Synthesis and characterization of fluorinated PEO-b-PDMS-b-fluorinated PEO by free radical addition

Fluorinated poly(ethylene oxide) propyl-b-polydimethylsiloxane-b-propyl fluorinated poly(ethylene oxide)(FPEO-b-PDMS-b-FPEO) was synthesized by a free radical addition of carbon-hydrogen of polyether segments of poly(ethylene oxide) propyl-b-polydimethylsiloxane -b-propyl poly(ethylene oxide)(PEO-b-PDMS-b-PEO) to hexafluoropropylene(HFP) using tert-butyl peroxypivalate as an initiator.In order to reduce the possibility of side reaction,the protection and deprotection via silylation were used for the end-...     

Radical solution copolymerisation of vinylidene fluoride with hexafluoropropene

The radical copolymerisation in solution of vinylidene fluoride (or 1,1-difluoroethylene (VDF)) with hexafluoropropylene (HFP) initiated by di-tert-butyl peroxide is presented. A series of eight copolymerisation reactions was investigated with initial [VDF]_o/[HFP]_o molar ratios ranging from 5.0/95.0 to 85.2/14.8. Both co-monomers copolymerised in this range of copolymerisation. Moreover, only VDF homopolymerised in these conditions. The copolymer compositions of these random-type copolymers were calculated by means of ¹⁹F NMR spectroscopy which allowed the respective amount of each monomeric unit in the copolymer to be quantified. The Tidwell and Mortimer method led to the assessment of the reactivity ratios, r_i, of both co-monomers showing a higher incorporation of VDF in the copolymer (r_HFP = 0.12 ± 0.05 and r_VDF = 2.9 ± 0.6 at 393 K). Alfrey-Price's Q and e values of HFP were calculated to be 0.002 (from Q_VDF = 0.008) or 0.009 (from Q_VDF = 0.015) and +1.44 (versus e_VDF = 0.40) or +1.54 (versus e_VDF = 0.50), respectively, indicating that HFP is an electron-accepting monomer. The thermal properties of these fluorinated copolymers were also determined. Except for those containing a high amount of VDF, they were amorphous. Each showed one glass transition temperature (T_g) only, and from known laws of T_g, that of the homopolymer of HFP was assessed. It was compared with that obtained from the literature after extrapolation and is discussed.     

Green synthesis of methyl trifluoropyruvate catalyzed by solid acids

Solid acids – NiSO₄/Al₂O₃, Fe₂(SO₄)₃/Al₂O₃ and TiO₂/SO₄²⁻ – appeared to be effective catalysts for the acid catalyzed synthesis of methyl ester of trifluoropyruvic acid. They are active at 150–180 °C.     

One stone two birds: Degradation of persistent organic pollutants to a valuable industrial chemical production of pentafluoropropionyl fluoride from HFPO oligomers catalyzed by cesium fluoride in tetraglyme

Hexafluoropropylene oxide (HFPO) oligomers are toxic, bioaccumulative, and persistent organic pollutants (POPs). Consuming the harmful chemicals to prevent them from releasing to nature is of serious significance as far as both natural environments and human health are concerned. In this study, investigation on degradation of HFPO oligomers to pentafluoropropionyl fluoride (PPF), a valuable industrial chemical, is reported. Different combinations of alkali metal fluoride in either diglyme or tetraglyme under both flask and batch autoclave conditions were examined. Under the optimal reaction conditions, HFPO oligomers (n = 2-10) were completely degraded to PPF in over 90% yield. Reactions on 200 g scale were tested and no deduction of efficiency was observed, which indicates the potential for practical industrial application of this chemistry.     

全氟己酮中间体全氟丙酰氟及全氟环氧丙烷的合成研究进展

全氟己酮是优良的灭火剂和清洁剂,环境友好且性能优异。本文对其合成工艺进行探究,指出了以六氟丙烯为原料的合成工艺具有工业化的前景,并对六氟丙烯工艺中的重要中间体六氟丙酰氟及六氟环氧丙烷(HFPO)的合成方法进行了分析,指出分子氧液相氧化六氟丙烯制HFPO及使用鼓泡反应器将HFPO异构化成全氟丙酰氟是最有应用前途的工业合成方法。     

Preparation of trifluoroiodomethane via vapor-phase catalytic reaction between hexafluoropropylene oxide and iodine

Based on our previous investigation on the reaction mechanism to produce difluorocarbene and subsequent CF₃I starting with CHF₃ and I₂, a new route for preparing CF₃I at a relative low temperature, 200 °C, has been developed via a vapor-phase catalytic reaction between hexafluoropropylene oxide with I₂ in the presence of KF supported on activate charcoal as a catalyst. The influence of reaction temperature and reaction time on the amount of CF₃I was investigated. In the reaction process, coke-formation was suggested on the surface of catalysts by means of BET, XPS and TG-DTA analysis. The process for the formation of CF₃I and by-products is also discussed.     

Synthesis of an original poly(vinylidene fluoride-co-hexafluoropropylene)-g-perfluoropolyether graft copolymer

The synthesis of one original poly(vinylidene fluoride-co-hexafluoropropylene)-g-perfluoropolyether graft copolymer, achieved from the radical terpolymerization of vinylidene fluoride (VDF), hexafluoropropylene (HFP) and a perfluoropolyether (PFPE) bearing an ω-allylic group, is presented. This functional PFPE was synthesized from the condensation of an ω-carboxylic PFPE with an allyl amine. The terpolymerization was initiated by t-butyl peroxide in a perfluorohexane/acetonitrile mixture. NMR spectroscopy enabled the VDF, HFP and allyl amido PFPE base units contained in the terpolymer to be assessed, showing the good incorporation of VDF and the poor reactivity of HFP.     

Use of bis(trifluoromethyl)peroxy dicarbonate as initiator in the radical homopolymerisation of vinylidene fluoride (VDF) and copolymerisation of VDF with hexafluoropropylene

The radical homopolymerisation in acetonitrile of vinylidene fluoride (or 1,1-difluoroethylene, VDF) and the copolymerisation of VDF with hexafluoropropylene (HFP) initiated by bis(trifluoromethyl)peroxy dicarbonate are presented. Different reactions and different reactants were chosen to monitor the polymerisation in terms of initiating radicals generated from this initiator. Homopolymers and copolymers thus obtained were characterised by and NMR spectroscopy. From the assignments of the characteristic signals, an overall reaction mechanism is proposed that explains each step of the polymerisation. Particularly, an interpretation of the polymer microstructures and the presence of end-groups arising from the radical initiator as well as from eventual transfers is suggested. Among some of the microstructures, the trifluoromethoxy end-group was noted to be present in both PVDF and poly(VDF-co-HFP) (co)polymers, as generated from the decomposition of the initiator. This trifluoromethoxy end-group enabled the assessment of the molecular weights of PVDF and poly(VDF-co-HFP) (co)polymers. Thermal properties of the copolymers were also determined, showing that original fluoroelastomers possessing CF₃ end-groups are obtained endowed with low T_g and good thermal stability.     

Chain elongation during thermolysis of tetrafluoroethylene and hexafluoropropylene: Modeling of mechanistic hypotheses and elucidation of data needs

Thermolysis of tetrafluoroethylene at ≤500 °C is well-known to lead to equilibration with octafluorocyclobutane; at ≈600 °C this mixture forms hexafluoropropylene; and at slightly more forcing conditions the latter is converted to octafluoroisobutylene (and/or octafluoro-2-butene). This chain-elongation behavior contrasts with the familiar cracking of non-fluorinated olefins and the thermodynamic rationale is provided herein. Several mechanisms have been proposed in the literature without a clear choice. Kinetic modeling herein of available product/kinetic data with use of current thermochemical and kinetic parameters supports a key role for difluorocarbene formed from dissociation of tetrafluoroethylene. Arbitrary selection between unfortunately inconsistent available measurements and/or computations of elementary rate constants, with modest adjustments, allowed data matches with either a direct insertion into an olefinic C-F bond or an addition to the olefin to give a 1,3-biradical followed by a 1,2-fluorine shift. In contrast, a 1,2-fluorine shift in the starting olefin to generate a carbene, followed by carbene combination, seems unlikely. However, the modeling was only partially successful, especially for hexafluoropropylene as feed which seems a comparatively inefficient source of difluorocarbene. This highlights the need for improved experimental thermolysis data at low conversion, independent elementary rate constants for key steps, and enthalpies of formation of fluorocarbons and their reactive intermediates, especially C₃F₆.