Radiation-cured polyisoprene/C60 fullerene nanocomposite: Part 2: Synthesis in decalin

The γ irradiation of polyisoprene and C₆₀ solutions in decalin at 50, 100 and 150 kGy was employed to prepare polyisoprene/C₆₀ nanocomposites. The nanocomposites were obtained as black gels. The excess of decalin was removed by treatment with methanol and acetone and the dried collapsed gels were studied by FT-IR spectroscopy and thermogravimetric analysis (TGA–DTG) and also by differential thermal analysis (DTA). The thermal stability was found to be enhanced by the presence of C₆₀ fullerene and by the crosslinking density.For reference, also the radiolysis of C₆₀ in decalin and the radiolysis of polyisoprene in decalin were studied. The data obtained were useful for the interpretation of the network structure of the polyisoprene/C₆₀ nanocomposites and their thermal behaviour.     

Influence of fullerene C60 on the kinetics of toluene evaporation

The kinetic dependences of the relative weight loss of the solvent from dilute solutions of fullerene C₆₀ in toluene under ambient conditions were determined. Evaporation of the pure solvent is slower than that of the same solvent from dilute solutions (≤0.01%).     

Thermodynamic properties of fullerene C60 solutions in a mixture of tetrachloromethane and toluene

The solubility of fullerene C₆₀ in the tetrachloromethane-toluene system is measured over the entire range of compositions of the mixed solvent in the temperature range 298.15–338.15 K. An equation is proposed for describing the solubility of C₆₀ as a function of the temperature and the composition of the mixed solvent. The equation is used for calculating the thermodynamic characteristics of solution of the fullerene. It is found that, in the investigated C₆₀-CCl₄/C₆H₅CH₃ system, two types of solid solvates of the fullerene with the solvent are formed. The enthalpies and temperatures of incongruent melting of the crystalline solvates are determined by differential scanning calorimetry. The thermodynamic characteristics of solution and solvation of C₆₀ in CCl₄ and C₆H₅CH₃ are obtained. It is shown that the entropy factor plays a decisive role in the temperature dependence of the Gibbs energy of solvation of the fullerene.     

Theoretical studies of C60/C70 fullerene derivatives: C60O and C70O

A semiempirical (AM1) calculation on the structures and stabilities of isomers of the fullerene derivatives C₆₀O and C₇₀O is carried out. The ozonolysis reaction mechanism and the thermodynamics of the compounds are studied. The two isomers of C₆₀O (56 bond and 66 bond) formed by an oxygen atom bridging across a C-C bond have an epoxide-like or an annulene-like structure. According to the ozonolysis reaction mechanism and kinetic factor analysis, the possible products of this ozonolysis reaction are C₆₀O with oxygen bridging over the 66 bond (C_2v) as an epoxide-like isomer and that with oxygen bridging over the 56 bond (C_s) as an annulene-like isomer. Further, the sixteen isomers of C₇₀O (both epoxide-like and annulene-like structures) have been studied with respect to the same reaction mechanism. The most possible product in this ozonolysis reaction contains oxygen bridging across in the upper part (66 bond in C₇₀O-2 or C₇₀O-4) as an epoxide-like structure. The other possible product is C₇₀O-8 (annulene-like structure), in which oxygen bridges across an broken equatorial CC bond in C₇₀ (D_5h). The vibrational frequency analysis and the electronic structure of the selected C₆₀O and C₇₀O isomers are generated for experimental characterisation. The experimental results indicate that C₆₀O and C₇₀O may decompose into the odd number fullerenes C₅₉ and C₆₉. We therefore studied the structures of C₅₉ and C₆₉ also.     

Synthesis and properties of water-soluble derivatives of fullerene C60

Procedures for synthesized of water-soluble forms of fullerene C₆₀ and its derivatives were developed.     

C60富勒烯亚氨基四氟苯甲酸苯甲酯的制备及表征

C60与芳基叠氮化合物反应生成的芳基亚氨基衍生物热稳定性好,在甲苯、氯仿、丙酮中溶解性能好,能用作生物、医学和建筑超导材料。具有特有的化学性质,可以用来制备氮杂C60。     

Synthesis and identification of heterocyclic derivatives of fullerene C60: unexpected reaction of anionic C60 with benzonitrile

During the reaction of reduced C60 with benzyl bromide in benzonitrile, a novel cis-1 C60 adduct, 1,4-dibenzyl-2,3-cyclic phenylimidate C60 (1), was obtained rather than the expected product of 1,4-dibenzyl C60. The structure of compound 1 was analyzed by X-ray single-crystal diffraction, identifying the presence of a five-membered heterocycle at a [5,6] bond of C60. One of the heteroatoms is assigned as a nitrogen atom; however, the identity of the other heteroatom cannot be determined unambiguously by crystallography due to similarity between the nitrogen and oxygen atoms. A related compound (2) bearing the same heterocycle was obtained from anionic C60 benzonitrile solution when no benzyl bromide was added. The structure of compound 2 was determined by NMR, MALDI FT-ICR MS, and UV-vis. Results from MALDI FT-ICR MS for compound 2 show unambiguously that the second heteroatom is an oxygen atom, which is probably from traces of water in the solvent. Control experiments of the reactivity of the neutral, monoanionic, dianionic, and trianionic C60 have shown that the reactive species for the unexpected reaction is the C60 trianion.     

Kinetic modelling of the thermal oxidation of polyisoprene elastomers. Part 1: Unvulcanized unstabilized polyisoprene

The thermal oxidation of an unvulcanized, unstabilized polyisoprene rubber (IR) has been studied in the 40-140 °C temperature range. Ageing was monitored by FTIR determination of double bonds and carbonyl groups, mass uptake measurement, and weight average molar mass determination. A mechanistic scheme based on the standard scheme for radical chain oxidation, but taking into account the diversity of initiation processes and the existence of inter- and intramolecular radical additions to double bonds, was built. The kinetic model derived from this scheme is composed of seven differential equations to be solved in discrete thickness layers to take into account the kinetic control by oxygen diffusion. This system was numerically solved using a Matlab program dedicated to stiff systems of differential equations. The elementary rate constants and other kinetic parameters were then determined from experimental data, using an inverse approach. A set of physically reasonable parameter values was obtained, thus allowing us to envisage lifetime predictions at low temperature (long term). The results led to observations difficult to make from classical analytical studies, for instance the predominance of bimolecular hydroperoxide decomposition among other initiation modes or the competition between intermolecular hydrogen abstraction and intramolecular addition of peroxy radicals to double bonds.     

A new surface-enhanced Raman scattering system for C60 fullerene: Silver nano-particles/C60/silver film

Surface-enhanced Raman scattering (SERS) spectrum of very good quality of “silver nano-particles/C60/silver film” system was reported for the first time by using the pyridine as a intermediate to connect and nest the C60 molecules to the gap of silver nano-particles and silver film. Experiment results show that the ternary system of “silver nano-particles/C60/silver film” is very effective and active. Not only was the number of vibrational modes greatly increased, especially some modes that were forbidden in Raman spectrum, but also were the significant Raman bands splitted as well as frequencies up and down shifted, respectively, arising from symmetry lowering and selection rule relaxing of C60 induced by the silver surface. Furthermore, the splitting of the Raman modes is consistent with the calculation based on group theory. The adsorption of C60 molecules is oriented on pentagons of C60 on the silver surface. It is difficult to separate the contributions of the electromagnetic and chemical mechanisms to the great enhancement of the Raman signal. On the one hand, the silver nanoparticles modified on the silver film play an important role in magnifying the surface local electric field near the silver surface through resonant surface plasmon excitation. On the other hand, charge transfer factor may not be neglected.     

Synthesis of [60]fullerene acetals and ketals: reaction of [60]fullerene with aldehydes/ketones and alkoxides

The reaction of C(60) with propionaldehyde (butyraldehyde or phenylacetaldehyde) and MeONa-MeOH or EtONa-EtOH in anhydrous chlorobenzene in the presence of air at room temperature unexpectedly gave rare fullerene acetals 2aa-cb, while the reaction of C(60) with acetone (acetophenone, cyclohexanone, or cyclopentanone) and MeONa-MeOH or EtONa-EtOH under the same conditions afforded the uncommon fullerene ketals 4aa-db. A possible reaction mechanism for the formation of the fullerene acetals and ketals is proposed based on further experimental results.     

[2 + 3]-Cycloadditions to C60 fullerene. Synthesis of pyrrolidinofullerenes

Pyrrolidinofullerenes were synthesized by reaction of C₆₀ fullerene with N-methylglycine and substituted aromatic aldehydes.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1695–1697.Original Russian Text Copyright © 2004 by Loginova, Gunkin.This revised version was published online in April 2005 with a corrected cover date.     

Interaction of fullerene C60 with 3-amino-1-propanol

The C₆₀ radical anions formed in the interaction of c₆₀ with 3-amino-1-propanol under a vacuum were characterized by ESR and near-IR spectroscopy. in the air, a compound was obtained whose composition corresponds to the C₆₀NH₂CH₂CH₂CH₂OH=13.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1145, June, 1994.We thank the Russian Foundation for Basic Research (Grant No. 93-03-18001) for financial support.     

Thermochemistry of C60 and C70 fullerene solvates

In an effort to improve understanding of dissolution behaviour of fullerenes and their simple chemical derivatives the binary systems of C₆₀, C₇₀ and the piperazine monoadduct of [60] fullerene C₆₀ N₂C₄H₈ with a series of aromatic solvents have been studied by means of DSC. In certain systems solid solvates have been found to be the thermodynamically stable phases relative to saturated solution at room temperature. Identified solid solvates were characterized by their compositions, temperatures and enthalpies of incongruent melting transitions. The regularities in thermodynamic stability of the solvated crystals have been discussed along with dissolution properties of fullerenes and the derivative. Certain correlations have been observed.     

Synthesis and characterization of difluoromethylene-homo[60]fullerene, C60(CF2)

Refluxing of the o-DCB solution of C60 with CF2ClCOONa and 18-crown-6 leads to formation of C60(CF2)n (n = 1-3); the monoadduct C60(CF2) has been found to consist of the main [6,6]- and minor [5,6]-isomers, both having an open structure.     

Synthesis and stability of linear and star polymers containing [C60] fullerene

Linear and symmetric star block copolymers of styrene and isoprene containing [C₆₀] fullerene were synthesized by anionic polymerization and appropriate linking postpolymerization chemistry. In all block copolymers, the C₆₀ was connected to the terminal polyisoprene (PI) block. The composition of the copolymers was kept constant (～30% wt PI), whereas the molecular weight of the diblock chains was varied. The polymers were characterized with a number of techniques, including size exclusion chromatography, membrane osmometry, and ¹H NMR spectroscopy. The combined characterization results showed that the synthetic procedures followed led to well‐defined materials. However, degradation of the fractionated star‐shaped copolymers was observed after storage for 2 months at 4 °C, whereas the nonfractionated material was stable. To further elucidate the reasons for this degradation, we prepared and studied a four‐arm star copolymer with the polystyrene part connected to C₆₀ and a six‐arm star homopolymer of styrene. These polymers as well as linear copolymers end‐capped, through ? N<, with C₆₀ were stable. Possible reasons are discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2494–2507, 2001     

Synthesis and characterization of fullerene nanowhiskers by liquid-liquid interfacial precipitation: influence of C60 solubility

Fullerene nanowhiskers (FNWs) composed of C(60) fullerene molecules were prepared using the liquid-liquid interfacial precipitation (LLIP) method in the carbon-disulfide (CS(2)) and isopropyl alcohol (IPA) system. The electron microscopic images reveal the formation of non-tubular FNWs. The X-ray diffraction (XRD) pattern studies indicate the presence of fcc crystalline structure and unusual triclinic structure in the FNWs. The selected area electron diffraction pattern (SAED) analysis demonstrates the existence of triclinic and electron beam assisted fcc to tetragonal crystalline phase transformation. The formation of triclinic structure might be validated due to the partial polymerization of FNWs at C(60) saturated CS(2)-IPA interface. The high solubility of C(60) in CS(2) solvent system results in partial polymerization of FNWs. The polymerization of fullerene molecules in the FNWs has been further confirmed using Raman spectroscopy.     

C60 and C70 fullerene isomers generated in flames. Detection and verification by liquid chromatography/mass spectrometry analyses.

Fullerenes C60 and C70, generated by combustion, have been shown previously to be produced in controlled laminar flames accompanied by other compounds having fullerene-like characteristics. Analysis of these additional compounds by high-performance liquid chromatography, coupled on-line with mass spectrometry has identified them as isomers of the C60 and C70 fullerenes. The newly observed isomers have characteristic UV spectra and are thermally unstable, undergoing conversion to the more stable fullerenes with a half-life of about 1 h in boiling toluene (111 degrees C). Isomers of C60 and C70 fullerenes previously have been studied theoretically, but not observed experimentally. The flame-generated material also contains C60O and C70O compounds, as well as C76 and higher carbon clusters.     

Pyrimidine ortho-quinodimethanes. Part 2: Synthesis of new [60]fullerene adducts based on substituted pyrimidine derivatives and their 1H NMR dynamic study

The Diels–Alder reaction of various pyrimidine ortho-quinodimethanes generated in situ with C₆₀ gives access to a variety of new fullerodihydroquinazoline derivatives. This variety is increased since substituents on the pyrimidine ring can be easily modified before or after its reaction with C₆₀. Variable temperature ¹H NMR spectra provided thermodynamic parameters related to the boat-to-boat interconversion of the cyclohexene ring fused to the fullerene moiety. The mass spectra of the prepared cycloadducts show that the retro-Diels–Alder process takes place easily with elimination of the corresponding diene molecule.     

Crosslinking and ageing of C labelled polyisoprene part 1: Synthesis and polymerisation of 4-C-isoprene

4-¹³C-isoprene was prepared by the Wittig reaction. All reaction steps were optimised using unlabelled compounds. By reaction with triphenyl phosphine, ¹³C labelled methyl iodide afforded labelled methyl-triphenyl phosphine iodide in 84% yield. This reacted with meth acrolein with production of 4-¹³C-isoprene in 64% yield. Labelled polyisoprene was prepared by anionic polymerisation initiated by t-butyl lithium. Based on ¹³CH₃I the overall yield is ca 30%. The polymer was characterized by ¹H and ¹³C NMR spectroscopy. The contribution of each microstructure was [cis 1-4, 72%]; [trans 1-4, 10%]; [3-4, 18%].     

DFT studies on endohedral fullerene C@C60: C centers the C60 cage

Structural and electronic properties of C@C₆₀ were studied via Hartree–Fock self-consistent field (SCF) and density functional B3LYP levels of theory with the STO-3G, 6-31G(d) and 6-31G(d, p) basis sets. Both singlet and triplet were considered. The triplet structure with C on the center of the C₆₀ cage was proved to be global minimum on the C@C₆₀ molecular potential energy surface. The calculated HOMO-LUMO gaps as well as the electron affinity (EA) and the ionization potential (IP) were also presented as an indicator of the kinetic stability.