WO2018011378A1 - Method for the synthesis of a polyolefin by means of romp in the presence of a ruthenium-based catalyst - Google Patents

Abstract

The present invention relates to a method for the synthesis of a polyolefin by means of a photoinitiated ROMP reaction involving a cyclic olefin in the presence of a ruthenium-based catalyst of formula (I), in which the catalyst is generated in situ under UV radiation from an inactive ruthenium complex of formula [RuCl₂(L)]₂ and an imidazoli(ni)um salt of formula (III).

Description

 Process for synthesizing a polyolefin with ROMP in the presence of a ruthenium catalyst

The present invention relates to the synthesis of polyolefins by ring opening metathesis using a ruthenium-based catalyst. More particularly, it relates to a new process for the synthesis of polyolefins in which the ruthenium catalyst is generated in situ from an inactive ruthenium complex such as [RuCl 2 (/ -cymene)] and a salt. photosensitive imidazoli (ni) um.

 Polyolefins obtained from cycloolefins, such as norbornene and its derivatives, dicyclopentadiene or cyclooctene, find many applications as structural materials for the exterior parts of heavy vehicles, for example construction machines, or as technical materials in sports products or products of everyday life (eg household appliances) [1].

 In general, polyolefins are obtained by ring opening metathesis polymerization (known by the name "ROMP" for "Ring-Opening Metathesis Polymerization" in English) using ruthenium-based catalysts (Ru). . Ruthenium catalysts, commonly used in the metathesis of olefins, are so-called "Grubbs" catalysts [2].

 However, these catalysts are not completely satisfactory in that they do not allow a control of the polymerization in space or in time, the reaction starting as soon as the catalyst is added or under the action of an increase in temperature.

 To overcome this drawback, alternative catalysts based on ruthenium, tungsten or osmium have been developed to allow a photo-priming of the reaction of ROMP ([3] - [7]).

 Unfortunately, the preparation of these catalysts is based on the complex and expensive synthesis of ligands that associate and dissociate with the metal depending on the wavelength of irradiation. These catalysts have rarely made it possible to obtain stable systems at room temperature and having a high catalytic activity after UV irradiation.

For example, WO 2015/065649 and Weitekamp et al. [8] propose the synthesis of polyolefins by ROMP and their application in photolithography. The catalysts based on ruthenium used are catalysts known as "Grubbs".

We can also mention Delaude et al. [9] which propose ruthenium catalysts for the photo-polymerization of cyclooctene, prepared from the complex [RuCl ₂ (/? - cymene)] 2 and carbene type ligands (NHCs), the latter being obtained previously or generated in situ from imidazohum chloride by deprotonation using potassium tert-butylalcoxide or potassium hydride.

The present invention aims to propose a novel route of synthesis of polyolefins to overcome the aforementioned drawbacks.

 More specifically, it proposes to generate in situ an active ruthenium catalyst from the photo-degradation of a specific imidazole (ni) um salt.

 The present invention thus relates, according to a first of its aspects, to a process for the synthesis of a polyolefin by a photoinitiated reaction of metathesis ring opening polymerization (ROMP) of a cycloolefin, said reaction being carried out in the presence a ruthenium-based catalyst of formula (I):

 (I)

characterized in that said ruthenium catalyst is generated in situ under UV irradiation from:

A ruthenium complex of formula [RuCl ₂ (L)] ₂ (II), L representing a ligand with a cyclic structure, aromatic or comprising at least two nonadjacent C = C double bonds, optionally substituted with one or more groups (Ci-C ₆₎ alkyl; and an imidazole salt (ni) um of formula (III): AT

(Ci-C6) alkyl, non-aromatic carbocyclic groups, C3-C12 groups and (C ₆ -C2o) aryl optionally substituted;

. R2 and R2 ', identical or different, are selected from the groups (Ci-C ₆₎ alkyl, a hydrogen atom and a halogen atom; or

 R2 and R2 'together with the carbon atoms which carry them form an optionally substituted benzene ring;

. A ^" is selected from:

 - anions of formula

wherein R 3, R _4, R5 and R5, identical or different, are selected from the groups (C ₆ -C2o) aryl and optionally substituted (Ci-C ₆₎ alkyl, provided that at least two of the groups R3, R ₄ , R5 and 5 represent optionally substituted (C ₆ -C 20) aryl groups; and

 - anions of formula

in which : . E represents a methylene group optionally substituted by a (C 1 -C 3) alkyl group, in particular methyl; or a carbonyl group; and

 . R 8, R 9, R 10, R 11 and R 12, which are identical or different, are chosen from a hydrogen atom and an optionally substituted benzoyl group;

 or two of Rs, R9, Rio, R11 and R12 form together with the benzene ring which carries them a poly (hetero) cyclic aromatic group, optionally substituted, in particular chosen from an optionally substituted naphthyl group and a xanthone group; and represents a single bond or a double bond.

According to another of its aspects, it also relates to a photopolymerization medium comprising, in addition to one or more cycloolefin (s), at least one imidazole (ni) um salt of formula (III) according to the invention and a Inactive ruthenium complex of formula [RuCl ₂ (L)] ₂ (II) such as [RuCl ₂ (/? - cymene)] 2.

 The imidazole (ni) um salts specifically used according to the invention, having a structure corresponding to the chemical formula (III) indicated above, are more simply referred to below in the text as " Imidazole (ni) salts of the invention.

 The term "imidazole (ni) um salts" is intended to mean imidazolium salts (represents a double bond) or imidazolinium salts (represents a single bond).

 Preferably, the salts used according to the invention are imidazolium salts, that is to say in the above-mentioned chemical formula (III) represents a double bond.

 Similarly, we designate more simply in the following text, under the name

"Ruthenium catalyst", the ruthenium-based catalysts of formula (I) above, capable of activating the metathesis polymerization of ring opening of cycloolefins.

The present invention also relates to the imidazol (ni) um salts of formula (III) as defined above, as well as to a process for their preparation. In particular, according to another of its aspects, the present invention relates to the imidazolium salts of formula (III) chosen from:

 . 1,3-diisopropylimidazolium tetrabiphenylborate;

 . 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetraphenylborate; . 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetrabiphenylborate; and

. 1,3-dimethylimidazolium tetraphenylborate.

According to another of its aspects, it also relates to the use of an imidazole salt (ni) um of formula (III) according to the invention, for generating, under UV irradiation, in the presence of a ruthenium complex of formula [RuCl ₂ (L)] ₂ (II), a ruthenium-based catalyst of formula (I) above, in particular in situ during a photo-initiated reaction of ROMP of a cycloolefin.

The process for synthesizing polyolefins according to the invention proves advantageous in several ways.

Firstly, it allows the synthesis of ruthenium-based metathesis catalysts with much lower costs since the catalysts are generated in situ during the synthesis of polyolefins and at a lower cost. Indeed, ROMP inactive ruthenium complexes such as [RuCl ₂ (/ cymene)] ₂ are generally commercially available. As for the imidazole (ni) um salts used to generate the ruthenium-based catalyst, they can be easily obtained, as detailed in the rest of the text, from imidazol (ni) um halides and from alkali metal salts.

Furthermore, as illustrated in the examples which follow, the synthesis method according to the invention makes it possible to access, with high conversion yields, polyolefins, for example polynorbornenes, polydicyclopentadienes or norbornene / dicyclopentadiene copolymers. , having high molecular weights, in particular between 2000 and 2000,000 g.mol- ¹ , and low polydispersity indices.

The method of the invention advantageously allows a control of the polymerization in space (in other words, as detailed in the rest of the text, a selective polymerization of certain predefined zones of a deposited layer of photopolymerizable composition) and over time, the polymerization starting only after irradiation of the UV light-curing compositions.

 Without wishing to be bound by the theory, the photo-degradation under UV irradiation of the imidazole salts (ni) um considered according to the invention makes it possible to generate in situ compounds of the N-heterocyclic carbene (NHCs) type. In the presence of a totally inactive ruthenium complex such as [RuCl 2 (/? - cymene)] 2, a ruthenium-based complex, active as a ROMP catalyst, is thus formed.

 By way of example, the generation of a ruthenium catalyst according to the process of the invention from an imidazolium salt of formula (III) according to the invention and of the inactive catalyst [RuCl 2 (/? - cymene )] 2 can be represented schematically as follows:

The imidazole (ni) um salts according to the invention can thus be qualified as "photosensitive" salts. One of the degradation products under the effect of irradiation with UV radiation of a light-sensitive imidazole (ni) um salt according to the invention is an N-heterocyclic carbene. After UV irradiation, the polymerization of the cycloolefins present in the photopolymerizable medium is thus directly initiated by the ruthenium catalyst generated in situ according to the invention.

 The polymerization process according to the invention can be carried out in the presence of a photosensitizer, which makes it possible, in certain cases, to increase the kinetics of the photo-initiated reaction.

Finally, as detailed in the rest of the text, according to an alternative embodiment, the polymerization process according to the invention can be operated in bulk, thus advantageously avoiding the use of organic solvent. Other characteristics, variants and advantages of the process for synthesizing polyolefins according to the invention will emerge more clearly on reading the description, examples and figures which will follow, given by way of illustration and not limitation of the invention.

 In the remainder of the text, the expressions "between ... and ...", "ranging from ... to ..." and "varying from ... to ..." are equivalent and mean to mean that terminals are included unless otherwise stated.

 Unless otherwise indicated, the expression "comprising / including a" shall be understood as "comprising / including at least one".

SALT OF AZOLKNDUM

As stated above, the formation of the ruthenium catalyst according to the invention involves an imidazole salt (ni) um having the following general structure (III):

A ^"

R,

 in which :

. R 1 and R 1, which may be identical or different, are chosen from (C 1 -C 6) alkyl groups, non-aromatic C ₃ -C ₁₂ carbocyclic groups and optionally substituted (C ₆ -C 20) aryl groups;

. R ₂ and R ₂ ', which may be identical or different, are chosen from (C ₁ -C ₆ ) alkyl groups, a hydrogen atom and a halogen atom; or

 R2 and R2 'together with the carbon atoms which carry them form an optionally substituted benzene ring;

. A ^" is selected from:

- anions of formula

in which R ₃ , R ₄ , Rs and Re, which are identical or different, are chosen from optionally substituted (C ₆ -C 20) aryl and (C ₁ -C ₆ ) alkyl groups, provided that at least two of the R ₃ groups are , R ₄ , R ₅ and Re represent optionally substituted (C ₆ -C 20) aryl groups; and

 - anions of formula

 in which :

. E represents a methylene group optionally substituted with a (C ₁ -C ₃ ) alkyl group, in particular methyl; or a carbonyl group; and

 . R8, R9, Rio, Ru and R12, which are identical or different, are chosen from a hydrogen atom and an optionally substituted benzoyl group,

 or two of Rs, R9, Rio, R11 and R12 form together with the benzene ring which carries them a poly (hetero) cyclic aromatic group, optionally substituted, in particular chosen from an optionally substituted naphthyl group and a xanthone group; and represents a single bond or a double bond.

By "(C ₁ -C ₆ ) alkyl group" is meant a saturated aliphatic group, linear or branched, comprising from 1 to 6 carbon atoms. By way of example, mention may be made of methyl, ethyl, isopropyl and tertiary butyl groups.

By "non-aromatic C ₃ -C ₁₂ carbocyclic group" is meant a monocyclic radical or a condensed or bridged di- or tri-cyclic radical. By monocyclic radical is meant a cycloalkyl, for example a cyclohexyl. By condensed or bridged di- or tri-cyclic radical is meant, for example, bicyclo [2,2,1] heptyl, tricyclo [2,2,2] octyl or adamantyl. By "(C ₆ -C ₂₀ ) aryl group" is meant an unsaturated group, monocyclic or consisting of fused, carboxylic rings. As an example of an aryl group, mention may be made of the phenyl radical.

 "Aromatic poly (hetero) cyclic group" means a group having two or more rings (rings) fused (ortho-fused or ortho- and peri-condensed) to each other, that is to say having two in two, at least two carbons in common, of which at least one of said rings is aromatic, and may optionally include one or more heteroatoms.

 In particular, a poly (hetero) cyclic group according to the invention is formed from two to six rings, the rings comprising, independently of each other, from 4 to 6 members and being optionally substituted.

 Insofar as at least one of the rings is aromatic, the polycyclic group may be partly aromatic or totally aromatic.

 In particular, the aromatic poly (hetero) cyclic group is formed from 2 to 6 fused rings with 6-membered, optionally substituted, preferably from 2 to 6 fused benzene rings, advantageously from 2 to 4 fused benzene cycles, of which at least one one of the rings comprises a heteroatom.

 As examples of aromatic poly (hetero) cyclic group according to the invention can be mentioned naphthyl groups, optionally substituted, for example substituted with one or more groups (C 1 -C 4) alkoxy and / or (C 1 -C 4) alkyl, and xanthone .

According to one particular embodiment, the imidazole (ni) um salt used according to the invention has the aforementioned formula (III) in which R 1 and R 1 ', which may be identical or different, are chosen from:

 - (C 1 -C 6) alkyl groups, in particular chosen from methyl, ethyl, isopropyl and tert-butyl, preferably methyl and isopropyl, in particular isopropyl;

 - (C3-Cy) cycloalkyl groups, in particular cyclohexyl;

- C ₄ -C ₁₂ bridged di- or tri-cyclic groups, in particular an adamantyl group; - (C ₆ -C ₂₀ ) aryl groups, in particular phenyl groups, optionally substituted by one or more (C 1 -C 6) alkyl groups, and more particularly phenyl, 2,6-diisopropylphenyl and 2,4 groups; 6-trimethylphenyl.

 According to a more particularly preferred embodiment, R 1 and R 1, which are identical or different, are chosen from:

 - (C 1 -C 6) alkyl groups, in particular methyl or isopropyl and more particularly isopropyl;

 a phenyl group, optionally substituted with one or more (C 1 -C 6) alkyl groups, in particular with one or more methyl group (s), preferably a 2,4,6-trimethylphenyl group.

 In particular, R 1 and R 1 'can be chosen from methyl, isopropyl and 2,4,6-trimethylphenyl groups, in particular from isopropyl and 2,4,6-trimethylphenyl groups.

 According to a particular embodiment, Ri and Ri 'are identical.

According to an alternative embodiment, R 1 and R 1 'can be isopropyl groups.

 According to another variant embodiment, R 1 and R 1 'can be methyl groups.

 According to yet another embodiment, Ri and Ri 'may be 2,4,6-trimethylphenyl groups.

R ₂ and R ₂ ', which may be identical or different, in the formula (III) of the imidazole (ni) um salt according to the invention may be chosen from:

 - (C 1 -C 6) alkyl groups, in particular (C 1 -C 4) alkyl, and more particularly methyl;

 a hydrogen atom; and

 a halogen atom, in particular a chlorine, a bromine or a fluorine, and more particularly a chlorine.

According to a particular embodiment, R ₂ and R ₂ 'in formula (III) above are identical. In particular, they can represent hydrogen atoms. According to another variant embodiment, R ₂ and R ₂ 'together with the carbon atoms which carry them form a benzene ring optionally substituted with one or more (C ₁ -C ₆ ) alkyl groups, in particular methyl.

According to a first variant embodiment, in formula (III) represents a single bond. In other words, the salt of formula (III) is an imidazo linium salt.

According to another variant embodiment, in formula (III) represents a double bond. In other words, the salt of formula (III) is an imidazolium salt.

It is understood that the nature of the groups R 1, R 1 ', R ₂ and R ₂ ', and of the single or double nature of the binding of the imidazol (ni) um salt used, conditions the structure of the catalyst based on ruthenium formed according to the invention.

 According to one variant embodiment, the imidazo salt (III) used in accordance with the invention has the abovementioned formula (III) in which:

 . R 1 and R 1 'represent methyl groups, isopropyl groups or 2,4,6-trimethylphenyl groups, in particular isopropyl groups or 2,4,6-trimethylphenyl groups; and

. R ₂ and R ₂ 'represent hydrogen atoms.

According to a first variant embodiment, the formation of the ruthenium catalyst according to the invention involves a salt of imidazo li (ni) um having the following general structure (III-a):

 (III-a)

in which : . R 1 and R 1, which are identical or different, are chosen from (C 1 -C 6) alkyl groups, non-aromatic C ₃ -C ₁₂ carbocyclic groups and optionally substituted (C ₆ -C 20) aryl groups, in particular by one or more groups; (Ci-C ₆₎ alkyl;

. R ₂ and R ₂ ', which are identical or different, are chosen from groups

(Ci-C ₆₎ alkyl, a hydrogen atom and a halogen atom; or

R2 and R ₂ 'together with the carbon atoms which carry them form an optionally substituted benzene ring, in particular with one or more (C 1 -C 6) alkyl groups;

. R 3, R _4, R 5 and R 5, identical or different, are selected from the groups

(C ₆ -C 20) optionally substituted aryl and (C ₁ -C ₆ ) alkyl, provided that at least two, in particular at least three of R 3, R ₄ , R 5 and 5 are (C ₆ -C 20) groups optionally substituted aryl; and represents a single bond or a double bond. In particular, R 1, R 1 ', R ₂ , R ₂ ' and can take any of the definitions specified above.

Preferably, at least three of the groups R 3, R ₄ , R 5 and 5 bonded to the boron atom of the counteranion in the imidazolium salt (III) according to the invention represent groups ( C ₆ -C 20) aryl optionally substituted with one or more substituents R 7, which may be identical or different.

According to a particularly preferred embodiment, the four R 3, R ₄ , R 5 and Re groups bonded to the boron atom of the counteranion in the imidazole (ni) um salt according to the invention represent (C _{6) groups.} -C2o) optionally substituted aryl. These imidazole (ni) um salts according to the invention can be referred to as "imidazole tetraarylborate (ni) um".

The (C ₆ -C 20) aryl groups bonded to the boron atom may for example be chosen from phenyl or naphthalenic groups, preferably phenyl groups, said groups optionally carrying one or more R 7 substituents.

The substituent (s) R7 may be chosen from (C ₆ -C 20) aryl groups, especially phenyl groups, a hydroxyl group, halogen atoms, a nitro group, and the like. According to a particularly preferred embodiment, at least two or even at least three or even the four groups R 3, R ₄ , R 5 and 5 are chosen from phenyl and biphenyl groups.

According to a particular embodiment, R 3, R _4, R 5 and 5 are identical. They then represent (C ₆ -C 20) aryl groups optionally substituted with one or more substituents R 7, which may be identical or different.

By way of example, R 3, R ₄ , R 5 and 5 may represent phenyl or biphenyl groups.

According to another particular embodiment, R 3, R _4, R 5 and 5 are different.

They can be, for example, chosen from (C ₆ -C 20) aryl groups. For example, one of the groups R 3, R ₄ , R 5 and 5 may be biphenyl, and the other three phenyl groups.

In another variant, one of the groups R 3, R ₄ , R 5 and 5 may be an alkyl group, the other three optionally substituted (C ₆ -C 20) aryl groups, for example phenyl groups.

According to another embodiment of the invention, the formation of the ruthenium catalyst according to the invention involves a salt of imidazol (ni) um having the following general structure (III-b):

(III-b)

 in which,

. R 1 and R 1, which are identical or different, are chosen from (C 1 -C 6) alkyl groups, non-aromatic C 3 -C 12 carbocyclic groups and groups (C 6 -C ₂ o) aryl optionally substituted, in particular by one or more (Ci-C ₆₎ alkyl;

. R ₂ and R ₂ ', which may be identical or different, are chosen from (C ₁ -C ₆ ) alkyl groups, a hydrogen atom and a halogen atom; or

R ₂ and R ₂ 'together with the carbon atoms which carry them form an optionally substituted benzene ring, in particular with one or more (C 1 -C 6) alkyl groups;

 . E represents a methylene group optionally substituted by a (C 1 -C 3) alkyl group, in particular methyl; or a carbonyl group; and

. R8, R9, Rio, Ru and Ri ₂ , which are identical or different, are chosen from a hydrogen atom and an optionally substituted benzoyl group,

 or two of Rs, R9, Rio, R11 and R12 form together with the benzene ring which carries them a poly (hetero) cyclic aromatic group, optionally substituted, in particular chosen from an optionally substituted naphthyl group and a xanthone group; and

. represents a single bond or a double bond.

In particular, Ri, Ri ', R ₂ , R ₂ ' and can take any of the definitions specified above.

 According to a particularly preferred embodiment, the imidazole salt (ni) um is of formula (III-b) above wherein:

 . one of the groups Rs, R9, Rio, R11 and R12 represents benzoyl group, optionally substituted, the other groups representing hydrogen atoms; or

 . two of Rs, R9, R10, R11 and R12 form together with the benzene ring which carries them an optionally substituted naphthyl group, in particular optionally substituted by one or more (C 1 -C 4) alkoxy and / or (C 1 -C 4) alkyl groups; ; or a xanthone group.

 Preferably, the carboxylate-type counteranion of an imidazole salt (ni) um of formula (III-b) according to the invention is chosen from the following structure:

Advantageously, these counter anions are derived from commercially available carboxylic acid compounds, in particular phenylglyoxilic acid, xanthone acetic acid (or 2- (9-oxoxanthene-2-yl) propionic acid), ketoprofen (or (RS) -2- (3-benzoylphenyl) -propionic acid), naproxen (or 6-methoxy-α-methyl-2-naphthaleneacetic acid).

It is understood that the various embodiments indicated above can be combined, as far as possible, to define other specific variants of imidazole (ni) um salts of formula (III), in particular of formula (III). a) or (III-b), according to the invention.

As examples of imidazole salts (ni) um of formula (III-a) according to the invention, may be more particularly mentioned the following salts:

 . 1,3-diisopropylimidazolium tetraphenylborate;

 . 1,3-diisopropylimidazolium tetrabiphenylborate;

 . 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetraphenylborate;

. 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetrabiphenylborate;

 . 1,3-dimethylimidazolium tetraphenylborate; and

 . 1,3-bis (2,4,6-trimethylphenyl) imidazolinium tetraphenylborate.

As examples of imidazole salts (ni) um of formula (III-b) according to the invention, may be more particularly mentioned the following salts

 1,3-bis (2,4,6-trimethylphenyl) imidazolium 2- (9-Oxoxanthen-2-yl) propionate;

 . 1,3-bis (2,4,6-trimethylphenyl) imidazolium phenylglyoxylate;

 2- (3-benzoylphenyl) -propionate del, 3-bis (2,4,6-trimethylphenyl) imidazolium;

. 1,3-diisopropylimidazolium 2- (3-benzoylphenyl) -propionate. According to a particular embodiment, the imidazole salts (ni) ium considered according to the invention have the following general structure (VI):

AT

wherein A ^" is as defined above, and represents a single bond or a double bond, particularly a double bond.

More particularly, the imidazole (ni) um salts considered according to the invention have the following general structure (VI-a):

(Vl-a)

wherein R 3, R ₄ , R 5 and 5 are as previously defined, in particular represent phenyl or biphenyl groups; and represents a single bond or a double bond, particularly a double bond.

Preferably, the imidazolium salt used according to the invention is 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetrabiphenylborate or 1,3-bis (2,4,6-tetraphenylborate). trimethylphenyl) imidazolium, especially 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetrabiphenylborate. Synthesis of imidazol (ni) um salt

 The imidazole (ni) um salts of formula (III), in particular of formula (III-a) or (III-b), mentioned above, used according to the process of the invention, can be obtained easily, according to synthetic methods known to those skilled in the art, in particular from commercially available compounds.

 More specifically, the imidazole (ni) um salts can be synthesized via an anion exchange reaction between an imidazole (ni) um halide salt and an alkali metal salt.

 According to another of its aspects, the present invention thus relates to a process for preparing an imidazole salt (ni) um of formula (III), in particular of formula (III-a) or (ΙΠ-b), such as defined above, carrying out an anion exchange reaction between an imidazole (ni) um halide of formula (IV)

X

(Goes)

in which E, R ₃ , R ₄ , R ₅ , R ₆ , RS, R ₉ , R ₁₀ , R 11 and R 12 are as defined above; and Z is an alkali metal, especially sodium or potassium.

 Of course, it is up to those skilled in the art to adjust the synthesis conditions, such as, for example, the nature and the concentrations of reactants, in order to obtain the imidazole (ni) um salt of formula (III), in particular formula (III-a) or (ΙΠ-b), desired.

 The imidazole (ni) um halide of formula (IV) and the alkali metal salt of formula (V) may advantageously be commercially available or synthesized according to methods known to those skilled in the art.

 In particular, the alkali metal carboxylate salt of formula (V-b) can be obtained from the corresponding carboxylic acid, for example by reaction with an alkali metal hydroxide, for example with potassium hydroxide.

 The anion exchange reaction may be more particularly carried out in a solvent medium, for example in ethanol or trichloromethane.

 In practice, the synthesis of the imidazole (ni) um salt may be more particularly carried out by adding an alkali metal salt solution to a solution of the imidazol (ni) um halide salt. The imidazole (ni) um salt can then be recovered by precipitation and filtration.

POLYOLEFIN S SYNTHESE USING RUTHENIUM CATALYST

As specified above, the imidazole (ni) um salts of formula (III), in particular of formula (III-a) or (ΙΠ-b), considered according to the invention, in particular as described above, are advantageously used to generate, under UV irradiation, and in the presence of an inactive ruthenium complex, an active ruthenium catalyst for the cyclo-olefin ROMP.

 By "active" catalyst is meant a catalyst capable of activating cyclo-olefin ring opening metathesis polymerization (ROMP).

In contrast, the inactive ruthenium complex used according to the invention, of general formula [RuCl ₂ (L)] ₂ (II), does not make it possible to activate the polymerization of olefins.

 The ruthenium-based catalyst can be advantageously generated according to the invention in situ during the photo-initiated reaction of ROMP cycloolefins.

The invention thus relates, according to another of its aspects, to a photopolymerization medium, also called indifferently "photo-polymerizable medium" or "photo-polymerizable composition", comprising, in addition to one or more cycloolefins, at least:

 an imidazole salt (ni) um of formula (III), in particular of formula (III-a) or (III-b), as defined above; and

an inactive ruthenium complex of formula [RuCl ₂ (L)] ₂ (II), in particular as defined more particularly in the remainder of the text.

 The inactive ruthenium complex implemented according to the invention is of formula:

[RuCl ₂ (L)] ₂ (II)

 wherein L represents a cyclic structure ligand, aromatic or comprising at least two nonadjacent C = C double bonds, and optionally substituted by one or more (C 1 -C 6) alkyl groups.

According to a particular embodiment, the inactive ruthenium complex is of formula (II) in which L represents a ligand having an aromatic cyclic structure, in particular of the benzene type, optionally substituted by one or more (C ₁ -C ₆ ) alkyl groups, identical or different, chosen in particular from methyl and isopropyl groups.

As examples of ligands with an aromatic ring structure, mention may be made of benzene, γ-cymene, hexamethylbenzene and mesitylene. According to another particular embodiment, the inactive ruthenium complex is of formula (II) in which L represents a ligand with a cyclic structure, comprising at least two nonadjacent C = C double bonds and optionally substituted by one or more groups (Ci -C6) alkyl, in particular methyl.

 By way of examples of such ligands, 1,5-cyclooctadiene and pentamethylcyclopentadiene may be mentioned.

The inactive ruthenium complex of formula (II) can thus be more particularly chosen from the following complexes: [RuCl ₂ (/? - cymene)] 2, [RuCl ₂ (benzene)] ₂ , [RuCl ₂ (hexamethylbenzene)] ₂ , [RuCl ₂ (mesitylene)] ₂ , [RuCl ₂ (1,5-cyclooctadiene)] ₂ and [RuCl ₂ (pentamethylcyclopentadiene)] ₂ .

 It is advantageously ruthenium complexes well known and commercially available.

According to a particular embodiment, the inactive ruthenium complex implemented according to the invention is di-chlorobis (β-cymene) chloromethylium ([RuCl ₂ (p-cymene)] ₂ ).

 Advantageously, the photo-polymerization medium according to the invention is stable at room temperature, no polymerization reaction taking place before exposure of the medium to UV irradiation.

Advantageously, the polymerization process according to the invention can be carried out in the presence of at least one photosensitizer.

 Thus, the photo-polymerization medium may further comprise one or more photosensitizers.

The photosensitizer is more particularly chosen from photosensitizers activated by UV irradiation, for example those chosen from: acetophenone, acetophenone benzylketal, 1-hydroxycyclohexylphenylketone, 2,2-dimethoxy-1,2-diphenylethan-1-one , xanthone, fluorenone, fluorene bcnzaldéhycie, ^the anthraquinone, triphenyl lamine, carbazole, 3-methyl-acetophenone, 4-chloro-benzophenone, 4,4'-methoxy-benzophenone, 4,4 benzino-benzophenone, benzoinpropyl ether, benzoinethyl ether, benzyl methyl kethal 1- (4-isopropylphenyl) -2-hydroxy-2-methyl-propan-1-one, 2-hydroxy-2-methyl-1-phenylpropan -l-one, the thioxanthone. diethyl-thioxanthone, 2-isopropyl-thioxanthone, 4-isopropyl- thioxanthon the 2-ch loroth ioxanthone. 2-methyl-1- [4- (methyl-thio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethyl-amino-1- (4-morpholino-phenyl) -butane 4- (2-hydroxyethoxy) -phenyl- (2-hydroxy-2-propyl) ketone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis (2,6-methoxybenzoyl ⁾ oxide; ) -2,4,4- trimethyl-pentyl phosphine, and 1 ^'oligo (2-hydroxy-2-mcthyl-l- (4- (methylphenyl) phenyl) - propanone) and mixtures thereof.

 Preferably, the photosensitizer is chosen from 2-isopropropylthioxanthone, 4-isopropylthioxanthone and mixtures thereof.

 As illustrated in the examples, the use of a photosensitizer can advantageously make it possible, especially during the generation of the ruthenium-based catalyst from 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetraphenylborate. to reduce the irradiation time required for the generation of the catalyst and the subsequent polymerization time.

 The polymerization according to the process of the invention may be carried out in solution, in aqueous dispersed medium or in bulk.

 By "bulk" process is meant a polymerization occurring in the absence of a solvent, unlike a "solution" process.

 The term "aqueous dispersed medium" or "in aqueous dispersion" is used, a polymerization occurring in water, in the presence of at least one surfactant, in other words in the presence of one or more surfactants.

 By "surfactant" or "surfactant" is meant any compound having in its structure one or more hydrophilic parts and one or more hydrophobic parts. This hydrophilic / hydrophobic balance allows the surfactant to have an interfacial activity which makes it possible to ensure dispersion and stabilization of the aqueous and organic phases in the presence.

 In particular, the surfactant may be chosen from dispersing agents, also known as protective colloids or suspending agents, and emulsifying agents.

Examples of aqueous dispersed media are described in particular in document WO 2008/003729. In the case of a synthesis in solution, the photo-polymerization medium according to the invention may further comprise one or more solvents. The solvent (s) may be, for example, chosen from dichloromethane, 1,2-dichloroethane and acetonitrile.

 According to a particular embodiment, the solvent may be dichloromethane.

 The preparation of the photopolymerizable medium according to the invention is within the competence of those skilled in the art. It can be prepared, for example, by simply mixing the cycloolefins, the imidazole (ni) um salt, the ruthenium complex which is optionally inactive with one or more photosensitizers, and optionally in one or more solvents, for example dichloromethane.

 In the context of the implementation of one or more photosensitizers, the photosensitizer (s) / imidazole salt (ni) um molar ratio may be more particularly between 0.1 and 5 or else between 0.02 and 1. .

 In the context of the implementation of one or more solvents, the mass ratio solvent (s) / cycloolefins may be more particularly between 0.1 and 15, or between 0.1 and 10.

In the context of a synthesis in aqueous dispersed medium, the photopolymerization medium is an emulsion comprising an organic phase comprising the imidazole salt (ni) um of formula (III), in particular of formula (III-a) or ( ΙΠ-b), and the inactive ruthenium complex of formula (II) in an organic solvent and an aqueous phase comprising water and a surfactant.

 The size of the emulsion droplets is advantageously between 30 and 400 nm, or even between 200 and 400 nm.

The preparation of the photo-polymerizable medium in the form of an emulsion according to the invention is within the competence of a person skilled in the art. It can be prepared by simple mixing of the organic phase comprising the imidazol (ni) um salt of formula (III), in particular of formula (III-a) or (ΙΠ-b), and the inactive ruthenium complex of formula (II) and the aqueous phase comprising water and a surfactant, with magnetic stirring. In order to obtain a fine emulsion, it is possible to place the mixture under ultrasound for several minutes, for example between 1 and 60 minutes, or between 2 and 20 minutes. In the context of mass synthesis, the photo-polymerization medium is advantageously free of solvent.

 The solvent or solvents, optionally introduced to promote the mixing of the various compounds, are subsequently evaporated to obtain a photopolymerizable medium free of solvent.

 In another particular embodiment, the cycloolefin may be in liquid form at room temperature, as is the case, for example, with cyclooctene. The mixture of the various compounds to prepare a photopolymerizable composition according to the invention does not then require the addition of solvent.

It is up to those skilled in the art to adjust the nature and the concentration of the various compounds of the photo-polymerizable medium in order to conduct, as detailed in the rest of the text, the in situ generation of the ruthenium catalyst and the synthesis of the polyolefms. desired.

 According to one particular embodiment, the cycloolefins and the ruthenium complex of formula (II) are used in the photo-polymerizable medium in a cycloolefin / complex (II) molar ratio of between 10 and 300,000, preferably between 100 and 20 000 or between 500 and 22000.

 According to another particular embodiment, the imidazole salt (ni) um of formula (III), in particular of formula (III-a) or (ΙΠ-b), and the ruthenium complex of formula (II) are implemented in the photo-polymerizable medium in a molar ratio of imidazole salt (ni) um (III) / complex (II) between 0.01 and 100, in particular between 2 and 10. The synthesis of polyolefins according to the method of the invention may more particularly include at least the steps of:

 (i) having a photo-polymerizable medium as described above;

(ii) subjecting said photo-polymerizable medium of step (i) to irradiation

UV;

(iii) optionally, in the case of a liquid photopolymerizable medium comprising one or more solvents, let the medium obtained at the end of step (ii) react under visible light; and (iv) recovering the polyolefms thus obtained at the end of stage (ii) or (iii).

UV irradiation is the exposure of the photopolymerizable medium to UV radiation of wavelength between 200 and 400 nm.

The UV irradiation in step (ii) may be more particularly carried out using UV radiation having an irradiance of between 10 mW.cm ^-2 and 2000 mW.cm ^-2 , in particular between 10 mW.cm ^{" 2} and 500 mW.cm ^"2 .

 The skilled person is able to implement the appropriate devices to operate the desired irradiation. For example, UV irradiation can be performed by exposing the photopolymerizable medium to light from a xenon-mercury lamp.

 The UV irradiation time may be between 1 minute and 5 hours, in particular between 2 and 30 minutes, more particularly between 5 and 20 minutes.

The bringing together of an imidazole salt (ni) um according to the invention with the inactive complex [RuCl ₂ (L)] ₂ (II) makes it possible, under UV irradiation, to lead to the formation of a catalyst. ruthenium base capable of activating ROMP cycloolefins.

 The ruthenium catalysts generated in situ under UV irradiation according to the process of the invention are of formula (I) below:

 (I)

wherein R 1, R 1 ', R ₂ , R ₂ ', and L are as previously defined.

 It is understood that the nature of the catalyst generated according to the process of the invention depends on the imidazol (ni) um salt and the inactive catalyst used.

According to a particular variant embodiment, the process of the invention is carried out from the inactive ruthenium complex [RuCl ₂ (/? - cymene)] 2, to form a ruthenium-based catalyst of formula:

in which R 1, R 1 ', R ₂ , R ₂ ' and are as defined above, in particular represents a double bond. The synthesis of the polyolefins according to the invention can be carried out at temperatures ranging from 0 ° C. to 100 ° C. Preferably, it is carried out at room temperature.

 It is within the skill of those skilled in the art to adjust the operating conditions of the synthesis by ROMP to obtain the desired poly-olefins.

 Thus, in the context of a solution polymerization, the medium obtained at the end of the UV irradiation may be optionally allowed to react under visible light in step (iii) for a variable duration.

 Those skilled in the art are able to adjust the reaction time so as to obtain the desired characteristics for the polyolefins, in particular in terms of molecular weight and polydispersity index. Typically, the reaction time in step (iii) can be between 0 and 120 minutes.

 Still in the context of a polymerization carried out in a solvent medium, the polyolefins can be recovered, at the end of the polymerization, through the implementation of one or more precipitation steps, for example in methanol, and filtration .

 In the context of a bulk polymerization, the polyolefins can be recovered directly at the end of the UV irradiation.

APPLICATIONS The process of the invention can be used, for example, for the synthesis of norbornene polymers or co-polymers by means of ROMP or a derivative thereof, in particular hexanedioldinorbornene, dicyclopentadiene and / or cyclooctene.

 In particular, it can be used for the synthesis by means of ROMP of polynorbornene or one of its derivatives, polydicyclopentadiene or polycyclooctene.

 The term "norbornene derivatives" means monomers having a norbornene function. The norbornene derivatives may be more particularly prepared by a Diels-Alder reaction between cyclopentadiene or a derivative thereof such as pentamethylcyclopentadiene and unsaturated hydrocarbons (having a double or triple bond).

 According to a particular variant embodiment, the process of the invention is used for the synthesis of polynorbornene, polydicyclopentadiene, a norbornene / dicyclopentadiene copolymer or a norbornene / hexanedio-dinorbornene copolymer.

As mentioned above, the process of the invention advantageously makes it possible to access polyolefins of high molar mass.

In particular, the polyolefins obtained according to the process of the invention may have a molar mass of between 2,000 and 2,000,000 g.mol ^-1 , in particular greater than or equal to 10,000 g mol ^-1 , preferably greater than or equal to at 40,000 g.mol ^-1 .

The polyolefins obtained according to the process of the invention may have a polydispersity index of between 1.1 and 10.

 In particular, advantageously, the polyolefins obtained according to the process of the invention may have a low polydispersity index, for example less than or equal to 2.5, in particular less than or equal to 2, preferably less than or equal to 1 , 5 and more preferably less than or equal to 1.2.

For the purposes of the present invention, the term "polydispersity index", also known as the "polymolecularity index", is intended to mean the ratio I _p of the weight average molar mass M _w to the number-average molar mass M _n :

Ip = Mw / Mn M _n and M _w can be obtained by steric exclusion chromatography (CES) of a polymer solution in tetrahydrofuran (THF) after passing it on a gel column. This index I _p gives an indication of the extent of the distribution of the molar masses of the different macromolecules within a polymer. For a perfect polymer, where all the macromolecules would have the same length (and therefore the same molar mass), I _p would be equal to 1.

 Finally, the process of the invention makes it possible to obtain excellent yields. Thus, the degree of conversion to monomers may be more particularly greater than 70%, especially greater than 80%, and more preferably greater than 85%.

 The degree of conversion to monomers can be determined by γ-NMR analysis by Fourier transform infrared analysis (FTIR) or by gravimetry.

Particularly advantageously, the synthesis process according to the invention, in which the catalyst is generated in situ under UV irradiation, can be implemented to produce polyolefin-based coatings.

 Thus, according to another of its aspects, the invention also relates to the use of the method of the invention for producing a coating based on polyolefins.

 The photo-polymerizable composition according to the invention, as described above, can be deposited, prior to submission to UV irradiation, on a suitable substrate, for example a silicon wafer.

 At the end of the UV irradiation, and possibly after exposure to visible light, a film based on polyolefins is thus obtained on the substrate.

 The coating based on polyolefins may for example have a thickness ranging from 1 μιη to 1 mm, in particular from 30 μιη to 300 μιη.

 The formation of polyolefin-based coating finds a particularly interesting application for producing one or more patterns by photo lithography, as illustrated in Example 3 which follows.

 In the case of photolithography, only certain areas of the deposited layer of photopolymerizable composition are irradiated so as to create polymerized zones and unpolymerized zones which can then be eliminated.

The arrangement of the zones to be irradiated may for example be defined by a mask having the desired pattern and applied to the composition deposited on the substrate. prior to UV irradiation. At the end of the process of the invention, a film presenting the patterns of the mask can thus be obtained.

The photo-polymerization process according to the invention can also be implemented for stereolithography 3D printing.

 This technique, also called SLA ("Stereolithograph apparatus" in English) uses the principle of photo-polymerization for the manufacture of solid objects by superposition of thin slices of material. The radiation is controlled and directed by precise mirrors and scans the surface of the photo-polymerizable composition according to the shape of the object to be printed. Under the effect of irradiation, a solid layer is formed. The operation is then renewed to print, layer by layer, the object by photo-polymerization.

The invention will now be described by means of the following examples and figures, illustrating the implementation of the method of the invention.

 These examples and these figures are of course given by way of illustration and not limitation of the invention.

FIGURES

FIG. 1: Absorbance spectrum as a function of the wavelength obtained for the 1,3-diisopropylimidazolium tetraphenylborate synthesized in Example 1;

 2: Absorbance spectrum as a function of the wavelength obtained for the 1,3-diisopropylimidazolium tetrabiphenylborate synthesized in Example 1;

 3: absorbance spectra as a function of the wavelength obtained for the 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetraphenylborate synthesized as example i;

FIG. 4: Absorbance spectrum as a function of the wavelength obtained for the 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetrabiphenylborate synthesized in Example 1; Figure 5: Absorbance spectrum versus wavelength obtained for 1,3-bis (2,4,6-trimethylphenyl) imidazolium phenylglyoxylate synthesized as Example 2;

 Figure 6: Absorbance Spectrum versus Wavelength Obtained for 1,3-bis (2,4,6-trimethylphenyl) imidazolium Ketoprofenate Synthesized as Example 2;

 FIG. 7: Absorbance spectrum as a function of the wavelength obtained for the 1,3-diisopropylimidazolium ketoprofenate synthesized as Example 2;

 FIG. 8: Absorbance Spectrum as a function of the wavelength obtained for the 1,3-bis (2,4,6-trimethylphenyl) imidazolium methylxanthone acetate synthesized as Example 2;

Figure 9: NMR Spectrum ^! In CD2CI2 of the formulation obtained according to Example 3.1. after irradiation (254 nm) of the photopolymerizable composition 1 and exposure for 40 minutes to sunlight;

 Figure 10: Evolution of the degree of conversion to monomer as a function of time, before and after irradiation at 254 nm (irradiation time of 5 minutes (- · -) or 10 min (- ■ -)) of the photo-polymerizable composition 3 according to example 3.1. ;

 FIG. 11: Evolution of the degree of monomer conversion as a function of time, before and after irradiation at 254 nm (irradiation time of 10 min) of the photo-polymerizable compositions 1 (- ■ -), 2 (- · -) and 3 (- A-) prepared according to Example 3.2. ;

 12: Evolution of the degree of conversion to monomer as a function of time, before and after irradiation at 254 nm (irradiation time of 10 min) of the photopolymerizable compositions 2 (- ■ -) and 4 (- · -) prepared following example 3.3;

 FIG. 13: Scanning electron microscopy (SEM) format of the polynorbornene film formed according to Example 4;

 FIG. 14: Evolution of the degree of conversion to monomer as a function of time, after 10 minutes of irradiation at 350-365 nm of the photopolymerizable compositions 9 to 13 according to example 6.1.

15: Evolution of the degree of conversion to monomer as a function of time, after 10 minutes of 350-365 nm UV irradiation of the photopolymerizable compositions 9 and 14 to 16 according to Example 6.2. 16: Evolution of the degree of conversion to monomer as a function of time, after 10 minutes, 20 minutes or 30 minutes of 350-365 nm UV irradiation of the photo-polymerizable compositions 9 and 13 according to Example 6.3.

 17: Evolution of the degree of conversion to monomer as a function of time, after 10 minutes, 20 minutes or 30 minutes of 350-365 nm UV irradiation of the photo-polymerizable composition 17 according to Example 6.4.

 18: Evolution of the degree of conversion to monomer as a function of time, after 1 to 10 minutes of 350-365 nm UV irradiation of the photopolymerizable composition 23 according to Example 10.

 FIG. 19: Evolution of the degree of conversion to monomer as a function of time, after 5 minutes or 10 minutes of 350-365 nm UV irradiation of the photo-polymerizable composition 24 according to Example 10.

EXAMPLES

EXAMPLE 1

 Synthesis of tetraarylborate salts of imidazol (in) ium according to the invention

 Imidazol salts (ni) um (a), (b), (c), (d), (e) and (f) of formula (III-a) according to the invention and whose structures are presented in the following table 1 were synthesized. ri

 I.

 R i- B i- 4

D.

bond

Imidazole salts (ni) um Ri Ri 'R2 R ₂ 'R> Rt Rs Re

(a) IPrB (Ph) ₄ iPr iPr HH Ph Ph Ph Ph double (b) IPrB (bPh) ₄ iPr iPr HH bPh bPh bPh bPh double

(c) IMesB (Ph) ₄ My HH Ph Ph Ph Ph double

(d) IMesB (bPh) ₄ My Mesh HH bPh bPh bPh bPh double

(e) Me ₂ ImB (Ph) ₄ Me Me HH Ph Ph Ph Ph double

(f) SIMe (Ph) ₄ My HH Ph Ph Ph Ph Simple Ph

 TABLE 1

 iPr: isopropyl

 Ph: phenyl

 bPh: biphenyl

 Mes: 2,4,6-Trimethylphenyl

 IPr: 1,3-diisopropylimidazolium

 IMes: 1,3-bis (2,4,6-trimethylphenyl) imidazolium

 SIMes: 1,3-bis (2,4,6-trimethylphenyl) imidazolinium

Synthesis protocol

 The imidazole (ni) um (a) to (f) salts were synthesized via an anion exchange reaction between the corresponding sodium imidazole (ni) and sodium tetraarylborate bromide or chloride salts, according to the following protocol.

 A solution (A) of bromide or imidazole (ni) um chloride in ethanol and a solution (B) of sodium tetraarylborate in ethanol are prepared. Solution (B) is poured dropwise into solution (A). The white precipitate obtained is then filtered, washed with water and then dried in an oven overnight at 60 ° C.

The following Table 2 accounts for the nature and amounts introduced into each of the reagents for the preparation of the imidazolidi (ni) um (a) to (f) salts.

Reagents

IPrHBr salt IPrHCl IMesHBr Me2ImHCl SIMesHCl IMesHCl NaB (Ph) ₄ NaB (bPh) ₄

 0.67 g

 0.3 g (0.0013 0.24 g (0.0013

 (a) (0.0019 mol)

 mol) in 5 mol) in 5 - - in 5 mL

 mL of ethanol mL of ethanol

 ethanol

 0.6 g (0.00257 0.5 g (0.0027 2.24 g (0.0034

(b) mol) in 20 mol) in 5 - - mol) in 120 mL of ethanol mL of ethanol mL of ethanol

 3.4 g (0.01 5.38 g

 4 g (0.01 mol)

 (c) mol) in (0.0016 mol)

 - in 120 mL - 120 mL in 120 mL

 ethanol

 ethanol ethanol

 0.7 g

 0.8 g (0.002 (0.002 1.7 g (0.0025

(d) - mol) in 50 mol) in - mol) in 50 ml of ethanol 50 ml of ethanol of ethanol

 0.411 g

 (0.0034 1.59g (0.0047

 (e) mol) in mol) in 20

 20 mL mL ethanol

 ethanol

 1.064 g

 (0.0031 1.59g (0.0047

 (f) mol) in mol) in 20

 20 mL mL ethanol

 ethanol

TABLE 2

IPrHBr: 1,3-Diisopropylimidazolium bromide, synthesized in the laboratory;

IMesHBr: 1,3-bis (2,4,6-trimethylphenyl) imidazolium bromide, synthesized in the laboratory); IPrHCl: 1,3-diisopropylimidazolium chloride, marketed by ABCR under the reference No. AB 146607;

IMESHCl: 1,3-bis (2,4,6-trimethylphenyl) imidazolium chloride, sold by ABCR under the reference No. AB 130859.;

Me2lmHCl: 1,3-dimethylimidazolium chloride

SIMesHCl: 1,3-bis (2,4,6-trimethylphenyl) imidazolinium chloride

 NaB (Ph) 4: sodium tetraphenylborate sold by Sigma-Aldrich under the reference No. T25402-25G;

 NaB (bPh) 4: sodium tetrabiphenylborate, synthesized in the laboratory according to the protocol described in the publication Terhi Alaviuhkola et al., Chem.Eur.J.2005, 11,2071-2080.

Yield and characterization of synthesized imidazole (ni) um salts

(a) 1,3-Diisopropylimidazolium tetraphenylborate

 I PrB (Ph).

Yield: 98% (0.6 g)

NMR Ή (300 MHz, DMSO-d ₆ ); δ (ppm): 1.45 (d, 12H, Hi); 4.50 (m, 2H, H ₂ ); 6.78 (m, 20H, aromatics); 7.37 (d, 2H, H ₃ ); 8.42 (s, 1H, H ₄ )

¹³ C NMR (300 MHz, CD ₃ CN); δ (ppm): 22.50 (2C, Cl); 53.82 (Cl, C ₂ ); 122.05 (Cl, C ₅ ); 126.41 (2C, C ₆ ); 127.69 (2C, C ₃ ); 129.67 (2C, C ₇ ); 136.71 (Cl, C ₄ ); 164.69 (Cl, C ₈ ). ESI-MS (electro-nebulization mass spectrometer): m / z, (%) :(%): [ ^~ B (-Ph) 4] = 319.17; [2N ⁺ (-C9H17)] = 153.14; total mass of salt: [B- (Ph) ₄ +2 N ⁺ (-C9H17)] 472.31

UV-Vis: υ max (254) (mole ¹ X ^-1 cm ^-1 ) in CH ³ CN: 4500; Quartz tank thickness: 1 cm.

 The absorbance spectrum as a function of the wavelength obtained is represented in FIG.

(b) 1 3-diisopropylimidazolium tetrabiphenylborate

I PrB (bPh) ₄

Yield: 78% (1.53 g)

NMR Ή (300 MHz, CD3CN); δ (ppm): 1.46 (d, 12H, Hi); 4.47 (m, 2H, H ₂ ); 7.37 (m, 36H, aromatics); 7.62 (d, 2H, H ₃ ); 8.41 (s, 1H, H ₄ ).

¹³ C NMR (300 MHz, CD ₃ CN); δ (ppm): 22.7 (2C, Cl); 53.84 (Cl, C ₂ ); 121.66 (2C, C _3); 137.21 (Cl, C ₄ ); 125.20 (3C, aromatic C, 127.01 (CI, C aromatic, 127.38 (2C,

Caromatic), 129.57 (2C, Caromatic), 135.47 (IC, Caromatic), 137.19 (2C, Caromatic), 143.43 (IC, Caromatic).

ESI-MS: m / z, (%) :(%): [B (bPh) ₄ ] = 623.29; [2N ⁺ (-C9H17)] = 153.14; total mass of salt: [B- (bPh) ₄ ⁺ 2 N ⁺ (-C 9 H 17)] 776.43 g / mol for C ₅ H ₅₃ BN 2.

UV-Vis: υ max (254) (mole ¹ X ^-1 cm ^-1 ) in CH ³ CN: 24500; Quartz tank thickness: 1 cm The absorbance spectrum as a function of the wavelength obtained is shown in FIG.

(c) 1,3-trimethylphenyl) imidazolium tetraphenylborate

IM esB (Ph) ₄

Yield: 94% (5.84 g)

NMR Ή (300 MHz, DMSO-d ₆ ); δ (ppm): 2.13 (s, 12H, H ₇ , ₉ ); 2.36 (s, 6H, ¾); 6.69 (t, 4H, H ₃ , ₅ ); 7.17 (m, 20H, Η " _1κμιε ); 8.27 (s, 2H, H10); 9.64 (s, 1H, H ").

¹³ C NMR (300 MHz, DMSO-d ₆ ); δ (ppm): 16.58 (4C, C ₇ , ₉ ); 20.23 (2C, C ₈ ); 121.35 (2C, aromatic); 124.49 (aromatic IC, C); 125.02 (4C, C ₃ , ₅ ); 129.24 (2C, C10); 130.29 (4C, C ₂ , 6); 134.00 (1C, Ci); 135.35 (2C, Caromatic); 138.19 (2C, C ₄ ); 140.06 (1C, Cn);

ESI-MS: m / z, (%) :(%): [B (Pri) ₄ ] = 319.17; [2N ⁺ (-C21H25)] = 305.20; total mass of salt: [-B (Ph) ₄ ⁺ 2 N ⁺ (-C21H25)] = 624.37 g / mol for C45H45BN2.

UV-Vis:? Max (254) (mole ¹ X ^-1 cm ^-1 ) in CH ₃ CN: 7335; Quartz tank thickness: 1 cm

 The absorbance spectrum as a function of the wavelength obtained is represented in FIG.

3. (d) 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetrabiphenylborate

 IM esBCbP hh

Yield: 90% (1.7 g)

NMR Ή (300 MHz, CD ₃ CN); δ (ppm): 1, 92 (s, 12H, H _{7, 9);} 2.34 (s, 6H, H ₈ ); 7.34 (m, 36H, aromatics); 7.79 (t, 4H, H ₃ , ₅ ); 8.64 (s, 1H, H 0).

¹³ C NMR (300 MHz, DMSO-d ₆ ); δ (ppm): 16.36 (4C, C ₇ ); 20.36 (2C, C ₈ ); 124.45 (4C,

C ₃ , ₅ ), 125.1 1 (3C, Caromatic), 126.41 (1H, Caromatic), 126.54 (2C, Caromatic), 129.08

(2C, C10); 129.79 (2C, Caromatic); 131, 35 (4C, C ₂ , 6); 134.05 (2C, Cl); 134.80 (aromatic IC, C); 136.41 (2C, aromatic C); 139.03 (2C, C ₄ ); 141, 12 (Cl, C n); 142.39 (CI,

Caromatic) ·

ESI-MS: m / z, (%) :(%): [B (bPh) ₄ ] = 623.29; [2N ⁺ (-C21H25)] = 305.20; total mass of the salt: [-B- (bPh) ₄ ⁺ 2 N ⁺ (-C21H25)] = 928.49 g / mol for C ₆ 9H ₆ iBN ₂ .

UV-Vis: υ max (254) (mole ¹ X ^-1 cm ^-1 ) in CH ₃ CN: 33846; Quartz tank thickness: 1 cm

The absorbance spectrum as a function of the wavelength obtained is shown in FIG. (e) 1,3-dimethylimidazolium tetraphenylborate

Me ₂ ImB (Ph) ₄

Yield: 76%

NMR Ή (300 MHz, DMSO-d6); δ (ppm): 3.80 (s, 6H, Hi); 6.80 (t, 4H, aromatics); 6.93 (t, 8H, aromatics); 7.34 (m, 8H, aromatics); 7.63 (s, 2H, H ₂ ); 8.92 (s, 1H, H ₃ ).

¹³ C NMR (300 MHz, DMSO-d6); δ (ppm): 35.91 (2C, Cl); 121, 80 (2C, C_tic); 123.69 (2C, C _2); 125.60 (4C, Cad only); 135.81 (8C, Canticle); 137.24 (1 C, C ₃ ).

Yield: 84%

NMR Ή (300 MHz, DMSO-d ₆ ); δ (ppm): 2.30 (s, 6H, H ₈ ); 2.35 (s, 12H, H _{7, 9);} 4.43 (s,

4H, H ₂ ); 6.80 (t, 4H, aromatics); 6.94 (t, 8H, aromatics); 7, 10 (s, 4H, aromatics); 7.20 (m, 4H, aromatics); 8.99 (s, 1H, Hi).

¹³ C NMR (300 MHz, DMSO-d6); δ (ppm): 17.18 (4C, C ₂ ); 20.56 (2C, Cl); 50.88 (2C, C ₅ ) 121.5 (4C, C ₃ ); 125.3 1 (4C, aromatic C); 129.32 (4C, aromatic C); 130.41 (1 C, Ce);

135.38 (8C, Caromatic); 139.67 (4C, Caromatic); 160.28 (2C, C _4).

EXAMPLE 2

 Synthesis of carboxylate salts of imidazoKin um according to the invention

Imidazol salts (ni) um (g), (h), (i) and (j) of formula (III-b) according to the invention and whose structures are presented in the following Table 3 were synthesized.

TABLE 3 iPr: isopropyl

 Mes: 2,4,6-Trimethylphenyl

 PA: Phenylglyoxylate

 Keto: Ketoprofenate

 Xanth: Methylxanthone acetate

 Bz: Benzoyl

 OXth: 9-oxoxanthen-2-yl

 IPr: 1,3-diisopropylimidazolium

 IMes: 1,3-bis (2,4,6-trimethylphenyl) imidazolium

Protocol of synthesis of salts

 The imidazole (ni) um (g) to (j) salts were synthesized via an anion exchange reaction between the corresponding imidazolium (III) chloride and potassium carboxylate salts, according to the protocol. next.

 A solution (A) of imidazole (ni) um chloride in ethanol or trichloromethane and a solution (B) of potassium carboxylate in ethanol or trichloromethane are prepared. Solution (B) is poured dropwise into solution (A). The mixture is stirred for 1 hour at room temperature or at 60 ° C, then filtered on celite at room temperature. The solvent is then evaporated and the product thus obtained is optionally dried under vacuum at 60 ° C or 40 ° C overnight. Finally, the imidazole (ni) um salt is recovered.

Synthesis of potassium carboxylates

 Phenylglyoxylate potassium:

993 mg (6.62 mmol) of phenylglyoxilic acid are dissolved in 18 ml of a solution of potassium hydroxide (C = 0.55 mol.L ¹ ) in ethanol. The mixture is then stirred for 1 hour. The precipitate formed is then filtered and dried. The final yield is 90%.

 Potassium ketoprofenate:

2.160 g (8.5 mmol) of ketoprofen are dissolved in 4 mL of CHCl 3 and added to 8 mL of an aqueous solution of potassium hydroxide (C = 1 mol.L ^-1 ) .The two-phase mixture is then left underneath. stirring for 30 minutes then the aqueous phase is recovered and the water is evaporated, a white solid is then recovered and dried, the final yield is 83%. Methylxanthone potassium acetate:

0.102 g (0.38 mmol) of methylxanthone acetic acid (2- (9-Oxoxanthen-2-yl) propionic acid) are dissolved in 5 mL of CHCl 3 to which are added 5 mL of distilled water and 0.3 mL of an aqueous potassium hydroxide solution (C = 1 mol l ^"l). the biphasic mixture was then stirred for 30 minutes and then the aqueous phase is recovered and the water is evaporated. a white solid is then recovered and dried The final yield is 100% (0.38 mmol).

The following Table 4 accounts for the nature and amounts of each of the reagents for the preparation of the imidazolidine (ni) um (g) to (j) salts.

 TABLE 4

IPrHCl: 1,3-diisopropylimidazolium chloride, marketed by ABCR under the reference No. AB 146607;

 IMESHCl: 1,3-bis (2,4,6-trimethylphenyl) imidazolium chloride, sold by ABCR under the reference No. AB 130859.;

 KPA: Potassium phenylglyoxylate prepared according to the method described above.

KKeto: potassium ketoprofenate prepared according to the method described above.

KXanth: Methylxanthone potassium acetate prepared according to the method described above. Yield and characterization of synthesized imidazole (ni) um salts (g) 1,3-b-trimethylphenyl) imidazolium phenylglyoxylate

Yield: 70% (0.74 mmol)

NMR Ή (400 MHz, CDCl ₃ ): 10.71 (s, 1H); 7.71 (d, 2H); 7.44 (d, 2H), 7.34 (t, 1H), 7.20 (q, 2H); 6.89 (s, 4H); 2.23 (s, 6H); 2.08 (s, 12H).

¹³ C NMR (300 MHz, CD ₃ CN); δ (ppm):?

UV-Vis: ε ₂₅₄ (m.p.L.ccm ¹ ) in CH ₃ CN: 7728; £ ₃₆₅ (mo ^ cm ^ .L ¹⁾ in CH ₃ CN: 96; Quartz tank thickness: 1 cm.

 The absorbance spectrum as a function of the wavelength obtained is shown in FIG.

(h) 1,3-b-trimethylphenyl) imidazolium ketoprofenate

 Yield: 95%

NMR Ή (400 MHz, CDCl ₃ ): 11.49 (s, 1H); 7.76-7.32 (m, 9H); 7.27 (s, 1H); 7.14 (t, 1H); 6.95 (s, 4H); 3.00 (quad, 1H); 2.26 (s, 6H); 2.06 (s, 12H); 1.04 (d, 3H).

¹³ C NMR (300 MHz, CD ₃ CN); δ (ppm):

UV-Vis: ₂₅₄ £ (mo ^ cm ^ .L ¹⁾ in CH ₃ CN: 15560; £ ₃₆₅ ⁽¹ mol L ¹ cm ^1..) In CH ₃ CN: 97; Quartz tank thickness: 1 cm.

The absorbance spectrum as a function of the wavelength obtained is shown in FIG. (i) 1, 3-diiso ropylimidazolium ketoprofenate

 Yield: 75%

NMR Ή (400 MHz, CDCl ₃ ): 0.81 (s, 1H); 7.80-7.40 (m, 6H); 7.32 (t, 1H); 7.21 (d, 2H); 4.81 (quint, 2H); 3.72 (quad, 1H); 1.48 (m, 15H).

¹³ C NMR (300 MHz, CD3CN); δ (ppm):?

UV-Vis: δ 254 (mol .LL · cm ¹ ) in CH3CN: 12395; Quartz tank thickness: 1 cm. The absorbance spectrum as a function of the wavelength obtained is shown in FIG.

(i) Methylxanthone Acetate-bis (2,4,6-trimethylphenyl) imidazolium

 Yield: 83%

 NMR Ή (400MHz, CDCl3): 10.96 (s, 1H); 8.39-7.05 (m, 9H); 6.49 (s, 4H); 3.32 (quad, 1H); 2.32 (s, 6H); 2.14 (s, 12H); 1.21 (d, 3H).

UV-Vis: 254 £ (mo ^ ^ .L ¹ .cm) in CH3CN: 20005; ₃₆₅ (mol, ^{1. 1} cm ^-1 ) in CH ³ CN: 923; Quartz tank thickness: 1 cm.

 The absorbance spectrum as a function of the wavelength obtained is represented in FIG. 8.

EXAMPLE 3

 Synthesis of polynorbornenes in solution according to the process of the invention

Photopolymerizable compositions, denoted "Compositions 3", were prepared by mixing, in variable proportions, the tetraarylborate type salts. imidazolium (salts (c) and (d)), prepared according to Example 1 above, in powder form, the ruthenium complex of formula [RuCl 2 (/ -cymene)] 2 (marketed by Alfa Aesar under the reference No. L 19126) in powder form and norbornene in powder form (sold by Alfa Aesar under the reference No. LU 103) in deuterated dichloromethane (CD2Cl2).

 The proportions of the compounds used in each of the photo-polymerizable compositions are specified below.

3.1. Variation of UV irradiation time

 TABLE 5

Polymerization conditions

The photopolymerizable composition 3 is exposed to sunlight for 1h30, then subjected to UV irradiation (254 nm) at 10 mW.cm ^-2 for a period of 5 minutes or 10 minutes. react to sunlight for 70 minutes.

 The composition is precipitated in methanol, and the formed polyolefins are recovered by filtration and analyzed.

Results

NMR analyzes ^! H done every 30 minutes allow to follow the formation of polynorbomene.

The analysis of the composition by 1 H NMR after 40 minutes of exposure to sunlight following the irradiation, confirms the good formation of polynorbomene. Indeed, on the NMR spectrum ^! H (Figure 9) are the proton resonance peaks of the C = C double bond of polynorbomene at 5.20 ppm and 5.35 ppm. The conversion rate to monomer can be determined by calculating the ratio of peak intensities to 5.20 and 5.35 ppm of polynorbonene (IPN) and 6 ppm of norbornene (IN) according to: r = IPN / (IPN) + IN).

 The evolution of the monomer conversion rate as a function of time, before and after irradiation (5 or 10 min of irradiation), is represented in FIG.

 Fourier transform infrared (FTIR) and gravimetric analysis lead to similar results in terms of conversion rate to monomer.

The analysis of the polymers, in the composition obtained 10 minutes, 40 minutes and 70 minutes after the UV irradiation, is carried out by size exclusion chromatography (CES) in THF.

The results obtained in terms of average molecular weight (M _n) of weight average molecular weight (M _w) and polydispersity index (I _p, M _w / M _n) are shown in following Table 6 .

 TABLE 6

Conclusion

It is apparent from this test that it is possible with the process according to the invention to obtain, with a high degree of conversion, polyolefins of high molecular mass and low polydispersity index. 3.2. Variation of the molar ratio between the imidazolium tetraarylborate salt and the ruthenium complex [RuCl 2 (p-cymene)] 2

 The following photo-polymerizable compositions 1, 2 and 3 were prepared according to the protocol indicated above.

 TABLE 7

Polymerization conditions

The photopolymerizable compositions are exposed to sunlight for 1h30, then subjected to UV irradiation (254 nm) at 10 mW.cm ^-2 for a period of 10 minutes, and then left to react with sunlight. for 70 minutes.

 The compositions are precipitated in methanol, and the formed polyolefins are recovered by filtration and analyzed.

Results

 The evolution of the monomer conversion rate as a function of time, before and after irradiation, for the three compositions analyzed, determined as described in Example 3.1. previous, is shown in Figure 11.

 Fourier transform infrared (FTIR) and gravimetric analysis lead to similar results in terms of conversion rate to monomer.

The results of the polymer analysis by CES, under the conditions detailed in Example 3.1. previous, are presented in Table 8 below. Time of 10 minutes 40 minutes 70 minutes reaction after M _n M _w M _n M _w M _w UV irradiation (g / mol) (g / mol) Ip (g / mol) (g / mol) IP (g / mol) ( g / mol) IP

Composition 1 151000 278600 1.84 98400 226500 2.3 148500 263000 1.77

Composition 2 163905 234427 1.4 294621 353743 1.2 311751 353929 1.1

Composition 3 10273 42200 4.1 21390 75656 3.5 298803 404089 1.35

 TABLE 8

Conclusion

 The use of the imidazolium tetraarylborate salt and ruthenium comp [RuC (γ-cymene)] in a molar ratio of IMesB (Ph) 4 / [RuCl 2 (γ-cymene)] 2 of 3 (composition 2) allows access to high norbornene conversion rates, while obtaining polyolefins of high molecular weight and low polydispersity index.

3.3. Variation in the nature of imidazolium salt

 The following photo-polymerizable compositions were prepared according to the protocol indicated above.

 TABLE 9

Polymerization conditions

The photopolymerizable compositions are exposed to sunlight for 1h30, then subjected to UV irradiation (254 nm) at 10 mW.cm ^-2 for a period of 10 minutes, and then left to react with sunlight. for 40 minutes. The compositions are precipitated in methanol, and the formed polyolefins are recovered by filtration and analyzed.

Results

 The evolution of the monomer conversion rate as a function of time, before and after irradiation, for the two compositions analyzed, determined as described in Example 3.1. previous, is represented in FIG.

 Fourier transform infrared (FTIR) and gravimetric analysis lead to similar results in terms of conversion rate to monomer.

The results of the polymer analysis by CES, under the conditions detailed in Example 3.1. previous, are presented in the following table 10.

 TABLE 10

Conclusion

It emerges from these tests that the photo-polymerizable composition employing the salt IMesB (bPh) 4 makes it possible to obtain, according to the process of the invention, higher norbornene conversions than with the composition implementing the salt. IMesB (Ph) ₄ .

EXAMPLE 4

 Synthesis of polynorbornenes by mass according to the process of the invention

Polymerization conditions

The photo-polymerizable compositions 1 to 4, prepared in the preceding example 3, were spread on calcium fluoride pellets (CaF ₂ ) and left in the open air so that the solvent (dichloromethane) evaporated. The CaF ₂ pellets were then exposed to UV radiation using a polychromatic light from a medium pressure xenon-mercury arc lamp (Hamamatsu L8252, λ: 250-600 nm, "full irradiance" = I = 685 mW.cm ^"2 ) for a period of up to 600 s.

 The polynorbornenes obtained are recovered directly and analyzed.

Results

A real-time Fourier transform infrared (FTIR) analysis made it possible to determine the conversion rate as a function of time by observing the decrease in the intensity of the vibration band at 1334 cm ^-1 (characteristic deformation out of the = norbornene CH = plane) as well as the 1574 cm ^-1 vibration band (characteristic of the C = C stretching motion of norbornene). The monomer conversion rate was also confirmed by gravimetry.

 In all cases, monomer conversions greater than 85% were obtained after 600 seconds of irradiation.

Photolithography application

 The application of a TEM grid type mask, having a so-called "honeycomb" pattern before UV irradiation on the composition 3, deposited on a silicon wafer and dried, prepared as described previously, made it possible to obtain at the end of the irradiation, a "patterned" film presenting the patterns of the mask, after washing it with methanol.

The UV irradiation was carried out for 10 min by means of a Hg-Xe lamp equipped with a reflector for a short UV wavelength producing a light beam with a power of 80 mW crrf ² for λ <300 nm ( and for a total irradiance of 600 mW crrf ² ). This medium-pressure Hg-Xe lamp (L8252, 200 W, Hamamatsu) was connected to a flexible waveguide (LC6, Hamamatsu) generating a beam of light focused on the sample placed 3 cm from the exit of the guide wave.

Such a polynorbornene film is observable by scanning electron microscopy (SEM) (FIG. 13). EXAMPLE 5

 Synthesis of polynorbornenes in solution according to the process of the invention

The following photo-polymerizable compositions 5 and 6 were prepared by mixing, in variable proportions, the tetraarylborate salt of imidazolium (c), prepared according to Example 1 above, in powder form, the ruthenium complex of formula [RuCl 2 (? - cymene)] 2 (sold by Alfa Aesar under the reference No. L 19126) in powder form (denoted "Ru"), norbornene (denoted "NB") in powder form (marketed by Alfa Aesar under the reference No. LU 103), and isopropylthioxanthone (called "ITX"), in deuterated dichloromethane (CD2Cl2).

 The proportions of the compounds used in each of the photo-polymerizable compositions are specified below.

5.1. Variation of the molar ratio between the monomer and the ruthenium complex (NB / Ru), in the presence of ITX

 TABLE 11

Polymerization conditions

The photopolymerizable compositions are subjected to UV light irradiation of 350-365 nm for a period of 10 minutes. They are then allowed to react at ambient temperature and visible light for 10 minutes. The compositions are precipitated in methanol, and polyolefins formed are recovered by filtration and analyzed by SEC in THF and ^J H NMR

Results

 The evolution of the monomer conversion rate as a function of time, after irradiation, for the two compositions analyzed, was determined as described in Example 3.1.

 The analysis of the polymers, in the compositions obtained 10 minutes after the UV irradiation, and after precipitation in methanol, is carried out by size exclusion chromatography (CES) in THF.

The results obtained in terms of average molecular weight (M _n) of weight average molecular weight (M _w) and polydispersity index (I _p, M _w / M _n) are shown in Table 12 below .

 TABLE 12

Conclusion

It emerges from these tests that the photo-polymerizable formulation 6 using the salt IMesBPli4 and isopropylthioxanthone (ITX) makes it possible, according to the process of the invention, to obtain fast norbornene conversions (barely 10 minutes). and can reach large molar masses (about 1,350,000 g.mol ^-1 ).

5.2. Variation of the molar ratio between the monomer and the ruthenium complex (NB / Ru), in the absence of ITX

The following photo-polymerizable compositions 7 and 8 were prepared according to the protocol indicated above, in the absence of isopropylthioxanthone.

Polymerization conditions

 The photopolymerizable compositions are subjected to UV light irradiation at 350-365 nm for a period of 30 minutes. They are then allowed to react at room temperature and visible light for a certain time (see Table 14 below).

The compositions are precipitated in methanol, and polyolefins formed are recovered by filtration and analyzed by SEC in THF and ^J H NMR

Results

 The evolution of the monomer conversion rate as a function of time, after irradiation, for the two compositions analyzed, was determined as described in Example 3.1.

 The analysis of the polymers, in the compositions obtained 120 or 1390 minutes after the UV irradiation, and after precipitation in methanol, is carried out by size exclusion chromatography (CES) in THF.

The results obtained in terms of number average molecular weight (M _n ), weight average molecular weight (M _w ) and polydispersity index (I _p , M _w / M _n ratio) are collated in the following table 14. .

 TABLE 14

Conclusion

 These tests demonstrate that in the absence of ITX, it is necessary to irradiate 30 minutes and let polymerize longer to achieve conversions between 75 and 95%.

EXAMPLE 6

 Synthesis of polynorbornenes in solution according to the process of the invention

The following photo-polymerizable compositions 9 to 13 were prepared as previously described.

The proportions of the compounds used in each of the photo-polymerizable compositions are specified below.

6.1. Variation of the amount of ITX

 TABLE 15 Polymerization conditions

 The photopolymerizable compositions are subjected to UV light irradiation at 350-365 nm for a period of 10 minutes.

 They are then allowed to react at ambient temperature and visible light for a certain duration (see Table 16 below).

The compositions are then precipitated in methanol, and polyolefins formed are recovered by filtration and analyzed by SEC in THF and ^J H NMR in CDCl3. Results

 The evolution of the monomer conversion rate as a function of time, after irradiation, for the five compositions analyzed, determined as described in Example 3.1. previous, is shown in Figure 14.

 The analysis of the polymers, in the compositions obtained 360 or 390 minutes after the UV irradiation and after precipitation in methanol, is carried out by size exclusion chromatography (CES) in THF.

The results obtained in terms of number-average molecular weight (M _n ), weight-average molecular weight (M _w ) and polydispersity index (I _p , M _w / M _n ratio) are collated in the following table 16 .

 TABLE 16 Conclusion

 The variation of the ITX content with respect to the amounts of IPrB (Pli4) and pro-catalyst [RuCl2 (γ-cymene)] 2 has little influence on the polymerization rate after light irradiation.

These experiments make it possible to show that the photo-polymerization is also possible using the imidazolium salt IPrBPh ₄ in the presence of ITX. It is however slower than with IMesBPh ₄ .

6.2. Variation of the amount of imidazolium salt

The following photo-polymerizable compositions 14 to 16 were prepared according to the protocol indicated above.

Polymerization conditions

 The photopolymerizable compositions are subjected to UV light irradiation at 350-365 nm for a period of 10 minutes.

 They are then allowed to react at room temperature and visible light for a certain time (see Table 18 below).

The compositions are then precipitated in methanol, and the polyolefins formed are recovered by filtration and analyzed and analyzed by SEC in THF and by

Results

The evolution of the monomer conversion rate as a function of time, after irradiation, for the four compositions analyzed, determined as described in FIG. Example 3.1. previous, is shown in Figure 15 and summarized in Table 18 below.

 TABLE 18

 Conclusion

The increase in the amount of IPrBPh ₄ relative to the amount of procatalyst [RuCl2 (/? - cymene)] 2 makes it possible to accelerate the polymerization rate for the same UV irradiation time, and more particularly for a ratio IPrBPh ₄ / [RuCl ₂ (/? - cymene)] 2 of 10 (Composition 16).

6.3. Variation of UV irradiation time

Photocomponent composition- polymerizable photopolymerizable composition 13

 Report

 molar

 540/1/2/1 540/1/2/10

NB / Ru / IPrBh ₄ /

 ITX

Norbornene 0.1 g (1.064.10 ^-3 mol) 0.1 g (1.064.10 ^-3 mol)

Salt

of imidazolium 0.0019 g (4.022 × 10 ^-6 mol) 0.0019 g (4.022 × 10 ^-6 mol) (a) IPrB (Ph) ₄

 [RuChip-

0.0012 g ⁽⁶ mol 1,96.1ο-) 0.0012 g ⁽⁶ mol 1,96.1ο-)

 cymene)] 2

ITX 0.0005 g (1.966.10 ^-6 mol) 0.005 g (1.966.10 ^-5 mol)

CD2CI2 1 mL 1 mL Polymerization conditions

 The photopolymerizable compositions 9 and 13 prepared according to Example 6.1 are subjected to UV light irradiation (350-365 nm) for periods of 10 minutes, 20 minutes or 30 minutes.

 They are then left to react at ambient temperature and visible light for a certain duration (see Table 19 below).

 The compositions are then precipitated in methanol, and the polyolefms formed are recovered by filtration and analyzed.

Results

 The evolution of the monomer conversion rate as a function of time, after irradiation, for the two compositions analyzed, determined as described in Example 3.1. previous, is shown in Figure 16.

 The analysis of the polymers, in the compositions obtained 360 or 450 minutes after the UV irradiation, is carried out by size exclusion chromatography (CES) in THF.

The results obtained in terms of average molecular weight (M _n) of weight average molecular weight (M _w) and polydispersity index (I _p, M _w / M _n) are shown in Table 19 following .

TABLE 19 Conclusion

 The UV irradiation time has little influence on the polymerization kinetics when the IPrBPfu salt is employed.

 6.4. Variation in UV irradiation time and absence of ITX

 The following photo-polymerizable composition 17 was prepared according to the protocol indicated above, without ITX.

 TABLE 20

 Polymerization conditions

 The photopolymerizable composition is subjected to UV light irradiation at 350-365 nm for periods of 10, 20 or 30 minutes.

 The irradiated compositions are then allowed to react at room temperature and visible light for a certain time (see Table 21 below).

The compositions are then precipitated in methanol, and the polyolefins formed are recovered by filtration and analyzed and analyzed by SEC in THF and by

Results

 The evolution of the monomer conversion rate as a function of time, after irradiation (10, 20 or 30 minutes), for the compositions analyzed, determined as described in Example 3.1. previous, is shown in Figure 17.

The analysis of the polymer, in the compositions obtained 420 minutes or 270 minutes after the UV irradiation and precipitation in methanol, is carried out by size exclusion chromatography (CES) in THF. The results obtained in terms of average molecular weight (M _n) of weight average molecular weight (M _w) and polydispersity index (I _p, M _w / M _n) are shown in Table 21 following .

 TABLE 21

Conclusion

 In the absence of ITX with the IPrBP u salt, the kinetics of polymerization are comparable with those in the presence of ITX.

EXAMPLE 7

Influence of the nature of imidazol (ni) um salt on polymerization kinetics

 The following photo-polymerizable compositions 18 to 20 were prepared, as described previously, in the presence of ITX.

The proportions of the compounds used in each of the photo-polymerizable compositions are specified in Table 22 below.

Polymerization conditions

 The photopolymerizable compositions 18 to 20 are subjected to UV light irradiation (350-365 nm) for a period of 10 minutes.

 They are then allowed to react at room temperature and visible light for a certain time (see Table 23 below).

 The compositions are then precipitated in methanol, and the polyolefins formed are recovered by filtration and analyzed.

Results

The evolution of the monomer conversion rate as a function of time, after irradiation, for the compositions analyzed, is determined as described in Example 3.1. previous. Irradiation time Reaction time Rate of

 at 365 nm after UV irradiation conversion

 (min) (min) maximum (%)

Composition 18 10 30 88

 40 70

 120 70

 Composition 19 10

 210 72

 360 73

 20 63

 Composition 20 10

 120 80

 TABLE 23

 Conclusion

The kinetics of polymerization with the salt SIMesB (Ph) 4 and Me2IMB (Ph) 4 are slower than with the salt IMesB (Ph) ₄ .

 The salt IMesB (Ph) 4 is therefore most suitable for photopolymerization of norbornene in the presence of ITX.

EXAMPLE 8

 Photo-polymerization of DCPD (dicyclopentadiene)

The following photopolymerizable composition is prepared under nitrogen (weighing of the products in air and then placed under nitrogen) and placed in a borosilicate hemolysis tube. The tube is then placed in a horizontal position and then subjected to UV irradiation at 350-365 nm for 30 minutes with a power of 9.9 mW.cm ^-2 using a Bio-Link enclosure of the "BLX user manual" type. The film obtained is left in the tube overnight without irradiation and is then removed from the tube and then washed with methanol.

Result

 A film is obtained. Obtaining a rigid film after irradiation requires an irradiation time of 30 minutes (4 minutes for norbornene). The film introduced into THF at 70 ° C. does not dissolve after several hours. The film therefore has a total insolubility that confirms that the film is crosslinked.

EXAMPLE 9

 Photo-polymerization of a dicyclopentadiene / norbornene mixture 38/62

The following photo-polymerizable composition 22 is prepared under nitrogen (weighing the products in air and then put under nitrogen) and placed in a borosilicate hemolysis tube. The tube is then placed in a horizontal position and subjected to UV irradiation at 350-365 nm for 5 minutes with a power of 9.9 mW.cm ^-2 using a Bio-Link enclosure of the "BLX user manual" type. The film obtained is left in the tube overnight without irradiation and is then removed from the tube and then washed with methanol.

 TABLE 25

Result

 A film is obtained. Obtaining a rigid film after irradiation requires an irradiation time of 5 minutes (4 minutes for norbornene alone). The film introduced into THF at 70 ° C. does not dissolve after several hours. The film therefore has a total insolubility that confirms that the film is crosslinked.

EXAMPLE 10

 Synthesis of polynorbornenes in solution according to the process of the invention

The following photo-polymerizable compositions 23 and 24 are prepared by mixing, in variable proportions, the imidazolium carboxylate type salt (h), prepared according to the preceding example 2, in powder form, the ruthenium complex of formula [RuCl 2 (? - cymene)] 2 (sold by Alfa Aesar under the reference No. L19126) in powder form and norbornene in powder form (sold by Alfa Aesar under the reference No. Ll 1103) in deuterated dichloromethane (CD2CI2). The proportions of the compounds used in each of the photo-polymerizable compositions are specified in Table 26 below.

 TABLE 26

Polymerization conditions

 The photopolymerizable compositions are subjected to UV light irradiation (350-365 nm) for a period of 1 to 10 minutes.

 They are then allowed to react at room temperature and visible light for a certain period of time (see Table 27 below).

 The compositions are then precipitated in methanol, and the polyolefins formed are recovered by filtration and analyzed.

Results

The evolution of the monomer conversion rate as a function of time, after irradiation, for the compositions analyzed, determined as described in Example 3.1. previous is presented in Figures 18 and 19. Composition 23 Composition 24

 Time

 Reaction time Rate of reaction time Radiation rate at

 after irradiation conversion after irradiation conversion 365 nm

 UV (min) maximum (%) UV (min) maximum (%) (min)

 10 27

 40 52

 1 60 73

 90 84

 120 96

 10 50

 2 40 82 - - 60 96

 10 68

 25 83

 J

 35 93

 45,100

 15 82

 4 35 94 - - 45 100

10 44

20 60

10 73 30 61

30 88 90 80

J

 50 97 230 90

70 99 290 92

 350 93 410 94

15 85

 6 35 95 - - 55 98

 10 99.6

 o

 20,100

 10 52

20 59

10,100

 10 30 66

 20,100

 100 80 180 85

TABLE 27 Conclusion

 A photo-polymerizable composition using the IMesKeto salt with 10 molar equivalents relative to the Ruthenium pro-catalyst makes it possible to obtain, according to the process of the invention, total conversions to norbornene and for reaction times after irradiation included. between 10 and 120 minutes.

 More specifically, an irradiation of 8 minutes is sufficient to reach 100% conversions after 10 minutes of polymerization. Moreover, with this imidazolium salt, the use of ITX is not necessary because IMesketo has a UV-Visible absorption band at 365 nm.

 The use of 5 molar equivalents of IMesKeto salt relative to the Ruthenium pro-catalyst makes it possible, according to the process of the invention, to obtain 85-95% conversions to norbornene after 180 and 410 minutes with 5 to 10 hours. minutes of irradiation. In this case, the kinetics of polymerization is relatively slow. It is therefore preferable to use 10 equivalents of IMesKeto salt for faster polymerization.

EXAMPLE 11

 Photo-polymerization of DCPD (dicyclopentadiene)

 The following photo-polymerizable composition is prepared under nitrogen (weighing the products in air and then put under nitrogen) in a hemolysis tube. The tube is then placed in a horizontal position to form a film.

Subsequently, the mixture is irradiated under UV at 350-365 nm with a power of 9.9 mWcm ^-2 in a Bio-Link enclosure of type "BLX." A time of 20 minutes of irradiation is necessary to form a film enough rigid to be demolded.

 The film is left in the tube overnight without irradiation to finish the polymerization. It is then removed from the tube and washed with methanol.

The proportions of the compounds used in the composition are specified in Table 28 below.

 TABLE 28

Results

 Obtaining a rigid film after irradiation requires an irradiation time of 20 minutes. This time is much longer than for the norbornene monomer. This can be explained simply by a lower reactivity of DCPD which has a mixture of endo-exo stereoisomers with a majority of endo (about 75%). It is recognized that the endo stereoisomer is less reactive than the exo. The film is introduced into THF at 70 ° C. and remains insoluble after several hours. The film is therefore crosslinked.

EXAMPLE 12

 Photo-polymerization of a dicyclopentadiene / norbornene mixture 17/83

The following photo-polymerizable composition 26 is prepared under nitrogen (weighing the products under air and then put under nitrogen) in a hemolysis tube. The tube is then placed in a horizontal position to form a film. Subsequently, the mixture is irradiated under UV at 350-365 nm with a power of 9.9 mWcm ^-2 in a Bio-Link enclosure type "BLX." A time of 1 minute of irradiation is sufficient to have a film enough rigid to be demolded.

 After 1 min of irradiation, the film is left in the tube overnight without irradiation to be sure that the polymerization is complete. It is then removed from the tube and washed with methanol.

 The proportions of the compounds used in the composition are specified in Table 29 below.

 TABLE 29

Results

 Obtaining a rigid film after irradiation requires an irradiation time of only 1 minute. The film is introduced into THF at 70 ° C. The film has a total solubility in THF. The film is therefore uncrosslinked.

EXAMPLE 13

Photo-polymerization of hexanedioldinorbornene / norbornene mixture 6/94 The following photo-polymerizable composition 27 is prepared under nitrogen (weighing the products in air and then put under nitrogen) in a hemolysis tube. The tube is then placed in a horizontal position to form a film.

Subsequently, the mixture is irradiated under UV at 350-365 nm with a power of 9.9 mWcm ^-2 in a Bio-Link enclosure type "BLX." A time of 3 minutes of irradiation is sufficient to have a film enough rigid to be demolded.

 After irradiation, the film is left in the tube overnight without irradiation to be sure to obtain a complete polymerization. It is then removed from the tube and washed with methanol.

 The proportions of the compounds used in the composition are specified in Table 30 below.

 TABLE 30

Results

Obtaining a rigid film after irradiation requires an irradiation time of only 3 minutes. The film is introduced into THF at 70 ° C. The film remains insoluble in THF at 70 ° C. after several hours and is therefore considered to be crosslinked. EXAMPLE 14

 Norbornene ROMP with an imidazolium salt in aqueous dispersed medium

0.1 g of polyoxyethylene stearyl ether marketed under the name Brij ^® S100 (Mn ~ 4600g / mol) is dissolved in lOmL of distilled water sold under the designation Milli-Q ^® then introduced into a suitable pill. In a second pill, 0.8 mg of [RuCl ₂ (p-cymene)] 2 (1.31. IO ^"6 mol), 11.9 mg of salt (c) IMesBPh ₄ ^{(1.95.10" 5} mol), 0.103 g of hexadecane (4.55 × 10 ^-4 mol) and 0.12 g of Norbornene (1.27 × 10 ³ mol) are solubilized in 1.6 ml of Dichloroethane (DCE).

 The organic phase is then mixed with the aqueous phase with magnetic stirring for 1 hour at room temperature to form a pre-emulsion. This mixture is then placed under ultrasound for 6 minutes using a Sonic type of ultrasonicator with a maximum power of 750 W coupled with magnetic stirring. The power used during the preparation of the mini-emulsions corresponds to 50% of the maximum power. The mixture is sonicated under pulsation (9 seconds of ultrasound then 9 seconds of rest) and cooled with an ice bath to prevent overheating of the medium. A semi-transparent mini-emulsion having droplet sizes of the order of 300 nm is then obtained.

 This mini-emulsion is then placed in a quartz cuvette with an optical path of 1 mm and is subjected to UV irradiation (240-550 nm) using a Hamamatsu LC8 lamp equipped with a waveguide which is placed 1.5 cm from the bowl. After 2 hours of irradiation, the lamp is extinguished and the polymerization is maintained for 2 hours. The size of the particles obtained at this moment of the reaction is then 340 nm. The miniemulsion is then coagulated in ethanol and the polymer is recovered and dried for 24 hours under vacuum.

The conversion to norbornene is 40%. EXAMPLE 15

 Norbornene ROMP with an imidazolium salt in aqueous dispersed medium

0.1 g of polyoxyethylene stearyl ether sold under the name Brij ^® S100 (Mn ~ 4600g / mol) is dissolved in 10 mL of distilled water sold under the designation Milli-Q ^® then introduced into a suitable pill. In a second pillbox, 0.8 mg of [RuCl ₂ (p-cymene)] ₂ (1.31 × 10 ⁶ mol), 10.9 mg of salt (h) IMesKeto (1.95 × 10 ^-5 mol), 0.103 g of Hexadecane (4.55 × 10 ^-4 mol) and 0.12 g of norbornene (1.27 × 10 ³ mol) are solubilized in 1.6 ml of Dichloroethane (DCE).

 The organic phase is then mixed with the aqueous phase with magnetic stirring for 1 hour at room temperature to form a pre-emulsion. This mixture is then placed under ultrasound for 6 minutes using a Sonic type of ultrasonicator with a maximum power of 750 W coupled with magnetic stirring. The power used during the preparation of the mini-emulsions corresponded to 50% of the maximum power. The mixture is sonicated under pulsation (9 seconds of ultrasound then 9 seconds of rest) and cooled with an ice bath to prevent overheating of the medium. A semi-transparent mini-emulsion having droplet sizes of the order of 300 nm is then obtained.

 This mini-emulsion is then placed in a quartz cuvette with an optical path of 1 mm and is subjected to UV irradiation (240-550 nm) using a Hamamatsu LC8 lamp equipped with a waveguide which is placed 1.5 cm from the bowl. After 100 minutes of irradiation, the lamp is extinguished and the polymerization is maintained for 2 hours. The size of the particles obtained at this moment of the reaction is then 340 nm. The miniemulsion is then coagulated in ethanol and the polymer is recovered and dried for 24 hours under vacuum.

The conversion to norbornene is 72%. References

 [1] Mol J. C, J. Mol. Cat. A: Chem., 2004, 213, 39-45;

 [2] Grubbs R.H., Handbook of Metathesis, Weinheim: Wiley-VCH, 2003;

 [3] Naumann et al., Macromol. Rapid. Commun., 2014, 7, 682-701;

 [4] Monsaert et al., Chem. Soc. Rev., 2009, 38, 3360-3372;

 [5] Van der Schaff et al, Angew. Chem. Int. Ed, 1996, 35, 1845-1847;

 [6] Wang et al, Angew. Chem. Int. Ed, 2008, 47, 3267-3270;

 [7] Keitz et al., J. Am. Chem. Soc., 2009, 131, 2038-2039;

 [8] Weitekamp et al., J. Am. Chem. Soc., 2013, 135, 16817-16820; and

[9] Delaude et al., Chem. Common. 2001, 986-987.

Claims

1. Process for synthesizing a polyolefin by a photoinitiated ring-opening polymerization (ROMP) reaction of a cycloolefin, said reaction being carried out in the presence of a ruthenium-based catalyst of formula

(I):

 (I)

 characterized in that said ruthenium catalyst is generated in situ under UV irradiation from

A ruthenium complex of formula [RuCl ₂ (L)] ₂ (II), L representing a ligand with a cyclic structure, aromatic or comprising at least two nonadjacent C = C double bonds, optionally substituted with one or more groups (C1-C6) alkyl; and

 An imidazole salt (ni) um of formula (III):

A ^"

R, ÷ -ί ^, R.

 N N

R D '

 2 2

 (III)

in which :

. R 1 and R 1, which may be identical or different, are chosen from (C 1 -C 6) alkyl groups, non-aromatic C ₃ -C ₁₂ carbocyclic groups and optionally substituted (C ₆ -C ₂ O) aryl groups, in particular by one or more (C ₁ -C ₆ ) alkyl groups;

. R ₂ and R ₂ ', which may be identical or different, are chosen from (C ₁ -C ₆ ) alkyl groups, a hydrogen atom and a halogen atom; or R ₂ and R ₂ 'together with the carbon atoms which carry them form an optionally substituted benzene ring, in particular with one or more (C 1 -C 6) alkyl groups;

. A ^" is selected from:

 - anions of formula

R,

 R-B-R

R _j

wherein R _3, R _4, Rs and Re, identical or different, are selected from the groups (C 6 -C ₂ o) aryl and optionally substituted (Ci-C ₆₎ alkyl, provided that at least two of the groups R _3, R _4, Rs and Re represent groups (C 6 -C ₂ o) aryl optionally substituted; and

 - anions of formula

in which :

. E represents a methylene group optionally substituted with a (C ₁ -C ₃ ) alkyl group, in particular methyl; or a carbonyl group; and

 . Rs, R9, Rio, Ru and R12, which are identical or different, are chosen from a hydrogen atom and an optionally substituted benzoyl group,

 or two of Rs, R9, Rio, R11 and R12 form together with the benzene ring which carries them a poly (hetero) cyclic aromatic group, optionally substituted, in particular chosen from an optionally substituted naphthyl group and a xanthone group; and represents a single bond or a double bond.

2. Process according to the preceding claim, in which R 1 and R 1 'are chosen from (C 1 -C 6) alkyl groups, in particular methyl or isopropyl, and a phenyl group optionally substituted by one or more (C ₁ -C ₆ ) alkyl groups, in particular a 2,4,6-trimethylphenyl group.

3. Process according to any one of the preceding claims, in which R ₂ and R ₂ 'represent hydrogen atoms.

4. Method according to any one of the preceding claims, wherein R ₃ , R ₄ , Rs and Re are chosen from phenyl and biphenyl groups, in particular R ₃ , R ₄ , R ₅ and Re are identical.

 The method of any one of the preceding claims, wherein

. one of the groups Rs, R9, Rio, Ri and Ri ₂ represents benzoyl group, optionally substituted, the other groups representing hydrogen atoms; or

. two of Rs, R9, Rio, R11 and R ₂ together with the benzene ring which carries them an optionally substituted naphthyl, especially optionally substituted by one or more groups (Ci-C ₄₎ alkoxy and / or (C -C ₄ ) alkyl; or a xanthone group.

 The method of any one of the preceding claims, wherein represents a double bond.

 7. Process according to any one of the preceding claims, in which the imidazol (ni) um salt of formula (III) is chosen from:

 . 1,3-diisopropylimidazolium tetraphenylborate;

 . 1,3-diisopropylimidazolium tetrabiphenylborate;

 . 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetraphenylborate;

. 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetrabiphenylborate;

 . 1,3-dimethylimidazolium tetraphenylborate; and

 . 1,3-bis (2,4,6-trimethylphenyl) imidazolinium tetraphenylborate.

 The process according to any one of the preceding claims, wherein the ligand L is selected from benzene, γ-cymene, hexamethylbenzene, mesitylene, 1,5-cyclooctadiene and pentamethylcyclopentadiene, especially L is β-cymene.

The method of any one of the preceding claims comprising at least the steps of: (i) having a photo-polymerizable medium comprising one or more cycloolefin (s), at least one imidazole (ni) um salt of formula (III) and at least one ruthenium complex of formula [RuCl ₂ (L)] ₂ (II), said medium optionally further comprising one or more photosensitizers such as isopropylthioxanthone, and / or one or more solvents, in particular selected from dichloromethane, 1,2-dichloroethane and acetonitrile;

 (ii) subjecting said photo-polymerizable medium of step (i) to irradiation

UV;

 (iii) optionally, in the case of a liquid photopolymerizable medium comprising one or more solvents, let the medium obtained at the end of step (ii) react under visible light; and

 (iv) recovering the polyolefms thus obtained at the end of stage (ii) or (iii).

10. A method according to any one of the preceding claims, wherein the UV irradiation is carried out using UV radiation having an irradiance of between 10 mW.cm ^-2 and 2000 mW.cm ^-2 , in particular the irradiation time being between 1 minute and 5 hours, in particular between 2 and 30 minutes, more particularly between 5 and 20 minutes.

 11. Process according to any one of the preceding claims, useful for the synthesis of polymers or co-polymers of norbornene or a derivative thereof, in particular hexanedioldinorbornene, dicyclopentadiene and / or cyclooctene, in particular polynorbornene. , polydicyclopentadiene, norbornene / dicyclopentadiene copolymer or norbornene / hexanedioldinorbornene copolymer.

 12. A photo-polymerization medium comprising, in addition to one or more cycloolefin (s), at least:

 an imidazole salt (ni) um of formula (III) as defined according to any one of claims 1 to 7; and

a ruthenium complex of formula [RuCl ₂ (L)] ₂ (II), L being as defined in claim 1 or 8.

13. The photo-polymerization medium according to the preceding claim, further comprising one or more polymerization photosensitizer (s), in particular isopropylthio xanthone.

14. A photo-polymerization medium according to claim 12 or 13, further comprising one or more solvents, in particular selected from dichloromethane, 1,2-dichloroethane and acetonitrile.

 15. A photo-polymerization medium according to any one of claims 12 to 14, being an emulsion comprising an organic phase comprising the imidazole salt (ni) um of formula (III) as defined according to any one of the claims. 1-7 and the inactive ruthenium complex of formula (II); L being as defined in claim 1 or 8, in an organic solvent and an aqueous phase comprising water and a surfactant.

 16. A photo-polymerization medium according to claim 12 or 13, said medium being free of solvent.

 17. Imidazolium salt chosen from:

 . 1,3-diisopropylimidazolium tetrabiphenylborate;

 . 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetraphenylborate; . 1,3-bis (2,4,6-trimethylphenyl) imidazolium tetrabiphenylborate; and. 1,3-dimethylimidazolium tetraphenylborate.

 18. Imidazoli salt (ni) um of formula (III-b) below:

 (III-b)

 in which,

. R 1 and R 1, which may be identical or different, are chosen from (C 1 -C 6) alkyl groups, non-aromatic C ₃ -C ₁₂ carbocyclic groups and optionally substituted (C ₆ -C ₂ O) aryl groups, in particular by one or more (C ₁ -C ₆ ) alkyl groups;

. R ₂ and R ₂ ', which may be identical or different, are chosen from (C ₁ -C ₆ ) alkyl groups, a hydrogen atom and a halogen atom; or

R ₂ and R ₂ 'together with the carbon atoms which carry them form an optionally substituted benzene ring, in particular with one or more (C 1 -C 6) alkyl groups;

 . E represents a methylene group optionally substituted by a (C 1 -C 3) alkyl group, in particular methyl; or a carbonyl group; and

 . R8, R9, Rio, R11 and R12, which are identical or different, are chosen from a hydrogen atom and an optionally substituted benzoyl group,

 or two of Rs, R9, Rio, R11 and R12 form together with the benzene ring which carries them a poly (hetero) cyclic aromatic group, optionally substituted, in particular chosen from an optionally substituted naphthyl group and a xanthone group; and represents a single bond or a double bond.

 Use of a salt of imidazole (ni) um of formula (III)

AT

in which :

 . Ri and Ri ', identical or different, are chosen from groups

(Ci-C6) alkyl, non-aromatic carbocyclic groups, C3-C12 groups and (C 6 -C ₂ o) aryl optionally substituted, in particular by one or more (Ci-C ₆₎ alkyl;

. R ₂ and R ₂ ', which may be identical or different, are chosen from (C ₁ -C ₆ ) alkyl groups, a hydrogen atom and a halogen atom; or

R ₂ and R ₂ 'together with the carbon atoms which carry them form an optionally substituted benzene ring, in particular with one or more (C 1 -C 6) alkyl groups;

. A ^" is selected from: - anions of formula

wherein R _3, R _4, Rs and Re, identical or different, are selected from the groups (C 6 -C ₂ o) aryl and optionally substituted (Ci-C ₆₎ alkyl, provided that at least two of the groups R ₃ , R ₄ , R ₅ and Re represent optionally substituted (C ₆ -C ₂₀ ) aryl groups; and

 - anions of formula

 in which :

. E represents a methylene group optionally substituted with a (C ₁ -C ₃ ) alkyl group, in particular methyl; or a carbonyl group; and

 . R8, R9, Rio, Ru and R12, which are identical or different, are chosen from a hydrogen atom and an optionally substituted benzoyl group,

or two of Rs, R9, Rio, R11 and R12 form together with the benzene ring which carries them a poly (hetero) cyclic aromatic group, optionally substituted, in particular chosen from an optionally substituted naphthyl group and a xanthone group; and represents a single bond or a double bond, to generate, under UV irradiation, in the presence of a ruthenium complex of formula [RuCi 2 (L)] 2 (II), L being as defined in claim 1 or 6, a ruthenium catalyst of formula (I):

and / or R ₃ , R ₄ , R _{5 and} R ₆ and / or R ₅ , R ₉ , R ₁₀ , R 11 and R 12 and / or are as defined in claims 2 to 6.

 21. Use according to claim 19 or 20 for generating a catalyst of formula (I) in situ during a photoinitiated reaction of ring opening polymerization by metathesis of a cycloolefin.

 22. Use of the method as defined in any one of claims 1 to 11 for producing a coating based on polyolefins.

 23. Use according to the preceding claim, for producing one or more patterns by photolithography.