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Copolymers of 1,1-difluoroethene with tetrafluoroethene, chlorotrifluoroethene, and bromotrifluoroethene have been prepared by emulsion polymerization, and their crystallinity has been investigated by means of x-ray diffraction. The results are discussed in relation to copolymer composition and structure.

Several fluoroalcohols have been prepared by the free-radical addition of methanol, ethanol and isopropanol to such fluoro-olefins as C3 F6, CFH[dbnd]CF-CF3, (CF3)zCFCF[dbnd]CFCF3 and H(CF2)4CF[dbnd]CF2. Proper experimental conditions for their synthesis are described. Owing to their strong tendency to form hydrogen bonds, fluoroalcohols are excellent solvents for polymeric materials which possess receptive sites for hydrogen bonding formation. The solvent power of the fluoroalcohols on some polar polymers, mostly aliphatic polyamides, has been tested. 2,2,3,4,4,4-Hexafluorobutanol (HFB) shows the best solvent ability among compounds of this class. Its properties and solvent power have been evaluated and compared to those of trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP).

19F nuclear matnetic resonance spectra of vinylidene fluoride-hexafluoropropene copolymers and vinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymers are reported and discussed. Their interpretation allows average composition and sequence distribution to be determined. Sequence distribution is shown to be relevant in determining the trend of glass transition temperatures and in the study of the mechanism of vulcanization.

The Fox, Gordon-Taylor-Wood, Johnston and Barton equations have been applied to predict the glass transition temperatures, Tg of vinylidene fluoride-hexafluoropropene (VDF-HFP) copolymers and VDF-HFP-tetrafluoroethene (TFE) terpolymers. The Fox equation fails to describe the co- and terpolymer systems. The experimental data for VDF-HFP copolymers are well interpreted by the Gordon-Taylor-Wood equation. The Johnston and Barton equations, based on sequence distribution, yield good results for VDF-HFP and VDF-HFP-TFE. The assumptions made about kinetic constants of propagation and the Tg contributions of alternating monomer dyads and polyTFE are also discussed.

Copolymers of tetrafluoroethene (TFE) with hexafluoropropene (HFP) have been prepared in the 0-14mol% HFP composition range. Their melting temperatures (Tm), enthalpies (ΔHf) and entropies (ΔSf) of first and second fusion, and crystallinities (X) according to x-ray diffraction(x.r.d.) and differential scanning calorimetry (d.s.c.) have been determined. The results indicate that ΔHf/Xx.r.d of the polymer crystals decreases with higher HFP content.

Copolymers of vinylidene fluoride (VDF) with fluoroolefins of the series CF2CFX (X = F, Cl, Br, CF3 and C5F11) have been synthesized in the 0–16 mole % CF2CFX range. Results of physico-chemical characterisation by means of DSC techniques (Tg, TM, ΔHf) and X-ray diffraction are examined and related to the nature of the substituent of the fluoroolefin. The Tg/TM ratio varies from 0.5 for the VDF homopolymer to higher values at increased CF2CFX content, although to a different extent for the various series of copolymers. The results show that the Beaman-Boyer empirical rule (Tg/TM=2/3), developed for homopolymers, also applies to some copolymeric systems.

Tetrafluoroethene (TFE)–chlorotrifluoroethene (CTFE) and TFE–bromotrifluoroethene (BTFE) copolymers have been synthesized by solution copolymerization over the entire range of comonomer composition. Crystallinity data are reported and first- and second-order transitions have been investigated by DSC. Glass transition temperatures of TFE-CTFE copolymers vary in a nonlinear fashion in the range defined by the homopolymers conforming best to the Johnston equation; the behavior in the TFE-BTFE system is more linear. Whereas TFE-BTFE copolymers show a steep decrease of melting temperature at higher BTFE content, due to the amorphous character of the polymers, more regular behavior was found for TFE-CTFE copolymers. Enthalpies of fusion are also reported. The results are discussed in relation to copolymer composition and structure and are compared with data on tetrafluoroethene–hexafluoropropene (FEP) fluorocarbon resins.

Hexafluoropropene (HFP) — 1,1-difluoroethene (VDF) copolymers have been synthesized in the 0–16 mole % HFP range and the results of a physico-chemical characterization by means of XRD (cristallinity index) and DSC techniques are related to the microstructure of the polymers, as determined by 19F NMR. The addition of a small percentage of the HFP comonomer does not affect the polymorphism of poly(vinyl-idenefluoride).

The comonomer system based on vinylidene fluoride (VDF) and hexafluoropropene (HFP) has been polymerized in soapless emulsion, at various pressures of the gaseous feed and different concentrations of the free-radical initiator. The particle size and number, evaluated as a function of conversion, suggest a rather long nucleation period. In Smith-Ewart's Interval II the limiting particle number decreases with increasing monomer fugacity (which is proportional to the monomer concentration in water), and increases with increasing initiator concentration. The kinetic data cannot be fully accounted for by changes of particle number. On the contrary, there is evidence that the average number of free radicals per particle is affected by experimental conditions and follows a trend very similar to that predicted by Stockmayer's model.

The alkaline dehydrofluorination of Vinylidene Fluoride (VDF) -Hexafluoropropene (HFP) copolymers in dimethylacetamide has been reported by Schmiegel [1]. Basing on the reduction of 19F NMR signals related to HFP-VDF-HFP sequences and the apprearance of small low-field resonances attributed to allilic CF3, he suggested that the reaction takes place at HFP-VDF-HFP sequences, to give conjugated dienes and α, β unsaturated ketones deriving from OH− addition to dienes. This communication presents a study of the dehydrofluorination of VDF-HFP copolymers in THF, by alcoholic KOH. The reaction has been followed by analysis of the fluoride ion in solution. The intrisinc viscosity of the polymer did not change after elimination of up to 7.9 x 10−4 moles F− per g polymer. Higher reaction extents resulted in a decrease of intrinsic viscosity, suggesting polymer chain degradation. The reation products exhibit IR absorptions at 1720, 1684 and 1638 cm−1, that can be attributed to isolated double bonds and/or carbonil groups. No IR bands indicate conjugation that is also not evidenced by UV spectra. 19F NMR spectra are similar to those reported by Schmiegel, but show a larger variety of new CF3 signals, both in the low-field and the usual CF3 regions. The Tg of the unsaturated polymers and the reation of these products with phenate anions have also been studied.

Copolymers of Bromotrifluoroethene (BTFE) with Tetrafluoroethene (TFE) and with 1,1-Difluoroethene (VDF) have been synthesized in the whole composition range by solution polymerization in 1,2,2-Trichloro-1,1,2-Trifluoroethane (FC 113), free radical initiator bis(4-terg.butylcyclohexyl)percarbonate, reaction temperature 40°C, monomer conversion < 10%. Monomer composition was adjusted in order to yield the desired copolymer. Polymer composition was determined by elementary chemical analysis. The reactivity radios for BTFE-TFE copolymerization have been computed: rBTFETFE = 0.24, rTFEBTFE = 0.82 19F NMR spectra of BTFETFE and BTFEVDF copolymers are also reported and discussed. The latter show patterns similar to those of VDF-Chlorotrifluoroethene copolymers.

Phase transfer catalysis (PTC) in dehydrofluorination of polyvinylidene fluoride (PVDF) has been recently investigated. Operating at 70–90°C on powder or film PVDF with aqueous NaOH 4–5 N and a PTC catalyst an amount of 9–100% of unsaturation was obtained [1] . No information was given about degradation of the polymer that likely seems to occur in these conditions. Aim of this work is a preliminary study on the PTC dehydrofluorination of vinylidene fluoride-hexafluoropropene copolymers in a wide range of composition (HFP from 0 to 40 mol %) and operating in milder conditions than above (T = 25–50°C, NaOH < 0.5 N, with a ratio meq base/g polymer ranging from 1 to 3). The level of unsaturation was detected by F− analysis in the aqueous phase on the assumption that the elimination of one HF affords one unsaturation in the polymer chain. The resulting structure has been studied by I.R. and N.M.R. spectra. Polymer degradation, indicated by the decrease of the intrinsic viscosity, seems to occur only by strong alkaline treatment. In our reaction conditions no change of the intrinsic viscosity is observed with unsaturation content up to 4%. The ability to give unsaturation has been related to the HFP content in the copolymer. The results show an increase of the rate of dehydrofluorination with increasing HF content.