Rheology of Graphene Oxide Dispersions

Vallés, Cristina

doi:10.1002/9781119069447.ch4

Cited by 13 publications

(13 citation statements)

References 77 publications

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“…Further increase in shear rate increases the stress, which is due to breaking up of the flocs fully into dispersed GO flakes. 63 Similar trends were observed and reported for dispersions in water. 37,48 Oscillatory stress sweep measurements are performed to investigate the linear viscoelastic regime.…”

supporting

confidence: 81%

Graphene Oxide Liquid Crystal Membranes in Protic Ionic Liquid for Nanofiltration

Mahalingam

Wang

Nunes

2018

ACS Appl. Nano Mater.

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Graphene oxide (GO) liquid crystals are of great interest for membrane preparation. Vacuum filtration has been frequently adopted as small-scale manufacturing method. The main challenge is to obtain thin and robust layers with high permeation and selectivity by methods that could be applied in large scale. GO liquid crystals are mostly formed by dispersion in water. For the first time, we demonstrate that GO can form lyotropic liquid crystalline nematic phase dispersions in protic ionic liquid and be fabricated as membranes for nanofiltration. The well-balanced electrostatic interaction between ionic liquid and GO promotes and stabilizes the alignment of GO nanosheets even when concentrations as low as 9 mg GO /mL are used, providing the ideal rheology for the dispersion casting and membrane preparation. Robust membranes with GO layers as thick as 1 m with high permeance (37 L m-2 h-1 bar-1) and 99.9 % rejection of dyes with molecular weight 697 g/mol were obtained. We confirmed the liquid crystal formation by the detection of birefringence and the rheological behavior and explained the liquid crystal formation as an interplay between hydrogen bonding and electrostatic interactions.

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supporting

confidence: 81%

Graphene Oxide Liquid Crystal Membranes in Protic Ionic Liquid for Nanofiltration

Mahalingam

Wang

Nunes

2018

ACS Appl. Nano Mater.

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“…The solubility of GO in water is limited only by the formation of a nematic phase and by the associated viscosity of solutions at high GO concentrations. 3 It was also reported that GO is soluble in organic solvents such as DMF, N-methyl-2-pyrrolidone, and ethylene glycol. 4,5 At the same time, it was found to be insoluble in methanol (MeOH) and ethanol (EtOH).…”

Section: Introductionmentioning

confidence: 99%

New insights into the solubility of graphene oxide in water and alcohols

Neklyudov

Khafizov

Sedov

et al. 2017

Phys. Chem. Chem. Phys.

132

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aOne of the main advantages of graphene oxide (GO) over its non-oxidized counterpart is its ability to form stable solutions in water and some organic solvents. At the same time, the nature of GO solutions is not completely understood; the existing data are scarce and controversial. Here, we demonstrate that the solubility of GO, and the stability of the as-formed solutions depend not just on the solute and solvent cohesion parameters, as commonly believed, but mostly on the chemical interactions at the GO/solvent interface. By the DFT and QTAIM calculations, we demonstrate that the solubility of GO is afforded by strong hydrogen bonding established between GO functional groups and solvent molecules.The main functional groups taking part in hydrogen bonding are tertiary alcohols; epoxides play only a minor role. The magnitude of the bond energy values is significantly higher than that for typical hydrogen bonding. The hydrogen bond energy between GO functional groups and solvent molecules decreases in the sequence: water 4 methanol 4 ethanol. We support our theoretical results by several experimental observations including solution calorimetry. The enthalpy of GO dissolution in water, methanol and ethanol is À0.1815 AE 0.0010, À0.1550 AE 0.0012 and À0.1040 AE 0.0010 kJ g À1 , respectively, in full accordance with the calculated trend. Our findings provide an explanation for the well-known, but poorly understood solvent exchange phenomenon.

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“…9 of the prepared samples can be compared to the pseudoplastic liquids. Here graph of shear rate increases almost linear to the applied shear stress which corresponds to pseudoplastic behavior [18,[36][37][38][39].…”

Section: Flow Behaviormentioning

confidence: 99%