Crosslinkable compositions based on vinylidene fluoride-trifluoroethylene polymers

Abstract

The present invention relates to crosslinkable compositions comprising vinylidene fluoride (VDF)/trifluoroethylene (TrFE) polymers and a fluorine-containing crosslinking agent of formula (A) [agent (Cz)]: {N.sub.3[S(O).sub.g1].sub.s1}.sub.na(R.sub.H).sub.nhR.sub.f(R.sub.H).sub.nh{[S(O).sub.g2].sub.s2N.sub.3}.sub.na, formula (A) wherein each of g1 and g2, equal to or different from each other, is 1 or 2, each of s1 and s2, equal to or different from each other, is 0 or 1, each of na and na is independently zero or an integer of 1 to 3, provided that the sum na+na is at least 2, each of R.sub.H and R.sub.H, equal to or different from each other, is a C.sub.1-C.sub.12 hydrocarbon group free of fluorine atoms, nh and nh, equal or different from each other are independently 0 or 1, and R.sub.f is selected from the group consisting of i) a C.sub.3-C.sub.20 fluorocarbon group, possibly comprising one or more ethereal oxygen atoms, ii) an oligomer comprising copolymerized units of vinylidene fluoride and trifluoroethylene, to a process for the manufacture of said compositions, to a method for curing the same, and to the use of said copolymers in electrical and electronic devices.

Claims

1. A crosslinkable composition comprising: at least one semi-crystalline fluoropolymer (F) possessing a detectable melting point when submitted to DSC measurements according to ASTM D3418 and comprising recurring units derived from vinylidene fluoride (VDF) and from 10% to 50% by moles with respect to the total moles of recurring units of fluoropolymer (F) of recurring units derived from trifluoroethylene (TrFE); and at least one crosslinking agent (Cz) of formula (A):
{N.sub.3[S(O).sub.g1].sub.s1}.sub.na(R.sub.H).sub.nhR.sub.f(R.sub.H).sub.nh{[S(O).sub.g2].sub.S2N.sub.3}.sub.na(A) wherein each of g1 and g2, equal to or different from each other, is 1 or 2, each of s1 and s2, equal to or different from each other, is 0 or 1, each of na and na is independently zero or an integer of 1 to 3, provided that the sum na+na is at least 2, each of R.sub.H and R.sub.H, equal to or different from each other, is a C.sub.1-C.sub.12 hydrocarbon group free of fluorine atoms, nh and nh, equal or different from each other are independently 0 or 1, and R.sub.f is selected from the group consisting of i) a C.sub.3-C.sub.20 fluorocarbon group, optionally comprising one or more ethereal oxygen atoms, and ii) an oligomer comprising copolymerized units of vinylidene fluoride and trifluoroethylene.

2. The crosslinkable composition of claim 1, wherein crosslinking agent (Cz) is an agent of formula (B):
N.sub.3(CH.sub.2).sub.mR.sup.B.sub.f(CH.sub.2).sub.mN.sub.3(B) wherein each of m and m is independently an integer of 1 to 6, and R.sup.B.sub.f is a C.sub.3-C.sub.10 fluorocarbon group, optionally comprising one or more ethereal oxygen atoms.

3. The crosslinkable composition of claim 2, wherein crosslinking agent (Cz) is an agent of formula (C):
N.sub.3(CH.sub.2).sub.m(CF.sub.2).sub.nc(CH.sub.2).sub.mN.sub.3(C) wherein each of m and m is independently an integer of 1 to 6, and nc is an integer of 4 to 10.

4. The crosslinkable composition of claim 1, wherein crosslinking agent (Cz) is an agent of formula (D):
N.sub.3[S(O).sub.g1]R.sup.D.sub.f[S(O).sub.g2]N.sub.3(D) wherein each of g1 and g2, equal to or different from each other, is 1 or 2, and R.sup.D.sub.f is a C.sub.3-C.sub.20 fluoroalkyl group, optionally comprising one or more ethereal oxygen atoms.

5. The crosslinkable composition of claim 4, wherein crosslinking agent (Cz) is an agent of formula (E):
N.sub.3SO.sub.2R.sup.E.sub.fSO.sub.2N.sub.3(E) wherein R.sup.E.sub.f is a C.sub.3-C.sub.20 fluoroalkyl group, optionally comprising one or more ethereal oxygen atoms.

6. The crosslinkable composition of claim 1, wherein fluoropolymer (F) comprises from 0.01% to 15% by moles with respect to the total moles of recurring units of fluoropolymer (F) of at least one cure-site monomer (CS), wherein monomer (CS) is an ethylenically unsaturated monomer comprising at least one reactive group selected from the group consisting of: an azide group; a nitrile group; and an alkyne group.

7. The crosslinkable composition of claim 6, wherein fluoropolymer (F) comprises from 0.01% to 15% by moles with respect to the total moles of recurring units of fluoropolymer (F) of at least one monomer (Az) comprising an azide group, wherein monomer (Az) is a monomer of formula (I):
CX.sub.1X.sub.2CX(O).sub.pR.sub.f(CH.sub.2).sub.n[S(O).sub.q].sub.sN.sub.3(I) wherein: X, X.sub.1 and X.sub.2, equal to or different from each other, are independently H or F, p is 0 or 1, n is 0 to 4, s is 0 or 1, q is 1 or 2, R.sub.f is a divalent (hydro)fluorocarbon group, optionally interrupted by one or more ethereal oxygen atoms.

8. The crosslinkable composition of claim 7, wherein monomer (Az) is a monomer of formula (II):
CX.sub.1X.sub.2CXOR.sub.f(CH.sub.2).sub.n[S(O).sub.q].sub.sN.sub.3(II) wherein: X, X.sub.1 and X.sub.2, equal to or different from each other, are independently H or F, n is 0 to 4, s is 0 or 1, q is 1 or 2, R.sub.f is a divalent (hydro)fluorocarbon group, optionally interrupted by one or more ethereal oxygen atoms.

9. The crosslinkable composition of claim 7, wherein monomer (Az) is a monomer of formula (IV):
CX.sub.1X.sub.2CXR.sub.f(CH.sub.2).sub.n[S(O).sub.q].sub.sN.sub.3(IV) wherein: X, X.sub.1 and X.sub.2, equal to or different from each other, are independently H or F, n is 0 to 4, s is 0 or 1, q is 1 or 2, R.sub.f is a divalent (hydro)fluorocarbon group, optionally interrupted by one or more ethereal oxygen atoms, wherein the sp.sup.2 hybridized carbon atom of the terminal double bond CX is bound to a sp.sup.3 carbon atom of the R.sub.f group.

10. A process for the manufacture of the crosslinkable composition of claim 1, comprising mixing: at least one semi-crystalline fluoropolymer (F) comprising recurring units derived from vinylidene fluoride (VDF) and from 10% to 50% by moles with respect to the total moles of recurring units of fluoropolymer (F) of recurring units derived from trifluoroethylene (TrFE); and at least one crosslinking agent (Cz) of formula (A):
{N.sub.3[S(O).sub.g1].sub.s1}.sub.na(R.sub.H).sub.nhR.sub.f(R.sub.H).sub.nh{[S(O).sub.g2].sub.S2N.sub.3}.sub.na(A) wherein each of g1 and g2, equal to or different from each other, is 1 or 2, each of s1 and s2, equal to or different from each other, is 0 or 1, each of na and na is independently zero or an integer of 1 to 3, provided that the sum na+na is at least 2, each of R.sub.H and R.sub.H, equal to or different from each other, is a C.sub.1-C.sub.12 hydrocarbon group free of fluorine atoms, nh and nh, equal or different from each other are independently 0 or 1, and R.sub.f is selected from the group consisting of i) a C.sub.3-C.sub.20 fluorocarbon group, optionally comprising one or more ethereal oxygen atoms, and ii) an oligomer comprising copolymerized units of vinylidene fluoride and trifluoroethylene.

11. A method of forming a cured shaped part, the method comprising crosslinking the crosslinkable composition of claim 1, such that a cured shaped part is formed.

12. A method for manufacturing an electrical or electronic device, the method comprising processing the crosslinkable composition of claim 1, and crosslinking the processed crosslinkable composition.

13. The process of claim 10, wherein crosslinking agent (Cz) is an agent of formula (B):
N.sub.3(CH.sub.2).sub.mR.sup.B.sub.f(CH.sub.2).sub.mN.sub.3(B) wherein each of m and m is independently an integer of 1 to 6, and R.sup.B.sub.f is a C.sub.3-C.sub.10 fluorocarbon group, optionally comprising one or more ethereal oxygen atoms.

14. The process of claim 13, wherein crosslinking agent (Cz) is an agent of formula (C):
N.sub.3(CH.sub.2).sub.m(CF.sub.2).sub.nc(CH.sub.2).sub.mN.sub.3(C) wherein each of m and m is independently an integer of 1 to 6, and nc is an integer of 4 to 10.

15. The process of claim 10, wherein crosslinking agent (Cz) is an agent of formula (D):
N.sub.3[S(O).sub.g1]R.sup.D.sub.f[S(O).sub.g2]N.sub.3(D) wherein each of g1 and g2, equal to or different from each other, is 1 or 2, and R.sup.D.sub.f is a C.sub.3-C.sub.20 fluoroalkyl group, optionally comprising one or more ethereal oxygen atoms.

16. The process of claim 15, wherein crosslinking agent (Cz) is an agent of formula (E):
N.sub.3SO.sub.2R.sup.E.sub.fSO.sub.2N.sub.3(E) wherein R.sup.E.sub.f is a C.sub.3-C.sub.20 fluoroalkyl group, optionally comprising one or more ethereal oxygen atoms.

17. The process of claim 10, wherein fluoropolymer (F) comprises from 0.01% to 15% by moles with respect to the total moles of recurring units of fluoropolymer (F) of at least one cure-site monomer (CS), wherein monomer (CS) is an ethylenically unsaturated monomer comprising at least one reactive group selected from the group consisting of: an azide group; a nitrile group; and an alkyne group.

18. The process of claim 17, wherein fluoropolymer (F) comprises from 0.01% to 15% by moles with respect to the total moles of recurring units of fluoropolymer (F) of at least one monomer (Az) comprising an azide group, wherein monomer (Az) is a monomer of formula (I):
CX.sub.1X.sub.2CX(O).sub.pR.sub.f(CH.sub.2).sub.n[S(O).sub.q].sub.sN.sub.3(I) wherein: X, X.sub.1 and X.sub.2, equal to or different from each other, are independently H or F, p is 0 or 1, n is 0 to 4, s is 0 or 1, q is 1 or 2, R.sub.f is a divalent (hydro)fluorocarbon group, optionally interrupted by one or more ethereal oxygen atoms.

19. The process of claim 18, wherein monomer (Az) is a monomer of formula (II):
CX.sub.1X.sub.2CXOR.sub.f(CH.sub.2).sub.n[S(O).sub.q].sub.sN.sub.3(II) wherein: X, X.sub.1 and X.sub.2, equal to or different from each other, are independently H or F, n is 0 to 4, s is 0 or 1, q is 1 or 2, R.sub.f is a divalent (hydro)fluorocarbon group, optionally interrupted by one or more ethereal oxygen atoms.

20. The process of claim 18, wherein monomer (Az) is a monomer of formula (IV):
CX.sub.1X.sub.2CXR.sub.f(CH.sub.2).sub.n[S(O).sub.q].sub.sN.sub.3(IV) wherein: X, X.sub.1 and X.sub.2, equal to or different from each other, are independently H or F, n is 0 to 4, s is 0 or 1, q is 1 or 2, R.sub.f is a divalent (hydro)fluorocarbon group, optionally interrupted by one or more ethereal oxygen atoms, wherein the sp.sup.2 hybridized carbon atom of the terminal double bond CX is bound to a sp.sup.3 carbon atom of the R.sub.f group.

Description

PREPARATIVE EXAMPLE 1SYNTHESIS OF CF2CFOCF2CF2SO2N3 [MONOMER (Az1)]

(1) According to a procedure similar to the procedures disclosed in U.S. Pat. No. 6,365,693 (DUPONT DOW ELASTOMERS LLC) Apr. 2, 2002 and modified, as below detailed, the above referenced compound was synthesized. In a three necks round bottomed glass flask 1.375 g=21.15 mmoles of NaN.sub.3 were suspended in 13 ml of CH.sub.3CN, which has been previously dried by distillation over P.sub.2O.sub.5 and storage onto 3A molecular sieves. The mixture was stirred at 500 rpm at 20 C. for about 20 minutes; 5.05 g=18.03 mmoles of CF.sub.2CFOCF.sub.2CF.sub.2SO.sub.2F (VEFS) were then added dropwise during 19 min. The molar concentration of VEFS ([CF.sub.2CFOCF.sub.2CF.sub.2SO.sub.2F]) in the mixture was thus equal to 1.38 M. The exothermic reaction gave rise to a temperature increase of about 2 C. The reaction mixture, at the end of the addition was found to be milky and became translucent. The mixture was kept under stirring at 20 C. for 48 hours under inert N.sub.2 atomosphere. The reaction was brought to completion by heating the mixture for 3 hours at 40 C. The mixture was then cooled at 20 C., and this temperature was then maintained for additional 3 hours. The raw reaction mixture appeared to be an opalescent solution with no visible precipitate. This mixture was poured in 70 ml of distilled water, from which a clear and transparent oil having a acre smelling immediately separated.

(2) From quantitative .sup.19F-NMR determinations, the so precipitated oil was found to correspond to target product. Aqueous phase were separated and found to contain NaF as reaction by-product.

(3) Yield=57% with respect to the starting amount of VEFS.

(4) Selectivity towards .sup.a,bCF.sub.2.sup.cCFO.sup.dCF.sub.2.sup.eCF.sub.2SO.sub.2N.sub.3=78% moles.

(5) Remaining 22% moles was found to correspond to N.sub.3.sup.fCF.sub.2.sup.gCFHO.sup.hCF.sub.2.sup.iCF.sub.2SO.sub.2N.sub.3. .sup.19F-NMR; (CDCl.sub.3; ppm): a:110; b: 118; c: 133; d: 80,2; e: 110,4; f: 90; g: 142 (J.sup.1.sub.H,F=47 hz); h: 78---->83; i: 110,4 FT-IR (KBr; cm.sup.1): 1839 (CF.sub.2CFO st.); 2156 (N.sub.3 st.); 1421+1463 (SO.sub.2N.sub.3 st.); 1200-1100 (CF st.).

PREPARATIVE EXAMPLE 2SYNTHESIS OF CF2CFCF2OCF2CF2SO2N3 [MONOMER (Az2)]

(6) The precursor FSO.sub.2CF.sub.2CF.sub.2OCF.sub.2CFCF.sub.2 was prepared according to methods described in the literature (WLASSICS, I., et al. Perfluoro Allyl Sulfate (FAFS): a Versatile Buildng Block For New Fluoroallylic Compounds. Molecules. 2011, vol.16, p. 6512_6540.).

(7) Synthetic procedure described above for comparative azide compound (1) was modified so as to ensure minimizing contact between the allylether and the NaF (which is a by product of the reaction) and which could catalyze decomposition of vinyl ether precursor to perfluoropropylene and FO.sub.2SCF.sub.2COF.

(8) In a glass cylindrical jacketed reactor, with three inlets, 15.15 mmoles=5.00 g of FSO.sub.2CF.sub.2CF.sub.2OCF.sub.2CFCF.sub.2 were introduced, in combination with 90 l of a phase transfer agent commercially available as Aliquat (CH.sub.3N[(CH.sub.2).sub.7CH.sub.3].sub.3.sup.+Cl.sup.), corresponding to 1% v/v. The solution so obtained was cooled at 15 C. using a cryostat connected to the reactor racket. Using an automatic dispensing syringe containing a solution made of 7.5 ml of distilled H.sub.2O and 2.395 g=36.85 mmoles of NaN.sub.3, said solution was added dropwise at a rate of 0.1 eq. NaN.sub.3/h; reactor temperature was kept at 15 C. during the whole addition time (about 24 hours). Temperature was then raised to 20 C. for further 8 hours. At the end of the reaction, the reaction mixture was composed of two phases. Upper phase, composed of H.sub.2O, NaF and residual NaN.sub.3 was discarded. Lower phase was recovered and centrifuged at 15 C. and 4000 rpm during 20 minutes so as to eliminate solid particulate residues. A colorless and clear oil was obtained having a characteristic acre smell.

(9) Yield (after purification and separation)=65% moles.

(10) Selectivity=55/45 NBA=.sup.a,bCF.sub.2=.sup.cCF.sup.dCF.sub.2O.sup.eCF.sub.2.sup.fCF.sub.2SO.sub.2N.sub.3; BN.sub.3.sup.gCF.sub.2.sup.hCFH.sup.iCF.sub.2O.sup.lCF.sub.2.sup.mCF.sub.2SO.sub.2N.sub.3

(11) .sup.19F-NMR; (CDCl.sub.3; ppm): a:89; b: 102; c: 185.4; d: 72.3; e: 79.3 (AB); f: 109.3; g: 78->82 (m); h: 206 (J.sup.1.sub.H,F=48 hz); i: 74.5;---->83; I:79.3 (AB); m: 109.3.

(12) FT-IR (KBr; cm.sup.1): 1792 (CF.sub.2CFCF.sub.2 st.); 2163 (N.sub.3 st.); 1464+1384 (SO.sub.2N.sub.3 st.); 1200-1100 (CF st.).

PREPARATIVE EXAMPLE 3SYNTHESIS OF CH2CH(CF2)6CH2CH2N3 [MONOMER (Az3)]

(13) A di-iodinated precursor was manufactured by tetrafluoroethylene (C.sub.2F.sub.4) telomerization with iodine (I.sub.2) in the presence of diterbutylperoxide (DTBP), and isolating a I(CF.sub.2).sub.6I fraction.

(14) Ethylene addition was then performer with ethylene at a temperature of 180 C. and under a C.sub.2H.sub.4 pressure of 50 atm, so as to obtain corresponding addition product of formula ICH.sub.2CH.sub.2(CF.sub.2).sub.6CH.sub.2CH.sub.2I with a selectivity of more than 98,5%. Less than 1.5% moles of the telomer gave rise to the oligomer I(C.sub.2H.sub.4).sub.2(CF.sub.2).sub.6CH.sub.2CH.sub.2I.

(15) The compound of formula ICH.sub.2CH.sub.2(CF.sub.2).sub.6CH.sub.2CH.sub.2I was submitted to partial dehydro-iodination with 0.5 molar equivalent of KOH in C.sub.2H.sub.5OH at 75 C.; distillation of the raw reaction mixture enabled isolating ICH.sub.2CH.sub.2(CF.sub.2).sub.6CHCH.sub.2 with a purity of about 95% by moles.

(16) In a glass reactor equipped with a condenser cooled with water, magnetic stirring, thermometer and dropping funnel, were introduced 0.876 g (13.48 mmoles) of NaN.sub.3, solubilized in 11 ml of distilled H.sub.2O, and 341 l of phase transfer catalyst Aliquat (1% on total volume), which remained as separated phase.

(17) So formed dishomogeneous mixture was cooled at 3 C. using an ice bath. An homogeneous solution containing 5.0 g (10.37 mmoles) of ICH.sub.2CH.sub.2 (CF.sub.2).sub.6CHCH.sub.2 in 20 ml of CH.sub.2Cl.sub.2 was then added dropwise during 15 minutes. After 1 hour stirring (750 rpm) at 3 C., the reaction mixture was let to slowly revert to 25 C. during 60 minutes, and maintained at this temperature for additional 23 hours. Lower phase was then separated, and gel chromatography separation conditions were tested by TLC (developed in I.sub.2 chamber), yielding two dots, a first dot (R.sub.f=0) which was found to be the residual Aliquat, showing at .sup.1H-NMR analysis typical aliphatic peaks between 1.5 and 0.5 ppm; and a second dot (R.sub.f=0.42), which was found to be the target azide compound.

(18) The CH.sub.2Cl.sub.2 solution was then chromatographied through a silica column having h=15 cm and diameter=1.5 cm, using n-hexane (4 times volume of the column) as eluent. The combined organic eluated fractions were dried over MgSO4 and then filtered. After removal of the solvent at 30 C. under vacuum (from 760 to 25 mm Hg), a pale yellow oil having an acre smell was obtained.

(19) Isolated Yield=94.7% moles

(20) Selectivity=100%

(21) Density=1.730 g/ml.

(22) .sup.aCH.sub.2=.sup.bCH.sup.cCF.sub.2.sup.dCF.sub.2.sup.eCF.sub.2.sup.fCF.sub.2.sup.gCF.sub.2.sup.hCF.sub.2.sup.iCH.sub.2.sup.lCH.sub.2N.sub.3

(23) .sup.19F-NMR; (CDCl.sub.3; ppm): c:112.2; d: 118.8; e: 120.6; f: 121; g: 119.4; g: 112.2.

(24) .sup.1H-NMR (CDCl.sub.3; ppm): a: 6.0 (m); b: 5.8 (m).

(25) FT-IR (KBr; cm.sup.1): 2955 (CH.sub.2st); 2107 (N.sub.3 st.); 1654 (CH.sub.2CH st.); 1255 (CN st.); 1200-1140 (CF st.).

PREPARATIVE EXAMPLE 4SYNTHESIS OF N3SO2CF2CF2OC4F8OCF2CF2SO2N3[AZIDE AGENT (Cz1)]

(26) A disulfonylfluoride precursor was obtained by radical dimerization of CF.sub.2CFOCF.sub.2CF.sub.2SO.sub.2F (VEFS) in the presence of F.sub.2; molar composition as determined by .sup.19F-NMR of the raw precursor was found to correspond to a 70/30 mol/mol mixture of FSO.sub.2CF.sub.2CF.sub.2O(CF.sub.2).sub.4OCF.sub.2CF.sub.2SO.sub.2F over sum of (FSO.sub.2CF.sub.2CF.sub.2OCF(CF.sub.3)).sub.2FSO.sub.2CF.sub.2CF.sub.2OCF(CF.sub.3)CF.sub.2CF.sub.2OCF.sub.2CF.sub.2SO.sub.2F.

(27) In a glass round-bottomed flask, equipped with condenser cooled with water, magnetic stirring, thermometer and dropping funnel, 1.27 g (19.56 mmoles) of NaN.sub.3 and 14 ml of CH.sub.3OH were introduced. The opalescent mixture was then cooled at 3 C. with an ice bath; once cooled down at this set-point temperature, 5.00 g (8.36 mmoles=16.7 meq) of the above mentioned di-sulfonylfluoride isomers was added dropwise during about 17 minutes.

(28) During this addition, exothermic reaction caused a temperature increase of about 10 C., with temperature rising from 3 C. to about 13 C. Once the temperature reverted back to 3 C., the mixture was maintained under stirring (750 rpm) at such temperature for 60 minutes. Then, the temperature was warmed to room temperature (20 C.) during 60 minutes and further maintained under stirring at such temperature for additional 15 hours. At the end of the reaction, the mixture was washed with 75 ml of distilled water. A colorless oil, slightly opalescent, immediately precipitated, which was filtered through a PTFE membrane (0.2 m) to provide a perfectly clear and colorless oil.

(29) Conversion of SO.sub.2F groups: 99% moles

(30) Yield=60% moli

(31) Selectivity=100%

(32) Isomers molar ratio (linear/branched): 75.5/24.5

(33) Density=1.68 g/ml

(34) N.sub.3SO.sub.2.sup.aCF.sub.2.sup.bCF.sub.2O.sup.bCF.sub.2.sup.cCF.sub.2.sup.cCF.sub.2.sup.bCF.sub.2O.sup.bCF.sub.2.sup.aCF.sub.2SO.sub.2N.sub.3; N.sub.3SO.sub.2.sup.aCF.sub.2.sup.bCF.sub.2O.sup.dCF(.sup.eCF.sub.3).sup.cCF.sub.2.sup.bCF.sub.2O.sup.bCF.sub.2.sup.aCF.sub.2SO.sub.2N.sub.3;

(35) .sup.19F-NMR; (CDCl.sub.3; ppm): a: 111 (m) e 114 (m); b: 75 (m); c: 121 (m); d: 139 (m); e: 80 (m).

(36) FT-IR (KBr; cm.sup.1): 2283 e 2155 (N.sub.3 st.); 1460 e 1422 (SO.sub.2N.sub.3 st.); 1200-1140 (CF st.).

PREPARATIVE EXAMPLE 5SYNTHESIS OF N3CH2CH2(CF2)6CH2CH2N3[AZIDE AGENT (Cz2)]

(37) A di-iodinated precursor was manufactured by tetrafluoroethylene (C.sub.2F.sub.4) telomerization with iodine (I.sub.2) in the presence of diterbutylperoxide (DTBP), and isolating a I(CF.sub.2).sub.6I fraction.

(38) Ethylene addition was then performed with ethylene at a temperature of 180 C. and under a C.sub.2H.sub.4 pressure of 50 atm, so as to obtain corresponding addition product of formula ICH.sub.2CH.sub.2(CF.sub.2).sub.6CH.sub.2CH.sub.2I with a selectivity of more than 98.5%. Less than 1.5% moles of the telomer gave rise to the oligomer I(C.sub.2H.sub.4).sub.2(CF.sub.2).sub.6CH.sub.2CH.sub.2I.

(39) A procedure similar to techniques described in the literature (KARIMI ZARCHI, M. A., et al. A mild and clean synthesis of alkyl azides from alkyl halides mediated by poly(4-vinylpyridine)-supported sodium azide under non-aqueous conditions. J. Appl. Polym. Sci. 2011, vol. 121, p. 1916-1920.; ITO, M., et al. A simple and conveniente synthesis of alkyl azides under mild conditions. Synthesis. 1995, no. 4, p. 376-378.) was followed for introducing N.sub.3 group; the procedure followed is detailed herein below. In a glass round-bottomed flask, equipped with condenser cooled with water, magnetic stirring, thermometer and dropping funnel, 2.13 g (32.8 mmoles) of NaN.sub.3 homogeneously dissolved in 11 ml of distilled water were introduced. Then 310 l of a phase transfer catalyst commercially available as Aliquat (CH.sub.3N[(CH.sub.2).sub.7CH.sub.3].sub.3.sup.+Cl.sup.), were also introduced, and immediately separated from the aqueous phase. The reaction mixture was then cooled down under stirring (1000 rpm) at 3 C. with an ice bath, and 5.00 g (8.2 mmoles=16.4 meq) of ICH.sub.2CH.sub.2(CF.sub.2).sub.6CH.sub.2CH.sub.2I diluted in 20 ml di CH.sub.2Cl.sub.2 were added dropwise during about 15 minutes.

(40) After 60 minutes stirring at 3 C., the temperature was let to revert to room temperature (24 C.) during 90 minutes. Mixture was then maintained at 24 C. and 1000 rpm during 15 hours. A colour change was noticed during the course of the reaction; at the end of the addition, the lower organic phase (comprising CH.sub.2Cl.sub.2) was reddish, because of the presence of CH.sub.2 I moieties, while, as the reaction proceeded, said phase discoloured progressively and became pale yellowish, due to the formation of CH.sub.2N.sub.3, which is a colorless chromophore. In parallel, upper aqueous phase progressively was found to change from colorless (NaN.sub.3) to yellow/orange (NaI). The lower organic phase was recovered and dried on MgSO.sub.4; after filtration, CH.sub.2Cl.sub.2 was then evaporated. A waxy white solid was thus obtained, containing residual traces of Aliquat. The solid was thus re-dissolved in CH.sub.2Cl.sub.2 and was eluted on a SiO.sub.2 column with 4 volumes of CH.sub.2Cl.sub.2, while Aliquat remained entrapped in the column.

(41) Conversion=95.2% moles

(42) Yield=95% moles

(43) N.sub.3 functionality=1.905 (the presence of 4.8% moles of end groups of formula CF.sub.2I).

(44) N.sub.3.sup.aCH.sub.2.sup.bCH.sub.2.sup.cCF.sub.2.sup.dCF.sub.2.sup.eCF.sub.2.sup.eCF.sub.2.sup.dCF.sub.2.sup.cCF.sub.2.sup.bCH.sub.2.sup.aCH.sub.2N.sub.3

(45) .sup.19F-NMR; (CDCl.sub.3; ppm): c:115; d: 122; e: 124;

(46) .sup.1HNMR (CDCl.sub.3; ppm): a: 2.95; b: 3.4.

(47) FT-IR (KBr; cm.sup.1): 2955 (CH.sub.2 st); 2100 (N.sub.3 st.); 1263 (CN st.); 1200-1140 (CF st.).

PREPARATIVE EXAMPLE 6SYNTHESIS OF VDF/TrFE OLIGOMER TERMINATED WITH N3 GROUPS [AZIDE AGENT (Cz3)]

(48) A very low molecular weight VDF/TrFE oligomer was manufactured by emulsion polymerization using C.sub.4F.sub.8I.sub.2 as chain transfer agent. Quantitative .sup.19F-NMR analyses in DMSO d.sub.6 gave following characterization for the oligomer: Mw=20659 g/moles; VDF=86% moles; TrFE=13.7% moles; CF.sub.2CH.sub.2I=0.2% moles; CF.sub.2CH.sub.2OH=0.43% moles. End groups of formula CF.sub.2CH.sub.2I, of high stability, were obtained during polymerization by scission of end groups of formula CH.sub.2CF.sub.2I, obtained from chain transfer agent, which have very poor stability. These are the groups which were to be reactive sites for nucleophilic substitution with NaN.sub.3. End groups of formula CF.sub.2CH.sub.2OH were obtained from hydrolysis of end groups of formula CF.sub.2CH.sub.2I still occurred during polymerization in aqueous phase in the presence of radical initiator APS.

(49) In a glass round-bottomed flask, equipped with condenser cooled with water, magnetic stirring, thermometer and dropping funnel, 9.24 g (0.894 moles, in view of Mw=20659) of the above mentioned oligomer in powder form dissolved in 70 ml of DMSO, were introduced, thus providing a 6.37 mM polymer solution and a 12.8 M solution of reactive groups of formula CF.sub.2CH.sub.2I.

(50) A large excess of NaN.sub.3 (90 mg=1.38 mmol=1543 meq) was then added at 20 C. during 10 minutes and the solution was heated at 45 C. The solution became dark red, because of the formation of NaI within about 2 hours. The reaction was pursued for additional 3 hours, until achieving a total reaction time of 5 hours.

(51) At the end of the reaction, the oligomer comprising azidic group was precipitated by pouring the solution in 500 ml of distilled water. The oligomer was recovered as a fibrous and rubbery solid; it was rinsed on a cellulose filter over a Bchner funnel with about 2 liters of distilled water and then with 2 portions (300 ml each) of CH.sub.2Cl.sub.2 so as to extract residual DMSO adsorbed into the oligomer or swelling the same.

(52) The oligomer was finally dried in an oven at 50 C. under reduced pressure (10 mm Hg). Analyses yielded following results:

(53) Mw azidic oligomer=20650 g/mol; Yield=64% wt vs. initial weight of polymer; Acetone solubility: complete at 20 C.; FT-IR (DMSO; cm.sup.1):2115 (N.sub.3 st.).

Polymerization RunsPreparation of VDF-TrFE Polymers

POLYMERIZATION EXAMPLE 7POLYMERIZATION OF VDF/TrFE IN THE PRESENCE OF MONOMER (Az2) (5% MOLES) [POLYMER (F1)]

(54) In an AISI 316 steel up and over autoclave 46.2 ml of demineralized water were introduced. At room temperature, 3.38 g of sodium based micro emulsion obtained as described in Example 1 of U.S. Pat. No. 7,122,608 (SOLVAY SOLEXIS S. P. A.) Oct. 17, 2006, 0.55 g of monomer (Az2) of formula CF.sub.2CFCF.sub.2OCF.sub.2CF.sub.2SO.sub.2N.sub.3 were then added, followed by 2.36 absolute bar of TrFE, 9.07 absolute bar of VDF which were metered from cylinders. Then, using a pump, 270 ml of a solution of ammonium peroxidisulphate (APS) diluted in water with a concentration of 0.1% in weight were fed to start polymerization. Then the temperature was brought to set-point temperature of 70 C., wherein pressure value in the autoclave was found to be 23.1 absolute bars.

(55) Keeping constant the reaction temperature, the pressure was let to fall down to 14.2 abs bar. Then the reactor was cooled at room temperature, the latex was recovered and freezed for 48 hours and once unfreezed the so-coagulated polymer was washed with demineralized water and dried at 80 C. for 48 hours. 6.2 grams of polymer were obtained, whose nominal composition was as follows: VDF: 71.5% moles; TrFE: 23.5% moles; monomer (Az2): 5% moles.

POLYMERIZATION EXAMPLE 8POLYMERIZATION OF VDF/TrFE IN THE PRESENCE OF MONOMER (Az1) (10% Moles) [POLYMER (F2)]

(56) Same procedure as detailed in Polymerization Example 3 was followed except by using 1.1 g of monomer (Az1) of formula CF.sub.2CFOCF.sub.2CF.sub.2SO.sub.2N.sub.3 instead of monomer (Az2). Final pressure was about zero. 9.1 grams of polymer were obtained, whose nominal composition was as follows: VDF: 67.5% moles; TrFE: 21.5% moles; monomer (Az1): 10% moles.

POLYMERIZATION EXAMPLE 9POLYMERIZATION OF VDF/TrFE IN THE PRESENCE OF MONOMER (Az1) (5% MOLES) [POLYMER (F3)]

(57) Similar procedure as in Polymerization Example 3 was followed, except by using 0.55 g of monomer (Az1) of formula CF.sub.2CFOCF.sub.2CF.sub.2SO.sub.2N.sub.3 instead of monomer (Az2), and setting set-point polymerization temperature at 105 C., and continuing polymerization 'till pressure fell to 4.2 abs bar. 9.6 g of polymer were obtained, whose nominal composition was as follows: VDF: 71.5% moles; TrFE: 23.5% moles; monomer (Az1): 5% moles.

POLYMERIZATION EXAMPLE 10POLYMERIZATION OF VDF/TrFE IN THE PRESENCE OF MONOMER (Az3) (10% MOLES) [POLYMER (F4)]

(58) Same procedure as detailed in Polymerization Example 6 was followed except by using 1.1 g of monomer (Az3) of formula CH.sub.2CH(CF.sub.2).sub.6CH.sub.2CH.sub.2N.sub.3 instead of monomer (Az1) and 2 ml of an organic initiator, namely ditert butyl peroxide (DTBP), instead of the APS aqueous solution. With a set-point temperature of 105 C., final pressure was about 3.4 abs bar. 8.3 grams of polymer were obtained, whose nominal composition was as follows: VDF: 67.5% moles; TrFE: 21.5% moles; monomer (Az3): 10% moles.

(59) Characterization of the Polymers (F-1) to (F-4)

(60) The polymers obtained from Examples 4 to 7 were submitted to DSC analyses according to ASTM D 3418 and to gel permeation chromatography for molecular weight determination. Results are detailed in table herein below.

(61) TABLE-US-00001 TABLE 1 T.sub.g T.sub.xx T.sub.Curie2 T.sub.m2 GPC Polymer ( C.) ( C.) ( C.) ( C.) Mp* (F1) - Ex. 7 6.0 66.2 93.5 110 59000 (F2) - Ex. 8 23.3 60.6 91.8 91.8 28000 (F3) - Ex. 9 24.2 70.4 108.6 108.6 34000 (F4) - Ex. 10 19.7 97.2 120 129 43000 *Mp is the sequence molecular weight, as determined by GPC
Manufacture of Films and Crosslinking Thereof Using Polymers (F1), (F2) and (F4) of Examples 7, 8, and 10
A) Spin Coating

(62) Specimens of the polymers (F1), (F2) and (F4) obtained as detailed in Examples 7, 8 and 10, were dissolved in cyclopentanone in admixture with azide agents (Cz1), (Cz2) and (Cz3) so as to provide, after 3 hours stirring at a temperature of 40 C., clear solutions having a concentration of 8% in weight.

(63) Said solutions were loaded into a Laurell WS-650 LITE SERIES spin coater and spin-coated at a speed of 2000 rpm onto glass substrates in order to obtain very thin polymeric layers on glass as substrates. The polymer layers so obtained were dried at 85 C. for 2 minutes. For each example, two polymeric films on glass were prepared.

(64) All the samples obtained by the spin coating process, were all homogeneous, completely transparent and in the thickness range of 150-180 nm, as measured with Filmetrics F20 unit.

(65) Transparency of the films well demonstrate complete miscibility of the azide agents (Cz1), (Cz2) and (Cz3) in the host polymer matrices, which is a particularly advantageous behaviour of the fluorinated crosslinking agents used in the composition of this invention.

(66) B) Crosslinking:

(67) The polymer films obtained as above detailed were submitted to cross-linking procedures, either via thermal treatment or by UV treatment.

(68) Thermal treatment consisted in maintaining samples of films in a ventilated oven at a temperature of about 120 to 135 C.

(69) For UV treatment, samples of films were passed through a semi automatic cross linker device, based on a UV lamp and equipped with a moving belt carrying the samples. Procedure was repeated so as to achieve the below detailed residence time under UV exposure.

(70) In order to verify if the samples were crosslinked, pure acetone was poured on the films after treatment above: insolubility in such conditions was considered to be a clear evidence of suitable crosslinking. Results are summarized in the following tables.

(71) TABLE-US-00002 TABLE 2 Polymer (F1) From Ex. 7 Curing agent (type) (Cz1) (Cz2) (Cz3) Polymer/curing 90/10 wt/wt 90/10 wt/wt 90/10 wt/wt agent Film thickness (m) 173 152 165 Solubility in acetone soluble soluble soluble before any treatment Thermal treatment: 130 C. for 20 minutes Solubility in acetone insoluble insoluble insoluble UV treatment: 4 seconds Solubility in acetone insoluble insoluble insoluble

(72) TABLE-US-00003 TABLE 3 Polymer (F2) From Ex. 8 Curing agent (type) (Cz1) (Cz2) (Cz3) Polymer/curing 90/10 wt/wt 90/10 wt/wt 90/10 wt/wt agent Film thickness (m) 175 175 175 Solubility in acetone soluble soluble soluble before any treatment Thermal treatment: 130 C. for 20 minutes Solubility in acetone insoluble insoluble insoluble UV treatment: 4 seconds Solubility in acetone insoluble insoluble insoluble

(73) TABLE-US-00004 TABLE 4 Polymer (F3) From Ex. 10 Curing agent (type) (Cz1) (Cz2) (Cz3) Polymer/curing 90/10 wt/wt 90/10 wt/wt 90/10 wt/wt agent Film thickness (m) 175 175 175 Solubility in acetone soluble soluble soluble before any treatment Thermal treatment: 130 C. for 20 minutes Solubility in acetone insoluble insoluble insoluble UV treatment: 4 seconds Solubility in acetone insoluble insoluble insoluble

(74) Table herein above well demonstrate that curable composition according to the invention are effectively crosslinked under effect either of thermal treatment or of UV treatment. Furthermore, visual inspection of the cured films showed no inhomogeneity nor white spots or other defects which might be originated by uneven crosslinking behaviour and/or uneven crosslinking density distribution.