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.     

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.     

Synthesis,characterization, and nucleotidic chain cleavage ability of uncharged water soluble poly(ethylene glycol)‐fullerene derivatives with an amphiphilic character

Water‐soluble fullerenes containing two poly(ethylene glycol) branches [Full‐(PEG)₂] were prepared starting from commercial poly(ethylene glycol)‐monomethyl ethers and C₆₀ [Full‐(PEG)₂]s chemical characterization was made by FT‐IR, NMR, and MALDI‐TOF mass spectrometric analyses. Their thermal stability was determined by TGA experiments. The capability of C₆₀‐derivatives to induce oligonucleotide cleavage under visible light irradiation was also ascertained. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2154–2153, 2008     

Functionalization of Fullerenes with Cyclopentadienyl and Anthracenyl Capped Polymeric Building Blocks via Diels–Alder Chemistry

Cyclopentadienyl (Cp) capped polymers [polyethylene glycols (PEGs), = 2 000 g · mol⁻¹], react readily with fullerenes in a 1:1 molar ratio (relative to the amount of fullerenes and Cp‐end groups) at ambient temperature within 5 min in the absence of any catalyst in a Diels–Alder (DA) reaction to provide fullerene‐PEG hybrids. Similarly, anthracenyl capped PEGs react with fullerenes (in a 1:3 molar ratio) in DA reactions to yield the corresponding hybrids, albeit over a period of 1.5 h at 80 °C and a lesser conversion. The efficiency of the transformation is monitored via electrospray ionization mass spectrometry (ESI‐MS), demonstrating that the fullerenes can be transformed into polymer hybrids; most efficiently when Cp‐functional polymer is used as the diene. In addition, the obtained hybrids were subjected to UV/Vis as well as thermogravimetric analysis further underpinning the formation of mono‐substituted C₆₀‐PEG hybrids [wt.‐%^exp 70 ± 5 (PEG), 30 ± 5 (C₆₀), wt.‐%^theo 68 (PEG), 32 (C₆₀)].

     

The synthesis of N-isocyanurato-substituted aziridino[1,2][60]fullerenes

N-Isocyanurato-substituted aziridino[1,2][60]fullerenes were synthesized for the first time as the main products by the reaction of isocyanurato-substituted azides with C₆₀. The thermal stability and the electrochemical behavior of the compounds synthesized were studied.     

Quantum dot-sensitized solar cells employing Pt/C60 counter electrode provide an efficiency exceeding 2%

A microporous platinum/fullerenes (Pt/C 60) counter electrode was prepared by using a facile rapid thermal decomposition method,and the quantum-dot sensitized solar cell (QDSSC) of Pt/C 60-TiO 2-CdS-ZnS and Pt/C 60-TiO 2-CdTe-ZnS was fabrication.The technique forms a good contact between QDs and TiO 2 films.The photovoltaic performances of the as-prepared cells were investigated.The QDSSCs with Pt/C 60 counter electrode show high power conversion efficiency of 1.90% and 2.06%,respectively (under irradiation of a simulated solar light with an intensity of 100 mW cm 2),which is comparable to the one fabricated using conventional Pt electrode.     

Tandem mass spectrometry of aminated fullerene derivatives

The products of the reaction between fullerenes (C₆₀/C₇₀) and dimethylamine were investigated by fast atom bombardment (FAB) mass spectrometry and tandem mass spectrometry (MS/MS). The FAB mass spectrum shows peaks corresponding to the addition of up to eight dimethylamine species, exclusively to C₇₀. MS/MS reveals an unusual fragmentation pattern. The mass spectrum of the reaction products, together with a number of tandem mass spectra, are shown.     

Thermal properties of solvolysis lignin-derived polyurethanes

Thermal properties of polyurethane (PU) films prepared from solvolysis lignin (SL), polyethylene glycol (PEG) and diphenylmethane diisocyanate (MDI) were examined by differential scanning calorimetry and thermogravimetry. In the SL—PEG—MDI system, the SL content, the molecular weight (M_n) of PEG and the NCO/OH ratio were changed in order to control the thermal properties. Glass transition temperatures (T_g's) of the prepared PU's were dependent on the SL content, the M_n of PEG and the NCO/OH ratio. However, the T_g of PU was significantly influenced by the SL content: the increment of T_g was ca. 150 K when the SL content in PEG increased from 0 to ca. 50%. The decomposition of the PU's was markedly dependent on the content of SL. Other factors, such as the NCO/OH ratio and the M_n of PEG, are less dominant compared with the SL content. This fact suggests that the dissociation between the isocyanate groups and the phenolic OH groups in SL may be the major factor in the whole process of the thermal decomposition of the PU containing SL     

Microwave-treated layered double hydroxides containing Ni and Al: The effect of added Zn

Ni containing layered double hydroxides (LDHs) have been prepared by precipitation and hydrothermally treated under microwave irradiation for different periods of time. The solids have been calcined at three temperatures corresponding to stable phases formed during thermal decomposition of LDHs. The properties of the irradiated samples and of the calcined products were studied in order to ascertain whether the ageing treatment under microwave irradiation modifies not only the properties of the layered materials, but also the properties of the calcined products. A structural and textural study was carried out by PXRD, FT-IR and Vis-UV spectroscopy, thermal analyses (DTA and TG), N₂ adsorption/desorption at −196 °C and TEM microscopy; the reducibility of the nickel species was studied as well by TPR. The results show that the microwave treatment leads to better crystallized LDHs with modified thermal stability and reducibility. In addition, the degree of crystallinity of the layered precursors and their textural properties determine the properties of their thermal decomposition products.     

Thermal decomposition and creation of reactive solid surfaces

Three chromia precursors, namely CrO₃, (NH₄)₂Cr₂O₇ and chromia gel, were subjected to thorough thermal analysis by means of TG and DTA. The thermal decomposition products obtained by calcination of these precursors at various temperatures (150–500°) for 5 h were investigated by infrared and X-ray techniques. The results obtained allowed a thorough physicochemical characterization of the intermediate steps and products throughout the thermal decomposition.     

The thermal desorption mass spectra of polytetrafluoroethylene modified under the action of radiation at elevated temperatures

The products of the pyrolysis of polytetrafluoroethylene (PTFE) in a vacuum modified under the action of gamma irradiation in the molten state were studied mass spectrometrically at various temperatures. Radiation modification was found to cause the appearance of an additional stage of the thermal decomposition of PTFE at decreased temperatures compared with not irradiated PTFE. The chemical composition of the gas components of thermal decomposition substantially changes after the irradiation of PTFE, which increases the molecular weight of decomposition products. A comparison with the results of an additional study of the thermal decomposition of tetrafluoroethylene copolymer with hexafluoropropylene is evidence of the formation of side CF₃ groups in PTFE under irradiation. Data on the composition of gaseous products of PTFE radiolysis under gamma irradiation were obtained.     

Thermal decomposition of ammonium copper chromate: effect of the addition of barium

The influence of the addition of barium (as barium chromate) to ammonium copper chromate on its thermal decomposition has been investigated by TG, DTG and DTA in the temperature range 303–1273 K. The solid products formed in the decomposition at different temperatures were characterised by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and also by measuring their specific surface area. The addition of BaCrO₄ at different concentrations (0–19.8%) was found not to change the general trend in the decomposition of ammonium copper chromate (which occurs in four distinct steps), except small changes in the temperature corresponding to DTG and DTA peaks. However, the sintering (or crystal growth) of the solid product is largely reduced by the presence of BaCrO₄.     

Thermal Stability of C60-Methylnaphthalenes Solvates

The crystalline solvates containing fullerenes and (di)methylnaphthalenes were investigated by thermal analyses and X-ray diffraction methods. It was found that C₆₀ with (di)methylnaphthalenes forms two types of stable solvates: either at the molar ratio 1:2 decomposing at temperatures close to 100°C or at 1:1 molar ratio decomposing in the temperature range 120–214°C. Crystalline lattice and thermal stability of the solvates depends on the structure of the solvent molecules. The strong solute-solvent interaction is also manifested by the modification of the C₆₀ absorption spectra in solution. The results are discussed using semiempirical quantum chemistry methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Decomposition and Glass Transition Temperature of Poly(methyl Methacrylate) and Poly(isobutyl Methacrylate)

Abstract

The thermal decomposition and the glass transition temperatures of poly(methyl methacrylate) (PMMA) and poly(isobutyl methacrylate) (PiBuMA) were studied with a differential scanning calorimeter (DSC). The undecomposed and decomposed polymers were analyzed by gel permeation chromatography (GPC) for molecular weight distributions and by DSC for changes in the thermal properties and glass transition temperatures, T. In the isothermal decomposition of PMMA and PiBuMA, depolymerization reactions exclusively are operative. During low temperature decompositions, longer PMMA chains depolymerize first. These are followed by the shorter chains. In the case of PiBuMA, the shorter chains depolymerize first. Some of these undergo chain recombinations to yield very high molecular weight products. For identical values of weight loss, the respective decomposition temperatures for PiBuMA are 40 to 70 K lower than those for PMMA. The activation energies of decomposition (42 kJ/mol for PMMA and 67 kJ/mol for PiBuMA) have been found to be lower than those reported in the literature. Although T_g∞ of PiBuMA (331 K) agrees well with the literature value (326 K), T_g∞ of atactic PMMA (394 K) is higher than the reported value (378 K).     

Synthesis of carbon nanofibers from poly(ethylene glycol) with controlled structure

Through fine tuning of synthesis conditions, we successfully synthesized three types of carbon nanofiber (CNF) (herring-bone carbon nanofiber, platelet carbon nanofiber, and cup-stacked carbon nanofiber) by the thermal decomposition of a mixture of poly(ethylene glycol) (PEG) and nickel chloride (NiCl₂). A series of experimental results demonstrated that the key factors for the selective synthesis of these CNFs were the (1) NiCl₂/PEG ratio, (2) drying time of the polymeric mixture, (3) state of PEG (liquid or solid) before temperature rising, and (4) temperature profile during the thermal decomposition. Changes in these conditions contributed to the formation of Ni catalyst particles from the catalyst NiCl₂ with different morphology, thereby resulting in the growth of different types of CNF or amorphous carbon products according to the catalyst particle’s shape. Also, we found that the mechanism of CNF growth in this synthesis method was fundamentally the same as that in chemical vapor deposition (CVD).     

Thermal behaviour and degradation of a liquid crystalline alkylene-aromatic polyester: Poly(decamethylene-fumaroyl-bis-4-oxybenzoate)

The thermal behaviour and degradation of an alkylene-aromatic liquid crystalline polyester, poly(decamethylene-fumaroyl-bis-4-oxybenzoate), were studied by thermogravimetric analysis under dynamic conditions and by pyrolysis-gas chromatography and pyrolysis-gas chromatography/mass spectrometry in the temperature range 450-650 °C. Among the degradation products detected, maleic anhydride, phenol, 4-hydroxybenzoic acid and the corresponding decenyl ester were the most abundant. The type and the composition of the pyrolysis products gave useful information about the mechanism of thermal degradation. The polyester decomposition starts with a free-radical scission in the mesogenic fragment and continues with electrocyclic reactions in the spacer. The influence of fullerene C₆₀ addition and of the deuteration of the decamethylene spacer on thermal behaviour and degradation were investigated.     

New approach on the development of plasticized polylactide (PLA): Grafting of poly(ethylene glycol) (PEG) via reactive extrusion

In this work, new ways of plasticizing polylactide (PLA) with low molecular poly(ethylene glycol) (PEG) were developed to improve the ductility of PLA while maintaining the plasticizer content at maximum 20 wt.% PLA. To this end, a reactive blending of anhydride-grafted PLA (MAG-PLA) copolymer with PEG, with chains terminated with hydroxyl groups, was performed. During the melt-processing, a fraction of PEG was grafted into the anhydride-functionalized PLA chains. The role of the grafted fraction was to improve the compatibility between PLA and PEG. Reactive extrusion and melt-blending of neat and modified PLA with PEG did not induce any dramatic drop of PLA molecular weight. The in situ reactive grafting of PEG into the modified PLA in PLA/PEG blends showed a clear effect on the thermal properties of PLA. It was demonstrated by DSC that the mobility gained by PLA chains in the plasticized blends yielded crystallization. The grafting of a fraction of PEG into PLA did not affect this process. However, DSC results obtained after the second heating showed an interesting effect on the T_g when 20 wt.% PEG were melt blended with neat PLA or 10 wt.% MAG-PLA. In the latter case, the T_g displayed by the reactive blend was shifted to even lower temperatures at around 14 °C, while the T_g of neat PLA and PLA blended with 20 wt.% PEG was around 60 and 23 °C, respectively. Regarding viscoelastic and viscoplastic properties, the presence of MAG-PLA does not significantly influence the behavior of plasticized PLA. Indeed, with or without MAG-PLA, elastic modulus and yield stress decrease, while ultimate strain increases with the addition of PEG into PLA.     

氧化锰纳米管及其超级铝热剂:制备及对环三亚甲基三硝胺热分解的影响

采用水热法制备了MnO₂纳米管,以其与纳米铝粉为原料,采用超声分散复合的方法,制备了超级铝热剂Al/MnO₂.利用粉末X射线衍射(XRD)、扫描电子显微镜(SEM)及能量散射光谱仪(EDS)对产物的物相、组成、形貌和结构进行分析表征,并运用差示扫描量热法(DSC)研究了MnO₂纳米管及其超级铝热剂对环三亚甲基三硝胺热分解特性的影响.结果表明,水热法制备的纳米MnO₂呈管状均匀分布,球形纳米Al与管状纳米MnO₂相互依附,分散较均匀;MnO₂纳米管及其超级铝热剂的加入均改变了环三亚甲基三硝胺的热分解行为及分解历程,使原有占主导的液相分解变为二次的气相反应加剧,使环三亚甲基三硝胺主分解峰形发生了明显的改变.     

氧化锰纳米管及其超级铝热剂:制备及对环三亚甲基三硝胺热分解的影响

采用水热法制备了MnO2纳米管,以其与纳米铝粉为原料,采用超声分散复合的方法,制备了超级铝热剂Al/MnO2。利用粉末X射线衍射(XRD)、扫描电子显微镜(SEM)及能量散射光谱仪(EDS)对产物的物相、组成、形貌和结构进行分析表征,并运用差示扫描量热法(DSC)研究了MnO2纳米管及其超级铝热剂对环三亚甲基三硝胺热分解特性的影响。结果表明,水热法制备的纳米MnO2呈管状均匀分布,球形纳米Al与管状纳米MnO2相互依附,分散较均匀;MnO2纳米管及其超级铝热剂的加入均改变了环三亚甲基三硝胺的热分解行为及分解历程,使原有占主导的液相分解变为二次的气相反应加剧,使环三亚甲基三硝胺主分解峰形发生了明显的改变。