Synthesis and Characterization of Graphene Oxide Derivatives via Functionalization Reaction with Hexamethylene Diisocyanate

Abstract

Graphene oxide (GO), the oxidized form of graphene, shows unique properties including high mechanical strength, optical transparency, amphiphilicity and surface functionalization capability that make it attractive in fields ranging from medicine to optoelectronic devices and solar cells. However, its insolubility in non-polar and polar aprotic solvents hinders some applications. To solve this issue, novel functionalization strategies are pursued. In this regard, this study deals with the preparation and characterization of hexamethylene diisocyanate (HDI)-functionalized GO. Different reaction conditions were tested to optimize the functionalization degree (FD), and detailed characterizations were conducted via elemental analysis, Fourier-transformed infrared (FT-IR) and Raman spectroscopies to confirm the success of the functionalization reaction. The morphology of HDI-GO was investigated by transmission electron microscopy (TEM), which revealed an increase in the flake thickness with increasing FD. The HDI-GO showed a more hydrophobic nature than pristine GO and could be suspended in polar aprotic solvents such as N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO) as well as in low polar/non-polar solvents like tetrahydrofuran (THF), chloroform and toluene; further, the dispersibility improved upon increasing FD. Thermogravimetric analysis (TGA) confirmed that the covalent attachment of HDI greatly improves the thermal stability of GO, ascribed to the crosslinking between adjacent sheets, which is interesting for long-term electronics and electrothermal device applications. The HDI-GO samples can further react with organic molecules or polymers via the remaining oxygen groups, hence are ideal candidates as nanofillers for high-performance GO-based polymer nanocomposites.

Tailorable Synthesis of Highly Oxidized Graphene Oxides via an Environmentally-Friendly Electrochemical Process

“…The different exfoliation conditions tested along with the nomenclature of the EGO samples obtained herein are summarized in Table 1. For comparative purposes, a GO was also synthesized from flake graphite via a modified Hummers' method, as reported elsewhere [31], in the presence of a mixture of concentrated K 2 S 2 O 8 , H 2 SO 4 , and P 2 O 5 at 80 • C for a few hours. The product was filtered, dried, and oxidized for a second time by adding H 2 SO 4 , KMnO 4 , and cold water.…”

Sustainable Jatropha Oil-Based Membrane with Graphene Oxide for Potential Application in Cu(II) Ion Removal from Aqueous Solution

“…However, (-OH) stretching band in JPU/GO 0.65 wt% sample was reduced with the overlapping of (-NH) stretching. This was due to the higher GO functionalized as GO loading increased [63]. The appearance of another peak was observed near 867 cm −1 , 864 cm −1 , and 870 cm −1 for JPU/GO 0.35 wt%, JPU/GO 0.50 wt%, and JPU/GO 0.65 wt% samples, respectively, which was predicted to be (-CH) vibration.…”

“…The appearance of another peak was observed near 867 cm −1 , 864 cm −1 , and 870 cm −1 for JPU/GO 0.35 wt%, JPU/GO 0.50 wt%, and JPU/GO 0.65 wt% samples, respectively, which was predicted to be (-CH) vibration. The reactivity of isocyanate toward hydroxyl (-OH) groups also depended on whether they were free or hydrogen bonded due to the higher activation energies required for the reaction as provided by hydrogen-bonded alcohols than free alcohols [63][64][65]. Free hydroxyl groups could be observed in the spectra range near 3821 cm −1 , 3852 cm −1 , and 3843 cm −1 for JPU/GO 0.35 wt%, JPU/GO 0.50 wt%, and JPU/GO 0.65 wt% samples, respectively [59].…”

Influence of Oxidation Degree of Graphene Oxide on the Shear Rheology of Poly(ethylene glycol) Suspensions

“…The peaks at 3340 cm −1 for the GO 2 h spectrum and 3211 and 3066 cm −1 for the GO 96 h arise from the −OH stretch from carboxylic acids and hydrogen bonds derived from moisture in the samples. However, the peaks that appear at the frequencies of 2920 and 2872 cm −1 in the GO 96 h spectrum suggests symmetrical and asymmetric C-H stretching that can be related to the appearance of local defects in the GO nanosheets [41]. The appearance of peaks associated with C-H agree with the results of Raman spectroscopy, which presented a higher I D /I G ratio for GO 96 h. Atomic force microscopy (AFM) was used to analyze the morphology of the GO obtained, and results are depicted in Figures 6 and 7.…”