Graphene-based Polymer Research Articles

Flexible Poly(vinyl alcohol)/Reduced Graphene Oxide Coated Carbon Composites for Electromagnetic Interference Shielding

Flexible poly(vinyl alcohol)/reduced graphene oxide coated activated carbon (PVA/RGO@AC) composite films with extremely low graphene amounts were prepared by using AC as segregators and substrates. Decoration of AC with graphene to create an individual RGO-sheet-coated AC structure leads to a dramatic increase in the conductivity of AC and effectively prevents the restacking and agglomeration of graphene. The percolation threshold of the PVA/RGO@AC composites is as low as 0.17 wt % for RGO@AC, and, in particular, only 0.017 wt % RGO is needed. A high conductivity of 10.90 S/m and an impressive electromagnetic interference shielding effectiveness (EMI SE) of 25.6 dB with an absorption-dominated mechanism are achieved for PVA/RGO@AC composites with a low RGO loading of 1.0 wt %. The specific EMI SE of the composite reaches 17.5 dB/mm, outperforming most of the reported pioneering graphene-based polymer composites with such a low RGO amount. The excellent electrical property and outstanding EMI shielding per...

Embedded large strain sensors with graphene-carbon black-silicone rubber composites

Wearable electronics have generated a strong demand for stretchable, skin-mountable and flexible sensors. This paper provides an effective technique for fabricating conductive networks using graphene-based polymer composites. Graphene-carbon black-silicone rubber (G-CB-SR) composites were cast in a mould, and a film was fabricated to make a composite strain sensor. Here we investigate how the remarkably different geometry affects the effective conductivity and piezoresistive properties of the composites. The electromechanical response of the G-CB-SR composites showed highly reversible and durable behaviour. It was stretchable up to 300%, and the gauge factor (GF) depended on the composition of the composites. The large strain sensors made of high-quality G-CB-SR film was achieved by solution intercalation with low-cost production and easy scalability.

Highly thermally conductive layered polymer composite from solvent-exfoliated pristine graphene

Highly thermally conductive polymer composites are urgently required to resolve the heat dissipation issue of rapidly evolving electronic devices. Owing to two-dimensional plane structure and extremely high thermal conductivity, graphene is an ideal thermally conductive filler for polymer composites. In view of the increasing maturity of solvent exfoliation technique and its ability to produce high-quality graphene on a large scale at low cost, we aim to develop highly thermally conductive polymer composites from solvent-exfoliated, plane defect-free graphene, instead of oxidation-exfoliated, plane defect-rich graphene. Solvent-exfoliated pristine graphene/poly(vinylidene fluoride) composites with well-ordered layered structure are produced through a simple, scalable doctor-blading process. The combination of high-quality solvent-exfoliated pristine graphene and well-ordered layered microstructure forms high-efficiency, directional and dense pathways for phonon transport, and thus endows the polymer composites with high thermal conductivities (41.64 W/mK), surpassing the previously reported oxidation-exfoliated graphene-based polymer composites (2.1–19.5 W/mK). It provides a new route to fabricate highly thermally conductive composites from solvent-exfoliated pristine graphene.

Advances in graphene-based polymer composites with high thermal conductivity

Advances in graphene-based polymer composites with high thermal conductivity

Graphene-based polymer dispersed liquid crystals display- an overview

Generally, the indium tin oxide (ITO) has been utilized as the transparent electrode in the polymer dispersed liquid crystals (PDLC) films display and in other opto-electronics devices. However, such ITO electrodes are high cost, which is because of the cost of indium metal and its processing onto glass substrate. In such circumstances, graphene could serve as a smart choice that can be employed as the transparent electrode on glass substrate which can be used in the PDLC films. Graphene provides low resistivity, high chemical stability, high optical transmittance, and mechanical strength that make graphene as an excellent transparent electrode. Consequently in the present timings, graphene and graphene oxide (GrO) based transparent electrodes demonstrate great potential for the fabrication of various smart flexible displays, and opto-electronics applications. The current review work presents some of the past and present ongoing developments in polymer dispersed liquid crystals (PDLC) fabricated with graphene and graphene oxide (GrO) electrodes as transparent electrodes.

Effect of Graphene Nano-Additives on the Local Mechanical Behavior of Derived Polymer Nanocomposites.

In this study, indentation tests of graphene-based polymer nanocomposites were carried out to determine the local elastic mechanical properties. The samples consist of epoxy matrix with graphene additives. Additives were added at levels of 0% as a control, 0.5%, 1%, 2.5%, 5% and 10% by weight. The local elastic properties such as moduli and hardness were calculated. After each indentation, the prints were characterized using scanning electron microscopy (SEM). It seems that the local mechanical properties of nanocomposite samples were improved as the amount of nano-additives increased. Based on the curve displacement and surface imaging, we can conclude that the nano-additives influenced the overall plastic mechanical behavior of the samples. For simulating micro-indentation test, a finite element analysis model was developed using ABAQUS software and compared to experimental tests. Good correlation was observed.

A Simple Method of Fabricating Graphene-Polymer Conductive Films

Abstract In this study, polydimethylsiloxane and graphene were used to fabricate surface electrodes for electrocardiographic (ECG) sensing. A simple and inexpensive method was developed to fabricate graphene-based polymer films. In this method, graphene was inlaid in polydimethylsiloxane by polymer infiltration. The polymer films were successfully used in ECG measurements and performed as well as conventional silver/silver chloride wet electrodes. Few motion artifacts were observed with the graphene films when body postures were changed and during walking. The presented approach is low-cost and suitable for mass production, holding great promise in fabricating polymer electrodes for medical monitoring.

Electrically Conductive Graphene-Based Biodegradable Polymer Composite Films with High Thermal Stability and Flexibility

Cellulose nanofibril (CNF) and graphene (GR) powder were added into polylactic acid (PLA)/polypyrrole (PPy) composite films via a low-cost, eco-friendly, low-temperature, and in-situ polymerization synthesis, which obtain novel flexible and conductive polylacticacid-cellulose nanofibril-graphene/polypyrrole (PLA–CNF–GR/PPy) composite films. The CNF was embedded in the PLA matrix to enhance the mechanical properties. Remarkably, when a few GR (1%) powder was added, the tensile strength of composite films increased by 5.6%, respectively, compared with pure PLA–CNF, and increased by 17.6% compared with the PLA. The GR and CNF had a positive influence on mechanical properties of composite films. In addition, the PLA–CNF–GR/PPy composite films exhibited many unique properties when GR powder was introduced, including high thermal stability, and especially electrical conductivity. The electrical conductivity of the PLA–CNF–GR/PPy composite films increased from 0.12 to 1.06[Formula: see text]S/cm as the content of GR powder increased from 0 to 10%. The PLA–CNF–GR-10/PPy also demonstrated excellent flexible stability, only 7.5% deviation after over 100 bending cycles. Furthermore, we designed and found that the exploration of a flexible solid-state supercapacitor assembled with PLA–CNF–GR-10/PPy composite electrodes had a capacitance of 30[Formula: see text]F/g at a current density of 0.5[Formula: see text]A/g. Although it was not quite as prominent as the capacitance, it provided an innovative means for preparing the conductive composite films. Based on these advantages the PLA–CNF–GR/PPy could be considered as sensors, flexible electrodes, and flexible displays. It also opens a new field of potential applications of biodegradable materials.

Bottom-up fabrication of graphene-based conductive polymer carpets for optoelectronics

The covalent attachment of a one dimensional (1D) polymer brush onto a two-dimensional (2D) material presents an appealing strategy to fabricate anisotropic polymer membranes, namely “polymer carpets”.

Three-dimensional graphene-based polymer nanocomposites: preparation, properties and applications.

Motivated by the unique structure and outstanding properties of graphene, three-dimensional (3D) graphene-based polymer nanocomposites (3D-GPNCs) are considered as new generation materials for various multi-functional applications. This review presents an overview of the preparation, properties and applications of 3D-GPNCs. Three main approaches for fabricating 3D-GPNCs, namely 3D graphene based template, polymer particle/foam template, and organic molecule cross-linked graphene, are introduced. A thorough investigation and comparison of the mechanical, electrical and thermal properties of 3D-GPNCs are performed and discussed to understand their structure-property relationship. Various potential applications of 3D-GPNCs, including energy storage and conversion, electromagnetic interference shielding, oil/water separation, and sensors, are reviewed. Finally, the current challenges and outlook of these emerging 3D-GPNC materials are also discussed.

Highly aligned graphene oxide/waterborne polyurethane fabricated by in-situ polymerization at low temperature

AbstractNanocomposites of waterborne polyurethane (WPU) containing graphene oxide sheets (GO) were prepared by an in-situ polymerization method at low temperature. The morphology and interface structure were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Without undergoing complicated functionalization processes, GO can be finely embed into a WPU matrix and present high degree of orientation at high GO contents, due to the formation of chemical bonds and hydrogen bonding. From the Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and dynamic mechanical analysis (DMA) results, incorporation of GO exists in two ways and shows inverse effects. At a content of 2.0 wt.% GO loading, the tensile elastic modulus of the GO-WPU film increased by 193% to neat WPU. The nanocomposites also displayed 30°C higher thermal stability than WPU in thermogravimetric (TG) curves. This environment-friendly method may pave the way to design graphene-based polymer composites.

Molecular junctions for thermal transport between graphene nanoribbons: Covalent bonding vs. interdigitated chains

Proper design and manufacturing thermal bridges based on molecular junctions at the contact between graphene platelets or other thermally conductive nanoparticles would provide a fascinating way to produce efficient heat transport networks for the exploitation in heat management applications. In this work, using Non Equilibrium Molecular Dynamics, we calculated thermal conductance of alkyl chains used as molecular junctions between two graphene nanoribbons, both as covalently bound and as Van der Waals interdigitated chains. Effect of chain length, grafting density, temperature and chain interdigitation were systematically studied. A clear reduction of conductivity was found with increasing chain length and decreasing grafting density, while lower conductivity was observed for Van der Waals interdigitated chains compared to covalently bound ones. The importance of molecular junctions in enhancing thermal conductance at graphene nanoribbons contacts was further evidenced by calculating the conductance equivalence between a single chain and an overlapping of un-functionalized graphene sheets. As an example, one single pentyl covalently bound chain was found to have a conductance equivalent to the overlapping of an area corresponding to about 152 carbon atoms. These results contribute to the understanding of thermal phenomena occurring within networks of thermally conductive nanoparticles, including graphene nanopapers and graphene-based polymer nanocomposites, which are or high interest for the heat management application in electronics and generally in low-temperature heat exchange and recovery.

In situ exfoliation of graphite in solid phase for fabrication of graphene/polyamide-6 composites

In this study, we reported a new in situ method to prepare the polyamide-6 (PA6)/graphene nanoplates by solid state shear milling. The PA6/graphene nanoplates compounding powder was prepared with the addition of 10 wt% of graphite. During the milling process, graphite was in situ exfoliated into few-layer graphene sheets in the PA6 matrix in solid phase. Using this compounding powder, the PA6/graphene composites were fabricated with different contents of graphene by melting dilution process. The number of graphene layers was 4–6 which was confirmed by high-resolution Transmission electron microscopy and Atomic Force Microscope. The exfoliation process of graphite was also demonstrated by Scanning electron microscopy observation. Both Raman and X-ray diffraction proved that the thickness of graphite was reduced significantly. The thermal conductivity of the composites with 5.0 wt% of graphene loading was increased by 85% and the yield strength was also appreciably enhanced. The results showed that solid phase in situ exfoliation method paves a new way to prepare graphene-based polymer composites on a large-scale with high performance.

The role of stearic acid for silver nanoparticle formation on graphene and its composite with poly(lactic acid)

Graphene-based polymer nanocomposites have received much attention in the field of new hybrid materials, and in the enhancement of properties and diversification of applications. In this work, reduced graphene (rGO) and silver nanoparticles (AgNPs) were cooperated with poly(lactic acid) (PLA) (a semi-crystalline and brittle polymer) to improve mechanical strength and conductivity of the composites. The effect of various concentrations of stearic acid (SA—a precursor) on the formation of silver nanoparticles on graphene and its composite with PLA was studied for the first time. The rGO and AgNPs were first prepared using SA to enhance the AgNPs formation and improve surface wetting of rGO/AgNPs in PLA. The XPS atomic concentration of AgNPs in rGO-Ag-SA1 composite (1:1 mass ratio of SA: graphene oxide) was 5.77%, while, 2.55% in the rGO-Ag composite without SA. This enhancement is due to substitution of AgNPs onto the epoxy and hydroxyl groups on the graphene sheet. In addition, tensile strength of PLA–rGO–AgNPs–SA was higher than neat PLA when AgNPs and SA were added into the composites, especially the composite of PLA–rGO–Ag–SA1 which showed the highest strength increase of 47%. The volume resistivity of PLA–rGO–Ag–SA1 film was also two times lower than PLA–rGO–Ag; thus, this graphene-based composite of PLA–rGO–Ag showed a significant advantage for applications where antistatic properties are required along with an improvement of PLA’s tensile strength.

Correlation between mechanical dissipation and improved X-band electromagnetic shielding capabilities of amine functionalized graphene/thermoplastic polyurethane composites

Graphene-based polymer nanocomposites have demonstrated significant promise to create commercially viable electromagnetic interference (EMI) shielding to protect the next-generation of electronic materials from radiative pollution. In the present study, we carry out a systematic analysis of the dynamic mechanical, dielectric, electrical and X-band shielding properties of thermoplastic polyurethane (TPU) elastomer filled with amine functionalized graphene obtained by the rapid thermal expansion of graphite oxide. By preparation of nanocomposites based on modified and unmodified graphene using solution mixing and hot compression moulding, we demonstrate that the modification with 2-aminoethyl methacrylate enhances the EMI shielding from 14 to 25dB. We also show by fracture analysis, cross-sectional transmission electron microscopy and dynamic mechanical analysis that the modification significantly strengthens the interfacial interactions between TPU and the functionalized graphene at the same filler loading. We find that the dominant shielding mechanism is through absorption and discuss the correlation between the viscoelastic mechanical loss tangent and the more effective dissipation of absorbed EM radiation which might account for the discrepancy between the theoretically predicted and experimentally observed EMI SE.

Graphene-based Polymer Nanocomposites: Recent Advances and Still Open Challenges

Background: From its appearance in the scientific literature, graphene has received much interest, first from the scientific community and then, after the scale-up of the methods suitable for its production, from the industrial world. Nowadays, this nanofiller has to be considered as one of the most promising and performing materials ever discovered: in fact, it is deserving application in different fields, including nanoelectronics, quantum physics, catalysis, energy research and engineering of nanocomposites and biomaterials. The remarkable growth in science, graphene underwent during the last 15 years, is strictly connected to its peculiarities, such as high Young’s modulus, high fracture strength, remarkable thermal and electrical conductivity, large specific surface area, high charge carrier mobility and also biocompatibility. At present, one of the application fields where graphene is gaining a lot of success refers to the fabrication of polymer composites on a commercial scale and low/affordable cost, including both thermoplastic and thermosetting host matrices. These composites do exploit the homogeneous dispersion level of the nanofiller within the polymer matrix, mainly for enhancing the electrical and thermal conductivity of this latter, as well as its mechanical properties, in a remarkable way, even in the presence of very low graphene loadings. In addition, the obtained nanocomposites usually show higher thermal stability with respect to the unfilled polymer matrix. At present, there are about six main areas related to emerging applications for this nanofiller, including displays/screens, biomedical devices, memory chips, fuel cells/batteries, inks, coatings and, from an overall point of view, new smart materials. Keywords: Exfoliation, graphene, graphene oxide, graphene-based composites, reduced graphene oxide, thermoplastic matrices, thermosetting matrices.

Improving mechanical and electrical properties of poly(vinyl alcohol-g-acrylic acid) nanocomposite films by reinforcement of thermally reduced graphene oxide

Graphene has drawn an astounding research interest in recent years, owing to its exceptional properties. The scaled-up and trustworthy production of graphene derivatives, such as graphene oxide (GO) and thermally reduced graphene oxide (TRGO), offer wide variety of possibilities to synthesize graphene-based polymer materials for various applications. In the present work, poly(vinyl alcohol-g-acrylic acid) films were prepared by grafting polyacrylic acid chains onto polyvinyl alcohol backbone employing a free radical polymerization system in the presence of crosslinking agent, N,N′-methylenebisacrylamide (MBA). The graphene was homogeneously dispersed into the prepared polymer using thermal mechanical agitation technique. The so prepared nanocomposites were undertaken for structural and morphological characterization using FTIR, SEM, XRD, Raman Spectroscopy, DLS, Zetasizer and AFM analysis, respectively. The electrical conductive and mechanical properties of prepared nanocomposite films were also investigated.

Constructing 3D Graphene Networks in Polymer Composites for Significantly Improved Electrical and Mechanical Properties

Graphene-based polymer composites with superior electrical and mechanical performance are highly desirable because of their wide range of applications. However, due to the mismatch between charge jumping and the load transfer of adjacent graphene sheets, it remains difficult to achieve significant, simultaneous improvements in electrical and mechanical properties of graphene-polymer composites. To overcome this issue, we here propose an effective strategy to constructed unique 3D conductive networks in which the compatibility of graphene and polymer can be improved by controlled decoration of few-defect graphene sheets, while segregated graphene networks retain good charge-jumping capability. The final composites exhibit an ultra-low electrical conductive percolation threshold of 0.032 vol % and an ultra-high electrical conductivity of 60 S/m at only 2.45 vol %, superior to most of the reported results. They also reveal significantly improved thermodynamic properties, tensile strength, and toughness. We believe that such a simple, industrially feasible method contributes to boost the development of high-performance, functional graphene-polymer composites.

3D printing of CNT- and graphene-based conductive polymer nanocomposites by fused deposition modeling

Fused deposition modeling (FDM) is limited by the availability of application specific functional materials. Here we illustrate printing of non-conventional polymer nanocomposites (CNT- and graphene-based polybutylene terephthalate (PBT)) on a commercially available desktop 3D printer leading toward printing of electrically conductive structures. The printability, electrical conductivity and mechanical stability of the polymer nanocomposites before and after 3D printing was evaluated. The results show that 3D printed PBT/CNT objects have better conductive and mechanical properties and a better performance than 3D printed PBT/graphene structures. In addition to that, printing more than one material (multi-materials) and challenges in using abrasive conductive fillers (i.e., CNT and graphene) are also discussed. Overall this study demonstrates that a commercially available desktop 3D printer can be used to fabricate low-cost functional objects.

Pt-Pd nanoparticles decorated sulfonated graphene-poly(3,4-ethylene dioxythiophene) nanocomposite, An efficient HER electrocatalyst

The main purposes of this work were minimizing the levels of expensive electrocatalyst such as platinum and palladium for maximizing hydrogen evolution at low overpotentials. Here, different compositions of platinum and palladium nanoparticles were applied so that the minimum amount of platinum as a high efficient HER electrocatalyst was achieved. Moreover, a newly prepared nanocomposite, sulfonated graphene-based conductive polymer (poly(3,4–ethylene dioxythiophene), PEDOT), was used as a support of the loaded Pt and Pd nanoparticles. This prepared nanocomposite was assigned as PtxPd(1−x)NPs/PEDOT–SG, which x was changed from 0.0 to 1.0. Preparation and performance of this nanocomposite were characterized using various analytical and electrochemical methods. The results obtained from voltammetry and impedance spectroscopy studies indicated different electrochemical manners of the electrocatalyst towards reducing protons into hydrogen, contained various compositions of Pd and Pt. Among these results, the highest Tafel slope and exchange current, as well as the lowest overpotential, were respectively determined as 57 mV decade−1, 0.301 μA and 0.1726 V (vs. Ag/AgCl), when the HER was investigated at Pt0.5Pd0.5NPs/PEDOT–SG/GCE. The nanocomposite remained stable until 500th cycle of the potential. Summarily, the results of this study were the preparation of the efficient, stable and low-cost HER electrocatalyst.