The purpose of this work is the structural analysis of graphene oxide (GO) and by means of a new structural model to answer the questions arising from the Lerf–Klinowski and the Lee structural models. Surface functional groups of GO layers and the oxidative debris (OD) stacked on them were investigated after OD was extracted. Analysis was performed successfully using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), X-ray photoemission spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, solid-state nuclear magnetic resonance spectroscopy (SSNMR), standardized Boehm potentiometric titration analysis, elemental analysis, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The analysis showed that graphene oxide layers, as well as oxidative debris contain different functional groups such as phenolic –OH, ketone, lactone, carboxyl, quinone and epoxy. Based on these results, a new structural model for GO layers is proposed, which covers all spectroscopic data and explains the presence of the other oxygen functionalities besides carboxyl, phenolic –OH and epoxy groups.

In this study, mixed matrix membranes (MMMs) consisting of graphene oxide (GO) and functionalized graphene oxide (FGO) incorporated in a polymer of intrinsic microporosity (PIM-1) serving as a polymer matrix have been fabricated by dip-coating method, and their single gas transport properties were investigated. Successfully surface-modified GOs were characterized by Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The effect of FGO loading on MMM morphology and performance was investigated by varying the FGO content in polymer matrix from 9 to 84 wt.%. Use of high FGO content in the polymer matrix helped to reveal difference in interaction of functionalized fillers with PIM-1 and even to discuss the change of FGO stiffness and filler alignment to the membrane surface depending on functional group nature.Electronic supplementary materialThe online version of this article (10.1186/s11671-018-2771-3) contains supplementary material, which is available to authorized users.

Graphene oxide/sulphur compound was synthesized by Hammers method. The chemical composition, presence/quantity of functional groups, exfoliation level, number of layers, crystallite size of graphene oxide/sulphur were characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy images. The current-voltage characteristics of the samples were measured in air at room temperature. In the I - V characteristic curve of graphene oxide/sulphur compound with the ratio of oxygen to carbon of 3.54 and that to sulphur of 42.54, negative differential resistance was observed. The negative differential resistance is attributed to current carrier transitions between the localized states formed by functional groups.

The current study summarizes the findings of the single gas transport performances of the mixed matrix thin-film composite membranes (TFCM) consisting of metal-organic frameworks (MOFs) incorporated into the polymer of intrinsic microporosity (PIM-1). The Mg-MOF-74, MIL-53, TIFSIX-3, and Zn 2 (bim) 4 were investigated as stand-alone materials and as incorporated into the PIM-1 polymer matrix serving as a selective layer of thin-film composite membranes by various methods: Fourier-transform infrared spectroscopy (FTIR), solid-state NMR (SSNMR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM).The effect of MOF-loading and nature on mixed-matrix membrane (MMM) morphology and operation were analyzed by varying the MOF content in the polymer matrix from 2 to 10 wt.% with respect to dry polymer weight. The results show that the incorporation of MOFs into the PIM-1 polymer matrix boosts the permeance and selectivity of H 2 and O 2 over N 2 , and the prepared PIM-1/TIFSIX_4 mixed matrix membrane shows better separation performance for CO 2 /CH 4 than that of pure PIM-1. Such membranes can be good candidates for ammonia purge gas, oxygen enrichment, and acid gas treatment applications.

In the present study the thermal behavior of phosphorus-and phosphorus/nitrogen-containing functional polymers was studied. The polymers were synthesized via oxidative chlorophosphorylation reaction of butadiene rubber and were subsequently subjected to hydrolysis, aminolysis and/or alcoholysis in order to introduce appropriate functionalities. The successful modifications of the polymer and presences of functional groups were determined using Fourier Transform Infrared Spectroscopy. It was found that the product of hydrolysis of the modified butadiene rubber contains acidic groups in its structure, the products of aminolysis and alcoholysis contain both acidic and amine and/or an alcohol derived moieties. The kinetic analyses of the thermal decomposition reaction were evaluated using thermogravimetric analysis and subsequently Friedman and Ozawa-Flynn-Wall methods. It was shown that degradation of the cross-linked polymers depends on the attached functional groups. The mass loss and the overall kinetic parameters of degradation showed complex mechanisms which characterize these thermal reactions.

considerable attention since 1980. [5] Despite the significant attention paid to the improvement of properties, most of the polymers studied did not exceed the Robeson upper bound, and none of them found use in the efficient separation system. [6] To obtain higher permeability and better selectivity, several approaches have been implemented, such as thermal rearrangement of the polymers, [7] formation of mixed matrix membranes (MMMs) by incorporation of metal-organic frameworks (MOFs), [8] covalent organic frameworks (COFs), [9] and other fillers into the polymer matrix. Every year, the drinking water demand increases, and thus energy-efficient water separation becomes more and more significant in terms of safe water supply in the world. Since we need to supply the world population with drinkable water from salty ocean, seas, and brackish water, water needs to be separated from its constituents such as salts, organic compounds, and bacteria. The primary membrane separation methods used widely for this purpose are forward osmosis (FO), reverse osmosis (RO), ultrafiltration (UF), nanofiltration (NF), microfiltration (MF), and electrodialysis reversal desalination (ERD). As a robust and low-energy-consuming technique, membrane distillation (MD) has recently received extensive attention. For this purpose, hydrophobic microporous polymeric membranes based on polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), etc., are implemented. In MD, a hot water stream circulates on the surface of the hydrophobic membrane, while only water vapor can pass through the porous structure of the membrane. The separated water vapor afterwards condenses on cold surfaces. Lee et al. reported that an electrospun perfluorooctyltriethoxysilane-coated titanium dioxide/polyvinylidene fluoride-co-hexafluoropropylene (F-TiO 2 /PVDF-HFP) membrane showed superhydrophobicity and a high water flux of 40 L m −2 h −1 compared to pristine PVDF membranes, [10] while the water flux of the PVDF nanofibrous hydrophobic membranes reinforced with fabric substrate was 49 kg m −2 h −1. [11] Being a 2D material, graphene oxide (GO) has attracted extensive attention in membrane science as a potential material due to its mechanical strength, [12] the possibility for property alteration by covalent and noncovalent chemical bonding, [13] and its cost-effective production. Recent works [14] show how GO incorporation affects the selectivity of polyimide-and Graphene oxide is functionalized with poly(2-diethylaminoethyl) methacrylate (PDEAEMA), and the resulting material is used as a selective layer of a thin-film composite membrane (TFCM). The polymer synthesis is carried out by surfaceinitiated atom transfer radical polymerization (SI-ATRP) from bulk and also from single-layer graphene oxide (GO). The polymer brushes synthesized by the "grafting from" method are characterized by size exclusion chromatography (SEC), nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infrared (FTIR) spectroscopy, thermal gravimetric analys...

The sulfur content present in graphene oxide prepared by Hummers' method has only been addressed by few papers so far. By modified Hammers method we synthesized thermally stable in ambient environment multilayer sulphur-doped graphene oxide. The samples were heat treated in an electrical furnace setup at different ambient temperatures and their crystallite size and linear coefficient of thermal expansion were extracted from Raman band intensity peak ratio as a function of temperature. We found unusually large (in comparison with graphene oxide) contraction on heating of multilayer two weight percent sulphur-doped graphene oxide with carbon to oxygen ratio of 2.3 in a narrow temperature range (308-318 K) with the lowest value of the linear thermal expansion coefficient of -18 ppm 1/K. Based upon an examination of the synthesized sulphur-doped graphene diffractograms, it is suggested that negative thermal expansion stems from the phonon backscattering by the sulphur impurity sites and the edges of the layers. The obtained experimental results have potential practical applications for fabrication of solar cells, sensors, lubricators, thermal actuators and also wavelike (second sound) thermal transport structures.

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