Graphene oxide-anchored reactive sulfonated copolymer via simple one pot condensation polymerization: proton-conducting solid electrolytes

A rapid and efficient post-polymerization functionalization of poly(urea-co-urethane) (PUU) onto the graphene oxide (GO) nanosheets has been developed to produce super-acidic polymer/GO hybrid nanosheets. Thus, the surface of GO nanosheets were functionalized with 3-(triethoxysilyl)propyl isocyanate (TESPIC) from hydroxyl groups to yield isocyanate functionalized graphene oxide nanosheets. Then, sulfonated polymer/GO hybrid nanosheets were prepared by condensation polymerization of isocyanate-terminated pre-polyurea onto isocyanate functionalized graphene oxide nanosheets through the formation of carbamate bonds. FTIR and TGA results indicated that TESPIC modifier agent and poly(urea-co-urethane) were successfully grafted onto the GO nanosheets. The grafting efficiency of poly(urea-co-urethane) polymer onto the GO nanosheets was estimated from TGA thermograms to be 205.9%. Also, sulfonated polymer/GO hybrid nanosheets showed a proton conductivity as high as 3.7 mS cm^?1. Modification and morphology of GO nanosheets before and after modification processes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD).     

Graphene oxide modification with graft polymers via nitroxide mediated radical polymerization

We demonstrate a method to modify the surface of graphene oxide (GO) by grafting polymer chains using nitroxide mediated radical polymerization (NMRP). Surface modification by NMRP was achieved using GO functionalized with 2,2,6,6-tetramethyl-piperidine 1-oxyl (TEMPO, T) to produce graphene oxide-TEMPO (GO-T). GO prepared from graphite by the Hummer's method was facilely functionalized in one step with T. Graft polymerization reactions of styrene and isoprene were carried out using nitroxide chemistry to control the polymerization and the ‘grafting from the surface’ polymerization technique. GO-T acts as a multifunctional macroalkoxyamine initiating and controlling the polymerization in the presence of monomer. The grafting reactions were performed by dispersing GO-T in dimethylformamide and heating at 130 °C in the presence of monomer to form graphene oxide-g-polystyrene-TEMPO (GO-g-PS-T) and graphene oxide-g-polyisoprene-TEMPO (GO-g-PI-T). FT-IR, Raman, XPS, XRD, TGA and TEM data are consistent with the attachment of the TEMPO group to the GO surface and with polystyrene and polyisoprene being grafted onto the GO surface. The amount of PS and PI grafted to GO-T was estimated from TGA data to be approximately 34% for a 7 h reaction time and 68% for a 144 h reaction time, respectively.     

Janus graphene oxide nanosheets prepared via Pickering emulsion template

Janus graphene oxide (GO) nanosheets functionalized by amino-containing chemicals were prepared via Pickering emulsion template. A wax-in-water Pickering emulsion was used to mask one side of GO nanosheets in order to achieve asymmetric chemical functionalization. Janus particles were obtained by removing the oil phase. The successful reaction of epoxy groups on the surface of GO with amino-containing chemicals was confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). The asymmetric surface structure of Janus GO nanosheets was detected by atomic force microscope (AFM) and X-ray diffraction (XRD). The efficient stabilization of an oil-in-water Pickering emulsion by Janus GO was proved. Polymer microspheres fabricated by using Janus GO as Pickering stabilizer had a more hydrophilic surface compared with those stabilized by symmetrically modified GO.     

Incorporation of silica network and modified graphene oxide into epoxy resin for improving thermal and anticorrosion properties

In this study, the silica network and functionalized graphene oxide (GO) were incorporated into the epoxy coating systems, which was aimed to improve the thermal property and corrosion resistance of epoxy coatings. First, tetraethyl orthosilicate (TEOS) oligomers and epoxy hybrid was fabricated through sol–gel method. Then the (3-aminopropyl) triethoxysilane (APTES) modified graphene oxide (FGO) was added into the epoxy hybrid composite to obtain anticorrosion coatings. Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), Raman spectrum, and X-ray photoelectron spectrum were conducted to evaluate the structural information of GO and APTES modified GO nanosheets. The results indicated that the APTES successfully grafted onto the surface of GO sheets. Besides, TGA curves, electrochemical measurements and salt spray test were also carried out to characterize the thermal performance and corrosion resistance of GO based epoxy coatings. The TGA results revealed that the thermal performance of epoxy coating containing silica network and FGO nanofiller (ES/FGO) was significantly strengthened compared to pure epoxy. The initial degradation temperature of epoxy coating was increased from 300 to 343.7°C after incorporation of silica component and FGO. The EIS measurements demonstrated that the impedance modulus of ES/FGO was significantly higher than neat epoxy, which indicated that the corrosion resistance of epoxy was substantially strengthened after introduction of silica component and FGO. The corrosion rate and inhibition efficiency of epoxy composite coatings were also shifted from 1.237 × 10⁻⁷ mm/year and 76.6% (for neat epoxy) to 1.870 × 10⁻⁹ mm/year and 99.6% (for ES/FGO), respectively. The salt spray test also revealed that the silica and FGO can improve the corrosion resistance of epoxy coating. Additionally, the dispersion of GO sheets was also enhanced after the modification of APTES siloxane.     

Improvement of interfacial properties in bismaleimide composites using functionalized graphene oxide grafted carbon fiber

A hierarchical reinforcement, which was used to improve the interfacial properties of bismaleimide (BMI) composites, was prepared by grafting functionalized graphene oxide (GO) onto a carbon fiber surface. The GO and carbon fibers were first functionalized separately to create interactional functional groups on their surfaces. The grafting process was then realized by an amidation reaction of the amine and acyl chloride function groups formed on GO and carbon fibers, respectively. The surface groups of functionalized GO and carbon fibers were identified by an X‐ray photoelectron spectroscopy (XPS). The resulting reinforcement was further characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic contact angle analysis. Experimental results showed that the functionalized GO were successfully grafted onto the carbon fibers surfaces and significantly increased the surface energy of carbon fibers. The study also indicated that the prepared hierarchical reinforcement could significantly improve the interfacial adhesion of resulting BMI composite. POLYM. ENG. SCI., 58:886–893, 2018. © 2017 Society of Plastics Engineers     

A novel monolithic Pd catalyst supported on cordierite with graphene coating

Immobilization on a structured substrate is a prerequisite for exploiting practical applications for graphene as a catalytic support. Here we report that graphene oxide (GO) nanosheets can readily form a stable coating on a cordierite honeycomb substrate without any need of stabilizers. FT-IR and ¹H NMR characterization revealed that GO nanosheets were probably immobilized on the cordierite surface by hydrogen bonding. TEM analysis indicated that palladium particles loaded on the graphene/cordierite exhibited a uniform size of less than 5 nm, which led to 4 times higher activity for styrene hydrogenation than that loaded on the cordierite.     

Grafting of poly(acrylic acid) onto poly(amidoamine)-functionalized graphene oxide via surface-mediated reversible addition-fragmentation chain transfer polymerization

Graphene oxide was modified with third-generation poly(amidoamine) (PAMAM) to obtain dendrimer-grafted GO (DGO) with high content of functional groups. DGO's amine groups were conjugated with S-(thiobenzoyl)thioglycolic acid as proved by XPS and poly(acrylic acid) was grafted onto surface via RAFT polymerization (DGO@PAA). FT-IR results approved the synthesis of samples whereas TGA revealed 40.3% grafting of PAA. XRD patterns showed that with further modification, d-spacing increased. According to Raman spectra, modification resulted in more disordered structure whereas DGO@PAA showed a high value of I_D/I_G. Morphological studies were performed by SEM and TEM that showed a polymeric layer covered the surface of nanosheets.     

Synthesis and exfoliation of isocyanate-treated graphene oxide nanoplatelets

A number of functionalized graphite oxides were prepared by treatment of graphite oxide (GO) with organic isocyanates. These isocyanate-treated GOs (iGOs) can then be exfoliated into functionalized graphene oxide nanoplatelets that can form a stable dispersion in polar aprotic solvents. Characterization of iGOs by FT-IR spectroscopy and elemental analysis suggested that the isocyanate treatment results in the functionalization of the carboxyl and hydroxyl groups in GO via formation of amides and carbamate esters, respectively. The degree of GO functionalization can be controlled via either the reactivity of the isocyanate or the reaction time. When used with functionalized isocyanates, the described methodology allows for the elaboration of graphene oxide nanoplatelets with different surface functional groups.     

Morphology,thermal, mechanical,and barrier properties of graphene oxide/poly(lactic acid) nanocomposite films

To improve the physical and gas barrier properties of biodegradable poly(lactic acid) (PLA) film, two graphene nanosheets of highly functionalized graphene oxide (0.3 wt% to 0.7 wt%) and low-functionalized graphene oxide (0.5 wt%) were incorporated into PLA resin via solution blending method. Subsequently, we investigated the effects of material parameters such as loading level and degree of functionalization for the graphene nanosheets on the morphology and properties of the resultant nanocomposites. The highly functionalized graphene oxide (GO) caused more exfoliation and homogeneous dispersion in PLA matrix as well as more sustainable suspensions in THF, compared to low-functionalized graphene oxide (LFGO). When loaded with GO from 0.3 wt% to 0.7 wt%, the glass transition temperature, degree of crystallinity, tensile strength and modulus increased steadily. The GO gave rise to more pronounced effect in the thermal and mechanical reinforcement, relative to LFGO. In addition, the preparation of fairly transparent PLA-based nanocomposite film with noticeably improved barrier performance achieved only when incorporated with GO up to 0.7wt%. As a result, GO may be more compatible with hydrophilic PLA resin, compared to LFGO, resulting in more prominent enhancement of nanocomposites properties.     

Preparation of polyimide/siloxane‐functionalized graphene oxide composite films with high mechanical properties and thermal stability via in situ polymerization

An effective approach to prepare polyimide/siloxane‐functionalized graphene oxide composite films is reported. The siloxane‐functionalized graphene oxide was obtained by treating graphene oxide (GO) with 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetra‐methyldisiloxane (DSX) to obtain DSX‐GO nanosheets, which provided a starting platform for in situ fabrication of the composites by grafting polyimide (PI) chains at the reactive sites of functional DSX‐GO nanosheets. DSX‐GO bonded with the PI matrix through amide linkage to form PI‐DSX‐GO films, in which DSX‐GO exhibited excellent dispersibility and compatibility. It is demonstrated that the obvious reinforcing effect of GO to PI in mechanical properties and thermal stability for PI‐DSX‐GO is obtained. The tensile strength of a composite film containing 1.0 wt% DSX‐GO was 2.8 times greater than that of neat PI films, and Young's modulus was 6.3 times than that of neat PI films. Furthermore, the decomposition temperature of the composite for 5% weight loss was approximately 30 °C higher than that of neat PI films. © 2015 Society of Chemical Industry     

Increased optical nonlinearities of graphene nanohybrids covalently functionalized by axially-coordinated porphyrins

Two graphene oxide (GO)-based nanohybrid materials possessing covalent linkages to axially-coordinated tetraphenylporphyrin (TPP), GO–TPP, were prepared and were characterized by Fourier transform infrared (FT-IR), Ultraviolet–visible (UV–Vis) absorption, steady state fluorescence, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), thermogravimetric analysis (TGA), elemental analysis and Raman spectroscopic techniques. The nonlinear optical properties and optical limiting performance of GO, GO–TPP nanohybrids and the free porphyrins dihydroxotin(IV) tetraphenylporphyrin (SnTPP) and the phosphorus-cored porphyrin (PTPP) were investigated using nanosecond and picosecond Z-scan measurements at 532 nm. At the identical mass concentration of 0.2 mg mL⁻¹, GO–TPP nanohybrids exhibited enhanced nonlinear optical properties and optical limiting performance, ascribed to a combination of nonlinear scattering and/or two-photon absorption with reverse saturable absorption, and the photo-induced electron or energy transfer from the electron-donor porphyrin moiety to the acceptor graphene.     

金刚烷胺/氧化石墨烯复合材料的制备及其吸附性能

以氧化石墨烯和金刚烷为原料，通过水相合成法制备了金刚烷胺功能化氧化石墨烯复合材料A/GO，以FT-IR、XRD和XPS对A/GO进行了结构表征，并考察了A/GO对有机染料的吸附性能。结果表明，与氧化石墨烯相比，A/GO对甲基蓝（AB93）表现出高效吸附性，其吸附动力学和吸附等温模型分别符合拟二级动力学和Langmuir模型，理论最大吸附容量（qm）为1250.0 mg/g。热力学分析表明，A/GO吸附AB93是自发的放热过程。A/GO吸附AB93对盐（NaCl和KCl）表现出良好的耐盐性，而CaCl2能有效地促进A/GO吸附AB93。对于刚果红和AB93等的混合染料体系，A/GO能选择性吸附AB93。     

Silicon nanowire arrays-induced graphene oxide reduction under UV irradiation

This paper reports on efficient UV irradiation-induced reduction of exfoliated graphene oxide. Direct illumination of an aqueous solution of graphene oxide at λ = 312 nm for 6 h resulted in the formation of graphene nanosheets dispersible in water. X-Ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, atomic force microscopy (AFM) and electrochemical measurements (cyclic voltammetry and electrochemical impedance spectroscopy) suggest a restoration of the sp(2) carbon network. The results were compared with graphene nanosheets prepared by photochemical irradiation of a GO aqueous solution in the presence of hydrogenated silicon nanowire (SiNW) arrays or silicon nanowire arrays decorated with silver (SiNW/Ag NPs) or copper nanoparticles (SiNW/Cu NPs). Graphene nanosheets obtained by illumination of the GO aqueous solution at 312 nm for 6 h in the presence of SiNW/Cu NPs exhibited superior electrochemical charge transfer characteristics. This is mainly due to the higher amount of sp(2)-hybridized carbon in these graphene sheets found by XPS analysis. The high level of extended conjugated carbon network was also evident by the water insoluble nature of the resulting graphene nanosheets, which precipitated upon photochemical reduction.     

Synthesis of magnetic citric‐acid‐functionalized graphene oxide and its application in the removal of methylene blue from contaminated water

A magnetic nanocomposite of citric‐acid‐functionalized graphene oxide was prepared by an easy method. First, citric acid (CA) was covalently attached to acyl‐chloride‐functionalized graphene oxide (GO). Then, Fe₃O₄ magnetic nanoparticles (MNPs) were chemically deposited onto the resulting adsorbent. CA, as a good stabilizer for MNPs, was covalently attached to the GO; thus MNPs were adsorbed much more strongly to this framework and subsequent leaching decreased and less agglomeration occurred. The attachment of CA onto GO and the formation of the hybrid were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction spectrometry and transmission electron microscopy. The specific saturation magnetization of the magnetic CA‐grafted GO (GO‐CA‐Fe₃O₄) was 57.8 emu g^?1 and the average size of the nanoparticles was found to be 25 nm by transmission electron microscopy. The magnetic nanocomposite was employed as an adsorbent of methylene blue from contaminated water. The adsorption tests demonstrated that it took only 30 min to attain equilibrium. The adsorption capacity in the concentration range studied was 112 mg g^?1. The GO‐CA‐Fe₃O₄ nanocomposite was easily manipulated in an external magnetic field which eases the separation and leads to the removal of dyes. Thus the prepared nanocomposite has great potential in removing organic dyes. © 2014 Society of Chemical Industry     

Glass fiber coated with graphene constructed through electrostatic self‐assembly and its application in poly(lactic acid) composite

A method to construct glass fiber/graphene material via the electrostatic self‐assembly was proposed. The graphene oxide (GO) nanosheets were firstly prepared from graphite according to Hummer's methods. Oppositely charged GO is successfully introduced to the surface of the GF cationized by 3‐aminopropyltriethoxysilane (APTES) treatment in the solution with mild agitation. Sequently, glass fibers coated with graphene (GF/CRG) were obtained after chemical reduction. The graphene content was characterized by TGA and XPS tests and the value of about 0.7 wt % was obtained. Composites of poly(lactic acid) and GF/CRG were prepared through melt blending. Thermogravimetric analysis (TGA) results shows that more than 50% graphene remains on the surface of GF after processing, which indicates a strong binding between GF and graphene. GF/CRG has significant influences on crystallization and mechanical property of PLA: the crystallinity of PLA increases from 27.61 to 51.29%; the tensile strength of the PLA–GF/CRG composite is about 63% larger than the pure PLA at the GF/CRG content of 10 wt %. This new method can apply to making composites with high performance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43296.     

Synthesis and properties of click coupled graphene oxide sheets with three‐dimensional macromolecules

A facile click chemistry approach to the functionalization of three‐dimensional hyperbranched polyurethane (HPU) to graphene oxide (GO) nanosheets is presented. HPU‐functionalized GO samples of various compositions were synthesized by reacting alkyne‐functionalized HPU with azide‐functionalized GO sheets. The morphological characterization of the HPU‐functionalized GO was performed using transmission electron microscopy and its chemical characterization was carried out using Fourier transform‐infrared spectroscopy, nuclear magnetic resonance spectroscopy, and X‐ray photoelectron spectroscopy. The graphene sheet surfaces were highly functionalized, leading to improved solubility in organic solvents, and consequently, enhanced mechanical, thermal, and thermoresponsive and photothermal shape memory properties. The strategy reported herein provides a very efficient method for regulating composite properties and producing high performance materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43358.     

Thermal and mechanical properties of liquid silicone rubber composites filled with functionalized graphene oxide

To improve the thermal and mechanical properties of liquid silicone rubber (LSR) for application, the graphene oxide (GO) was proposed to reinforce the LSR. The GO was functionalized with triethoxyvinylsilane (TEVS) by dehydration reaction to improve the dispersion and compatibility in the matrix. The structure of the functionalized graphene oxide (TEVS‐GO) was evaluated by Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra, X‐ray diffraction (XRD), and energy dispersive X‐ray spectroscopy (EDX). It was found that the TEVS was successfully grafted on the surface of GO. The TEVS‐GO/LSR composites were prepared via in situ polymerization. The structure of the composites was verified by FTIR, XRD, and scanning electron microscopy (SEM). The thermal properties of the composites were characterized by TGA and thermal conductivity. The results showed that the 10% weight loss temperature (T₁₀) increased 16.0°C with only 0.3 wt % addition of TEVS‐GO and the thermal conductivity possessed a two‐fold increase, compared to the pure LSR. Furthermore, the mechanical properties were studied and results revealed that the TEVS‐GO/LSR composites with 0.3 wt % TEVS‐GO displayed a 2.3‐fold increase in tensile strength, a 2.79‐fold enhancement in tear strength, and a 1.97‐fold reinforcement in shear strength compared with the neat LSR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42582.     

In situ polymerization of polyimide‐based nanocomposites via covalent incorporation of functionalized graphene nanosheets for enhancing mechanical,thermal, and electrical properties

In this study, we report an effective method to fabricate high‐performance polyimide (PI)‐based nanocomposites using 3‐aminopropyltriethoxysilane functionalized graphene oxide (APTSi‐GO) as the reinforcing filler. APTSi‐GO nanosheets exhibit good dispersibility and compatibility with the polymer matrix because of the strong interfacial covalent interactions. PI‐based nanocomposites with different loadings of functionalized graphene nanosheets (FGNS) were prepared by in situ polymerization and thermal imidization. The mechanical performance, thermal stability, and electrical conductivity of the FGNS/PI nanocomposites are significantly improved compared with those of pure PI by adding only a small amount of FGNS. For example, a 79% improvement in the tensile strength and a 132% increase in the tensile modulus are achieved by adding 1.5 wt % FGNS. The electrical and thermal conductivities of 1.5 wt % FGNS/PI are 2.6 × 10^?3 S/m and 0.321 W/m·K, respectively, which are ～10¹⁰ and two times higher than those of pure PI. Furthermore, the incorporation of graphene significantly improves the glass‐transition temperature and thermal stability. The success of this approach provides a good rationale for developing multifunctional and high‐performance PI‐based composite materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42724.     

Functionalized graphene‐reinforced rubber composite: Mechanical and tribological behavior study

A functionalized graphene, fluorinated graphene nanosheets (FGS), and SiO₂ nanoparticles as reinforcing fillers were employed to improve the mechanical properties of the solution styrene butadiene and butadiene rubber composites (SSBR‐BR). The results showed that the mechanical properties of SSBR‐BR composite filled with FGS were substantially improved than those of the unfilled and equivalent filler loaded graphene oxide (GO) and reduced graphene oxide (rGO) filled SSBR‐BR composites. It can be ascribed to the fact that the hydrophobic surface of FGS can be endowed the good dispersion in rubber matrix and stronger interfacial interaction between rubber and fillers. The tribological properties of these composites are also investigated. The results reveal that incorporation of GO, rGO, and FGS in SSBR‐BR composites can decrease antiwear properties because the existence of layered graphene promotes to tear and peel off. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44970.     

Forward osmosis water desalination: Fabrication of graphene oxide-polyamide/polysulfone thin-film nanocomposite membrane with high water flux and low reverse salt diffusion

This paper investigates the synthesis of graphene oxide (GO)-incorporated polyamide thin-film nanocomposite (TFN) membranes on polysulfone substrate for forward osmosis applications. The GO nanosheets were embedded into polyamide layer using different concentrations (0.05?0.2 wt%). The results represented the alteration of polyamide surface by GO nanosheets and enhancing the surface hydrophilicity by increasing the GO loading. The results showed that the water flux for 0.1 wt% GO embedded nanocomposite (TFN) membrane was 34.7 L/m² h, representing 90% improvement compared to the thin-film composite, while the salt reverse diffusion was reduced up to 39%.