Impact of fullerenes on the thermal stability of melt processed polystyrene and poly(methyl methacrylate) composites

The impact of the two fullerenes C₆₀ and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) on the thermal and thermo-oxidative stability of the corresponding melt processed composites with the two polymers polystyrene (PS) and poly(methyl methacrylate) (PMMA), was studied using both dynamic and isothermal thermogravimetric analysis (TGA). For each polymer, three different composites with C₆₀ loadings of 1.0 wt% and 3.0 wt% and PCBM loadings of 1.0 wt% were considered. The aim of this work was to compare the stabilization effect of both fullerenes on PS and PMMA. The results obtained show unequivocally that, although PCBM has lower thermal and thermo-oxidative stability than C₆₀, the PS-PCBM and PMMA-PCBM composites have higher thermal and thermo-oxidative stability than the corresponding PS-C₆₀ and PMMA-C₆₀ composites. These results corroborate our previous reports, on showing that PCBM is better than C₆₀ at improving the thermal and thermo-oxidative stability of polymers which degrade through radical degradation mechanisms.     

Use of cerium oxide (CeO(2)) as a packing material for the chromatographic separation of C(60) and C(70) fullerenes

Cerium oxide (CeO₂) was tested as a packing material in liquid chromatography for the separation of C₆₀ and C₇₀ fullerenes. The separation of C₆₀ and C₇₀ fullerenes could be achieved within 20 min by using pure n-hexane as the mobile phase. Furthermore, some higher fullerenes could also be separated in less than 40 min. The peak area was reproducible to a large extent. The separation of fullerenes by liquid chromatography on CeO₂ is shown to be an effective method for their isolation in large amounts. The column efficiency of the CeO₂ column was compared with commercial silica gel and ODS columns. The main advantage of the CeO₂ column is its ability to separate large amounts of fullerenes (C₆₀ and C₇₀) in toluene.     

Homo- and methano[60]fullerenes with chiral attached moieties--1H and 13C NMR chemical shift assignments and diastereotopicity effects

(1)H and (13)C NMR chemical shift predictions of homo- and methano[60]fullerenes containing chiral centers in attached fragment were made using the two-dimensional NMR technique (HH COSY, (1)H-(13)C HSQC and HMBC) and the quantum chemistry GIAO calculation method in the PBE/3ζ approach. The influence of a chiral substituent on the (13)C chemical shifts of diastereotopic fullerene carbons was estimated by comparing the calculated and experimental (13)C NMR spectra. The resonances of the fullerene carbons in α-, β- and δ-positions relative to the position of the substituent exhibit the greatest diastereotopic splitting.     

Pressure effect on heterogeneous trifluoromethylation of fullerenes and its application

The first systematic study of heterogeneous fullerene trifluoromethylation using an innovative gradient-temperature gas-solid reactor revealed a significant effect of CF₃I pressure on the conversion of C₆₀ and C₇₀ into trifluoromethylated products and on the range of fullerene(CF₃)_n compositions that were obtained. The design of the reactor allowed us to lower the residence times of fullerene(CF₃)_n species in the hot zone which resulted in the significant differences in relative isomeric distributions as compared to the earlier methods. For the first time, gram quantities of trifluoromethylated fullerenes were prepared using the new reactor, and the selective synthesis of a single-isomer C₆₀(CF₃)₂ was developed. The relative reactivity of C₇₀ as a CF₃ radical scavenger was found to be much lower than that of C₆₀, especially at an early radical addition stage, which led to the cost-efficient synthesis of C₆₀(CF₃)₂ from a fullerene extract.     

Effects of UV irradiation on physico‐mechanical properties of EPDM/buckminsterfullerene composite

Ethylene propylene diene rubber‐fullerene (EPDM/C60) composite, partially crosslinked by ultraviolet (UV) radiation, was prepared and characterized for crosslink density, mechanical properties and thermal behavior. FT‐IR analysis showed peak disappearance at 1688 cm^?1, corresponding to the unsaturation of EPDM, and the appearance of new peaks relating to the formation of oxidation products of C60, such as epoxide, keto, aldehyde and carboxylic groups. Solubility studies demonstrated the dissolution of pristine EPDM in toluene even after a longer period of UV exposure, whereas EPDM/C60 composite became insoluble and/or swollen after 6 hr of UV exposure, indicating the formation of partial crosslinking between EPDM and C60. Differential scanning calorimetry (DSC) measurements revealed an increase in the glass transition temperature peak of UV‐cured EPDM. Thermogravimetric analysis (TGA) showed that UV exposure reduced the thermal decomposition temperature of EPDM/C60, pristine EPDM and dicumyl peroxide (DCP)‐cured EPDM. The modulus, tensile stress and elongation at break of EPDM/C60 composites were greatly influenced by the duration of UV irradiation. Comparison of UV‐cured EPDM/C60 composite with DCP‐cured EPDM confirmed the superior strength properties of the former system. Copyright © 2004 John Wiley & Sons, Ltd.     

A New Approach to C60-Containing Polyphosphazenes by Polymerization of Phosphonitrile Chloride Trimer in the Presence of C60

A novel synthetic strategy was developed to prepare polyphosphazenes containing C60 moieties. Thus, the phosphonitrile chloride trimer underwent thermal ring-opening polymerization （ROP） in the presence of C60 molecules to yield the reactive macromolecular intermediate, C60-containing poly（dichlorophosphazene）. And then, the other groups could be linked to the phosphazene backbone by nucleophilic substitution reaction of the chlorine atoms in this intermediate to produce a series of C60-containing polyphosphazene. The polymer exhibits good solubility in common organic solvents and is thermally stable.     

AM1 treatment of some (nH2+mC)@C60 systems

Some (nH₂+mC)@C₆₀ systems (2H₂+4C)@C₆₀, (3H₂+4C)@C₆₀ and (H₂+5C)@C₆₀, are considered for AM1 (RHF) type semiempirical quantum chemical treatment. They were found to be stable and endothermic. In the case of (2H₂+4C)@C₆₀ and (H₂+5C)@C₆₀ systems, one of the hydrogen molecules possess elongated σ-bonding indicative of some sort of homolytic dissociation.     

Redox Properties of Isozazolo[60]fullerenes with Regard to Substituents and Molecular Structure

Abstract

A series of isoxazolo[60]fullerene derivatives 1(a-k), 5 and 6(l-n) have been synthesized by [2+3]cycloadditions of the corresponding nitriloxides to C₆₀. The phenyl-, 1,4- and 1,2-biphenyl substituents are substituted with electron donor groups in different distances and orientations in order to determine their influence on the redox properties of these fullerene derivatives. The redox- behavior was measured by cyclic voltammetry. In compounds 1b-g, 5l-n and 6l-n no significant shift relative to the reference compound la could be found. The insertion of an o-phenylene spacer between the isoxazoline ring and the phenyl ring substituted by donor groups in derivatives lh-k causes a shift of the first reduction potential by 30 mV (1h, 1k) and 60 mV (1i) towards more negative values compared to the reference 1a. Because of the o-phenylene spacer the plane of the donor-phenyl ring is forced into a close and parallel orientation to surface of the fullerene suitable for through-space interaction. This geometry was proven by X-ray structure determination of 1k.     

A theoretical study on a fullerene derivative C54N4 and some of its protonated forms

Semiempirical quantum chemical calculations at the level of AM1 (restricted Hartree–Fock) have been performed on a fullerene derivative, C₅₄N₄, theoretically obtained from C₆₀ and its mono and diprotonated forms. All these structures are stable, but endothermic in nature. Some calculated geometrical and physicochemical properties of these have also been reported.     

富勒烯[C60]杂环化合物的合成进展

综述了近年来通过环加成反应合成三元、五元、六元和七元杂环C₆₀衍生物的进展.     

光催化固氮:人工光合成的新途径（英文）

氨不仅是一种广泛使用的化工原料,还可用作重要的能源载体.哈伯法合成氨被认为是20世纪最伟大的发明之一,为人类社会的发展做出了巨大贡献.同时,氨合成过程每年需要消耗世界总能源的1%–2%.因此,开发绿色清洁的氨合成方法一直是世界范围内工业界和学术界关注的热点.随着人工光合成太阳燃料研究的蓬勃发展,利用太阳能光催化的方式实现在温和条件下合成氨吸引了越来越多研究者的兴趣,因为这是一条最为理想的能源利用途径,即直接利用太阳能将氮气和水转化为氨.近期,该研究领域涌现了一系列有代表性的研究工作,报道了利用半导体光催化剂实现太阳能到氨的转化,虽然整体效率仍很低,但是已经证明了利用太阳能直接将氮气转化为氨的可能性.光催化合成氨过程中,最具挑战的是氮气分子在半导体光催化剂表面的吸附和活化.研究表明,通过在半导体光催化剂表面引入空位或者缺陷可有效地增加氮气的吸附,且很可能成为氮气分子活化并参与反应的活性中心.此外,借鉴自然界豆类植物固氮酶的独特结构,利用其对于氮气分子高效活化的独特优势,构建自然-人工杂化体系也是提升氮气吸附与活化的有效策略之一.本综述将从合成氨过程中氮气的吸附与活化问题入手,分别从缺陷与空位调控和固氮酶两个方面的策略考虑,结合几个典型的光催化剂体系(如卤氧化铋,二氧化钛及水滑石等)作为示例,介绍空位调控与模拟固氮酶策略对太阳能光催化固氮的影响并分析其可能的机理.虽然人工光合成固氮研究取得了一些进展,但是目前效率太低,亟需从基础科学问题的认识和理解上有新的突破,如氮气分子的吸附与活化微观过程、空位可控调变策略、新型光催化剂的开发与表界面修饰、氨氧化逆反应的抑制策略及精确的理论模拟指导人工光合成固氮体系的构建等.最后,对人工光合成固氮研究方向面临的挑战和未来的发展方向进行了总结与展望.     

A ready access to unprecedented N-anilinopyrazolino[60]fullerenes

A simple and efficient method for the preparation of new synthons based on versatile amino-functionalize pyrazoline[60]fullerene is described. These intermediates are useful in the preparation of new derivatives for applications in materials science. Finally, electrochemical studies of the newly prepared compounds have been performed in solvents with different polarities.     

PHOTOCATALYTIC HYDROGEN EVOLUTION FROM WATER SPLITTING UNDER VISIBLE LIGHT IRRADIATION ON NOVEL PHOTOCATALYST FULLENES-PVP-ZN0.999NI0.001S

Fullerenes (C60/C70) linked up to Ni-doped ZnS through the medium of an amphalic polymer polyvinyl pyrrolidone (PVP) to form a new kind of photocatalyst for hydrogen evolution from aqueous Na2S/Na2SO3 solution under visible light irradiation, the photocatalytic activities of this novel photocatalyst C60/C70-PVP-Zn0.999Ni0.001S are 3-5 fold higher compared with that of precurse catalyst Zn0.999Ni0.001S. This result could be attributed to Schottky barrier layer built between C60/C70 and Zn0.999Ni0.001S due to the electro-negativity of C60 and characteristic of being used as a multiple electron acceptor. C60 or C60/C70, its moiety, with its low energy first excited singlet state, is a good energy acceptor and in addition readily accepts multiple electrons, making it a potential electron accumulate as we know, which could protect the separation between electrons and holes against combination. This is an important reason for the marked increase of amount of H2 evolution during the photocatalytic process for the composite system C60/C70-PVP-Zn0.999Ni0.001S.     

C60(Fullerene)及其卤化衍生物在阴离子聚合中的研究

综述了近年来C60及其卤化衍生物在阴离子聚合中的研究进展。在阴离子聚合中，C60可以直接与反应而进入主链，形成超枝化结构；C60可作为阴离子聚合的偶联剂，形成星形和线形结构；C60阴离子可以引发阴离子聚合。介绍了偶联产物结构控制的方法，以及偶联产物的稳定性。氯化富勒烯也可以作为阴离子聚合的偶联剂，生成星形结构聚合物。     

Separation of polycyclic aromatic hydrocarbons with a C60 bonded silica phase in microcolumn liquid chromatography

A chemically bonded C₆₀ silica phase was synthesized as a stationary phase for liquid chromatography (LC) and its retention behavior evaluated for various polycyclic aromatic hydrocarbons (PAHs) using microcolumn LC. The results indicate that the C₆₀ bonded phase offers selectivity different from that of octadecylsilica (ODS) bonded phases in the separation of isomeric PAHs. With the C₆₀ phase, PAH molecules having a partial structure similar to that of the C₆₀ molecule, e.g. triphenylene and perylene, were retained longer than with ordinary ODS stationary phases. The results also show that good correlation exists between the retention data with this C₆₀ bonded phase and with C₆₀ itself as the stationary phase.     

Synthesis and Characterization of C60-Containing Poly（ethylene oxide）

C60-Containing poly(ethylene oxide) (PEO) was synthesized by a new method.Molecular structural characterization for the polymers was presented by ^1H-NMR, infrared and UV-Vis spectra.     

Preparation of pyrenebutyric acid-modified magnesia-zirconia stationary phases using phosphonate as spacers and their application to the separation of fullerenes

A novel method was proposed for the preparation of pyrenebutyric acid-modified magnesia-zirconia stationary phases. Pyrenebutyric acid was grafted to magnesia-zirconia composites with different pore sizes via the sodium salt of cis-(3-methyloxiranyl)phosphonic acid (fosfomycin) as spacers. Aminated fosfomycin was first absorbed onto the surface of magnesia-zirconia composites during the preliminary step to provide amino and hydroxy reactive sites. And then the pyrenebutyric acid was covalently attached to the amine or hydroxyl groups via amide or ester bonds. The resulting stationary phases were characterized by elemental analysis, diffused reflectance FT-IR, nitrogen adsorption analysis and ¹³C solid state NMR spectra. The HPLC separation of fullerenes on the new stationary phases with different pore sizes was also investigated. The chromatographic performance showed a dependence on the pore size of the magnesia-zirconia matrix. Little retention of fullerenes was observed on the stationary phase with pore sizes about 4.5 nm. However, on the modified magnesia-zirconia with pore sizes about 10 nm, selectivity factors (α) for C₇₀/C₆₀ separation were determined to be 1.76, 2.29, 2.41, 3.10, with carbon disulfide, chlorobenzene, xylene and toluene as mobile phases, respectively. And the high solubility of fullerenes in these solvents dramatically increased the overall potential with regard to preparative fullerene purification. Among the reported stationary phases with pyrene ligands, the pyrenebutyric acid-modified magnesia-zirconia (PYB-F-(ZrO₂-MgO)) with larger pore sizes exhibited the best selectivity for fullerenes. The thermodynamic and kinetic behavior of fullerenes was also examined.     

Synthesis of C60‐containing polyphosphazenes from a new reactive macromolecular intermediate: Polyphophazene azides

A novel synthetic strategy was developed to prepare polyphosphazenes containing C₆₀ moieties as side chains. Thus, a new reactive macromolecular intermediate, polyphosphazene azides ( P1 ), was obtained from poly(dichlorophosphazene) by the direct nucleophilic substitution reaction. Then the azide group in P1 reacted with C₆₀ molecules to afford the first example of C₆₀‐containing polyphosphazenes ( P2 and P3 ). The polymers are soluble in common organic solvents. Molecular structural characterization for the polymers was presented by ¹H NMR, ¹³C NMR, IR, ultraviolet–visible spectra, and gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 194–199, 2004