Polymer nanocomposites based on polyamide 6 modified with fulleroid fillers

Polymer nanocomposites based on polyamide and fulleroid modifiers are synthesized through in situ polymerization, and their mechanical and electric properties are studied. After introduction of 0.001–0.1 wt % fulleroid modifiers, Young’s modulus and the strength of thermoplastic composites increases by 15–20%, practically independently of the amount of filler. This circumstance is due to the fact that the introduction of fulleroid fillers causes selective crystallization of polyamide 6 only in the α form. The introduction of fullerene fillers considerably improves the tribological characteristics of polymer nanocomposites, thereby decreasing the friction coefficient by a factor of 2. The electric properties of nanocomposites are studied also.     

Polymer Nanocomposites Containing Fullerene C60 Nanofillers

Summary: The effect of fulleroids (fullerene C₆₀, mixture of C₆₀/C₇₀ and fulleroids soot which used for fullerenes production) and carbon fillers (carbon black, graphite) on mechanical properties of polymer nanocomposites based on reactoplasts (epoxy resins) and thermoplasts (polyamide-12) was investigated. The nanocomposites were prepared by in situ polymerization. It was found that additives of these fillers did not influenced on the properties of reactoplasts. Therefore, the tensile modulus and tensile strength of thermoplast based polymer nanocomposites are improved by about 30-40% with loading of 0.02-0.08 fulleroids materials. Best results were obtained for a mixture of C₆₀/C₇₀.     

Preparation of fullerene С<Subscript>60</Subscript> dispersions in water

Stable colloidal dispersions of fullerene С₆₀ in water free of organic solvents have been obtained. The addition of a С₆₀ solution to a water–acetone mixture has been shown to cause a solvatochromic effect.     

Volume properties and refraction of aqueous solutions of bisadducts of light fullerene С60 and essential amino acids lysine,threonine, and oxyproline (С60(C6H13N2O2)2, С60(C4H8NO3)2, and С60(C5H9NO2)2) at 25°C

Concentration dependences of the density of aqueous solutions of bisadducts of light fullerene С₆₀ and essential amino acids are studied by pycnometry. Concentration dependences of the average molar volumes and partial volumes of components (Н₂О and corresponding bisadducts) are calculated for С₆₀(C₆H₁₃N₂O₂)₂–Н₂О, С₆₀(C₄H₈NO₃)₂–Н₂О, and С₆₀(C₅H₉NO₂)₂–Н₂О binary systems at 25°C. Concentration dependences of the indices of refraction of С₆₀(C₆H₁₃N₂O₂)₂–Н₂О, С₆₀(C₄H₈NO₃)₂–Н₂О, and С₆₀(C₅H₉NO₂)₂–Н₂О binary systems are determined at 25°C. The concentration dependences of specific refraction and molar refraction of bisadducts and aqueous solutions of them are calculated.

     

Investigation of fullerene C60 effect on properties of polymethylmethacrylate exposed to ionizing radiation

Effect of fullerene C₆₀ was investigated on thermal, mechanical and optical properties of polymethylmethacrylate (PMMA) under ionizing radiation. It was stated that fullerene C₆₀ behaves as an effective antirad with respect to PMMA. Fullerene C₆₀ addition raises temperature of destruction for polymer subjected to electron radiation by 20-25 °C, lowers the rate from 4 to 4.5 times and increases the activation barrier for radiated PMMA destruction reaction. Fullerene C₆₀ addition promotes improvement of strength properties of PMMA: for films containing C₆₀ addition and else subjected to electron radiation treatment a decrease in rupture strength is 10-15%, for samples containing no fullerene it equals ∼25%. Interaction of free radicals with fullerene at radiation treatment influences optical characteristics of PMMA films.     

DSC investigation of the polystyrene films filled with fullerene

Polystyrene composite films with different content of C₆₀?+?C₇₀ fullerene mix have been obtained from o-xylene solutions. The mass fraction of fullerene was varied from 0.01 to 0.1 mass%. The glass transition temperatures and specific heat capacities in range of 293?C423?K have been determined for the films by DSC method. The plasticization of the polymer is observed in thermal properties of the films under influence of small fullerene additions. The values of T _g and C _P decrease and thermal coefficient of heat capacity b increase as fullerene content increases up to 0.02 mass%. The effect of interaction between polymer and fullerene molecules on thermal properties becomes evident at higher fullerene content in range from 0.02 to 0.1 mass%. At this the values of T _g and C _P increase and b coefficient decrease with increasing content of fullerene. Concentration dependence of C _P and b values is less steep for polymer composite films in elastic state at temperatures above T _g. Molecular interactions in the composites are discussed in view of our-self and literature data.     

Radical scavenging efficiency of different fullerenes C60-C70 and fullerene soot

This investigation was undertaken to determine the antioxidant activity of a range of fullerenes C₆₀ and C₇₀ in order to rank them according to their comparative efficiency. The model reaction of initiated (2,2′- azobisisobutyronitrile, AIBN) cumene oxidation was used to determine rate constants for addition of radicals to fullerenes. Measurements of oxidation rates in the presence of different fullerenes showed that the antioxidant activity as well as the mechanism and mode of inhibition were different for fullerenes C₆₀ and C₇₀ and fullerene soot. All fullerenes - C₆₀ of gold grade, C₆₀/C₇₀ (93/7, mix 1), C₆₀/C₇₀ (80 ± 5/20 ± 5, mix 2) and C₇₀ operated as alkyl radical acceptora, whereas fullerene soot surprisingly retarded the model reaction by a dual mode similar to that for the fullerenes and with an induction period like many of the sterically hindered phenolic and amine antioxidants. For the C₆₀ and C₇₀ the oxidation rates were found to depend linearly on the reciprocal square root of the concentration over a sufficiently wide range thereby fitting the mechanism for the addition of cumylalkyl radicals to the fullerene core. This is consistent with literature data on the more ready and rapid addition of alkyl and alkoxy radicals to the fullerenes compared with peroxy radicals. Rate constants for the addition of cumyl radicals to the fullerenes were determined to be k_(333K) = (1.9 ± 0.2) × 10⁸ (C₆₀); (2.3 ± 0.2) × 10⁸ (C₆₀/C₇₀, mix 1); (2.7 ± 0.2) × 10⁸ (C₆₀/C₇₀, mix 2); (3.0 ± 0.3) × 10⁸ (C₇₀), M⁻¹ s⁻¹. The increasing C₇₀ constituent in the fullerenes leads to a corresponding increase in the rate constant.The fullerene soot inhibits the model reaction according to the mechanism of trapping of peroxy radicals; the oxidation proceeds with a pronounced induction period and kinetic curves are linear in semi-logarithmic coordinates.For the first time the effective concentration of inhibiting centres and inhibition rate constants for the fullerene soot have been determined to be fn[C₆₀−soot] = (2.0 ± 0.1) × 10⁻⁴ mol g⁻¹ and k_inh = (6.5 ± 1.5) × 10³ M⁻¹ s⁻¹ respectively.The kinetic data obtained specify the level of antioxidant activity for the commercial fullerenes and scope for their rational use in different composites. The results may be helpful for designing an optimal profile of composites containing fullerenes.     

Metal chelate monomers based on nickel(II) cinnamate and chelating N-heterocycles as precursors of nanostructured materials

Metal chelate monomers (MCMs) have been widely used as precursors for the production of advanced functional polymers and nanomaterials. In this articel, new metal chelate monomers based on nickel(II) cinnamate (cinn) and various chelating N-heterocycles, [Ni(cinn)₂(bpy)(C₂H₅OH)] and [Ni(cinn)₂(phen)(C₂H₅OH)₂] (bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline), were first synthesized and characterized. A detailed analysis of the main stages and features of the kinetics of thermolysis of MCMs was carried out. Metal-polymer nanocomposites with a core-shell structure containing metal nanoparticles evenly distributed in a stabilizing nitrogen-containing polymer matrix were obtained by thermolysis at 300?°C. Thermolysis at 450?°C resulted in pure nickel oxide nanoparticles. The nature of the ligand has been shown to affect the structure and size of the product obtained. The tribological characteristics of nanoparticles as additives to lubricating oils were studied using the pin-on-disc tribometer. At the optimum concentration of nanoparticles, the coefficient of friction is the smallest, and an increase in the concentration above the optimum level leads to an increase in the coefficient of friction.     

Glass transition and relaxation behavior of epoxy nanocomposites

With advances in nanoscience and nanotechnology, there is increasing interest in polymer nanocomposites, both in scientific research and for engineering applications. Because of the small size of nanoparticles, the polymer–filler interface property becomes a dominant factor in determining the macroscopic material properties of the nanocomposites. The glass‐transition behaviors of several epoxy nanocomposites have been investigated with modulated differential scanning calorimetry. The effect of the filler size, filler loading, and dispersion conditions of the nanofillers on the glass‐transition temperature (T_g) have been studied. In comparison with their counterparts with micrometer‐sized fillers, the nanocomposites show a T_g depression. For the determination of the reason for the T_g depression, the thermomechanical and dielectric relaxation processes of the silica nanocomposites have been investigated with dynamic mechanical analysis and dielectric analysis. The T_g depression is related to the enhanced polymer dynamics due to the extra free volume at the resin–filler interface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3849–3858, 2004     

Thermal decomposition of ammonium perchlorate based mixture with fullerenes

The effects of fullerenes, including fellerene soot (FS), extracted fullerene soot (EFS) and pure C₆₀ on the thermal decomposition of ammonium perchlorate (AP) compared with traditional carbon black (CB) catalyst has been studied by employing thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy (IR) and ignition temperature experiments. The results showed that the addition of CB and FS to AP reduced the activation energy as well as the temperature at maximum decomposition rate, but that of EFS and pure C₆₀ had little effect on the thermal decomposition of AP, and among all catalysts, FS was the best one.     

Promotion of the γ‐phase of polyamide 6 in its nanocomposite with phosphate glass

The effect of tin fluorophosphate‐glass (Pglass) nanoparticles on the polyamide‐6 (PA6) matrix in Pglass/PA6 hybrids has been investigated by ¹³C solid‐state nuclear magnetic resonance (NMR). The crystallinity determined by direct‐polarization ¹³C NMR combined with longitudinal relaxation‐time (T_1C) filtering varied between 31 and 44%. T_1C‐filtered ¹³C spectra with cross polarization clearly showed resonances of both the α‐ and γ‐crystalline phases of PA6, typically at ratios near 45:55, while the similarly processed neat polymer contained only the α‐phase. This suggests that the Pglass promotes the growth of the γ‐crystalline phase. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 857–860, 2008     

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.     

Self-organization of poly(methyl methacrylate) and polystyrene macromolecules functionalized by fullerene C60

Poly(methyl methacrylate) and polystyrene functionalized by fullerene C₆₀ tend to form micellar structures comprising a fullerene cluster as a core and a macromolecular shell. Films prepared from PMMA-C₆₀ and PS-C₆₀ micellar solutions are polymer matrices with fullerene-containing globular structures uniformly distributed in the polymer bulk.     

Influence of inorganic fullerene‐like WS2 nanoparticles on the thermal behavior of isotactic polypropylene

A new family of thermoplastic nanocomposites based on isotactic polypropylene (iPP) and inorganic fullerene‐like tungsten disulfide (IF‐WS₂) has been successfully prepared. A very efficient dispersion of IF‐WS₂ material was obtained by mixing in the melted polymer without using modifiers or surfactants. The addition of IF‐WS₂ nanoparticles induces a remarkable enhancement of the thermal stability of iPP, as well as an increase in the crystallization rate of the matrix when compared with pure iPP. The nucleating efficiency of IF‐WS₂ solid lubricant nanoparticles on the α‐phase of iPP reaches very high values (60–70%), the highest values observed hitherto for polypropylene nanocomposites. The incorporation of IF‐WS₂ has also been observed to increase the size and stability of the crystals formed. The melting behavior of the nanocomposites indicates the formation of more perfect crystals as determined by differential scanning calorimetry and time‐resolved synchrotron X‐ray scattering experiments. The new nanocomposites show an increase in the storage modulus with respect to pure iPP measured by dynamic mechanical analysis. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2309–2321, 2007     

Interaction of polystyrene and fullerene C<Subscript>60</Subscript> in benzene: Composition and molecular properties of the product

The molecular properties and composition of fullerene-containing polystyrenes prepared through evaporation of solvent from the combined solution of a polymer and C₆₀ in benzene have been studied by viscometry, translational isothermal diffusion, GPC, UV spectroscopy, and electrooptical Kerr effect measurements. With this procedure of C₆₀ introduction into the polymer, a partial depolymerization of the parent polystyrene takes place. It has been shown that the composites contain fullerene in two forms: a smaller part of C₆₀ is bound to macromolecules, while a larger part of C₆₀ is incorporated into the composition of low-molecularmass adducts—the products arising from the interaction of fullerene with fullerene-induced depolymerized polystyrene.     

Extraction of fullerene mixture from fullerene soot with organic solvents

Investigation of extraction of fullerene mixture from the fullerene soot obtained by plasma erosion of graphite rod in helium atmosphere with different solvents such as α-chloronaphthalene, o-dichlorobenzene, o-xylene, toluene, benzene, carbon tetrachloride, and n-hexane at 25°C was carried out. Completeness and effectiveness of extraction as well as relative content of light (C₆₀, C₇₀) and heavy (C₇₆, C₇₈, C₈₄) fullerenes in the extract were evaluated.     

Studies on the mechanical and friction properties of polyamide 6-Cu/Si nanocomposites

Polyamide 6 nanocomposites reinforced with Cu/Si nanoparticles (PA6-Cu/Si) were prepared by the in-situ ring-opening polymerization of ?-caprolactam. The in-situ polymerization was critical for preventing the aggregation of Cu/Si nanoparticles. The Cu/Si nanoparticles in the nanocomposite retained their nano characteristics and were not oxidized by the amino groups in PA6. The structure of the as-fabricated PA6-Cu/Si nanocomposite was evaluated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and ultraviolet-visible absorption spectroscopy (UV-vis). The friction and wear resistance, mechanical strength, and antistatic performance of PA6-Cu/Si were also evaluated. The PA6 polymer chains prevent the Cu/Si nanoparticles from aggregation by coating the surface of the Cu/Si nanoparticles via physical adsorption or an electrostatic effect. The mass fraction of the Cu/Si nanoparticles also had a significant effect on the crystalline form of PA6. The γ crystalline form of PA6 was predominant at a high mass fraction of Cu/Si to PA6. Moreover, PA6-Cu/Si with improved mechanical properties and wear resistance was generated by tuning the amount of nano-Cu/Si filler added during the polymerization. PA6-Cu/Si with a nano-Cu/Si content of 0.5% possesses the highest tensile strength and wear resistance and shows promise in applications as a functional polymer-matrix composite.     

Star-shaped polymers with the fullerene C60 branching center

The anionic methods for the synthesis of homo- and heteroarm (hybrid) star-shaped polymers using fullerene C₆₀ aPre considered. The possibilities of fullerene C₆₀ as an agent of combination of living polymer chains and the procedures of transformation of polymer derivatives of C₆₀ (hexaadducts) into polyfunctional macroinitiators of anionic polymerization of vinyl monomers are shown. The methods for functionalization of polymer fullerene derivatives and their combinations into structures of complex controlled architecture are presented. The structural features and initiating properties of the living polymer fullerene derivatives and their role in the formation of heteroarm star-shaped macromolecules with the controlled number of branches and predetermined molecular weight characteristics of the arms are discussed. The hydrodynamic properties of the star-shaped fullerene-containing polymers are considered. The data on the small-angle neutron scattering study of self-organization of the stars in solutions are presented.     

Effect of doping fulllerene soots with metals on the conversion of methane into higher hydrocarbons

We have previously demonstrated that fullerene soots catalyze hydrogen-transfer reactions that are useful for hydrocarbon processing, including conversion of methane into higher hydrocarbons. In this paper we describe the effect of doping fullerene soot with alkali and transition metals for converting methane and other light hydrocarbons. The fullerene soot was found to lower the temperature threshold for methane activation compared to other carbons; however, the selectivity to C₂ hydrocarbons was quite low (20%). In contrast, when the soot was doped with metals such as Mn or K, the overall yield of hydrocarbons increased and selectivities as high as 80% were achieved. When potassium was used as a dopant, the selectivity to C₃ and C₄ hydrocarbons also increased.     

Moving of fullerene between potential wells in the external icosahedral shell

The results of the theoretical investigation of the behavior of fullerenes C₂₀ and C₆₀ inside the icosahedral external shell on example of carbon nanoclusters, C₂₀@С₂₄₀ and C₆₀@С₅₄₀, are presented in this article. The multiwell potential of interaction between fullerenes in investigated nanoclusters is calculated to reveal the regularities of moving for internal fullerene in the field of holding potential of the external shell. The possible variants of fullerenes C₂₀ and C₆₀ moving between the potential wells are predicted on base of topology data of the fullerenes relative positioning in nanoparticle and analysis of relief of the energy surface of interaction between fullerenes. The formulated prediction is confirmed by the data of the numerical experiment. The investigation of two‐shell fullerenes allows to conclude that the light fullerene С₂₀ will probably jump between the potential wells already at small temperatures (139–400 K) if the external shell is slightly bigger. © 2014 Wiley Periodicals, Inc.