Crosslinkable fluoropolymers

Abstract

The present invention pertains to a process for the manufacture of a crosslinkable fluoropolymer, to said crosslinkable fluoropolymer and the crosslinked fluoropolymer obtainable therefrom, to a film comprising said crosslinkable fluoropolymer or said crosslinked fluoropolymer and to uses of said crosslinked fluoropolymer film in various applications.

Claims

1. A crosslinkable fluoropolymer [polymer (FC)] comprising: first recurring units derived from vinylidene fluoride (VDF), from 10% to 50% by moles, with respect to the total moles of recurring units of said polymer (FC), of second recurring units derived from trifluoroethylene (TrFE), and from 0.01% to 10% by moles, with respect to the total moles of recurring units of said polymer (FC), of third recurring units derived from at least one functional hydrogenated monomer (HF), said third recurring units comprising a pendant side chain comprising an end group (E) of any of formulae (III-A) to (V-A):
OC(O)C(R.sub.3)CR.sub.1R.sub.2(III-A)
OC(O)NHC(O)C(R.sub.3)CR.sub.1R.sub.2(IV-A)
OC(O)ZC(R.sub.3)CR.sub.1R.sub.2(V-A) wherein each of R.sub.1, R.sub.2 and R.sub.3, equal to or different from each other, is independently a hydrogen atom or a C.sub.1-C.sub.3 hydrocarbon group, and Z is a bonding group of any of formulae (j) and (jj):
NHXOC(O)(j), and
NHXNHC(O)OXOC(O)(jj) wherein X and X, equal to or different from each other, are independently hydrocarbon groups selected from the group consisting of C.sub.1-C.sub.20 aliphatic groups, C.sub.5-C.sub.40 cycloaliphatic groups and C.sub.6-C.sub.50 aromatic, alkylaromatic and heteroaromatic groups.

2. The crosslinkable fluoropolymer [polymer (FC)] according to claim 1, wherein the pendent side chain of at least one monomer (H.sub.F) is a pendant side chain of any of formulae (VI) to (X):
C(O)OY-E(VI)
C(O)NHY-E(VII)
[C(O)].sub.nOROY-E(VIII)
[C(O)].sub.nOROC(O)NHY-E(IX)
[C(O)].sub.nOROC(O)OY-E(X) wherein Y is a C.sub.1-C.sub.10 hydrocarbon bonding group, optionally comprising at least one functional group, R is a C.sub.1-C.sub.5 hydrocarbon group, optionally comprising at least one hydroxyl group, n is 0 or 1, and E is an end group of any of formulae (III-A) to (V-A).

3. A process for the manufacture of the crosslinkable fluoropolymer [polymer (FC)] according to claim 1, said process comprising reacting: (A) at least one fluoropolymer [polymer (F)] comprising: first recurring units derived from vinylidene fluoride (VDF), from 10% to 50% by moles, with respect to the total moles of recurring units of said polymer (F), of second recurring units derived from trifluoroethylene (TrFE), and from 0.01% to 10% by moles, with respect to the total moles of recurring units of said polymer (F), of third recurring units derived from at least one functional hydrogenated monomer (H.sub.F), said third recurring units comprising a pendant side chain comprising an end group of any of formulae (I) and (II):
C(O)OR.sub.x(I)
OR.sub.x(II) wherein R.sub.x is a hydrogen atom or a C.sub.1-C.sub.5 hydrocarbon moiety comprising at least one hydroxyl group, and (B) at least one (meth)acrylic compound (MA) of any of formulae (III) to (V):
R.sub.1R.sub.2CC(R.sub.3)C(O)O-T(III)
R.sub.1R.sub.2CC(R.sub.3)C(O)NHC(O)O-T(IV)
R.sub.1R.sub.2CC(R.sub.3)ZC(O)O-T(V) wherein each of R.sub.1, R.sub.2 and R.sub.3, equal to or different from each other, is independently a hydrogen atom or a C.sub.1-C.sub.3 hydrocarbon group, T is a C.sub.1-C.sub.10 hydrocarbon end group comprising at least one functional group, and Z is a bonding group of any of formulae (j) and (jj):
NHXOC(O)(j), and
NHXNHC(O)OXOC(O)(jj) wherein X and X, equal to or different from each other, are independently hydrocarbon groups selected from the group consisting of C.sub.1-C.sub.20 aliphatic groups, C.sub.5-C.sub.40 cycloaliphatic groups and C.sub.6-C.sub.50 aromatic, alkylaromatic and heteroaromatic groups.

4. The process according to claim 3, wherein monomer (H.sub.F) is selected from the group consisting of (meth)acrylic monomers of formula (I-A) and vinyl ether monomers of formula (II-A): ##STR00007## wherein each of R.sub.4, R.sub.5 and R.sub.6, equal to or different from each other, is independently a hydrogen atom or a C.sub.1-C.sub.3 hydrocarbon group, R.sub.X is a hydrogen atom or a C.sub.1-C.sub.5 hydrocarbon moiety comprising at least one hydroxyl group, and R.sub.x is a C.sub.1-C.sub.5 hydrocarbon moiety comprising at least one hydroxyl group.

5. The process according to claim 3, wherein T is a C1-C10 hydrocarbon end group comprising at least one functional group selected from the group consisting of hydroxyl groups, cyclic alkyl ether groups, isocyanate groups, carboxylic acid groups, amine groups, aryl ether groups and alkoxy silane groups.

6. The process according to claim 3, said process being carried out in a liquid medium comprising at least one organic solvent (S).

7. The process according to claim 3, wherein monomer (H.sub.F) comprises an end group of formula (I), wherein R.sub.x is a hydrogen atom, and compound (MA) has any of formulae (III) to (V), wherein T is a C.sub.1-C.sub.10 hydrocarbon end group comprising at least one hydroxyl group, said process being carried out in the presence of at least one activating agent selected from the group consisting of N,N-dicyclohexylcarbodiimide, thionyl chloride, oxalyl dichloride and inorganic acids.

8. The process according to claim 3, wherein monomer (H.sub.F) comprises an end group of formula (I), wherein R.sub.x is a hydrogen atom, and compound (MA) has any of formulae (III) to (V), wherein T is a C.sub.1-C.sub.10 hydrocarbon end group comprising at least one cyclic alkyl ether group, said process being carried out in the presence of at least one activating agent selected from the group consisting of alkyl ammonium halides.

9. The process according to claim 3, wherein monomer (H.sub.F) comprises an end group of formula (I), wherein R.sub.x is a hydrogen atom, and compound (MA) has any of formulae (III) to (V), wherein T is a C.sub.1-C.sub.10 hydrocarbon end group comprising at least one amine group, said process being carried out in the presence of at least one activating agent selected from the group consisting of thionyl chloride and oxalyl dichloride.

10. A crosslinkable composition (CC) comprising: at least one crosslinkable fluoropolymer [polymer (FC)] according to claim 1, and at least one additive selected from the group consisting of crosslinking co-agents and crosslinking initiators.

11. The crosslinkable composition (CC) according to claim 10, wherein the crosslinking co-agent is a poly(meth)acrylic compound (PMA) comprising at least two end groups of formula (XI):
OC(O)C(R.sub.7)CR.sub.8R.sub.9(XI) wherein each of R.sub.7, R.sub.8 and R.sub.9, equal to or different from each other, is independently a hydrogen atom or a C.sub.1-C.sub.3 hydrocarbon groups.

12. The crosslinkable composition (CC) according to claim 10, wherein the crosslinking initiator is a photoinitiator (PI) or a thermal initiator (TI).

13. The crosslinkable composition (CC) according to claim 12, wherein the crosslinking initiator is a photoinitiator (PI) selected from the group consisting of alpha-hydroxyketones, phenylglyoxylates, benzyldimethyl ketals, alpha-aminoketones and bis acyl phosphines.

14. A crosslinkable fluoropolymer film [film (FC)] comprising at least one crosslinkable fluoropolymer [polymer (FC)] according to claim 1.

15. A process for the manufacture of a crosslinked fluoropolymer film [film (FCC)], said process comprising: (i) providing the crosslinkable fluoropolymer film [film (FC)] according to claim 14, and (ii) crosslinking the film (FC) provided in step (i).

16. The process according to claim 15, wherein under step (ii) the crosslinkable fluoropolymer film [film (FC)] provided in step (i) is crosslinked either by UV treatment under UV radiation or by thermal treatment.

17. A crosslinked fluoropolymer film [film (FCC)] obtainable by the process according to claim 15, said crosslinked fluoropolymer film [film (FCC)] comprising at least one crosslinked fluoropolymer [polymer (FCC)].

18. An electrical or electronic device comprising at least one crosslinked fluoropolymer film [film (FCC)] according to claim 17.

19. A crosslinkable fluoropolymer film [film (FC)] comprising at least one crosslinkable composition (CC) according to claim 10.

20. A crosslinkable fluoropolymer film [film (FC)] consisting of at least one crosslinkable fluoropolymer [polymer (FC)] according to claim 1.

Description

PREPARATIVE EXAMPLE 1

Synthesis of a VDF-TrFE-CTFE-AA Polymer [Polymer (F-1)]

(1) In an AISI 316 steel vertical autoclave equipped with baffles and stirrer, working at 570 rpm, 3.5 It. of demineralized water was introduced. The temperature was then brought to reaction temperature of 120 C. When this temperature was reached, 32.5 g of a microemulsion prepared according to Example 1 of U.S. Pat. No. 7,122,608 (SOLVAY SOLEXIS S.P.A.) 17 Oct. 2006, 5 bar of vinilidene fluoride and 0.5 bar of chlorotrifluoroethylene were introduced. A gaseous mixture of VDF-TrFE-CTFE in a molar nominal ratio of 63/28/9 was fed until reaching a pressure of 30 bar.

(2) The composition of the gaseous mixture present in the autoclave head was analyzed by G.C. The gaseous phase was found to be formed of the following compounds in the following molar percentages: 74% VDF, 21% TrFE, 5% CTFE. Then, by a metering pump, 20 ml of di-tert butyl peroxide (DTBP), 2 ml of a 35% by volume aqueous solution of acrylic acid and 15 ml of a 2% by weight aqueous solution of ammonium peroxidisulphate (APS) were fed.

(3) The polymerization pressure was maintained constant by feeding the above mentioned monomeric mixture; when 3% of the mixture had been fed, the temperature was lowered to 105 C., 2 ml of the aqueous solution of acrylic acid and 15 ml of the APS solution were fed every 15 g of polymer synthesized. When 300 g of the mixture had been fed, the reaction temperature was kept constant and the pressure was let fall down up to 15 bar. The reactor was then cooled to room temperature, the latex was unloaded and coagulated by freezing for 48 hours. The polymer was finally washed with demineralized water and dried at 80 C. for 48 hours.

(4) Characterization of the obtained polymer:

(5) MW: 291000 Dalton

(6) Second melting temperature (T.sub.m2): 118.6 C.

(7) Curie temperature (T.sub.Curie): 20.9 C.

(8) The amount of acrylic acid in the final polymer was found to be 6.08% by moles.

PREPARATIVE EXAMPLE 2

Synthesis of a VDF-TrFE-HEA Polymer [Polymer (F-2)]

(9) In an AISI 316 steel vertical autoclave equipped with baffles and stirrer, working at 570 rpm, 3.5 It. of demineralized water was introduced. The temperature was then brought to reaction temperature of 120 C. When this temperature was reached, 32.5 g of a microemulsion prepared according to Example 1 of U.S. Pat. No. 7,122,608 (SOLVAY SOLEXIS S.P.A.) 17 Oct. 2006 and 7.3 bar of vinilidene fluoride was introduced. A gaseous mixture of VDF-TrFE in a molar nominal ratio of 75/25 was fed until reaching a pressure of 30 bar.

(10) The composition of the gaseous mixture present in the autoclave head was analyzed by G.C. The gaseous phase was found to be formed of the following compounds in the following molar percentages: 82% VDF, 18% TrFE. Then, by a metering pump, 25 ml of di-tert butyl peroxide (DTBP) and 15 ml of a 15% by volume aqueous solution of 2-hydroxy ethyl acrylate were fed.

(11) The polymerization pressure was maintained constant by feeding the above mentioned monomeric mixture; when 3% of the mixture had been fed, the temperature was lowered to 105 C. and 15 ml of the aqueous solution of 2-hydroxy ethyl acrylate was fed every 15 g of polymer synthesized. When 575 g of the mixture had been fed, the reaction temperature was kept constant and the pressure was let fall down up to 15 bar. The reactor was then cooled to room temperature, the latex was unloaded and coagulated by freezing for 48 hours. The polymer was finally washed with demineralized water and dried at 80 C. for 48 hours.

(12) Characterization of the obtained polymer:

(13) MW: 264000 Dalton

(14) Second melting temperature (T.sub.m2): 141.6 C.

(15) Curie temperature (T.sub.Curie): 113.4 C.

(16) The amount of 2-hydroxyl ethyl acrylate in the final polymer was found to be 1% by moles.

EXAMPLE 1

Manufacture of a Crosslinkable Fluoropolymer [Polymer (FC-1)]

(17) In a 250 ml 4-necked glass reaction flask, equipped with a magnetic stirrer, a condenser, a thermometer and a dripping funnel, 9.36 g (44.55 mmols) of N,N-dicyclohexylcarbodiimide (DCCD) and 5.74 g (44.55 mmols) of hydroxy propyl acrylate isomers were dissolved in 10 ml of ethyl acetate at 3 C. with vigorous stirring. Once a homogeneous mixture was obtained, a homogeneous mixture of 22.9 g (17.82 meq) of the polymer prepared according to Preparative Example 1, containing 6.08% by moles of acrylic acid (EW=1286 g/eq), dissolved in 200 ml of ethyl acetate, was dripped thereto at 3 C. in 80 minutes. The glass reactor was shielded from direct light by covering it with an aluminium foil. Finally, a mixture of 0.43 g (3.56 mmols) of N,N-dimethylaminopyridine dissolved in 20 ml of ethyl acetate was dripped thereto in about 10 minutes at 3 C. The homogeneous mixture so obtained was kept at 3 C. with stirring for additional 60 minutes and then heated to 20 C. and kept under an inert atmosphere (N.sub.2) in the dark for 24 hours. The crude reaction mixture was then centrifuged at 3000 rpm for 30 minutes at 10 C. so as to let dicyclohexyl urea (DCU) precipitate. The crude acrylate-modified polymer was precipitated by pouring the crude mother liquor in H.sub.2O and filtering it using a Buchner funnel. The polymer was then washed with a total of 3 It. of distilled H.sub.2O. The wet modified polymer was then dissolved in 600 ml of ethyl acetate, dried over MgSO.sub.4 and filtered using a pressure filter. The anhydrous polymer was finally dried in a vacuum oven at 50 C. and 10 mm Hg of residual pressure.

(18) Conversion (of starting acrylate co-monomer): 13.8% by moles based on the recovered DCU.

(19) Amount of hydroxyl propyl acrylate incorporated: 2.04% by weight corresponding to 11 acrylate sites/100000 g/mole.

(20) EW: 8970 g/eq.

(21) Isolated yield: 100%.

EXAMPLE 2

Manufacture of a Crosslinkable Fluoropolymer [Polymer (FC-2)]

(22) In a 250 ml 4-necked glass reaction flask, equipped with a magnetic stirrer, a condenser, a thermometer and a dripping funnel, 15.0 g (11.66 meq) of the polymer prepared according to Preparative Example 1, containing 6.08% by moles of acrylic acid (EW=1286 g/eq), were completely dissolved in 130 ml of ethyl acetate. The reactor was placed in an inert atmosphere (N.sub.2) under vigorous stirring and heated to 55 C. The reactor was then cooled to 20 C. and a mixture of thionyl chloride (13.86 g, 116.6 mmols) and pyridine (0.92 g, 11.66 mmols) was dripped thereto in 60 minutes. The mixture was then heated to 75 C. with vigorous stirring for 3 hours and the volume of HCl gas evolved was measured. Once the conversion was completed, the crude mixture so obtained was filtered so as to remove side-products and then evaporated in a rotary evaporator at 70 C. and 100 mm Hg residual pressure. The evaporated solid was dissolved in 100 ml of ethyl acetate and submitted to three dissolution/evaporation cycles thus ensuring complete removal of excess thionyl chloride. The product was dissolved in 70 ml of ethyl acetate and heated to 75 C. with vigorous stirring under an inert (N.sub.2) atmosphere. A mixture of hydroxy propyl acrylate isomers (15.17 g, 116.6 mmol) dissolved in 30 ml of ethyl acetate was dripped thereto. Once HCl evolution stopped, the crude mixture was stirred at 75 C. for additional 5 hours. The crude polymer mixture was then evaporated at 70 C. and 18 mm Hg of residual pressure. The solid polymer obtained was finally washed with ethyl acetate and CH.sub.2Cl.sub.2 and dried in a vacuum oven at 65 C. for 4 hrs.

(23) Conversion (of starting acrylate co-monomer): 11% by moles.

(24) Isolated yield: 83.6%

(25) EW: 11217 g/eq=1.63% w/w of acrylate=9 acrylate sites/100000 g/mol.

EXAMPLE 3

Manufacture of a Crosslinkable Fluoropolymer [Polymer (FC-3)]

(26) The polymer (FC-3) was manufactured by reacting the polymer prepared according to Preparative Example 1 with glycidyl methacrylate at 85-95 C. in dimethylacetamide/acetonitrile solvent mixture in the presence of tetrabutyl ammonium bromide.

(27) Conversion of COOH groups: 10% by moles corresponding to 8 acrylate sites/100000 g/mole.

(28) Isolated yield: 35% by moles.

EXAMPLE 4

Manufacture of a Crosslinkable Fluoropolymer [Polymer (FC-4)]

(29) The polymer (FC-4) was manufactured by reacting the polymer prepared according to Preparative Example 1 with hydroxyl propyl acrylate isomers in the presence of a catalytic amount of H.sub.2SO.sub.4 at 85 C.-100 C. in dimethylacetamide/toluene solvent mixture.

(30) Conversion of COOH groups: 14.5% by moles corresponding to 12 acrylate sites/100000 g/mole.

(31) Isolated yield: 34%.

EXAMPLE 5

Manufacture of a Crosslinkable Fluoropolymer [Polymer (FC-5)]

(32) In a 2000 ml 4-necked glass reaction flask, equipped with a magnetic stirrer, a condenser, a thermometer and a dripping funnel, 220 g (171 meq) of the polymer prepared according to Preparative Example 1, containing 6.08% by moles of acrylic acid (EW=1286 g/eq), were completely dissolved in 1375 ml of ethyl acetate. The reactor was placed in an inert atmosphere (N.sub.2) under vigorous stirring and heated to 50 C. A mixture of oxalyl dichloride (109 g, 856 mmols) dissolved in 330 ml of ethyl acetate was dripped thereto in 60 minutes. The volume of HCl, CO and CO.sub.2 gases evolved was measured. Once gas evolution stopped, the mixture was heated to 50 C. with vigorous stirring for additional 3 hours. Once the conversion was completed, the crude mixture so obtained was filtered so as to remove side-products and then evaporated in a rotary evaporator at 55 C. and 180 mm Hg residual pressure. The evaporated solid was dissolved in 500 ml of ethyl acetate and submitted to two dissolution/evaporation cycles thus ensuring complete removal of excess oxalyl dichloride. The product was dissolved in 1000 ml of ethyl acetate and heated to 75 C. with vigorous stirring under an inert (N.sub.2) atmosphere. A mixture of hydroxy propyl acrylate isomers (128 g, 986 mmol) dissolved in 330 ml of ethyl acetate was dripped thereto in about 60 minutes. Once HCl evolution stopped, the crude mixture was stirred at 75 C. for additional 5 hours. The crude polymer mixture was then poured into a 10 It. flask containing 5 It. of distilled H.sub.2O and washed with additional 2 It. of distilled H.sub.2O. The solid polymer obtained was finally dried in a vacuum oven at 65 C. for 4 hrs.

(33) Conversion (of starting acrylate co-monomer): 27% by moles.

(34) Isolated yield: 84%

(35) EW: 4426 g/eq=4.16% w/w of acrylate=22 acrylate sites/100000 g/mol.

EXAMPLE 6

Manufacture of a Crosslinkable Fluoropolymer [Polymer (FC-6)]

(36) The polymer (FC-6) was manufactured by following the same procedure as detailed under Example 5 but using the polymer (F-3).

(37) Conversion (of starting acrylate co-monomer): 33% by moles.

(38) Isolated yield: 96%

(39) EW: 9097 g/eq=2.02% w/w of acrylate=11 acrylate sites/100000 g/mol.

COMPARATIVE EXAMPLE 1

(40) The polymer prepared according to Preparative Example 2, containing 1% by moles of 2-hydroxy ethyl acrylate (EW=7495 g/eq) (1 g, 0.133 meq) was dissolved in 20 ml of ethyl acetate at 20 C. The mixture was placed in a Petri dish to which 50 ml of a 10% v/v solution of methylene-4-4biscyclohexylisocyanate (0.02 mmol, 0.04 meq NCO) and 10 ml of a 2% solution of di-tert-butyl tin bislaurate as catalyst were added. The mixture so obtained was heated in an oven at 55 C. for 3 hours at atmospheric pressure. Following the thermal reaction, the solvent was evaporated and a film made from a crosslinked polymer with covalent urethane bonds was recovered from the Petri dish by adding 10 ml of distilled H.sub.2O. The wet film was dried in a vacuum oven at 50 C. and 10 mm Hg residual pressure. The film thereby provided was not soluble in ethyl acetate and other solvents such as acetone in which the polymers prepared according to Preparative Example 1 and Preparative Example 2 were soluble, thus confirming that the polymer forming the film is suitably crosslinked.

(41) A) Manufacture of films and crosslinking thereof using polymers (FC-1), (FC-2), (FC-3), (FC-4), (FC-5) and (FC-6) of Examples 1 to 6

(42) Specimens of any of the polymers obtained according to Examples 1 to 6 were dissolved in a mixture containing triethyl phosphate, propylene glycol monomethyl ether acetate and cyclopentanone so as to provide, after 3 hours of stirring at a temperature of 40 C., clear solutions having a concentration of 10% by weight for spin coating and of 0.9% by weight for ink jet printing.

(43) B) Spin Coating (SC)

(44) The solutions so obtained were loaded into a Laurell WS-650 LITE SERIES spin coater and spin-coated at a speed of 2000 rpm onto silicon wafer substrates in order to obtain very thin polymeric layers on silicon wafer as substrate. The polymer layers so obtained were dried at 85 C. for 20 minutes. For each example, two polymeric films on silicon wafer were prepared.

(45) The samples thereby obtained were all homogeneous and completely optically transparent. The thickness of the samples has been measured using a Filmetrics F20 unit.

(46) C) Ink Jet Printing (IJ)

(47) The solutions so obtained were loaded into a Dimatix DMP 2831 inkjet printer having a cartridge suitable for solvents and printed onto glass, silicon wafers and on ITO covered glass in order to obtain very thin polymeric layers on these substrates. The polymer layers so obtained were dried at 85 C. for 10 minutes. For each example, two polymeric films on glass were prepared.

(48) The samples thereby obtained were all homogeneous and completely optically transparent. The thickness of the samples has been measured using a Filmetrics F20 unit.

(49) D) Crosslinking:

(50) The polymer films obtained either by spin coating or by ink jet printing as detailed above were submitted to crosslinking either by UV treatment or by thermal treatment.

(51) Thermal treatment consisted in maintaining samples of films so obtained in a ventilated oven at a temperature of about 125 C. for 20 minutes. For UV treatment, samples of films obtained according to procedure A) but using a composition comprising any of the polymers obtained according to Examples 1 to 6 and at least one additive selected from the group consisting of crosslinking co-agents and crosslinking initiators were passed through a semi-automatic crosslinker device based on a UV lamp having a power of 13 mW/cm.sup.2 and equipped with a moving belt carrying the samples for 30 seconds equivalent to 3 steps of 10 seconds each. The crosslinking co-agent was selected from the group consisting of poly(meth)acrylic compounds (PMA).

(52) The crosslinking initiator was selected from the group consisting of photoinitiators (PI).

(53) E) Chemical Resistance Test:

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

(55) Results are summarized in Table 1 here below.

(56) TABLE-US-00001 TABLE 1 Solubility Film in acetone UV Thermal Film thickness before treatment treatment treatment Ex. 1 SC: 550 nm soluble partially partially IJ: 46 nm soluble soluble Ex. 1 + PMA SC: 630 nm soluble insoluble insoluble IJ: 49 nm Ex. 1 + PI SC: 600 nm soluble insoluble insoluble IJ: 47 nm Ex. 2 SC: 580 nm soluble partially partially IJ: 50 nm soluble soluble Ex. 2 + PMA SC: 600 nm soluble insoluble insoluble IJ: 53 nm Ex. 2 + PI SC: 590 nm soluble insoluble insoluble IJ: 52 nm Ex. 3 SC: 480 nm soluble partially partially IJ: 49 nm soluble soluble Ex. 3 + PMA SC: 500 nm soluble insoluble insoluble IJ: 51 nm Ex. 3 + PI SC: 530 nm soluble insoluble insoluble IJ: 50 nm Ex. 4 SC: 540 nm soluble partially partially IJ: 56 nm soluble soluble Ex. 4 + PMA SC: 590 nm soluble insoluble insoluble IJ: 59 nm Ex. 4 + PI SC: 610 nm soluble insoluble insoluble IJ: 58 nm Ex. 5 SC: 690 nm soluble partially partially IJ: 61 nm soluble soluble Ex. 5 + PMA SC: 640 nm soluble insoluble insoluble IJ: 57 nm Ex. 5 + PI SC: 660 nm soluble insoluble insoluble IJ: 58 nm Ex. 6 SC: 670 nm soluble partially partially IJ: 58 nm soluble soluble Ex. 6 + PMA SC: 620 nm soluble insoluble insoluble IJ: 57 nm Ex. 6 + PI SC: 630 nm soluble insoluble insoluble IJ: 57 nm Polymer (F-1) SC: 520 nm soluble soluble soluble IJ: 49 nm Polymer (F-2) SC: 540 nm soluble soluble soluble IJ: 45 nm Polymer (F-3) SC: 730 nm soluble soluble soluble IJ: 62 nm

(57) Results in Table 1 here above well demonstrate that polymers (FC) according to the invention such as those obtained according to Examples 1 to 6 are effective in crosslinking either by UV treatment or by thermal treatment to the same extent as crosslinked polymers obtained according to Comparative Example 1. On the contrary, the polymer (F-1), the polymer (F-2) and the polymer (F-3), said polymers being free from (meth)acrylic end groups, do not undergo crosslinking.