Search

Swelling is the most fundamental property of graphite oxides (GO). Here, a structural study of Brodie graphite oxide (BGO) swelling in a set of long chain 1‐alcohols (named C11 to C22 according to the number of carbons) performed using synchrotron radiation X‐ray diffraction at elevated temperatures is reported. Even the longest of tested alcohols (C22) is found to intercalate BGO with enormous expansion of the interlayer distance from ≈6Å up to ≈63Å, the highest expansion of GO lattice ever reported. Swelling transitions from low temperature α‐phase to high temperature β‐phase are found for BGO in all alcohols in the C11–C22 set. The transitions correspond to decrease of inter‐layer distance correlating with the length of alcohol molecules, and change in their orientation from perpendicular to GO planes to layered parallel to GO (Type II transitions). These transitions are very different compared to BGO swelling transitions (Type I) found in smaller alcohols and related to insertion/de‐insertion of additional layer of alcohol parallel to GO. Analysis of general trends in the whole set of 1‐alcohols (C1 to C22) shows that the 1‐alcohol chain length defines the type of swelling transition with Type I found for alcohols with C<10 and Type II for C>10. [ABSTRACT FROM AUTHOR]

Intercalation of very long molecules into the structure of multi-layered graphene oxide (GO) was studied using example of 1-hexadecanol (C16), an alcohol molecule with 16 carbon atoms. Brodie graphite oxide (BGO) immersed in excess of liquid C16 just above the melting point shows expansion of c-unit cell parameter from ∼6 Å to ∼48.76 Å forming a structure with two densely packed layers of C16 molecules in a perpendicular orientation relative to the GO planes (α-phase). Heating of the BGO-C16 α-phase in excess of C16 melt results in reversible phase transition into β-phase at 336–342K. The β-phase shows much smaller unit cell parameter of 29.83 Å (363K). Analysis of data obtained using vacuum-driven evaporation of C16 from the β-phase provides evidence for structure of β-phase consisting of five layers of C16 molecules in parallel to GO plane orientation. Therefore, the transition from α-to β-phase corresponds to change in orientation C16 molecules from perpendicular to parallel relative to GO planes and decrease in the amount of intercalated solvent. Cooling of the β-phase in absence of C16 melt is found to result in the formation of γ-phase with inter-layer distance of ∼26.5 Å corresponding to one layer of C16 molecules intercalated perpendicularly relative to the GO planes. Structures with one and two layers of C16 molecules parallel to GO planes were identified in samples with rather small initial loading of C16. Surprisingly rich variety of structures revealed in the BGO-C16 system provides opportunities to create materials with precisely controlled GO inter-layer distance. [Display omitted] • Intercalation of Brodie graphite oxide (BGO) immersed in 1-hexadecanol just above its melting point is found to result in a structure with extremely large lattice expansion (∼6 Å to ∼49 Å). • The structure of α-phase corresponds to intercalation of 2 layers of 1-hexadecanol in orientation approximately perpendicular relative to graphene oxide (GO) planes. • Reversible phase transition between α-phase (∼49Å) and β-phase (∼ 30Å) is found for BGO immersed in excess of 1-hexadecanol upon heating/cooling. • The transition from α-to β-phase corresponds to incongruent melting and change in orientation of intercalated 1-hexadecanol molecules. • Several other phases with smaller amount of intercalated alcohol molecules were observed using vacuum –driven removal of melt. [ABSTRACT FROM AUTHOR]

Swelling of graphene oxide (GO) membranes and bulk graphite oxide under confinement conditions is found to produce pressures up 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 µm 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. [ABSTRACT FROM AUTHOR]