded phase L can be quenched to room temperature for ethanol and DMF solvates.

The structure of graphene oxide membranes in liquid water, ethanol and water–ethanol mixtures

“…As shown in our earlier studies, the B-GO powder immersed in ethanol or methanol liquid media (one solvent monolayer state at ambient temperature d(001)=8.9Å) 28 ) exhibits first order phase transition into expanded phase (2-monolayer state) with lattice expansion by ~4Å 34 in good agreement with hydrodynamic size of ethanol molecule 38 . In strong contrast, the membranes showed absence of phase transitions and almost flat temperature dependence of d(001) upon cooling in ethanol and methanol liquid media (Figure 6).…”

“…The hydration/solvation properties GO membranes (in liquid water and ethanol) are surprisingly strongly different compared to precursor Brodie and Hummers graphite oxide powders. Hummers GO membranes demonstrate absence of "negative thermal expansion" 29 and Brodie GO membranes show absence of phase transitions 34 connected to insertion/de-insertion of alcohol upon temperature variations. The results allow to explain unusual permeation data of GO membranes exposed to water and ethanol vapours 21 .…”

Pressure‐Induced Water Insertion in Synthetic Clays

“…Otherwise, high pressure behaviour of Na-hectorite in water media shows surprisingly strong similarities to graphite oxide compression in liquid media considering rather different chemical composition and structure of these two types of materials. Crystalline swelling with pressure induced insertion of additional solvent layer (not correlated with pressure point of liquid media solidification) was observed previously for GO immersed in methanol, ethanol, DMF and acetone [9,[22][23] . Similarly, well defined step-like insertion of additional solvent monolayer is observed at certain pressure for Na-Hect immersed in water and shows no correlation with media solidification.…”

Graphite oxide swelling in molten sugar alcohols and their aqueous solutions

“…Distinctly different phases which correspond to the structures intercalated with one and two layers of solvent were reported in our earlier studies for BGO in liquid methanol, [41] ethanol, [42] DMF, [42] acetone, [43] acetonitrile, [44] and several others. [44] Multilayered intercalation of octanol was reported in our most recent study.…”

“…[45] Transitions between the phases with different number of intercalated solvent layers were found under variation of temperature or pressure. [40,42,45] Moreover, selective intercalation of methanol from water/methanol mixtures was observed for BGO. [46][47] In contrast, HGO shows no selectivity in sorption from binary mixtures, no phase transitions and absence of clearly distinct phases with certain amount of intercalated solvent.…”