新的四(氟烷基)(硅烷,R 1 R 2 R 3 R 4 Si [其中R i =(CH 2)n R F,n = 2或3,R F为全氟链,直链或直链)的合成和结构表征R 1 R 2 R 3 SiR'SiR 1 R 2 R 3 [R i = Me,-(CH 2)n R F和R'=-(CH 2)n R报告了F '(CH 2)n-。DSC已研究了这些新化合物的热性能以及先前制备的所有硅烷和乙硅烷的热性能。还给出了它们的折射率。
Controlled step-wise telomerization of vinylidene fluoride, hexafluoropropene and trifluoroethylene with iodofluorinated transfer agents
摘要:
Highly fluorinated cotelomers having the structure F(TFE)(w)(VDF)(x)(HFP)(y)(TrFE)(z)I containing one or several tetrafluoroethylene (TFE), vinylidene fluoride (or 1,1-difluoroethylene, VDF), hexafluoropropene (HFP) or trifluoroethylene (TrFE) base units were synthesized by thermal step-wise cotelomerization of these fluoroolefins with perfluoroalkyl iodides. H-1 and F-19 NMR allowed one to characterize these cotelomers and to assess the defects of chaining arid the molecular weights. While the monoadduct produced from VDF exclusively exhibits RFCH2CF2I structure, that prepared from TrFE was composed of RFCFHCF2I and RFCF2CFHI isomers, the ratio of which is directed from the electrophilicity of R-F* radical. The reactivity of the C-I bond in R-F-Q-CXY-I depends on the nature of the Q spacer and on the reactivity of the fluorinated monomer (e.g., thermal initiations of VDF, TrFE and HFP were efficient from 180, 195 and 210 degrees C, respectively). The mechanism of the addition of the radical generated from the iodinated transfer agent to the fluoroalkene is explained by means of its electrophilic attack to the more nucleophilic (i.e., the less electrophilic) side of the olefin. Ethylenation of these fluorocotelomers was successfully achieved from various initiations (thermal, redox or from peroxides) with best results from redox catalysis. Thermal properties of several fluorotelomers (glass transition temperatures, T-g and melting temperatures, T-m) were assessed. They were linked to the number of consecutive CF2 groups (for the crystalline zones) and bulky side groups which induced amorphous regions. (C) 2000 Elsevier Science S.A. All rights reserved.