Georges Kostov

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group. Part 10. Copolymerization of vinylidene fluoride (VDF) with 5-thioacetoxy-1,1,2-trifluoropentene for the obtaining of a novel PVDF containing mercaptan side-groups

The synthesis of novel perfluorovinyl thioacetoxy monomer (FSAc) and its copolymerization with vinylidene fluoride (VDF; also called 1,1-difluoroethylene) are presented. This monomer was obtained in good yield from the photochemical addition of thiol acetic acid to 1,1,2-trifiuoro-1,4-pentadiene. It was first hydrolyzed into 4,5,5-trifluoro-4-ene mercaptopentane, which did not homopolymerize, but under radical conditions underwent mainly a five-member cyclization. FSAc monomer was copolymerized with VDF either in bulk or in solution. 19F-NMR spectroscopy enabled one to quantify the respective amount of each monomeric unit in the copolymer. The reactivity ratios, ri, of both comonomers were determined from the Kelen and Tudos and the Tidwell and Mortimer methods and were found to be rVDF = 0.63 and 0.60 and rFSAc = 0.43 and 0.41 at 120°C, respectively. An azeotropic point was observed at 61 mol% of VDF and under this VDF percentage, lower incorporation of FSAc in the copolymer took place. Alfrey-Prices Q ...

Novel fluorinated monomers bearing reactive side groups Part 1. Preparation and use of ClCF2CFC1I as the telogen

Abstract The addition of IC1 to chlorotrifluoroethylene leading to a ClCF 2 CFClI ( I )/Cl 2 CFCF 2 I ( II ) mixture is described. Four different ways of initiation (thermal, photochemical, or the presence of redox catalysts or radical initiators) were used in order to get optimized yields and amounts of isomer I . Thermal initiation led to quantitative yields whereas the photochemically induced reaction usually produced the highest proportion of isomer I . Excellent yields of isomer I were obtained at 140 °C. The batch process was more interesting in both selectivity and yield. The activation energy of the reaction was 27 kJ mol −1 and elucidation of the mechanism was proposed in terms of a radical process.

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group.: Part 31 – synthesis of trifluorovinyl hydroxy and acetoxy monomers

Abstract The preparation of two functional perfluorovinyl monomers useful as comonomers in the copolymerization of commercially available monomers is presented. First, 1-iodo-1,2-dichloro-1,2,2-trifluoro ethane (1) was added to allyl alcohol under several initiating conditions and it was found that AIBN is the best initiator. Then, the selective reduction of the iodine atom in the presence of tributyl stannane gave ClCF2CFClC3H6OH quantitatively and its dechlorination was optimized leading to F2CCFC3H6OH in 50% overall yield from (1). This monomer was quantitatively acetylated by acetyl chloride. All these products and intermediates were characterized by 1 H , 19 F and 13 C-NMR spectroscopy, and simulated spectra were in very good agreement with those observed experimentally.

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group. Part 6 – synthesis of trifluorovinyl epoxide and its 1,2-diol

Abstract The preparation of the new ω-epoxide and 1,2-dihydroxy trifluorovinyl monomers useful as comonomers in the copolymerization of commercially available alkenes is presented. The addition of 1-iodo-1,2-dichloro-1,2,2-trifluoroethane to allyl acetate led quantitatively to the expected chlorotrifluorinated-2-iodo-1-acetate which underwent a thermal rearrangement yielding RF,ClCH2CH(OAc)CH2I even in the presence of a radical initiator that started to decompose at mild temperature. Whatever the amount of rearranged product, both these iodoacetates formed epoxides in alkali media giving two new compounds in high yields. Dechlorination yielded the trifluorovinyl epoxide (in 40% yield) and side products from the ring opening of the oxirane group. The mixture of halogenated epoxides was quantitatively hydrolysed into the halogenated -1,2-diol which was dechlorinated into F2C=CFCH2CH(OH)CH2OH in 58% yield. All these products and intermediates were characterized by 1 H , 19 F and 13 C NMR spectroscopy.

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group Part 2. Synthesis of nonconjugated dienes

Abstract The synthesis of various ω-perfluorovinyl synthons, especially 1,1,2-trifluoro-1,4-pentadiene 1 (F2C=CFCH2CH=CH2) is described. These products were prepared according to a three-step scheme via the photochemical addition of iodine monochloride to chlorotrifluoroe-thylene (CTFE) leading to ICF2CFCl2/ICFClCF2Cl isomers, the relative amount of which depending on the way of initiation. Their reaction with allyl acetate under radical conditions gave at least four isomers from the expected or rearranged compounds ClCF2CFClCH2CHXCH2Y or Cl2CFCF2CH2CHXCH2Y (with X, Y = I or OAc groups), the dechlorination and/or ‘deiodoacetatisation’ of which produced 1 and various 4,4,5,5,5-perhalogenopentanes as by-products. An optimization of the synthesis of 1 is proposed. All the compounds were characterized by 1H and 19F NMR.

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group—part 7. Copolymerization of tetrafluoroethylene with ω-hydroxy trifluorovinyl monomers †

The radical copolymerization of tetrafluoroethylene (TFE) and trifluorovinyl ω-hydroxy comonomers [F 2 C=CF(CH 2 ) m OH with m = 1 (FA1) and m = 3 (FA3)] for the synthesis of fluorinated polymers bearing hydroxy side groups is presented. FA1 was prepared by dehydrofluorination of 2,2,3,3-tetrafluoropropanol, whereas FA3 was obtained in a three-step scheme starting from the radical addition of 1,2-dichloroiodotrifluoroethane to allyl alcohol. The copolymerization conditions (in bulk or in solution in di n-butyl ether) and the polymer compositions considerably influenced the molecular weights, the molecular weight distributions, and the thermal properties of these copolymers. The kinetics of copolymerization of both couples enabled to determine the reaction order to the initiator (being 0.9) and the close values of apparent activation energies for [TFE/FA1 (E a = 52.4 kJ-mol -1 ) and for TFE/FA3 (E a = 46.8 kJ-mol -1 )] couples. From the Tidwell and Mortimer method, the relative reactivity ratios were calculated by elemental analysis or by 19 F-NMR spectroscopy, showing a higher reactivity of the TFE to incorporate the copolymer (r TFE = 2.47 and r FA1 = 0.41; r TFE = 1.57 and r FA3 = 0.45). The high values of the reaction order to the initiator and low molecular weights of copolymers were associated to the allylic chain transfer of the hydroxy comonomers and a mechanism of copolymerization was proposed. The comonomer diad and triad distribution was determined by the statistic theory and allowed one to calculate the average length of the comonomer sequences. Finally, the thermal decomposition of these cooligomers showed that those containing FA3 units are more thermostable than those synthesized from FA1, and that the higher the fluorinated alcohol content, the faster the thermal decomposition.

Synthesis and copolymerization of vinylidene fluoride (VDF) with Trifluorovinyl Monomers, 11

The radical telomerization of vinylidene fluoride with 1-chloro-1,2-dibromotrifluoroethane is presented. This dibrominated transfer agent was produced readily from the addition of bromine to chlorotrifluoroethylene in high yields. Four different ways of initiation (thermal, photochemical, or in the presence of redox catalysts or radical initiators) were used in order to obtain optimized yields and degrees of telomerization. Interestingly, the thermal process carried out at 210°C led to fair to good yields in contrast to photochemically induced reaction or that catalyzed by redox systems (this latter reaction produced the monoadduct only). When radical initiators were used, tert-butyl peroxypivalate was the most efficient one, despite the lower reaction temperature. 1 H and 19 F NMR spectra enabled the microstructure of VDF telomers to be described and to determine the cumulative average degrees of telomerization (DP n ). Similarly, gas chromatography, able to detect even the ninth-order adduct, was also useful to assess the DP n . The kinetics of telomerization of this reaction allowed the determination of the first three order transfer constants (C T i ) and led to C T ∞ = 1.3 at 75 °C.

New approaches to the synthesis of functionalized fluorine-containing polymers

Abstract The synthesis of functional fluorinated copolymers, containing a reactive lateral group, , is a multistage procedure. Different methods of synthesizing such compounds were developed and optimized to get efficient fluorinated monomers with various functional groups and X spacer. The copolymerization of these functional co-monomers (1) with commercially available fluoroalkenes (2) offers a wide range of novel functionalized fluoropolymers (3) with interesting properties such as: ion-exchange and catalytic properties, cross-linking, solubility, compatibility, better adhesion, etc. Download full-size image The copolymers of fluoroalkenes with ω-functional trifluorovinyl co-monomers were prepared in bulk, solution or emulsion, using free radical initiators and in some cases, redox systems. The other copolymers were synthesized by radiation-induced polymerization or grafting of functionalized co-monomers onto fluorinated films. The performance of some newly developed monomers are discussed in terms of efficiency, reactivity, polymerization mechanism and the main properties of the polymers synthesized. These characteristics (thermal, chemical and mechanical, cross-linking properties, ion-exchange capacity, electro-conductivity, etc.) are discussed, in consideration of the growing use of these materials for specific applications, such as elastomers or coatings with excellent thermal and chemical stability, fluorinated ion-exchange membranes, polymers with low surface energy and others.

Synthesis and polymerisation of fluorinated monomers bearing a reactive lateral group. Part 5 – Radical addition of iodine monobromide to chlorotrifluoroethylene to form a useful intermediate in the synthesis of 4,5,5-trifluoro-4-ene-pentanol

Abstract The synthesis of the new halogenated alcohol BrCF 2 CFClCH 2 CHICH 2 OH as a precursor of 4,5,5 trifluoro-4-ene pentanol F 2 CCFC 3 H 6 OH is based on a two-step process. First, the radical addition of iodine monobromide to chlorotrifluoroethylene (CTFE) led to the expected BrCF 2 CFClI (I) and ICF 2 CFClBr (II), but also to BrCF 2 CFClBr (III) and ICF 2 CFClI (IV), the amount of which determined by 19 F NMR depended on the reaction conditions: by feeding CTFE into IBr continuously or in batches; photochemical or thermal initiations, and with various initial [IBr] 0 /[CTFE] 0 molar ratios. In most cases, isomer (I) was mainly produced. The second step concerned the addition of such a mixture to allyl alcohol yielding the polyhalogenoalcohol with a quantitative conversion of (I). The reactivity of different halogeno end-groups of these isomers toward the allyl alcohol was discussed. Reduction of the iodine atom into hydrogen and the halogenated alcohol was accompanied by that of the bromine atom leading to BrCF 2 CFClC 3 H 6 OH and HCF 2 CFClC 3 H 6 OH (V). Dehalogenation of the former alcohol in the presence of zinc led to F 2 CCFC 3 H 6 OH while dehydrochlorination of (V) into trifluorovinyl hydroxy monomers was achieved in the presence of potassium hydroxide but in poor yields. Strategies starting from the radical additions of iodine monochloride and of iodine monobromide were compared showing that the former led to better overall yields of trifluorovinyl alcohol than the latter.

RADICAL ADDITION OF IODINE MONOCHLORIDE TO TRIFLUOROETHYLENE

Abstract The addition of iodine monochloride to trifluoroethylene (TrFE) leading to a ClCF2CFHI (I)/ClCFHCF2I (II) mixture is described. Four different ways of initiation (thermal, photochemical, presence of radical initiator, or redox catalyst) were used and all of them led to a high amount (>89%) of isomer (I). The amounts of (I) and (II) isomers were determined by 1H and 19F NMR and also they were deduced from those of ClCF2CFH2 and ClCFHCF2H obtained by selective reduction of the iodine atom of the former mixture, in the presence of tributylstannane. The reactivity of ICl to TrFE and the high proportion of isomer (I) were interpreted by means of a thermodynamical approach from the enthalpy of formation of (I) and (II), respectively, determined by semi-empirical computations. In addition, heats of formation of both isomers and interactions between SOMO of radicals and HOMO of fluoro-olefin enable to show that the mechanism of such a reaction occurs via the addition of I to the less fluorinated side of TrFE.