Effect of fulleroid materials on the mechanical and tribological properties and dielectric relaxation of polyamide 6 nanocomposites

The effect of fulleroid materials (fullerene С₆₀ and fullerene soot, which is used for fullerenes production) on the mechanical and tribological properties of polymer nanocomposites based on polyamide 6 (PA6) was investigated. Composites were synthesized by direct mixing in an extruder. The use of the nanoparticles was an effective way to decrease the friction coefficient of the polymer composites because the fillers had the same size as the segments of the surrounding polymer chains. The steady state coefficients of friction with addition of fulleroid fillers were lower than that of unfilled PA6. The lowest coefficient of friction was observed for PA6 filled with 1 wt% fullerene soot. Dielectric spectroscopy was used to investigate the influence of nanoparticles on the relaxation processes in the polymer matrix. It is found that the segmental relaxation processes become faster with the addition of fullerene С₆₀. In contrast, the secondary processes of PA6/fullerene C₆₀ nanocomposites were observed to slow down with the addition of fullerene C₆₀. This means that the local “molecular stiffness” is increased, and a phenomenological link between the secondary relaxation times and the mechanical properties explains the increase in the Young's modules of the nanocomposites upon the addition of С₆₀. These observations suggest that nanoparticles can have a qualitatively different effect on the matrix polymer dynamics at different length scales, and caution must be taken in comparing the changes in the dynamics associated with different relaxation processes. Copyright © 2016 John Wiley & Sons, Ltd.     

In situ latex synthesis of magnetic polymer nanocomposites for application in magnetorheological materials

A new magnetic polymer nanocomposite based on Fe₃O₄ nanoparticles and nature rubber was prepared by the in situ latex method. This process was fast, versatile, reliable, safe, environmentally friendly, and inexpensive. The magnetorheological effect and mechanical properties of magnetic polymer nanocomposites were investigated in detail. The tensile strength of magnetic polymer nanocomposites without other reinforcing fillers was about 14.6 MPa. At the same time, the relative and absolute magnetorheological effect was about 365.0% and 3.64 MPa, respectively, which were almost 10 times with respect to other magnetic polymer nanocomposites based on nature rubber. Furthermore, the relationships between microstructure and mechanical behavior of magnetic polymer nanocomposites were simulated and discussed by the numerical treatment of a new theoretical model associated with finite element analysis for explaining the micro‐mechanism of magnetic polymer nanocomposites with high performance. The work did not only provide a universal route for the rational design and preparation of magnetic polymer nanocomposites with simultaneously high magnetic sensitivity and mechanical properties for various applications but also propose a new method to improve dispersion of magnetic particles in nature rubber for various applications.     

High-efficiency quaternary polymer solar cells enabled with binary fullerene additives to reduce nonfullerene acceptor optical band gap and improve carriers transport

The polymer/small-molecule electron donor and nonfullerene organic electron acceptor are of structural similarity with both donor and acceptor molecules consisting of polycyclic fused-ring backbone and being decorated with alkyl-chains.In this study,we report that the introduction of binary fullerenes(C_(60)-/C_(70)-PCBM and C_(60)-/C_(70)-ICBA)into a nonfullerene binary system PBDB-T:ITIC reduces the polymer-nonfullerene acceptor intermixing,obtaining higher crystallinity with(100)crystal coherence length from 28 to 29–33 nm for the ITIC,and from 14 to 20–24 nm for the PBDB-T,and improved electron and hole mobilities both.Unprecedentedly,such a protocol reduces the ITIC optical band gap from 1.59 to 1.55 eV.As consequences,higher short-circuit current-density(17.8–18.4 vs.15.8 m A/cm~2),open-circuit voltage(0.92 vs.0.90 V)and fill-factor(0.72–0.73 vs.0.68)are simultaneously obtained,which ultimately afford higher efficient quaternary polymer solar cells with power conversion efficiencies(PCEs)up to 12.0%–12.8%comparing to the host binary device with 9.9%efficiency.For the polymer,ITIC,and ICBA/PCBM ternary blends,11%PCEs were recorded.The use of PCBM leads to larger red-shifting in thin film absorption and external quantum efficiency(EQE)response.Such effect is more pronounced when ICBA:PCBM mixture is used.These results indicate the size and shape of C_(60)and C_(70)as well as the substituent position of the second indene unit on C_(60)-/C_(70)-ICBA affect not only the blend morphology but also the electronic coupling in BHJ mixtures:the quaternary device performance increased in sequences of C_(70)-PCBM:C_(70)-ICBA→C_(70)-PCBM:C_(60)-ICBA→C_(60)-PCBM:C_(70)-ICBA→C_(60)-PCBM:C_(60)-ICBA.The resonant soft X-ray scattering(RSoXS)data indicated the most refined phase separation in the C_(60)-PCBM:C_(60)-ICBA based blend,corresponding to its best device function among the quaternary devices.These results indicate that the using of binary fullerenes as the acceptor additives allows for tuning nonfullerene blended film’s optical properties and filmmorphologies,shedding light on the designing high-performance multi-acceptor polymer solar cells.     

Influence of organo-clay on electrical and mechanical properties of PP/MWCNT/OC nanocomposites

The electrical, thermal and mechanical properties of nanocomposites, based on polypropylene (PP) filled by multi-walled carbon nanotubes (MWCNTs) and organo-clay (OC), were studied with the purpose of finding out the effect of OC on the microstructure of MWCNTs dispersion and PP/MWCNT/OC composites. It was found that addition of organo-clay nanoparticles improved nanotube dispersion and enhanced electrical properties of PP/MWCNT nanocomposites. Addition of organo-clay (MWCNT/OC ratio was 1/1) reduced the percolation threshold of PP/MWCNT nanocomposites from ?_c = 0.95 vol.% to ?_c = 0.68 vol.% of carbon nanotubes, while the level of conductivity became 2–4 orders of magnitude higher. The DSC and DMA analyses have shown that the influence of organo-clay on the thermal and mechanical properties of material was not significant in composites with both fillers as compared to PP/OC. Such an effect can be caused by stronger interaction of OC with carbon nanotubes than with polymer matrix.     

Nanoclay and crystallinity effects on the hydrolytic degradation of polylactides

Polylactide (PLA)-montmorillonite micro- and nanocomposites based on semicrystalline and amorphous polymers and unmodified and organomodified clays at 5 wt% content were produced by melt mixing and subjected to accelerated hydrolytic degradation over a temperature range of 50-70 °C. Degradation rate constants were higher for amorphous PLA and its composites than semicrystalline PLA and its composites as a result of increased permeation through the amorphous domains. Since the effective pH of the nanofillers and their hydrophilicity change through treatment with organomodifiers the degradation rate constants of the nanocomposites were significantly higher than those of the unfilled polymers; by contrast, those of the microcomposites were lower or slightly lower than those of the unfilled polymers possibly due to the reduction of the carboxyl group catalytic effect through neutralization with the hydrophilic alkaline filler. Although the degradation rate constants increased with increasing temperature from 50 to 70 °C, based on calculated activation energies the degradation kinetics did not differ significantly above and below the assumed T_g of 58-60 °C. Higher activation energies were observed for the semicrystalline polymer and its composites. It appears that bulk hydrolytic degradation starts from the interface between polymer and fillers for all samples resulting in significant morphological differences between nanocomposites, microcomposites and unfilled polymer.     

Reinforcement of recycled PP polymers by nanoparticles incorporation

Recycling process seems to be the most efficient way to reduce ecological impacts of used polymers. Nevertheless, the properties of the recycled PP polymer are proved to be insufficient during its reuse, particularly with regard to its thermo-mechanical and rheological behaviors. The incorporation of nanoparticles as fillers into polymer matrix seems to be one of the most successful solutions to upgrade recycled PP polymer. This paper presents an overview on the application of different nanofillers such as clay, calcium carbonate (CaCO₃), Silica (SiO₂), Zinc Oxide (ZnO), carbon black (CB), carbon nanotubes (CNT), antioxidizers and others into recycled PP matrix. Literature works on the effects of nanofillers on obtained nanocomposites are extensively studied. The first section deals with PP recycling and its impact on thermal, mechanical and rheological properties of the polymer. Then, the second part summarizes recent studies on the effects of nanoparticles incorporation on thermo-mechanical and rheological properties of recycled PP. Finally, recyclability of PP-based nanocomposites is discussed.     

Selective Functionalization of Fullerenes with N,N‐Dihalosulfonamides as an N1 Unit: Versatile Syntheses of Aza[60]fulleroids and Aziridino[60]fullerenes and their Application to Photovoltaic Cells

Highly selective and versatile methods for the synthesis of aza[60]fulleroids and aziridino[60]fullerenes from C₆₀ have been developed. The reactions utilized N,N‐dihalosulfonamides as an N₁ source. The photophysical, electrochemical, and thermal properties of the iminofullerenes were investigated by means of UV/Vis spectroscopy, cyclic voltammetry, and thermogravimetry, respectively. Furthermore, photovoltaic cells based on the synthesized iminofullerenes were fabricated. The power conversion efficiencies (PCEs) of the devices showed moderate values ranging from 1.33 to 2.35 %.     

Solubility of fullerenes in n-alkanoic acids C2–C9

The solubility of fullerene C₆₀ and a fullerene mixture [C₆₀ (75%), C₇₀ (24%), C_76–80 (1%)] in linear alkanoic acids (C₂–C₉) was determined at 20°C. The solubilities of C₆₀ and a fullerene mixture in carboxylic acids were examined in relation to the number of carbon atoms in the carboxylic acid.     

Thermal,mechanical and electroactive shape memory properties of polyurethane (PU)/poly (lactic acid) (PLA)/CNT nanocomposites

Polymer blend nanocomposites based on thermoplastic polyurethane (PU) elastomer, polylactide (PLA) and surface modified carbon nanotubes were prepared via simple melt mixing process and investigated for its mechanical, dynamic mechanical and electroactive shape memory properties. Chemical and structural characterization of the polymer blend nanocomposites were investigated by Fourier Transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD). Loading of the surface modified carbon nanotube in the PU/PLA polymer blends resulted in the significant improvement on the mechanical properties such as tensile strength, when compared to the pure and pristine CNT loaded polymer blends. Dynamic mechanical analysis showed that the glass transition temperature (T_g) of the PU/PLA blend slightly increases on loading of pristine CNT and this effect is more pronounced on loading surface modified CNTs. Thermal and electrical properties of the polymer blend composites increases significantly on loading pristine or surface modified CNTs. Finally, shape memory studies of the PU/PLA/modified CNT composites exhibit a remarkable recoverability of its shape at lower applied dc voltages, when compared to pure or pristine CNT loaded system.     

Mechanical and fire retardant properties of EVA/clay/ATH nanocomposites - Effect of particle size and surface treatment of ATH filler

Mechanical and flame retardant properties of ethylene vinyl acetate (EVA) copolymer/organoclay/alumina trihydrate (ATH) nanocomposites have been studied. ATH with different particle sizes, ATH1 (2.2-5.2 μm) and ATH2 (1.5-3.5 μm), and three different surface treatments, uncoated, fatty acid coated and silane coated, have been used. A synergistic effect was observed in EVA/organoclay/ATH nanocomposites with the total heat evolved (THE) and the heat release rate (HRR) lower than that of EVA/ATH composite. It was also found that mechanical and flame retardant properties are affected in different ways by the particle size and the surface treatment of ATH fillers. Improvements in tensile and flame retardant properties were observed in nanocomposites when uncoated ATH fillers and fatty acid coated ATH2 filler were used. On the other hand, silane coating on ATH1 and ATH2 improves limiting oxygen index (LOI) and leads to higher t_ignition and the best char stability after cone calorimeter test.     

Self-assembly of bilayer lipid membrane at multiwalled carbon nanotubes towards the development of photo-switched functional device

Bilayer lipid membrane (BLM) was self-assembled on a uniquely fabricated hydrophilic surface, containing N atoms from the carbon source of ethylene amine, of the multi-walled carbon nanotubes (MWNTs) to form the BLM/MWNTs nanocomposites. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and photoelectric experiments were taken to study the properties of the BLM/MWNTs nanocomposites. The thickness of the BLM, which was calculated from the CV data obtained at BLM/MWNTs electrode, turned out to be 4.38 nm, suggesting that the lipid self-assembled at the nanotubes surface was consistent with a bilayer structure. C₆₀-incorporated BLM could also be self-assembled at the nanotubes surface (C₆₀-BLM/MWNTs). The formation of BLM on the MWNTs surface blocked the diffusion of [Fe(CN)₆]^3/4− redox ions across BLM to the MWNTs electrode as no redox current was observed by CV measurement, whereas the incorporation of the electron mediator, C_60, resumed a pair of redox peaks at C₆₀-BLMs/MWNTs electrode. Moreover, the incorporation of C₆₀ led to a four order of magnitude reduction of the resistance of C₆₀-BLM/MWNTs (369.3 Ω) than that of BLM/MWNTs (3.238 × 10⁶ Ω). MWNTs electrode exhibited an intrinsic cathodic photocurrent (166 μA cm⁻²) while BLM/MWNTs electrode blocked photocurrent response of the MWNTs. Interestingly, C₆₀-BLM/MWNTs electrode resumed partial photoelectric properties (photo current: 65 μA cm⁻²) due to the electron mediation effect of C₆₀ incorporated into the lipid membrane. As a result, the novel self-assembled BLM/MWNTs nanocomposites provided a simple yet useful model to study the C₆₀-mediated photoelectric properties of the BLM/MWNTs which may be applicable to develop new biosensors and molecular devices.     

Quasi-liquid composites based on poly(ethylene terephthalate) films with fullerene and dichlorobenzene

Quasi-liquid composites based on poly(ethylene terephthalate) (PET) films with 9 wt% solution of the C₆₀ (70%) and C₇₀ (∼30%) fullerenes mixture in dichlorobenzene (DCB) have been obtained. It has been shown that PET swelling in the fullerene solution in DCB is accompanied by penetration of fullerene into the polymer structure, and PET films are deformed by the mechanism of intercrystallite crazing. As has been revealed by UV spectroscopy, fullerene incorporated into composite remains monomeric as in solution.     

Oxidation of C60 and C70 fullerites in air

The oxidation of C₆₀ and C₇₀ fullerites and C₆₀/C₇₀ mixture is accompanied by the decomposition of the carbon frameworks of the molecules at annealing temperatures of 250 and 445°C. Fourier-IR and HPLC studies show that the oxidation/decomposition of C₇₀ molecules is more active than that of C₆₀. The stages of fullerite interaction with oxygen while heating in air were determined.     

Novel nanocomposite based on EVA/PHBV/[60]Fullerene with improved thermal properties

A novel nanocomposite was prepared from ethylene-co-vinyl acetate copolymer (EVA) and poly-3-hydroxy butyrate-co-valerate (PHBV) in combination with small amounts of [60]Fullerene (C₆₀). The thermal degradation as well as the incorporation effect of C₆₀ on the thermo-oxidative decomposition of EVA/PHBV/C₆₀ nanocomposites was investigated using thermogravimetric analysis (TGA). In order to assess the level of stabilization of nanocomposites, the oxidation induction time test was also determined. The obtained results indicated that the dispersion of C₆₀ even at low loading (0.3, 0.5 and 0.7 wt.%) exerts a significant increase on the thermal stability properties of nanocomposite. The oxidation induction time values of nanocomposites were remarkably increased with the increase of C₆₀ amounts. Surprisingly, the oxidation induction time of EVA/PHBV/C₆₀ (0.3 wt.%) is 1643 s higher than that of unfilled EVA/PHBV blend.The flammability properties investigated in pyrolysis combustion flow calorimetry (PCFC) showed that the addition of C₆₀ could prolong the time to peak of Heat Release Rate (pHRR) of around 30 °C compared to EVA/PHBV blend. It was demonstrated that C₆₀ is inhibitor of the thermal and thermo-oxidative degradation of EVA/PHBV blend.     

Effects of Precursors and Plasma Parameters on Fullerene Synthesis in RF Thermal Plasma Reactor

Synthesis of fullerenes from graphite powders of different grade was studied in a radiofrequency (RF) plasma reactor. Dependence of fullerene yield on the properties and feed rate of precursors and on the helium content of plasma gas was studied in details. The fullerene yield was influenced by the mean size and the thermal conductivity of graphite particles on the one hand, and the helium content of the gas phase on the other. Soot containing fullerene mixture of 5.9% was produced in best conditions found in this work. The main component of the fullerene mixture was C₆₀. In addition, it contained about 30% of C₇₀ (corresponding to a C₆₀/C₇₀ mass ratio of 2.64). Higher fullerenes such as C₈₄ were also detected by mass spectroscopy (MS) and high performance liquid chromatography (HPLC).     

Thermally conductive and electrically insulative nanocomposites based on hyperbranched epoxy and nano‐Al2O3 particles modified epoxy resin

Novel epoxy nanocomposites based on a diglycidyl ether of bisphenol A (DGEBA) epoxy, an epoxy functionalized hyperbranched polymer (HTTE) and nano‐Al₂O₃ were synthesized with the aim of determining the effect of the nano‐Al₂O₃ particles and HTTE on the structure and properties of epoxy nanocomposites. The mechanical properties, thermal conductivity, bulk resistivity, and thermal stability of the nano‐Al₂O₃/HTTE/DGEBA ternary composites were evaluated and compared with the corresponding matrix. The improvement in impact properties of these nanocomposites was explained in terms of fracture surface analysis by SEM. The results indicate that the incorporation of nanoparticles and hyperbranched epoxy effectively improved the toughness of epoxy composites without sacrificing thermal conductivity and bulk resistivity compared to the neat epoxy and Al₂O₃/DGEBA, obtaining a well dispersion of nanoparticles in epoxy matrix and solving the drawbacks for single fillers filled epoxy nanocomposite. Copyright © 2010 John Wiley & Sons, Ltd.     

Electrochemical formation and properties of two-component films of transition metal complexes and C60 or C70

The electrochemically active polymers have been formed during electro-reduction carried out in solution containing fullerenes, C₆₀ or C₇₀, and transition metal complexes of Pd(II), Pt(II), Rh(III), and Ir(I). In these films, fullerene moieties are covalently bounded to transition metal atoms (Pd and Pt) or their complexes (Rh and Ir) to form a polymeric network. All films exhibit electrochemical activity at negative potentials due to the fullerene cages reduction process. For all studied metal complexes, yields of formation of films containing C₇₀ are higher than yields of electrodeposition of their C₆₀ analogs. C₇₀ /M films also exhibit higher porosity in comparison to C₆₀/M layers. The differences in film morphology and efficiency of polymer formation are responsible for differences in electrochemical responses of these films in acetonitrile containing supporting electrolyte only. C₇₀/M films shows more reversible voltammeric behavior in negative potential range. They also show higher potential range of electrochemical stability. Processes of film formation and electrochemical properties of polymers depend on the transition metal ions or atoms bonding fullerene cages into polymeric network. The highest efficiency of polymerization was observed for fullerene/Pd and fullerene/Rh films. In the case of fullerene/Pd films, the charge transfer processes related to the fullerene moieties reduction in negative potential range exhibit the best reversibility among all of the studied systems. Capacitance performances of C₆₀/Pd and C₇₀/Pd films deposited on the porous Au/quartz electrode were also compared. Capacitance properties of both films are significantly affected by the conditions of electropolymerization. Only a fraction of the film having a direct contact with solution contributes to pseudocapacitance. Capacitance properties of these films also depend on the size of cations of supporting electrolyte. The C₇₀/Pd film exhibits much better capacitance performance comparison to C₆₀/Pd polymer.     

Thermal behavior of a mixture of fullerenes and fullerites C60/70

The thermal behavior of a mixture of fullerites C_60/70 was studied by X-ray diffraction and IR and UV spectroscopy. The temperature range in which the molecular and crystal states degrade was determined (825?C875°C in a CO medium). In the C_60/70 mixture, fullerenes decomposed at lower temperatures than in pure C₆₀ and C₇₀; the decomposition temperature depended on the impurity (oxygen and solvent) content.     

Nonlinear optical properties of solutions of heavy fullerenes in the near-ultraviolet region

Nonlinear optical properties (particularly optical limiting) are determined for solutions of heavy fullerenes C₇₆ + C₇₈ + C₈₄ + C₉₀ + …, in the near-ultraviolet region (λ ≈ 280 ± 7 nm). It is shown that no optical limiting is observed in solutions of light fullerenes (C₆₀ and C₇₀), but found in solutions of water-soluble fullerenol-d (a mixture of oxypolyalcohols of fullerene C₆₀-C₆₀(OH) _n1O _n2, with their sodium salts) based on light fullerenes.     

The structure of fullerene films and their metallocene doping

Hexagonal close-packed (HCP) C₆₀ and C₇₀ films have been prepared by the Langmuir method and examined by electron microscopy and electron-diffraction analysis. It has been shown that the vacuum deposition of a C₆₀+C₇₀ mixture results in the formation of a film with small sized grains and a distorted C₆₀-HCP structure. The simultaneous deposition of C₆₀ and ferrocene results in the formation of a film with a changed morphology and an electron-diffraction pattern that contains a variable amount of ferrocene depending on the experimental conditions. The electron-diffraction pattern corresponds to the presence of the known molecular complex C₆₀[(C₅H₅)₂Fe]₂. The analogous simultaneous deposition of fullerene C₆₀ and cobaltocene results in the formation of a C₆₀ film stable in air and water, which contains carbon and cobalt (from the data of X-ray fluorescence, electron microscopy and microdiffraction). It has a different morphology and different diffraction patterns than pure C₆₀ films and, depending on the cobaltocene content (relative to that of fullerene), appears to be a fullerite film doped with various amounts of cobaltocenium fullende, which is an ionic compound.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1379–1383, August, 1994.The work was financially supported by the Russian Foundation for Basic Research (Projects 93-03-4676 and 93-03-18368).