High-resolution 19F and 1H NMR of a vinylidenefluoride telomer (original) (raw)
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Macromolecules, 2013
Advanced modern multidimensional solution NMR experiments have been used to deduce the sequence distribution in poly(VDF-co-HFP) copolymers. Assignment of 19 F resonances from different monomer-and regio-sequences in poly(VDF-co-HFP) copolymer were identified. In addition to corroborating some assignments reported in earlier literature, this work provides assignments of some new resonances from the spectra of poly(VDF-co-HFP) copolymer, which resulted from better dispersion of the resonances. These assignments are used for the monomer sequence analyses of two polymers using first-order Markovian statistics, and the relative reactivities of the monomers during polymerization are discussed. The results from this study provide insight into the polymerization chemistry for this fluoropolymer.
Structural and Mechanistic Studies of Telomerization of Vinyl Acetate by CDCl~ 3 via^ 1H NMR
Iranian Polymer Journal, 2008
K inetics of radical telomerization of vinyl acetate (VAc) with CDCl 3 as a telogen in the presence of AIBN initiator was studied by 1 H NMR. Structure of the chains was analyzed in detail by 1 H NMR spectroscopy technique. It was observed that two telomers with different α-ends including trichloromethyl-and dichloromethyl-terminated VAc telomers were formed during the telomerization reaction. Therefore, two different mechanisms of the transfer reaction to CDCl 3 telogen have been proposed which were supported in details by the abstraction of either deuterium or chlorine radicals from CDCl 3 molecules. 1 H NMR analysis also allowed us to calculate the conversion of VAc (X VAc ), number-average degree of polymerization (DPn), telomer percentage (%), and the ratio of the abstractions of deuterium radicals to chlorine radicals (R D/Cl ) from CDCl 3 molecules. These results showed that at the same conversion, at first, DPn decreases with increase of the initial concentration of AIBN but then increases. Also, DPn at the same conversion decreases by increasing of the R 0 and decreasing of the reaction temperature. Moreover, at the same conversion, telomer percentage increased by decreasing [AIBN] 0 and reaction temperature while decreased by decreasing of the R 0 (or equivalently [CDCl 3 ]). The highest yield of telomer was about 60%. There was not any significant difference between the R D/Cl at various conditions used in VAc telomerization by CDCl 3 . 1 H NMR analysis showed that the rate of the abstraction of deuterium radical from CDCl 3 molecule is favoured relative to its rate of chlorine radical abstraction. catalyst nM+YZ Y-(M) n -Z
Unexpected Radical Telomerisation of Vinylidene Fluoride with 2-Mercaptoethanol
Molecules, 2021
The radical telomerisation of vinylidene fluoride (VDF) with 2-mercaptoethanol as chain transfer agent (CTA) was studied to synthesise fluorinated telomers which bear a hydroxy end-group, such as H(VDF)nS(CH2)2OH, under thermal (di-tert-butyl peroxide as the initiator) or photochemical initiations. A careful structural study of a typical H-VDF-S(CH2)2OH telomer was performed by 1H and 19F NMR spectroscopy. These analytical methods allowed us to explore the selective addition of the thiyl radical onto the hydrogenated side of VDF, and the telomer containing one VDF unit was obtained selectively. Surprisingly, for higher [VDF]o initial concentrations, a monoadduct telomer was produced as well as PVDF homopolymer. This feature was related to the fast consumption of the CTA. The kinetics of radical telomerisation led to a quite high transfer constant of the CTA (40 at 140 °C) that evidences the formation of a monoadduct as the only telomer formed.
Magnetic Resonance in Chemistry, 2014
Fluoropolymers are usually insoluble in organic solvents. Insolubility of fluoropolymers limits basic characterization such as microstructural investigations. In the family of fluoropolymers, terpolymer of tetrafluorethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (VDF), named THV is one of the newest members. There are nine grades of THV available. Among the nine grades, THV-221 G is an ideal model polymer for basic characterization purposes. THV-221 G is soluble in solvents such as acetone and ethyl acetate. In the current report, both homonuclear and heteronuclear 2D NMR experiments were employed in solution on THV-221 G. The homonuclear gradient correlation spectroscopy NMR measurement revealed that THV has two adjacent TFE units in addition to TFE-HFP sequence orders. The fraction of the microstructures is quantified by the analysis of 1D solution 19 F NMR spectrum. Further, the gradient heteronuclear single quantum coherence experiment helped with the clarification of chemical environments of the units TFE, HFP, and VDF. The 1D solution 13 C NMR spectrum was helpful in clarifying sequence assignments of VDF. It is concluded that THV is a random polymer with a limited fraction of TFE-TFE and TFE-HFP sequence orders in addition to head-to-tail polymerization of VDF unit.
Magnetic Resonance in Chemistry, 2009
A complete 1 H, 19 F, and 13 C NMR assignment of a homologous series of polyfluorinated acids and alcohols is reported. These assignments were obtained chiefly through single and multiple-bond 1 H-13 C and 19 F-13 C correlation experiments (HSQC, HMBC). 19 F NOESY experiments were required for assignment of two compounds with diastereotopic 19 F nuclei in the CF 2 chain of the molecule.
Journal of Fluorine Chemistry, 1995
Thermal and redox-induced telomerizations of vinylidene fluoride (VDF) with linear (n-C4FgI) or branched (i-C3FTI) perfluoroalkyl iodides have been performed. In both cases, thermal telomerizations led to telomeric-type distributions of the first five (from linear telogen) or the first three (from branched telogen) adducts produced, with better yields at higher temperatures. The redox-initiated telomerization was more selective since it led to the first two adducts only. For both reactions, mono-and di-adducts were isolated and characterized by 1H and 19F NMR spectroscopy. Interestingly, both the diadducts were composed of two isomers (i.e. the expected telomer and RFCH2CF2CF2CH2I). Two mechanisms are proposed and it is assumed that the products may be obtained either by chain propagation or by stepwise telomerization. In addition, attack of the electrophilic radical on the nucleophilic side of VDF is discussed.
Fluorinated oligomers, telomers and (co)polymers: synthesis and applications
Journal of Fluorine Chemistry, 2001
An overview of the activities in¯uorine chemistry at the Laboratory of Macromolecular Chemistry of the Ecole Nationale Supe Ârieure de Chimie de Montpellier is presented, ranging from the synthesis of¯uorinated monomers and initiators to the properties and applications of the corresponding (co)polymers. Concerning the monomers, acrylic, vinyl, allyl, styrenic, epoxides or silicon-containing monomers have been prepared. Then, original telomers of¯uoroole®ns from various chain transfer agents, and their functionalizations have been described. Further,¯uorinated (co)polymers have been obtained and characterized: they can be produced either from radical (co)polymerization of commercially available or synthesized¯uoromonomers (e.g. acrylic, tri¯uorovinyl monomers), or from polycondensation (e.g.¯uorinated silicones or polyimides) or from polyaddition (e.g.¯uorinated polyurethanes). Finally, several properties and applications are given. #