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The rapid co-assembly of graphene oxide (GO) nanosheets and a surfactant at the oil/water (O/W) interface is harnessed to develop a new class of soft materials comprising continuous, multilayer, interpenetrated, and tubular structures. The process uses a microfluidic approach that enables interfacial complexation of two-phase systems, herein, termed as "liquid streaming" (LS). LS is demonstrated as a general method to design multifunctional soft materials of specific hierarchical order and morphology, conveniently controlled by the nature of the oil phase and extrusion's injection pressure, print-head speed, and nozzle diameter. The as-obtained LS systems can be readily converted into ultra-flyweight aerogels displaying worm-like morphologies with multiscale porosities (micro- and macro-scaled). The presence of reduced GO nanosheets in such large surface area systems renders materials with outstanding mechanical compressibility and tailorable electrical activity. This platform for engineering soft materials and solid constructs opens up new horizons toward advanced functionality and tunability, as demonstrated here for ultralight printed conductive circuits and electromagnetic interference shields., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

The current state-of-the-art mixing strategies of nanoparticles with insulating polymeric components have only partially utilized the unique electrical conductivity of graphene in nanocomposite systems. Herein, this paper reports a nonmixing method of direct creation of polymer/graphene nanocomposites from polymer blends via laser irradiation. Polycarbonate-laser-induced graphene (PC-LIG) nanocomposite is produced from a PC/polyetherimide (PC/PEI) blend after exposure to commercially available laser scribing with a power of ≈6 W and a speed of ≈2 cm s -1 . Extremely high electrical conductivities are obtained for the PC-LIG nanocomposites, ranging from 26 to 400 S m -1 , depending on the vol% of the starting PEI phase in the blend. To the authors' knowledge, these conductivity values are at least one order of magnitude higher than the values that are previously reported for conductive polymer/graphene nanocomposites prepared via mixing strategies. The comprehensive microscopy and spectroscopy characterizations reveal a complete graphitization of the PEI phase with columnar microstructure embedded in the PC phase., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Kinetic factors that facilitate carbon nanotube (CNT) migration in a polymer blend from a high-density polyethylene (HDPE) phase to a poly (p-phenylene ether) (PPE) phase were studied, with the objective to induce CNT migration and localization at the interface. Herein, a CNT filler was pre-localized in an HDPE polymer and then blended with PPE at different blend compositions of 20:80, 40:60, 60:40, and 80:20 of PPE/HDPE at a constant filler concentration of 1 wt%. The level of CNT migration was studied at different mixing times of 5 and 10 min. The electrical conductivity initially increased by 2–3 orders of magnitude, with an increase in the PPE content up to 40%, and then it decreased significantly by up to 12 orders of magnitude at high PPE content up to 100%. We determined that the extent of migration was related to the difference in the melt viscosity between the constituent polymers. A triblock copolymer styrene-ethylene/butylene-styrene (SEBS) was used to improve the blend miscibility, and 2 wt% copolymer was found to be the optimum concentration for the electrical properties for the two blend compositions of 20:80 and 80:20 of PPE/HDPE, at a constant filler concentration of 1 wt%. The introduction of the SEBS triblock copolymer significantly increased the conductivity almost by almost four orders of magnitude for PPE/HDPE/80:20 composites with 1 wt% CNT and 2 wt% SEBS compared to the uncompatibilized blend nanocomposite. The mechanical strength of the compatibilized blend nanocomposites was found to be higher than the unfilled compatibilized blend (i.e., without CNT), uncompatibilized blend nanocomposites, and the pristine blend, illustrating the synergistic effect of adding nanofillers and a compatibilizer. SEM and TEM microstructures were used to interpret the structure–property relationships of these polymer blend nanocomposites. [ABSTRACT FROM AUTHOR]

The interface between polymer matrices and nanofillers is critical for efficient interaction to achieve the desired final properties. In this work, block copolymers were utilized to control the interface and achieve optimum interfacial interaction. Specifically, we studied the compatibilizing effects of styrene-ethylene/butadiene-styrene (SEBS) and styrene-ethylene/propylene (SEP) block copolymers on the morphology, conductivity, and rheological properties of polypropylene-polystyrene (PP/PS) immiscible blend with 2 vol% multiwall carbon nanotube (MWCNT) at different blend compositions of PP/PS 80:20, 50:50 and 20:80. MWCNTs induced co-continuity in PP/PS blends and did not obstruct with the copolymer migration to the interface. Copolymers at the interface led to blend morphology refinement. Adding block copolymers at a relatively low concentration of 1 vol% to compatibilize the PP/PS 80:20 blend substantially increased the electrical conductivity from 5.15*10−7S/cm for the uncompatibilized blend to 1.07*10−2S/cm for the system with SEP and 1.51*10−3S/m for the SEBS system. These values for the compatibilized blends are about 4 orders of magnitude higher due to the interconnection of the droplet domains. For the PP/PS 50:50 blend, the SEBS copolymer resulted in a huge increase in conductivity at above 3 vol% concentration (conductivity increased to 3.49*10−3S/cm from 5.16*10−7S/cm). Both the conductivity and the storage modulus increased as the SEBS copolymer content was increased. For the PP/PS 20:80 blend, we observed an initial decrease in conductivity at lower copolymer concentrations (1–3 vol%) and then an increase in conductivity to values higher than the uncompatibilized system, but only at a higher copolymer concentration of 10 vol%. The triblock copolymer (SEBS), which had 60 wt% PS content, shows a more significant increase in rheological properties compared to the diblock copolymer (SEP). The morphology shows that the interaction between MWCNT and PS is stronger than the interaction between MWCNT and PP, hence there is selective localization of the nanofiller in the PS phase as predicted by Young's equation and by molecular simulation. [ABSTRACT FROM AUTHOR]

This study sheds light on the effect of nitrogen (N) doping of carbon nanotubes (CNTs) on medium-amplitude oscillatory shear (MAOS) response of CNT/polyvinylidene fluoride (PVDF) nanocomposites within a rheologically percolated concentration regime. Custom-synthesized CNTs without and with nitrogen heteroatom (at a nitrogen atomic percent of 3.85 at. %) were incorporated into a PVDF matrix using a miniature melt-mixer at different concentrations. In both cases, as confirmed by TEM investigations, a nanoscopic state of dispersion in the PVDF matrix was achievable using the applied melt mixing procedure. Our results indicated that N-doped nanocomposites, well below their electrical percolation, form a hybrid, load-bearing network structure where network interconnectivity is driven by N-doped CNT domains and near-surface regions of the PVDF phase. This hybrid network formation behavior combined with N-doped CNTs inferior aspect ratio and their higher susceptibility to breakage and length loss during the melt mixing process have led to delayed electrical percolation. In contrast, localized clustering and contact aggregation in a submicrometer scale was the dominant mode of network formation in the undoped CNT/PVDF nanocomposites. These microstructural inferences were further validated in the frame of molecular simulations and optical microscopy investigations. [ABSTRACT FROM AUTHOR]

Electrified and non‐electrified epoxy‐based nanocomposites holding highly and randomly aligned single‐walled carbon nanotube (SWCNT), respectively, were made by vacuum shock technique, where a DC electric field was used to align SWCNT. The alignment of SWCNTs in the electrified nanocomposites was verified via optical microscopy, SEM analysis, and Raman spectroscopy. Electrical characterization revealed that alignment of SWCNTs led to a significant improvement in electrical conductivity and electromagnetic interference shielding of the fabricated nanocomposites. For instance, the electrical conductivity of the electrified nanocomposites at 0.25 wt% and 0.60 wt% was 2.5 × 10−8 and 5.1 × 10−4 S·m−1, while the conductivity of non‐electrified nanocomposites was 1.1 × 10−11 and 5.6 × 10−5 S·m−1, respectively. With 3.0 mm thickness and 0.60 wt% SWCNT loading, the electrified and non‐electrified nanocomposites showed shielding effectiveness of 12.8 dB and 9.1 dB, respectively. These results revealed that electrification of SWCNT in epoxy‐based nanocomposites improved the level of conductive network formation, thereby enhancing electrical properties of the nanocomposites. POLYM. COMPOS., 39:E1139–E1148, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Conductive nanofibers of poly(vinylidene fluoride) ( PVDF) filled with polyaniline ( PANi)-coated multi-wall carbon nanotubes ( MWCNTs) were fabricated using the electrospinning technique. PANi is an intrinsically conductive polymer. The addition of PANi-coated MWCNTs to PVDF created short conductive strands on the surface of the nanofibers, facilitating the formation of a conductive network in the transverse direction of the nanofibers. Piezoelectricity along with electric conductivity makes these PVDF nanofibers promising for applications such as sensors and actuators. Electrospun PVDF nanofiber mats had higher piezoelectricity than melt-processed samples produced using traditional polymer processing techniques, such as compression molding. Spectroscopic imaging techniques were employed to study the effects of the filler and processing conditions on the nanofiber structure. X-ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry results indicated a large increase in the β-phase crystals of the PVDF nanofibers. This higher content of β-phase crystals enhanced the piezoelectricity of the nanofibers. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Nanocomposites using copper nanowires (CuNWs) or carbon nanotubes (CNTs) as fillers with polypropylene (PP) as matrix were prepared by miscible solution mixing and precipitation method. Comparative studies on electrical conductivity and electromagnetic interference shielding properties were reported. On the conductivity curve, a plateau was found for both CuNW/PP composite and CNT/PP composite. The plateaus are located at a different concentration range for each composite type: for CuNW/PP composite, it is between 0.8 and 1.7 vol %, while for CNT/PP composite the plateau occurs in a narrower range between 0.4 and 0.6 vol %. The shielding effectiveness (SE) increases with increased concentration of fillers. CNT/PP composite has higher SE at concentrations less than 2 vol %; the two curves cross near 10 dB at this point and at concentrations higher than 2 vol %, CuNW/PP composite has higher SE. © 2014 American Institute of Chemical Engineers AIChE J, 61: 296-303, 2015 [ABSTRACT FROM AUTHOR]

In this study, a numerical modeling approach was used to investigate the current-voltage behavior of conductive nanoplatelet-based nanocomposites. A three-dimensional continuum Monte Carlo model was employed to randomly disperse the nanoplatelets in a cubic representative volume element. A nonlinear finite element-based model was developed to evaluate the electrical behavior of the nanocomposite for different levels of the applied electric field. Also, the effect of filler loading on nonlinear conductivity behavior of nanocomposites was investigated. The validity of the developed model was verified through qualitative comparison of the simulation results with results obtained from experimental works. [ABSTRACT FROM AUTHOR]

In situ polymerization of aniline monomers in the presence of multiwall carbon nanotubes (MWCNTs) leads to core-shell nanostructures for use in conductive polymer composites. The conductivity of core-shell nanofibers can be tuned by altering coating thickness. These high-aspect-ratio MWCNT-polyaniline core-shell nanofibers are dispersed in polystyrene (PS) using solution mixing. These composites exhibit electrical percolation at a much lower concentration than MWCNT/PS composites. Polyaniline (PANi), when used as a coating layer, is able to attenuate electromagnetic (EM) waves via absorption. The dielectric measurements of MWCNT-PANi/PS composites show one order of magnitude increase in real electrical permittivity compared with that of MWCNT/PS composites, making them suitable for charge storage purposes. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional continuum percolation model was developed based on a Monte Carlo simulation approach to investigate the percolation behavior of an electrically insulating matrix reinforced with conductive nano-platelet fillers. The conductivity behavior of composites rendered conductive by randomly dispersed conductive platelets was modeled by developing a three-dimensional finite element resistor network. Parameters related to the percolation threshold and a power-low describing the conductivity behavior were determined. The piezoresistivity behavior of conductive composites was studied employing a reoriented resistor network emulating a conductive composite subjected to mechanical strain. The effects of the governing parameters, i.e., electron tunneling distance, conductive particle aspect ratio and size effects on conductivity behavior were examined. [ABSTRACT FROM AUTHOR]

The electromagnetic interference (EMI) shielding effectiveness (SE) and EMI shielding mechanisms of high structure carbon black (HS-CB)/polypropylene (PP) composites in the X-band frequency range were studied. Composite plates with three different thicknesses and five different electrical conductivities were studied. The reflection loss and absorption loss of the composites were quantified based on the electromagnetic radiation power balance. The results showed that for HS-CB/PP composites, absorption loss contribution to the overall attenuation is more than the contribution of the reflection loss. The ability of the theoretical model to predict the EMI shielding by reflection and absorption was found to be a function of the shielding plate thickness and conductivity. [ABSTRACT FROM AUTHOR]

This study intends to reveal the significance of the catalyst to substrate ratio (C/S) on the structural and electrical features of the carbon nanotubes and their polymeric nanocomposites. Here, nitrogen-doped carbon nanotube (N-MWNT) was synthesized via a chemical vapor deposition (CVD) method using three ratios (by weight) of iron (Fe) catalyst to aluminum oxide (Al2O3) substrate, i.e.,1/9, 1/4, and 2/3, by changing the Fe concentration, i.e., 10, 20, and 40 wt.% Fe. Therefore, the synthesized N-MWNT are labelled as (N-MWNTs)10, (N-MWNTs)20, and (N-MWNTs)40. TEM, XPS, Raman spectroscopy, and TGA characterizations revealed that C/S ratio has a significant impact on the physical and chemical properties of the nanotubes. For instance, by increasing the Fe catalyst from 10 to 40 wt.%, carbon purity increased from 60 to 90 wt.% and the length of the nanotubes increased from 1.2 to 2.6 µm. Interestingly, regarding nanotube morphology, at the highest C/S ratio, the N-MWNTs displayed an open-channel structure, while at the lowest catalyst concentration the nanotubes featured a bamboo-like structure. Afterwards, the network characteristics of the N-MWNTs in a polyvinylidene fluoride (PVDF) matrix were studied using imaging techniques, AC electrical conductivity, and linear and nonlinear rheological measurements. The nanocomposites were prepared via a melt-mixing method at various loadings of the synthesized N-MWNTs. The rheological results confirmed that (N-MWNTs)10, at 0.5–2.0 wt.%, did not form any substantial network through the PVDF matrix, thereby exhibiting an electrically insulative behavior, even at a higher concentration of 3.0 wt.%. Although the optical microscopy, TEM, and rheological results confirmed that both (N-MWNTs)20 and (N-MWNTs)40 established a continuous 3D network within the PVDF matrix, (N-MWNTs)40/PVDF nanocomposites exhibited approximately one order of magnitude higher electrical conductivity. The higher electrical conductivity of (N-MWNTs)40/PVDF nanocomposites is attributed to the intrinsic chemical features of (N-MWNTs)40, such as nitrogen content and nitrogen bonding types. [ABSTRACT FROM AUTHOR]

The similar molecular structure but different geometries of the carbon nanotube (CNT) and graphene nanoribbon (GNR) create a genuine opportunity to assess the impact of nanofiller geometry (tube vs. ribbon) on the electromagnetic interference (EMI) shielding of polymer nanocomposites. In this regard, GNR and its parent CNT were melt mixed with a polyvinylidene fluoride (PVDF) matrix using a miniature melt mixer at various nanofiller loadings, i.e., 0.3, 0.5, 1.0 and 2.0 wt%, and then compression molded. Molecular simulations showed that CNT would have a better interaction with the PVDF matrix in any configuration. Rheological results validated that CNTs feature a far stronger network (mechanical interlocking) than GNRs. Despite lower powder conductivity and a comparable dispersion state, it was interestingly observed that CNT nanocomposites indicated a highly superior electrical conductivity and EMI shielding at higher nanofiller loadings. For instance, at 2.0 wt%, CNT/PVDF nanocomposites showed an electrical conductivity of 0.77 S·m−1 and an EMI shielding effectiveness of 11.60 dB, which are eight orders of magnitude and twofold higher than their GNR counterparts, respectively. This observation was attributed to their superior conductive network formation and the interlocking ability of the tubular nanostructure to the ribbon-like nanostructure, verified by molecular simulations and rheological assays. [ABSTRACT FROM AUTHOR]

The electrical conductivity and percolation behavior of polymer blend nanocomposites were investigated as a consequence of polymer-filler interaction and blend morphology. The nanocomposites were derived from melt compounding of carbon nanotubes (CNTs) in polystyrene (PS)/polyamide 6 (PA6) blends. The electrical conductivity of co-continuous PS/PA6 (50/50) blends remained constant in the semi-conductive region (6.75 × 10 −8 –1.50 × 10 −7 S·cm −1 ) over a wide range of CNT loading (0.5–3.5 phr). Nevertheless, (50/50) blends presented higher electrical conductivity than PA6/CNT nanocomposites with the same effective CNT concentration. Contrary to common intuitions, at high loadings of CNTs, higher electrical conductivity was observed for the blends wherein the CNT-rich PA6 phase was in the form of dispersed droplet morphology rather than co-continuous one. For instance, at the CNT loading of 3.5 phr, the conductivity of blend with PS/PA6 volume ratio of (90/10) is approximately 4 orders of magnitude higher than co-continuous (50/50) blend. This observation is attributed to a two-level percolation mechanism (primary and secondary), as verified by optical and transmission electron microscopy. The primary percolation occurs by selective localization of CNTs in PA6 droplets due to their thermodynamic affinity for the PA6 phase. Once the PA6 droplets are impregnated with CNTs, the excess CNTs (at high loadings) localize in the PS phase and act as effective electrical bridges for the highly conductive PA6 droplets (secondary percolation). [ABSTRACT FROM AUTHOR]

Two different graphene nanosheets with different oxygen groups' localization were synthesized to investigate their effect on the electrical properties of graphene/epoxy nanocomposite coatings. Graphite natural flakes (NG) and expanded graphite (EG) were used as a carbon precursor to synthesize Edge functionalized (E-GO) and Basal Functionalized (B-GO) graphene nanosheets, respectively. Next, polymer nanocomposite coatings were fabricated by dispersing E-GO and B-GO into a waterborne epoxy matrix. Rheology was assisted in evaluating the dispersion state of the nanosheets in the epoxy matrix. B-GO exhibited better performance in network formation which can be related to the similarity of oxygen groups between B-GO and epoxy matrix. Next, the electrical conductivitie values of polymer nanocomposite coatings were measured after in-situ thermal reduction at 225 °C. The results indicated that polymeric coatings containing B-GO nanosheets represent higher electrical conductivity values compared to samples containing E-GO nanosheets despite the higher intrinsic electrical conductivity of E-GO compared to B-GO. This can be related to the improved ability of B-GO nanosheets to form an electrically conductive network inside the epoxy matrix. The electrical conductivity value of 0.5 S/m was obtained for polymeric coatings containing 0.8 vol% B-GO nanosheets with percolation thresholds of 0.17 vol%. The improved electrical conductivity can be correlated to the formation of the interphase region between the epoxy matrix and B-GO nanosheets which is the result of the similarity of the oxygen groups' nature in B-GO and epoxy. • Edge and basal functionalized graphene oxide nanosheets were synthesized. • The nature of oxygen-containing groups changed the interaction behavior of nanosheets and epoxy matrix. • Basal functionalized graphene nanosheets showed higher ability to form a three-dimensional network. • The improved electrical conductivity was correlated to the interphase region between the epoxy matrix and basal functionalized graphene nanosheets [ABSTRACT FROM AUTHOR]

Abstract: Multi-walled carbon nanotube (MWCNT)/polystyrene (PS) composites were injection molded into a mold equipped with three different cavities. A high alignment of MWCNTs in PS was achieved by applying high shear force to the melt. The effects of gate and runner designs and processing conditions, i.e., mold temperature, melt temperature, injection/holding pressure and injection velocity, on the volume resistivity of the composites were investigated in both the thickness and in-flow directions. The experiments showed that volume resistivity could be varied up to 7 orders of magnitude by changing the processing conditions in the injection molded samples. The electromagnetic interference shielding effectiveness (EMI SE) of the molded composites was studied by considering the alignment of the MWCNTs. The EMI SE decreased with an increase in the alignment of the injection-molded MWCNTs in the PS matrix. This study shows that mold designs and processing conditions significantly influence the electrical conductivity and shielding behavior of injection molded CNT-filled composites. [Copyright &y& Elsevier]

• High concentrated graphene nanosheets dispersion (20 mg/ml) in water was synthesized. • Electrical conductivity as high as 0.5 S/m at graphene loading level of 1.5 wt% was obtained. • A Facile processing method was used to fabricate conductive coatings. • High electrical permittivity values were achieved at graphene loading level of 1.5 wt%. In this work, we present a novel method to exfoliate graphite to graphene oxide nanosheets with single to 3 layers at concentration as high as 15 mg/ml. In the first step, graphite intercalated compound (GIC) was obtained through a chemical intercalation process. In the next step, GIC was expanded and used as the precursor to obtain oxidized graphite. Oxidized graphite was introduced into a high alkaline medium and a high-speed homogenizer was used to complete the exfoliation process. Raman spectroscopy, XPS, XRD, TGA, SEM and TEM were used to characterize the synthesized graphene oxide nanosheets. Electrically conductive coatings were prepared by adding and stirring graphene oxide dispersion into an epoxy-hardener pre-mixture. The prepared coatings were post cured at 100 °C followed by annealing at 225 °C to in situ reduce the incorporated graphene oxide to graphene nanosheets. High electrical conductivity values as 0.5 S/m was obtained for the epoxy-graphene nanocomposite at graphene loading level of 1.5 wt%, which is comparable to previously reported data using more complex and laborious fabrication methods. Cryo-SEM images were captured in the liquid phase to investigate electrical network formation in the polymeric matrix. [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel binary PVDF/PPy conductive blends, PVDF/MWCNT conductive nanocomposites. [•] Novel hybrid PVDF/PPy/MWCNT conductive nanocomposites. [•] Electrical conductivities of the hybrid were always much higher. [•] Addition of two conductive fillers had a synergistic effect on the conductivity. [ABSTRACT FROM AUTHOR]