Dispersion Of Graphene Oxide Research Articles

Silane-modified graphene oxide in geopolymer: Reaction kinetics, microstructure, and mechanical performance

Graphene oxide (GO) and 3-aminopropyltriethoxy silane (APTS) have been successfully used in geopolymers to solve specific problems. Nevertheless, the dispersion of GO to strengthen the matrix remains a challenge owing to the characteristic high alkalinity of geopolymer binders. Concurrently, independent addition of APTS to improve the workability severely retards geopolymer dissolution and condensation reactions. In this paper, an attempt is made to mutually exploit benefits of these two additives through a surface functionalisation approach whereby surface functional groups of GO were modified by APTS to provide repulsive effects that could better isolate the GO nanosheets from each other, while the accelerating effects of GO on the geopolymerisation process compensated for the retardation effects of APTS. The structure of GO-APTS was observed to be stable in the highly alkaline sodium silicate environment and significantly improved the dispersion of the nanosheets in the geopolymer composite according to the UV–Vis and SEM/TEM observations. Furthermore, the nucleation and reinforcing effects of GO were enabled by APTS. The GO-APTS–cement samples not only demonstrated better workability and transport properties compared with the reference and pure GO samples, but also superior mechanical strength, with improvements in tensile strength of ∼110% and ∼52% at 7 and 28 days, respectively. These findings evidence the effectiveness and potential of silane-functionalised GO in overcoming the dispersion issues experienced by GO in the highly alkaline media of geopolymers while simultaneously enhancing the mechanical and durability performance of geopolymer systems.

Fabrication and performance analysis of graphene oxide-based composite membrane to separate microplastics from synthetic wastewater

The pervasiveness of microplastics (MPs) jeopardize the entire environment and must be eradicated immediately. This study highlights the fabrication of a graphene oxide (GO)-polyvinyl alcohol (PVA) based composite membrane to separate high-density polyethylene (HDPE)-based MPs from wastewater using electrostatic repulsion mechanisms. The GO layers were stabilized by bonding with PVA using glutaraldehyde followed by deposition on a cellulose substrate via vacuum filtration. The bonding between GO and PVA via acetylation was confirmed by FTIR, while XRD indicated the well dispersion of GO in the PVA matrix. The surface morphology and composition of the composite membranes were analyzed using SEM and XPS respectively. Contact angle and zeta potential measurements were performed to confirm the hydrophilicity and negative surface charge of the membrane respectively. The optimum volume of the GO-PVA composite solution was used to control the membrane thickness, ensuring water permeation flux up to 179 L m2 h−1 bar−1 and maximize MP rejection. At pH 8 and 3 bar transmembrane pressures, 95 % of HDPE-MP rejection was observed in 15 s. These findings highlight the promising approaches for separating HDPE-based MPs from wastewater using GO-based composite membranes.

Compatibilization of novel GO-XNBR-g-GMAC/XNBR/XSBR nanocomposites: the relationship between structure and properties

ABSTRACT The current research aimed to investigate the different aspects of novel nanocomposites based on carboxylated acrylonitrile butadiene rubber (XNBR), carboxylated styrene butadiene rubber (XSBR), graphene oxide (GO), and glycidyl methacrylate-grafted XNBR compatibilizer (XNBR-g-GMAC) blend. For this purpose, the novel nanocomposites of GO-XNBR-g-GMAC/XNBR/XSBR with different XNBR, XSBR, and GO composition and with and without XNBR-g-GMAC were synthesized. The related characteristics including curing properties, swelling behavior, morphological, electrical and mechanical characteristics were studied through rheometry, swelling test, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observation, electrical resistivity, mechanical test, dynamic mechanical thermal analysis (DMTA), etc. Results of rheometric tests revealed that the addition of XNBR-g-GMAC and increasing GO content reduces the scorch time (t 5) and optimum cure time (t 90) and increases the crosslink density (CLD). So that the addition of 5 phr of compatibilizer and 1 phr of GO to the XNBR75/XSBR25 blend reduced the t 5 and t 90 by 29% and 34%, respectively. TEM micrograph confirms the GO dispersion in rubber matrix and SEM observation shows that incorporation of XNBR-g-GMAC and GO reduces dispersed-phase droplet size due to the improved compatibility of XNBR and XSBR. According to the DMTA result, all the samples except XNBR/XSBR (without XNBR-g-GMAC) show one glass transition temperature (T g) which means XNBR-g-GMAC successfully enhanced the compatibility of XNBR/XSBR. The mechanical properties of samples showed that by the increase of GO concentration tensile strength, elongation at break, modulus, fatigue life, and hardness increased. Testing surface temperature changes in constant voltage (75 V) showed that the addition of 0.3 phr GO showed the best result and the further increase of GO up to the value of 1 phr revealed the opposite result and caused a decrease of about 54%. The results of practical tests also confirm the theories.

Stability Study of Graphene Oxide-Bovine Serum Albumin Dispersions

In this work, a stability study of dispersions of graphene oxide and graphene oxide functionalized with polyethylene glycol (PEG) in the presence of bovine serum albumin is carried out. First, a structural characterization of these nanomaterials is performed by scanning electron microscopy, atomic force microscopy, and ultraviolet visible spectroscopy, comparing the starting nanomaterials with the nanomaterials in contact with the biological material, i.e., bovine fetal serum. The different experiments were performed at different concentrations of nanomaterial (0.125-0.5 mg/mL) and BSA (0.01-0.04 mg/mL), at different incubation times (5-360 min), with and without PEG, and at different temperatures (25-40 °C). The SEM results show that BSA is adsorbed on the surface of the graphene oxide nanomaterial. Using UV-Vis spectrophotometry, the characteristic absorption peaks of BSA are observed at 210 and 280 nm, corroborating that the protein has been adsorbed. When the time increases, the BSA protein can be detached from the nanomaterial due to a desorption process. The stability of the dispersions is reached at a pH between 7 and 9. The dispersions behave like a Newtonian fluid with viscosity values between 1.1 and 1.5 mPa·s at a temperature range of 25 to 40 °C. The viscosity values decrease as the temperature increases.

Effect of GO on the Structure and Properties of PEG/Biochar Phase Change Composites.

In recent years, phase change materials (PCMs) have been widely used in waste heat utilization, buildings, and solar and wind energy, but with a huge limitation from the low thermal conductivity, photothermal conversion efficiency, and low latent heat. Organic PCMs are eyecatching because of its high latent heat storage capability and reliability, but they still suffer from a lack of photothermal conversion and sharp stability. Here, we prepared sharp-stable PCMs by establishing a carbon material frame system consisting of graphene oxide (GO) and biochar. In particular, surfactants (CTAB, KH-560 and KH-570) were employed to improve the dispersity of GO in PEG. The differential scanning calorimetry results shows that the latent heat of PEG modified by CTAB grafted GO (PGO-CTAB) was the highest (191.36 J/g) and increased by 18.31% compared to that of pure PEG (161.74 J/g). After encapsulation of PGO-CTAB in biochar, the obtained composite PCM with the amount of biochar and PGO-CTAB in weight ratio 4:6 (PGO-CTAB/CS6(6)) possesses relatively high latent heat 106.51 J/g with good leak resistance and thermal stability, and with obviously enhanced thermal conductivity (0.337 W/(m·K)) and photothermal conversion efficiency (77.43%), which were higher than that of PEG6000 (0.325 W/(m·K), 44.63%). The enhancement mechanism of heat transfer and photothermal conversion on the composite PCM is discussed.

Characteristics of PVA/GO Composite Membranes Prepared Using Solution Casting Technique for Reducing Methylene Blue Concentration

In this study, the composite films of polyvinyl alcohol (PVA) and graphene oxide (GO) that referred as PVA/GO composites were prepared with a solution casting technique to be used as a filtration membrane. PVA/GO solution was prepared by mixing PVA powder, GO dispersion and aqueous solvent, then subjected to a hydrothermal process. The PVA/GO composite solution was cast on the glass substrate, then dried overnight so the solvent evaporated and then the composites films were removed from the substrate. The PVA/GO composite that characterized by SEM indicates that the GO is evenly dispersed within the PVA matrix. The FTIR spectrum of the composite has a sharp peak at 1655 cm-1 that associated with C=O and C=C bonds relating to GO characteristics. The TGA measurement results show that the PVA/GO composite film has better thermal stability than the PVA film. The PVA/GO composite films have been used as filtration membranes to reduce the concentration of methylene blue (MB) solutions contained in water. The filtration experiment that performed at various pressures showed that the permeability of the PVA/GO composite membranes was relatively constant at each pressure. Membrane permeability at pressures of 20 psi, 30 psi and 45 psi for PVA membranes are 1.95×10-3, 2.08×10-3 and 2.00×10-3 Darcy, while for PVA/GO composite membranes are 2.49×10-4, 1.22×10-3 and 2.23×10-3 Darcy

Improvement of Mechanical Properties and Solvent Resistance of Polyurethane Coating by Chemical Grafting of Graphene Oxide.

Waterborne polyurethane coatings (WPU) are widely used in various types of coatings due to their environmental friendliness, rich gloss, and strong adhesion. However, their inferior mechanical properties and solvent resistance limit their application on the surface of wood products. In this study, graphene oxide (GO) with nanoscale size, large surface area, and abundant functional groups was incorporated into WPU by chemical grafting to improve the dispersion of GO in WPU, resulting in excellent mechanical properties and solvent resistance of WPU coatings. GO with abundant oxygen-containing functional groups and nanoscale size was prepared, and maintained good compatibility with WPU. When the GO concentration was 0.7 wt%, the tensile strength of GO-modified WPU coating film increased by 64.89%, and the abrasion resistance and pendulum hardness increased by 28.19% and 15.87%, respectively. In addition, GO also improved the solvent resistance of WPU coatings. The chemical grafting strategy employed in this study provides a feasible way to improve the dispersion of GO in WPU and provides a useful reference for the modification of waterborne wood coatings.

Manipulation of mechanical and thermal properties of graphene oxide/nanoclay/unsaturated polyester hybrid nanocomposites by the surface chemistry and nanofiller composition

Dispersion of platelet-like nanominerals in low-viscous resins is a serious challenge; which arises from the strong interactions among the large surface area of the layers. Herein, we improved the dispersion of graphene oxide (GO) within unsaturated polyester (UP) resin and synergistically enhanced the mechanical and thermal properties of the resulting nanocomposites. In a multi-stage manner, GO was incorporated into a novel hybrid structure before adding to the polymer matrix alongside with benefited from the advantage of surface functionalization. Functional hybrid nanofiller skeletons comprising GO and nanoclay (NC) were designed and prepared at different composition ratios (25:75, 50:50 and 75:25) and different surface chemistries via modification with two thermal-resistant silane coupling agents, namely (3-Aminopropyl) triethoxysilane (APTES) and 3-(trimethoxysilyl) propyl methacrylate (MPS). The optimal loading of different hybrid structures into UP has been examined by applying three loading levels (0.25, 0.50 and 1.00 wt%). The results indicated the synergistic effects of GO and NC on the mechanical properties of UP, where the composition ratio of the hybrid constituents played a key role. Moreover, it was demonstrated that the range of composition ratio for the realization of synergistic reinforcement is strongly affected by the surface chemistry of the GO and NC. For UP matrix reinforced with APTES-modified hybrid nanofillers of GD:CD at 50:50 w/w composition, a higher tensile modulus compared to blank UP (≈+21.5%) was obtained due to boosted dispersion of nanoplatelets in UP matrix. The results of DMTA and TGA analyses suggested that there are two different UP/GO and UP/NC interfacial interactions in the composites containing unmodified hybrid nanofillers. However, after modification of hybrid nanofillers, the homogeneous dispersion of nanoplatelets boosted the interfacial interactions between nanofillers and polymer, such that higher properties were obtained.

The Influence of Nanoparticle Dispersions on Mechanical and Thermal Properties of Polymer Nanocomposites Using SLA 3D Printing

The synergistic integration of nanocomposites and 3D printing has opened a gateway to the future and is soon expected to surpass its rivalry with traditional manufacturing techniques. However, there is always a challenge associated with preparing a nanocomposite resin for polymerization-based 3D printing, which is the agglomeration of nanoparticles. Due to the high surface-area-to-volume ratio, the nanoparticles form clusters in the composite matrix, which affects the final properties. This paper aims to analyze the effects of graphene oxide (GO) dispersion on the mechanical and thermal properties of 3D-printed nanocomposites. In particular, a well-dispersed sonication dispersion route is employed for analyzing high and poor GO dispersions and their effects on different properties. After different microscopic analyses and testing, the optimum sonication condition was 30 min at an amplitude of 70%. In terms of mechanical properties, both tensile and compression strength first increased and then decreased gradually with different dispersions as well as varying GO concentrations. Furthermore, there was less or no effect on thermal stability. GO of 0.05 wt.% had the highest compression and tensile strength, while beyond 0.05 to 0.5 wt.%, both strengths reduced slowly. These 3D-printed nanocomposites have found their application in automotive, sports, and biomedical fields.

Polydopamine/polyethyleneimine co-crosslinked graphene oxide for the enhanced tribological performance of epoxy resin coatings

• GO were co-crosslinking modified through an environmentally friendly, simple and low-cost process. • Dispersion and surface activity of GO were enhanced by the covalently cross-linked network. • Friction and wear rate of the EP coating reduced by 31.9% and 62.7%, respectively. • Formation of GO lubrication transfer film played the role in friction and wear reduction. To enhance the wear resistance of graphene oxide (GO) nano-filled epoxy resin (EP) coatings with excellent dispersion, GO were modified using a co-crosslinking strategy between polydopamine (PDA) and polyethyleneimine (PEI) through an environmentally friendly, simple and low-cost process. High-density amino-branched PEI and highly adhesive PDA formed covalent bond cross-links with GO (PDA/PEI-GO) through the Michael addition and Schiff base reactions. With the introduction of amino active sites, the PDA self-polymerization reaction time was significantly shorted from 24 h to 6 h. The covalently cross-linked network increased the lamellar spacing of GO and enhanced the interfacial bonds between the PDA/PEI-GO lamellae and EP matrix. Due to the improved dispersion and surface activity of GO, the PDA/PEI-GO nano-filled EP coating exhibited excellent wear resistance. Reciprocating friction with GCr15 stainless steel ball, the average friction coefficient and wear rate of the coating were reduced by 31.9% and 62.7%, respectively, compared to the pure EP coating. In addition, the wear mechanism of the PDA/PEI-GO/EP coating changed from adhesive and fatigue wear to abrasive wear, and it maintained good wear resistance by forming a GO lubrication transfer film on the counterpart surface. Therefore, this study may provide a new strategy for improving the dispersion of graphene in wear-resistant polymer materials for practical applications.

Identification of Ultraviolet Photoinduced Presolvated Electrons in Water as the Reducing Agent in the Photoreduction of Graphene Oxide

Light-induced reduction of graphene oxide (GO) is a promising and an ingenious way of producing reduced GO (rGO) because it avoids the use of harsh chemicals. However, to date, the physicochemical mechanisms underlying photoreduction remain controversial. For example, there is no consensus on whether GO is reduced in water via direct excitation using ultraviolet (UV) laser light or via radiologically produced solvated electrons. Because of the photoinduced solvated electrons, the excited state of GO exhibits similar electronic absorption responses in the visible and near-infrared (NIR) wavelength range; therefore, distinguishing GO photoreduction dynamics from solvated electron dynamics via transient electronic absorption techniques is challenging. In this work, we used femtosecond-stimulated Raman spectroscopy (FSRS) to understand the ultrafast photoreduction dynamics of GO dispersion in water. Raman pump wavelength was selected to prevent the resonance of the excited-state Raman signal of water while obtaining the fingerprint Raman signals of GO. In contrast to the results of previous studies, our FSRS results indicate that upon UV excitation, the reduction of GO is triggered by the precursor of the solvated electron (presolvated electron) in 300 fs.

Influence of Nanostructuring Sensors Based on Graphene Oxide and PEDOT:PSS for Methanol Detection

Graphene oxide (GO) composites with conducting polymer poly (3,4-ethylenedioxythiophene)-poly (styrenensulfonate) (PEDOT:PSS) were applied as methanol vapor sensors. The active layer was prepared with neat polymer and its composites for different mixing ratios with GO. An optimal ratio was found with 3% (v/v) PEDOT:PSS in GO dispersion and submitted to an additional sonication treatment to change the nanostructure. Devices with treated active layers showed higher responses when applied to methanol vapor sensors. The improved responses are related to differences found on the composite surface. 2-D materials improve the organization of polymer chains, changing PEDOT availability, number of functional groups, and defects in GO. Theoretical analysis by density functional theory (DFT) simulations indicated that the average adsorption energy of methanol molecules is elevated, around −0.8 eV, and a simple mechanism was proposed to explain the response (variation of the layer electrical resistivity in the presence of methanol). The adsorption of vapor molecules on the active layer passivates the doping effect of PSS and GO on PEDOT, decreasing the number of empty states and consequently the conductivity along PEDOT chains. It was also observed that the passivation effect is much accentuated in composites than only in PEDOT:PSS, demonstrating the advantage of using GO composites for methanol vapor detection. Therefore, understanding the dependence of surface, vapor adsorption, and response signal, can improve the development of sensors to be used for gas detection in confined spaces.

Preparation, characterization, and compatibilization of novel rubber nanocomposites for mechanical applications: relationship between electrical properties, morphology, and rheology

In this paper, a novel rubber nanocomposite containing phenyl-vinyl-methyl-polysiloxane (PVMQ) and ethylene propylene diene monomer (EPDM) was produced during a two-roll mill procedure for mechanical applications. For this purpose, ethylene propylene diene monomer-grafted-maleic anhydride compatibilizer (EPDM-g-MAC) and graphene oxide (GO) was used as a compatibilizer and reinforcements to make a uniform composite. To study mechanical and physical characterizations, dynamic mechanical thermal analysis (DMTA), rheology, morphology, and curing characterizations of nanocomposites were investigated, which showed that compatibilizer makes GO dispersion uniformly. An electrical resistivity test was performed to study the electrical conductivity of the nanocomposites. The results indicate that the samples with higher GO content had a response to the electrical current. The curing study indicates that, by increasing the GO nanoparticles in the presence of EPDM-g-MAC, the curing properties are enhanced as well as mechanical properties by improving the bonding among GO, compatibilizer, and matrix [tensile strength (54%), modulus (68%), elongation-at-break (67%), hardness (81%), and fatigue (51%)]. FE-SEM and TEM images demonstrated that, by increasing GO nanoparticles in the presence of compatibilizer, the mean diameter of EPDM decreased in the substrate, which consequently increased the mechanical properties. The changes in surface temperature were investigated with constant voltage (75 V), which indicates that by increasing GO nanoparticles and electrical conductivity, the surface temperature increased significantly. The results of practical experiments showed good agreement with the theoretical results.

Assembling phenyl-modified colloidal silica on graphene oxide towards ethanol redispersible graphene oxide powder.

Recently, ethanol has shown promising potential in the large-scale reduction of graphene oxide (GO) into graphene. However, dispersion of GO powder in ethanol is a challenge due to its poor affinity, which hinders permeation and intercalation of ethanol between GO molecule layers. In this paper, phenyl-modified colloidal silica nanospheres (PSNS) were synthesized by phenyl-tri-ethoxy-silane (PTES) and tetra-ethyl ortho-silicate (TEOS) using a sol-gel method. PSNS was then assembled onto a GO surface to form a PSNS@GO structure by possible non-covalent π-π stacking interactions between the phenyl groups and GO molecules. The surface morphology, chemical composition, and dispersion stability were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, Raman spectroscopy, X-ray diffractometry, nuclear magnetic resonance, and particle sedimentation test. The results showed that the as-assembled PSNS@GO suspension had excellent dispersion stability with an optimal PSNS concentration of 5 vol% PTES. With the optimized PSNS@GO, ethanol can permeate between the GO layers and intercalate along with PSNS particles via formation of hydrogen bonds between assembled PSNS on GO and ethanol, achieving a stable dispersion of GO in ethanol. The optimized PSNS@GO powder remained redispersible after drying and milling according to this interaction mechanism which is favorable for large scale reduction processes. Higher PTES concentration may result in agglomeration of PSNS and formation of wrapping structures of PSNS@GO after drying and worsen its dispersion capability.

Получение и исследование физико-химических свойств покрытий на основе графеноподобных материалов

Dispersions of graphene oxide and its reduced form have been obtained. The resulting dispersions were characterized by UV spectroscopy. The features of the graphene oxide reduction process in the composition of coatings deposited on solid substrates (aluminum, optical glass, KDP single crystal) by interaction with various reducing agents: hydrazine hydrate, formalin, ascorbic and citric acids, and ammonium citrate are studied. Surface structures were studied by Raman spectroscopy. The surface morphology of coatings and the defectiveness of graphene-like materials obtained by the reduction of graphene oxide dispersions on the surface of substrates have been studied.

A graphene oxide (GO)–porous anodic alumina (PAA) bilayer system: How GO dispersion regulates the lower RH detection limit to near zero in conjugation with PAA

In RH-humidity sensors, improving the lower detection limit (LOD) with high sensing responsiveness is an unsolved problem to date.

Facile and scalable preparation of ultralight cobalt@graphene aerogel microspheres with strong and wide bandwidth microwave absorption

Cobalt@graphene aerogel microspheres (GCoAMs) with tunable porous structures are fabricated by using a unique spraying and crosslinking coagulation method. The graphene oxide (GO) and sodium alginate (SA) mixture aqueous dispersions were used for spraying. The cross-linking reaction occurs quickly between the carboxylic group of SA in the sprayed microdroplets and metal Co2+ in the collector bath, which fixes the microsphere shape and in-situ immobilizes the metal ion. After freeze-drying and the subsequent high-temperature thermal reduction, the ultralight GCoAMs are obtained. The pore structures of GCoAMs can be controlled by varying the GO/SA ratio. The GCoAMs exhibit strong and wide broadband microwave absorption due to its hierarchical porous structures and graphene/metal Co hybrid composition. At a GCoAMs loading content of 1.5 wt%, the minimal reflection loss reaches as high as −70.4 dB with a thin specimen thickness of 2.2 mm at 13.18 GHz and its effective absorption band achieves 5.65 GHz with a specimen thickness of 1.98 mm. At 2 wt% GCoAMs, the effective absorption band achieves 6.09 GHz with a specimen thickness of 2 mm, covering the whole Ku band. This work provides a novel, low-cost and easily scale-up method for preparing the lightweight and efficient microwave absorbers, which could be used in microwave telecommunication fields.

Apatite-Graphene and Apatite-Graphene Oxide Nanocomposites: Hybrid Materials with Tailored Biological and Luminescent Properties

Apatite nanocomposites with graphene (G) or graphene oxide (GO) nanoflakes, as well as with related carbonaceous materials, present promising applications in hard tissue engineering, biomedicine, or drug delivery. Different methodologies have been explored in the last years to prepare apatite-based nanocomposites. Sitting drop vapour diffusion (SDVD) methodology induces the heterogeneous nucleation of biomimetic apatite on the reinforcement material, improving biological properties of the nanocomposites. In this work SDVD was used to prepare G-apatite and GO-apatite nanocomposites. Prior to the SDVD experiments, G flakes were obtained by sonication-assisted liquid-phase exfoliation (LPE) using L-Alanine (L-Aln) as dispersing biomolecule, while a commercial aqueous Graphene Oxide (GO) dispersion was used for the nucleation essays in presence of the same biomolecules. A parallel set of nucleation experiments was performed in presence of Tb3+ ions, to endow the nanocomposites of luminescent properties. Characterization by XRD, FTIR, and TEM demonstrated the heterogeneous nucleation of needle-shaped apatite nanocrystals on the surfaces of G and GO flakes. Fluorescence spectroscopy certified the presence of Tb3+ ions in the nanocomposites resulting in luminescent materials which can be used in imaging or theragnostic. Finally, in vitro tests with human mesenchymal stem cells revealed excellent cytocompatibility and cell proliferation in presence of the nanocomposites.

Polymerization and Applications of Poly(methyl methacrylate)-Graphene Oxide Nanocomposites: A Review.

Graphene oxide (GO)-incorporated poly(methyl methacrylate) (PMMA) nanocomposites (PMMA-GO) have demonstrated a wide range of outstanding mechanical, electrical, and physical characteristics. It is of interest to review the synthesis of PMMA-GO nanocomposites and their applications as multifunctional structural materials. The attention of this review is to focus on the radical polymerization techniques, mainly bulk and emulsion polymerization, to prepare PMMA-GO polymeric nanocomposite materials. This review also discusses the effect of solvent polarity on the polymerization process and the types of surfactants (anionic, cationic, nonionic) and initiator used in the polymerization. PMMA-GO nanocomposite synthesis using radical polymerization-based techniques is an active topic of study with several prospects for considerable future improvement and a variety of possible emerging applications. The concentration and dispersity of GO used in the polymerization play critical roles to ensure the functionality and performance of the PMMA-GO nanocomposites.

Graphene oxide dispersion in epoxy resin prepared by direct phase transfer from ethanol: Rheology and aging

Graphene oxide addition to epoxy still presents challenges related to attaining optimized dispersion in scale-up production. Herein, the synthesis of high-quality GO by exfoliation in ethanol enabled the spontaneous phase transfer of GO from solvent to epoxy resin to produce a masterbatch with 1.5 wt.% GO content. Nanocomposites with 0.25 wt.%, 0.50 wt.% and 0.75 wt.% nanofiller contents were obtained by masterbatch dilution in epoxy resin. The results reveal the presence of a partial cross-linked network in these nanocomposites associated with the presence of GO, even without the use of a hardener. Thermogravimetric analysis showed the influence of GO on the oxidative decomposition mechanism of epoxy resin, whose behavior was assigned to strong interactions in the GO-epoxy interphase. Furthermore, the rheological behavior changes demonstrate the high quality of the GO dispersion in the resin obtained in this work. The nanocomposites showed high viscosity increases over time and pseudoplastic behavior, which was completely different from the neat epoxy resin. Aged nanocomposites without hardener present a first chemically cross-linked layer of epoxy to GO (∼ 10% for nanocomposite at 0.50 wt.% GO content) and a supramolecular coating interacting and entangled with these structures (> 40% of epoxy chains for EP-GO50).