CATALYST SYSTEM BASED ON A RARE EARTH METAL OCENSOR AND A COCATALYSATOR WITH MULTIPLE CARBON-MAGNESIUM BONDS

Description

[0001] The field of the present invention is that of catalytic systems usable in the preparation of telechelic polyolefins.

[0002] The synthesis of polyolefin by polymerization of an olefin in the presence of a catalyst system comprising a rare earth metallocene and a co-catalyst is well known. The co-catalyst is used to activate the metallocene towards polymerization. The co-catalyst may be an organolithium, an organomagnesium or an organoaluminum, as described for example in patent applications EP 1 092 731, WO 2004035639, WO 2007054224 and WO 2018224776. When the co-catalyst is an organomagnesium, it is typically a chloride of an organomagnesium or an organomagnesium in which the magnesium atom is linked to two aliphatic groups, such as dibutylmagnesium, butylethylmagnesium and butyloctylmagnesium.

[0003] It is also known that the synthesis of functional polyolefins from these catalytic systems requires a functionalization step. This functionalization step is subsequent to the polymerization reaction and is implemented by adding a modifying agent, generally at the end of polymerization. This first method allows the functionalization of only one end of the polymer chain. An alternative to this first method has been to propose using functional transfer agents instead of co-catalysts. These functional transfer agents described in patent applications WO2016092237 and WO2013135314 are, for example, organomagnesium compounds that carry an amine, ether or vinyl function. This alternative makes it possible to eliminate the additional functionalization step after the polymerization reaction to form functional polymers.But this alternative leads, like the first method, to the functionalization of only one end of the polymer chain, unless an additional functionalization step is carried out at the end of polymerization. There is therefore a concern to find a solution that allows the preparation of polyolefins functionalized at both chain ends using a process that is efficient and simpler.

[0004] The Applicants have discovered a catalytic system that allows the preparation of telechelic polymers by an efficient and simple process. The catalytic system has the characteristic of comprising a rare earth metallocene and a particular organomagnesium co-catalyst that contains two magnesium atoms each linked to a distinct carbon atom and constituting a distinct benzene ring substituted in a specific manner.

[0005] Thus, a first object of the invention is a catalytic system based on at least:of a metallocene of formula (Ia) or (Ib), of an organomagnesium compound as co-catalyst, {P(Cp 1< )(Cp 2< )Y} (Ia) Cp 3< Cp 4< Y (Ib) Y denoting a group comprising an atom of a rare earth, Cp 1< , Cp 2< , Cp 3< and Cp 4< , identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, P being a group bridging the two groups Cp 1< and Cp 2< , and comprising a silicon or carbon atom, the organomagnesium compound being a compound of formula (II) RB< -(Mg-RA< ) m -Mg-RA< (II) RB< being different from RA< , RB< comprising a benzene ring substituted by the magnesium atom, one of the carbon atoms of the benzene ring ortho to the magnesium being substituted by a methyl, an ethyl, an isopropyl or forming a ring with the carbon atom which is its nearest neighbor and which is meta to the magnesium,the other carbon atom of the benzene ring ortho to magnesium being substituted by a methyl, an ethyl or an isopropyl, RA< being a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups, m being a number greater than or equal to 1, preferably equal to 1.,

[0006] A second subject of the invention is a process for preparing a first telechelic polymer which comprises a step of polymerizing a monomer M in the presence of a catalytic system in accordance with the invention, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and their mixtures. The first telechelic polymer has the particularity of carrying at each of its ends a terminal group having a reactive carbon-magnesium bond.

[0007] A third subject of the invention is a process for preparing a second telechelic polymer which comprises a step of polymerization of a monomer M in the presence of a catalytic system in accordance with the invention, which polymerization step is followed by a step of functionalization with a modifying agent, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof. The second telechelic polymer has the particularity of carrying a functional group at each of its ends.

[0008] The invention also relates to a telechelic polymer of formula RB< -Mg-poly-RA< -poly-Mg-RB< , RA< and RB< being defined as previously, the name "poly" in the formula designating a polymer chain of a 1,3-diene, ethylene, an α-monoolefin or mixtures thereof. The telechelic polymer in accordance with the invention is capable of being obtained by a process in accordance with the invention, the second subject of the invention.

[0009] The invention also relates to a process for preparing a polymer which comprises a step of polymerization of a monomer M in the presence of a catalytic system in accordance with the invention and a termination reaction with a protic compound, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and their mixtures. Description

[0010] Any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​greater than "a" and less than "b" (i.e., excluding the limits a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from "a" to "b" (i.e., including the strict limits a and b).

[0011] Unless otherwise indicated, the rates of units resulting from the insertion of a monomer into a polymer are expressed as a molar percentage relative to the total number of monomer units constituting the polymer.

[0012] The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already in use, that is to say, they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0013] The expression "based on" used to define the constituents of the catalytic system means the mixture of these constituents, or the product of the reaction of some or all of these constituents with each other.

[0014] In the present application, the term metallocene is understood to mean an organometallic complex in which the metal, in this case the rare earth atom, is linked to two Cp 3< and Cp 4< groups or to a ligand molecule consisting of two Cp 1< and Cp 2< groups linked together by a P bridge. These Cp 1< , Cp 2< , Cp 3< and Cp 4< groups, identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, these groups being able to be substituted or unsubstituted. It is recalled that rare earths are metals and designate the elements scandium, yttrium and lanthanides whose atomic number varies from 57 to 71.

[0015] According to a first variant of the invention, the metallocene used as a basic constituent in the catalytic system in accordance with the invention corresponds to the formula (la) {P(Cp 1< )(Cp 2< )Y} (la) in which Y denotes a group comprising a rare earth atom, Cp 1< and Cp 2< , identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, P is a group bridging the two groups Cp 1< and Cp 2< , and comprising a silicon or carbon atom.

[0016] According to a second variant of the invention, the metallocene used as a basic constituent in the catalytic system in accordance with the invention corresponds to the formula (Ib) Cp 3< Cp 4< Y (Ib) in which Y denotes a group comprising an atom of a rare earth, Cp 3< and Cp 4< , identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted.

[0017] As substituted cyclopentadienyl, fluorenyl and indenyl groups, mention may be made of those substituted by alkyl radicals having 1 to 6 carbon atoms or by aryl radicals having 6 to 12 carbon atoms or by trialkylsilyl radicals such as SiMe 3 . The choice of radicals is also guided by the accessibility of the corresponding molecules that are substituted cyclopentadienyl, fluorenyl and indene, because the latter are commercially available or easily synthesized.

[0018] As substituted fluorenyl groups, mention may be made of those substituted in position 2,7, 3 or 6, particularly 2,7-ditertiobutyl-fluorenyl, 3,6-ditertiobutyl-fluorenyl. Positions 2, 3, 6 and 7 respectively designate the position of the carbon atoms of the rings as shown in the diagram below, position 9 corresponding to the carbon atom to which the P bridge is attached.

[0019] As substituted cyclopentadienyl groups, mention may be made of those substituted both in position 2 (or 5) and in position 3 (or 4), particularly those substituted in position 2, more particularly the tetramethylcyclopentadienyl group. Position 2 (or 5) designates the position of the carbon atom which is adjacent to the carbon atom to which the P bridge is attached, as shown in the diagram below.

[0020] As substituted indenyl groups, mention may be made in particular of those substituted in position 2, more particularly 2-methylindenyl, 2-phenylindenyl. Position 2 designates the position of the carbon atom which is adjacent to the carbon atom to which the P bridge is attached, as shown in the diagram below.

[0021] Preferably, the metallocene is of formula (Ia).

[0022] According to a preferred embodiment of the invention, Cp 1< and Cp 2< are identical and are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C 13 H 8 . The catalytic system according to this preferred embodiment has the particularity of leading to copolymers of butadiene and ethylene which comprise, in addition to ethylene monomer units and butadiene units, cyclic units, 1,2-cyclohexane units of the following formula:

[0023] The cyclic units result from a particular insertion of the monomers ethylene and 1,3-butadiene into the polymer chain, in addition to the conventional ethylene and 1,3-butadiene units, respectively -(CH 2 -CH 2 )-, -(CH 2 -CH=CH-CH 2 )- and -(CH 2 -CH(C=CH 2 ))-. The mechanism for obtaining such a microstructure is for example described in the document Macromolecules 2009, 42, 3774-3779.

[0024] Advantageously, Cp 1< and Cp 2< are identical and each represent an unsubstituted fluorenyl group of formula C 13 H 8 , represented by the symbol Flu.

[0025] According to a preferred embodiment of the invention, the symbol Y represents the group Met-G, with Met denoting the rare earth atom and G denoting a group comprising the borohydride unit BH 4 or denoting a halogen atom chosen from the group consisting of chlorine, fluorine, bromine and iodine. Advantageously, G denotes a chlorine atom or the group of formula (III): (BH 4 ) (1+y)- L y -N x (III) in which L represents an alkali metal selected from the group consisting of lithium, sodium and potassium, N represents a molecule of an ether, x, an integer or not, is equal to or greater than 0, y, an integer, is equal to or greater than 0.

[0026] Very advantageously, G denotes the group of formula (III).

[0027] Any ether that has the power to complex the alkali metal is suitable as an ether, especially diethyl ether and tetrahydrofuran.

[0028] According to any one of the embodiments of the invention, the metallocene metal useful for the purpose of the invention, in this case the rare earth, is preferably a lanthanide whose atomic number ranges from 57 to 71, more preferably neodymium, Nd.

[0029] The bridge P connecting the groups Cp 1< and Cp 2< preferably corresponds to the formula ZR 1< R 2< , in which Z represents a silicon or carbon atom, R 1< and R 2< , identical or different, each represent an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl. In the formula ZR 1< R 2< , Z advantageously represents a silicon atom, Si.

[0030] The metallocene useful for the synthesis of the catalytic system may be in the form of a crystallized or non-crystalline powder, or in the form of single crystals. The metallocene may be in a monomeric or dimeric form, these forms depending on the method of preparation of the metallocene, as for example described in patent application WO 2007054224 or WO 2007054223. The metallocene may be prepared in a conventional manner by a process analogous to that described in patent application WO 2007054224 or WO 2007054223, in particular by reaction under inert and anhydrous conditions of the salt of an alkali metal of the ligand with a rare earth borohydride in a suitable solvent, such as an ether, such as diethyl ether or tetrahydrofuran or any other solvent known to those skilled in the art. After reaction, the metallocene is separated from the reaction by-products by techniques known to those skilled in the art, such as filtration or precipitation in a second solvent.The metallocene is finally dried and isolated in solid form.

[0031] According to a particularly preferred embodiment, the metallocene is of formula (III-1), (III-2), (III-3), (III-4) or (III-5): [Me 2 Si(Flu) 2 Nd(µ-BH 4 ) 2 Li(THF)] (III-1) [{Me 2 SiFlu 2 Nd(µ-BH 4 ) 2 Li(THF)} 2 ] (III-2) [Me 2 SiFlu 2 Nd(µ-BH 4 )(THF)] (III-3) [{Me 2 SiFlu 2 Nd(µ-BH 4 )(THF)} 2 ] (III-4) [Me 2 SiFlu 2 Nd(µ-BH 4 )] (III-5) in which Flu represents the group C 13 H 8 .

[0032] Another basic constituent of the catalytic system according to the invention is the co-catalyst, an organomagnesium of formula (II) in which RB< is different from RA<, RB< comprises a benzene ring substituted by the magnesium atom, one of the carbon atoms of the benzene ring ortho to the magnesium being substituted by a methyl, an ethyl, an isopropyl or forming a cycle with the carbon atom which is its closest neighbor and which is meta to the magnesium, the other carbon atom of the benzene ring ortho to the magnesium being substituted by a methyl, an ethyl or an isopropyl, RA< is a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups, m is a number greater than or equal to 1, preferably equal to 1. RB< -(Mg-RA< ) m -Mg-R B< (II)

[0033] The organomagnesium compound of formula (II) therefore has the characteristic of comprising two magnesium atoms, each magnesium atom being linked to two carbon atoms. In the organomagnesium compound of formula (II), two magnesium atoms each share a first bond with a first carbon atom belonging to RB< and a second bond with a second carbon atom belonging to RA< . The first carbon atom constitutes the benzene ring of RB< . The second carbon atom constitutes the aliphatic hydrocarbon chain RA< which may contain within its chain one or more heteroatoms chosen from oxygen and sulfur or one or more arylene groups. In the preferred case where m is equal to 1, each magnesium atom therefore shares a first bond with a first carbon atom of RB< and a second bond with a second carbon atom of RA< .

[0034] RB< has the essential characteristic of comprising a benzene ring substituted by the magnesium atom. The two carbon atoms of the benzene ring of RB< ortho to the magnesium carry a substituent, identical or different. Alternatively, one of the two carbon atoms of the benzene ring of RB< ortho to the magnesium may carry a substituent, the other carbon atom of the benzene ring of RB< ortho to the magnesium may form a ring. The substituent is a methyl, an ethyl or an isopropyl. In the case where one of the 2 carbon atoms of the benzene ring of RB< ortho to the magnesium is substituted by an isopropyl, preferably the second carbon atom of the benzene ring of RB< ortho to the magnesium is not substituted by an isopropyl. Preferably, the carbon atoms of the benzene ring of RB< ortho to magnesium are substituted by methyl or ethyl.More preferably, the carbon atoms of the benzene ring of RB< ortho to magnesium are substituted by a methyl.

[0035] According to a preferred embodiment of the invention, the organomagnesium compound corresponds to the formula (IV-m) in which m is greater than or equal to 1, R 1 and R 5 , identical or different, represent a methyl or an ethyl, preferably a methyl, R 2 , R 3 and R 4 , identical or different, represent a hydrogen atom or an alkyl and RA< is a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups. Preferably, R 1 and R 5 represent a methyl. Preferably, R 2 and R 4 represent a hydrogen atom.

[0036] The organomagnesium compound of formula (IV-m) is of formula (IV-1) in the case where m is equal to 1.

[0037] According to a preferred variant, R 1 , R 3 and R 5 are identical in formula (IV-m), in particular in formula (IV-1). According to a more preferred variant, R 2 and R 4 represent a hydrogen and R 1 , R 3 and R 5 are identical. In a more preferred variant, R 2 and R 4 represent a hydrogen and R 1 , R 3 and R 5 represent a methyl.

[0038] In formulae (II) and (IV-m), in particular in formula (IV-1), RA< is a divalent aliphatic hydrocarbon chain which may contain within its chain one or more heteroatoms chosen from oxygen and sulfur or one or more arylene groups. Preferably, RA< is a branched or linear alkanediyl, a cycloalkanediyl or a xylenediyl radical. More preferably, RA< is an alkanediyl. Preferably, RA< contains 3 to 10 carbon atoms, in particular 3 to 8 carbon atoms. Even more preferably, RA< is an alkanediyl having 3 to 10 carbon atoms. Advantageously, RA< is an alkanediyl having 3 to 8 carbon atoms. Very advantageously, RA< is a linear alkanediyl. Particularly suitable RA< groups are 1,3-propanediyl, 1,4-butanediyl, 1,5-pentanediyl, 1,6-hexanediyl, 1,7-heptanediyl, 1,8-octanediyl.

[0039] According to any of the embodiments of the invention, m is preferably equal to 1 in formula (II), in particular in formula (IV-m).

[0040] The organomagnesium compound useful for the purposes of the invention as a co-catalyst can be prepared by a process, which comprises the reaction of a first organomagnesium of formula XMg-R A< -MgX with a second organomagnesium of formula RB< -Mg-X, X representing a halogen atom, preferably bromine or chlorine, RB< and RA< being as defined above. X is more preferably a bromine atom. The stoichiometry used in the reaction determines the value of m in formula (II) and in formula (IV-m). For example, a molar ratio of 0.5 between the quantity of the first organomagnesium and the quantity of the second organomagnesium is favorable to the formation of an organomagnesium compound of formula (II) in which m is equal to 1, whereas a molar ratio greater than 0.5 will be more favorable to the formation of an organomagnesium compound of formula (II) in which m is greater than 1.

[0041] To carry out the reaction of the first organomagnesium compound with the second organomagnesium compound, a solution of the second organomagnesium compound is typically added to a solution of the first organomagnesium compound. The solutions of the first organomagnesium compound and the second organomagnesium compound are generally solutions in an ether, such as diethyl ether, dibutyl ether, tetrahydrofuran, methyltetrahydrofuran or the mixture of two or more of these ethers. Preferably, the respective concentrations of the solutions of the first organomagnesium compound and the second organomagnesium compound are respectively 0.01 to 3 mol / L and 0.02 to 5 mol / L. More preferably, the respective concentrations of the first organomagnesium compound and the second organomagnesium compound are respectively 0.1 to 2 mol / L and 0.2 to 4 mol / L.

[0042] The first organomagnesium compound and the second organomagnesium compound may be prepared in advance by a Grignard reaction from magnesium metal and a suitable precursor. For the first organomagnesium compound and the second organomagnesium compound, the respective precursors are of formula XR A< -X and RB< -X, RA< , RB< and X being as defined previously. The Grignard reaction is typically carried out by adding the precursor to magnesium metal which is generally in the form of chips. Preferably, iodine (I 2 ) typically in the form of beads is introduced into the reactor before the addition of the precursor in order to activate the Grignard reaction in a known manner.

[0043] Alternatively, the organomagnesium compound useful for the purposes of the invention as a co-catalyst may be prepared by reacting an organometallic compound of formula MR A< -M and the organomagnesium compound of formula RB< -Mg-X, M representing a lithium, sodium or potassium atom, X, RB< and RA< being as defined above. Preferably, M represents a lithium atom, in which case the organometallic compound of formula MR A< -M is an organolithium. The reaction of the organolithium and the organomagnesium compound is typically carried out in an ether such as diethyl ether, dibutyl ether, tetrahydrofuran, methyltetrahydrofuran. The reaction is also typically carried out at a temperature ranging from 0°C to 60°C. The contacting is preferably carried out at a temperature between 0°C and 23°C.The contacting of the organometallic compound of formula MR A< -M with the organomagnesium of formula RB< -Mg-X is preferably carried out by adding a solution of the organometallic compound MR A< -M to a solution of the organomagnesium RB< -Mg-X. The solution of the organometallic compound MR A< -M is generally a solution in a hydrocarbon solvent, preferably n-hexane, cyclohexane or methylcyclohexane, the solution of the organomagnesium RB< -Mg-X is generally a solution in an ether, preferably diethyl ether or dibutyl ether. Preferably, the respective concentrations of the solutions of the organometallic compound and of the organomagnesium MR A< -M and RB< -Mg-X are respectively 0.01 to 1 mol / L and 0.02 to 5 mol / L. More preferably, the respective concentrations of the solutions of the organometallic compound and the organomagnesium compound MR A< -M and RB< -Mg-X are respectively 0.05 to 0.5 mol / L and 0.2 to 3 mol / L.

[0044] Like any synthesis carried out in the presence of organometallic compounds, the syntheses described for the synthesis of organomagnesium compounds useful for the purposes of the invention and for the synthesis of the organomagnesium compound in accordance with the invention, take place under anhydrous conditions under an inert atmosphere, in stirred reactors. Typically, the solvents and solutions are used under anhydrous nitrogen or argon.

[0045] Once the organomagnesium useful for the purposes of the invention is formed, it is generally recovered in solution after filtration carried out under an inert and anhydrous atmosphere. It can be stored before use in its solution in airtight containers, for example capped bottles, at a temperature between -25°C and 23°C.

[0046] Like any organomagnesium compound, the organomagnesium compound RB< -(Mg-R A< ) m -Mg-R B< useful for the purposes of the invention may be in the form of a monomeric entity (RB< -(Mg-R A< ) m -Mg-R B< ) 1 or in the form of a polymeric entity (RB< -(Mg-R A< ) m -Mg-R B< ) p ,, p being an integer greater than 1, in particular dimer (RB< -(Mg-R A< ) m -Mg-R B< ) 2 , m being as defined previously. Furthermore, whether it is in the form of a monomeric or polymeric entity, it may also be in the form of an entity coordinated to one or more molecules of a solvent, preferably an ether such as diethyl ether, tetrahydrofuran or methyltetrahydrofuran.

[0047] The catalytic system in accordance with the invention can be prepared in a conventional manner by a process analogous to that described in patent application WO 2007054224 or WO 2007054223. For example, the organomagnesium compound RB< -Mg-R A< -Mg-R B< useful for the purposes of the invention and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature ranging from 20 to 80°C for a period of between 5 and 60 minutes. The quantities of co-catalyst and metallocene reacted are such that the ratio between the number of moles of Mg in the co-catalyst and the number of moles of rare earth metal in the metallocene preferably ranges from 1 to 200, more preferably from 1 to less than 20. The range of values ​​from 1 to less than 20 is particularly more favorable for obtaining polymers with high molar masses. The catalyst system is usually prepared in a hydrocarbon solvent, aliphatic such as methylcyclohexane or aromatic such as toluene.Generally, after its synthesis, the catalytic system is used as is in the process for synthesizing the polymer in accordance with the invention.

[0048] Alternatively, the catalytic system in accordance with the invention may be prepared by a process analogous to that described in patent application WO 2017093654 A1 or in patent application WO 2018020122 A1. According to this alternative, the catalytic system further contains a preformation monomer chosen from a conjugated diene, ethylene or a mixture of ethylene and a conjugated diene, in which case the catalytic system is based at least on the metallocene, the organomagnesium RB< -Mg-R A< -Mg-R B< useful for the purposes of the invention and the preformation monomer.For example, the organomagnesium compound and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20 to 80°C for 10 to 20 minutes to obtain a first reaction product, then with this first reaction product, the preformation monomer chosen from a conjugated diene, ethylene or a mixture of ethylene and a conjugated diene is reacted for 1 hour to 12 hours at a temperature of 40 to 90°C. The conjugated diene as preformation monomer is preferably a 1,3-diene such as 1,3-butadiene, isoprene or a 1,3-diene of formula CH 2 =CR-CH=CH 2 , the symbol R representing a hydrocarbon chain having 3 to 20 carbon atoms, in particular myrcene or β-farnesene.The catalytic system thus obtained can be used immediately in the process according to the invention or be stored under an inert atmosphere, in particular at a temperature ranging from -20°C to room temperature (23°C), before its use in the synthesis of polymers.

[0049] Like any synthesis carried out in the presence of organometallic compounds, the synthesis of metallocene, the synthesis of organomagnesium and the synthesis of the catalytic system take place under anhydrous conditions under an inert atmosphere. Typically, the reactions are carried out from solvents and anhydrous compounds under anhydrous nitrogen or argon.

[0050] The catalytic system may be in the form of a solution when in the presence of a hydrocarbon solvent. The hydrocarbon solvent may be aliphatic such as methylcyclohexane or aromatic such as toluene. The hydrocarbon solvent is preferably aliphatic, more preferably methylcyclohexane. Generally, the catalytic system is stored in the form of a solution in the hydrocarbon solvent before being used in polymerization. This may then be referred to as a catalytic solution which comprises the catalytic system and the hydrocarbon solvent. According to any of the embodiments of the invention, the catalytic system preferably comprises a hydrocarbon solvent. When the catalytic system is in solution, its concentration is defined by the metallocene metal content in the solution.The metallocene metal concentration has a value preferably ranging from 0.0001 to 0.2 mol / L, more preferably from 0.001 to 0.03 mol / L.

[0051] The catalytic system according to the invention is intended to be used in processes for the synthesis of polymers, in particular elastomers usable in rubber compositions, for example for tires.

[0052] A first process allows the preparation of telechelic polymers which have the particularity of having a carbon-magnesium bond at each of their ends. The first process comprises a polymerization step in the presence of a catalytic system in accordance with the invention.

[0053] A second method allows the preparation of telechelic polymers which have the particularity of having a functional group at each of their ends. It comprises a polymerization step followed by a functionalization step with a modifying agent. The polymerization step is identical to that of the first method. The modifying agent is typically a compound known to react with a compound having a carbon-magnesium bond. Dihalogens and ketones are particularly suitable as modifying agents. The functional groups at the ends of the polymer are advantageously identical. The modifying agent is typically added to the polymerization medium. The functionalized polymer can be recovered using conventional techniques known to those skilled in the art, such as precipitation, evaporation of the solvent under reduced pressure, or stripping with steam.

[0054] A third method comprises a polymerization step and a termination reaction with a protic compound. The polymerization step is identical to that of the first method and the second method. The protic compound allows the polymerization to be stopped by a termination reaction without adding functions to the ends of the polymer. The protic compound is, for example, an alcohol such as methanol, ethanol, isopropanol, or water. It can be added to the polymerization medium. Alternatively, the polymerization medium can be poured into the protic compound such as methanol or into a solution containing the protic compound, for example, a toluene solution containing methanol.

[0055] According to a particular embodiment of the third method, the protic compound is a compound which allows the labeling of the ends of the polymer with an isotope of the hydrogen atom such as deuterium. Suitable labeled protic compounds are deuterated water and alcohols whose hydroxy group is OD. The polymer formed can be recovered according to conventional techniques known to those skilled in the art, such as for example by precipitation, by evaporation of the solvent under reduced pressure or by stripping with water vapor.

[0056] The polymerization reaction common to the three processes according to the invention is a polymerization reaction of a monomer M chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof. α-Monoolefin is understood to mean an α-olefin which has a single carbon-carbon double bond, the double bonds in aromatic compounds not being taken into account. For example, styrene is considered to be an α-monoolefin. Preferably, the monomer M is ethylene or a mixture of a 1,3-diene and ethylene or a mixture of a 1,3-diene, ethylene and an α-monoolefin such as styrene, the 1,3-diene advantageously being 1,3-butadiene, isoprene or mixtures thereof.

[0057] The polymerization is preferably carried out in solution, continuously or discontinuously. The polymerization solvent may be a hydrocarbon, aromatic or aliphatic solvent. Examples of polymerization solvents include toluene and methylcyclohexane. The monomer M may be introduced into the reactor containing the polymerization solvent and the catalytic system or, conversely, the catalytic system may be introduced into the reactor containing the polymerization solvent and the monomer M. The monomer M and the catalytic system may be introduced simultaneously into the reactor containing the polymerization solvent, in particular in the case of continuous polymerization. The polymerization is typically carried out under anhydrous conditions and in the absence of oxygen, in the optional presence of an inert gas. The polymerization temperature generally varies within a range of 25 to 120°C, preferably 30 to 100°C.It is adjusted according to the monomer to be polymerized. Preferably, the copolymerization is carried out at constant ethylene pressure.

[0058] During the polymerization of ethylene and 1,3-dienes in a polymerization reactor, a continuous addition of ethylene and 1,3-dienes may be carried out into the polymerization reactor, in which case the polymerization reactor is a fed reactor. This embodiment is particularly suitable for the synthesis of random copolymer.

[0059] Thus, by simple methods that include a polymerization reaction and a reaction with a modifying agent or a labeled protic compound, polymers can be synthesized whose two ends carry identical functional groups or are labeled with an isotope.

[0060] The chain-end labeled polymers and the chain-end functional polymers are obtained from telechelic polymers which have a carbon-magnesium bond at the ends and which are capable of being obtained by the first method. The telechelic polymers which have a carbon-magnesium bond at the ends therefore have the capacity to give rise on the one hand to the formation of polymers whose two ends are labeled by an isotope of the hydrogen atom, and on the other hand to the formation of polymers whose two ends carry identical functional groups.

[0061] Telechelic polymers having a carbon-magnesium bond at the ends may be represented by the formula (V) in which RA< and RB< are defined as previously, including according to the preferred embodiments described, the name "poly" denotes a polymer chain of a 1,3-diene, ethylene, an α-monoolefin or mixtures thereof. RB< -Mg-poly-R A< -poly-Mg-R B< (V)

[0062] Preferably, the polymer chain designated by the name "poly" is a polymer chain of ethylene or a polymer chain of a 1,3-diene and ethylene or a polymer chain of a 1,3-diene, ethylene and an α-monoolefin such as styrene. The 1,3-diene is a 1,3-diene or a mixture of 1,3-dienes. 1,3-dienes having 4 to 24 carbon atoms, such as 1,3-butadiene, isoprene and mixtures thereof, are particularly suitable as 1,3-dienes. According to a particular embodiment, the polymer chain designated by the name "poly" contains ethylene units, 1,3-butadiene units and cyclic units, 1,2-cyclohexane units. According to the particular embodiment in which the polymer chain designated by the name “poly” contains 1,2-cyclohexane units, it preferably contains at most 15% by mole.

[0063] According to any one of the embodiments of the invention, the polymer chain designated by the name “poly” preferably contains more than 50 mol% of ethylene unit.

[0064] According to a particularly preferred embodiment of the invention, the polymer chain designated by the name “poly” is a random polymer chain of a 1,3-diene and ethylene or a random polymer chain of a 1,3-diene, ethylene and an α-monoolefin such as styrene.

[0065] In summary, the invention is advantageously implemented according to any one of the following embodiments 1 to 42: Method 1: Catalytic system based at least on: a metallocene of formula (Ia) or (Ib), preferably (Ia), an organomagnesium compound as co-catalyst, {P(Cp 1< )(Cp 2< )Y} (Ia) Cp 3< Cp 4< Y (Ib) Y denoting a group comprising an atom of a rare earth, Cp 1< , Cp 2< , Cp 3< and Cp 4< , identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, P being a group bridging the two groups Cp 1< and Cp 2< , and comprising a silicon or carbon atom, the organomagnesium compound being a compound of formula (II) RB< -(Mg-RA< ) m -Mg-R B< (II) RB< being different from RA< , RB< comprising a benzene ring substituted by the magnesium atom, one of the carbon atoms of the benzene ring ortho to magnesium being substituted by a methyl, an ethyl,an isopropyl or forming a cycle with the carbon atom which is its nearest neighbor and which is meta to magnesium, the other carbon atom of the benzene ring ortho to magnesium being substituted by a methyl, an ethyl or an isopropyl, RA< being a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups, m being a number greater than or equal to 1,preferably equal to 1. Mode 2: Catalytic system according to mode 1 in which the metallocene is of formula (Ia). Mode 3: Catalytic system according to any one of modes 1 to 2 in which Cp 1< and Cp 2< are identical and are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C 13 H 8 . Mode 4: Catalytic system according to any one of modes 1 to 3 in which Cp 1< and Cp 2< each represent an unsubstituted fluorenyl group of formula C 13 H 8 . Mode 5: Catalytic system according to any one of modes 1 to 4, in which the symbol Y represents the group Met-G, with Met denoting the rare earth atom and G denoting a group comprising the borohydride unit BH 4 or denoting a halogen atom chosen from the group consisting of chlorine, fluorine,bromine and iodine. Mode 6: Catalytic system according to mode 5 in which G denotes a chlorine atom or the group of formula (III) (BH 4 ) (1+y)- L y -N x (III) in which L represents an alkali metal chosen from the group consisting of lithium, sodium and potassium, N represents a molecule of an ether, preferably diethyl ether or tetrahydrofuran, x, whether an integer or not, is equal to or greater than 0, y, an integer, is equal to or greater than 0. Mode 7: Catalytic system according to mode 6 in which G denotes the group of formula (III). Mode 8: Catalytic system according to any one of modes 1 to 7 in which the rare earth is a lanthanide whose atomic number varies from 57 to 71. Mode 9: Catalytic system according to any one of modes 1 to 8 in which the rare earth is neodymium. Mode 10: Catalytic system according to any one of modes 1 to 9 in which the bridge P corresponds to the formula ZR 1< R 2< ,Z representing a silicon or carbon atom, R 1< and R 2< , identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms. Mode 11: Catalytic system according to mode 10 in which R 1< and R 2< each represent a methyl. Mode 12: Catalytic system according to any one of modes 10 to 11 in which Z represents a silicon atom. Mode 13: Catalytic system according to any one of modes 1 to 12 in which the metallocene is of formula (III-1), (III-2), (III-3),(III-4) or (III-5): [Me 2 Si(Flu) 2 Nd(µ-BH 4 ) 2 Li(THF)] (III-1) [{Me 2 SiFlu 2 Nd(µ-BH 4 ) 2 Li(THF)} 2 ] (III-2) [Me 2 SiFlu 2 Nd(µ-BH 4 )(THF)] (III-3) [{Me 2 SiFlu 2 Nd(µ-BH 4 )(THF)} 2 ] (III-4) [Me 2 SiFlu 2 Nd(µ-BH 4 )] (III-5) Flu representing the C 13 H 8 group. Mode 14: Catalytic system according to any one of modes 1 to 13 in which if one of the 2 carbon atoms of the benzene ring of RB< ortho to magnesium is substituted by an isopropyl,the second carbon atom of the benzene ring of RB< ortho to magnesium is not substituted by isopropyl. Mode 15: Catalytic system according to any one of modes 1 to 14 in which the carbon atoms of the benzene ring of RB< ortho to magnesium are substituted by methyl or ethyl. Mode 16: Catalytic system according to any one of modes 1 to 15 in which the carbon atoms of the benzene ring of RB< ortho to magnesium are substituted by methyl. Mode 17: Catalytic system according to any one of modes 1 to 16 in which the organomagnesium compound is of formula (IV-m), R 1 and R 5 , identical or different, representing a methyl or an ethyl, preferably a methyl, R 2 , R 3 and R 4 , identical or different, being a hydrogen atom or an alkyl, RA< being a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups, m being a number greater than or equal to 1, preferably equal to 1. Mode 18: Catalytic system according to any one of modes 1 to 17 in which m is equal to 1. Mode 19: Catalytic system according to any one of modes 1 to 18 in which RA< is an alkanediyl, branched or linear, a cycloalkanediyl or a xylenediyl radical. Mode 20: Catalytic system according to any one of modes 1 to 19 in which RA< contains 3 to 10 carbon atoms. Mode 21: Catalytic system according to any one of modes 1 to 20 in which RA< contains 3 to 8 carbon atoms. Mode 22: Catalytic system according to any one ofmodes 1 to 21 in which RA< is a linear alkanediyl. Mode 23: Catalytic system according to any one of modes 1 to 22 in which the ratio between the number of moles of Mg in the co-catalyst and the number of moles of rare earth metal in the metallocene ranges from 1 to 200. Mode 24: Catalytic system according to any one of modes 1 to 23 in which the ratio between the number of moles of Mg in the co-catalyst and the number of moles of rare earth metal in the metallocene ranges from 1 to less than 20. Mode 25: Process for preparing a first telechelic polymer which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in any one of modes 1 to 24, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof. Mode 26: Process for preparing a second telechelic polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic systemdefined in any one of modes 1 to 24, which polymerization step is followed by a functionalization step with a modifying agent, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof. Mode 27: Process for the preparation of a polymer which comprises a step of polymerization of a monomer M in the presence of a catalytic system defined in any one of modes 1 to 24 and a termination reaction with a protic compound, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof. Method 28: Preparation process according to any one of methods 25 to 27 in which the monomer M is ethylene or a mixture of a 1,3-diene and ethylene or a mixture of a 1,3-diene, ethylene and an α-monoolefin. Method 29: Preparation process according to method 28 in which the 1,3-diene is 1,3-butadiene,isoprene or mixtures thereof. Mode 30: Telechelic polymer of formula (V) RB< -Mg-poly-RA< -poly-Mg-RB< (V) in which RB< is different from RA<, RA< is a divalent aliphatic hydrocarbon chain, interrupted or not by one or more oxygen or sulfur atoms or by one or more arylene groups, RB< comprising a benzene ring substituted by the magnesium atom, one of the carbon atoms of the benzene ring ortho to the magnesium being substituted by a methyl, an ethyl, an isopropyl or forming a cycle with the carbon atom which is its closest neighbor and which is meta to the magnesium, the other carbon atom of the benzene ring ortho to the magnesium being substituted by a methyl, an ethyl or an isopropyl, the name "poly" designates a polymer chain of a 1,3-diene, of ethylene, of an α-monoolefin or mixtures thereof, preferably a polymer chain of ethylene or a polymer chain of a 1,3-diene and ethylene oror a polymer chain of a 1,3-diene, ethylene and an α-monoolefin. Mode 31: Telechelic polymer according to mode 30 in which the polymer chain designated by the name "poly" is a polymer chain of ethylene or a polymer chain of a 1,3-diene and ethylene or a polymer chain of a 1,3-diene, ethylene and an α-monoolefin. Mode 32: Telechelic polymer according to any one of modes 30 to 31 in which the polymer chain designated by the name "poly" designates a polymer chain which contains ethylene units, 1,3-butadiene units and cyclic units, 1,2-cyclohexane units of the following formula. Mode 33: Telechelic polymer according to any one of modes 30 to 32 in which the polymer chain designated by the name "poly" denotes a polymer chain which contains more than 50 mol% of ethylene unit. Mode 34: Telechelic polymer according to any one of modes 30 to 33 in which the polymer chain designated by the name "poly" denotes a random polymer chain of a 1,3-diene, ethylene and an α-monoolefin. Mode 35: Telechelic polymer according to any one of modes 30 to 34 in which RA< is a branched or linear alkanediyl, a cycloalkanediyl or a xylenediyl radical. Mode 36: Telechelic polymer according to any one of modes 30 to 35 in which RA< contains 3 to 10 carbon atoms. Mode 37: Telechelic polymer according to any one of modes 30 to 36 in which RA< contains 3 to 8 carbon atoms. Mode 38: Telechelic polymer according to any one of modes 30 to 37 in which RA< is a linear alkanediyl.Mode 39: A telechelic polymer according to any one of modes 30 to 38 in which if one of the 2 carbon atoms of the benzene ring of RB< ortho to magnesium is substituted by an isopropyl, the second carbon atom of the benzene ring of RB< ortho to magnesium is not substituted by an isopropyl. Mode 40: A telechelic polymer according to any one of modes 30 to 39 in which the carbon atoms of the benzene ring of RB< ortho to magnesium are substituted by a methyl or an ethyl. Mode 41: A telechelic polymer according to any one of modes 30 to 40 in which the carbon atoms of the benzene ring of RB< ortho to magnesium are substituted by a methyl. Mode 42: Telechelic polymer according to any one of modes 30 to 41, in which RB< is of the following formula. R 1 and R 5 , identical or different, represent a methyl or an ethyl, preferably a methyl, R 2 , R 3 and R 4 , identical or different, being a hydrogen atom or an alkyl, the symbol * representing a direct attachment to the magnesium atom.

[0066] The above-mentioned characteristics of the present invention, as well as others, will be better understood upon reading the following description of the exemplary embodiments of the invention, given for illustrative and non-limiting purposes. Examples Example 1: preparation of a co-catalyst useful for the purposes of the invention, 1,5-di(mesitylmagnesium)-pentanediyl (DMMP).

[0067] Toluene and 2-methyltetrahydrofuran (MeTHF) used in the syntheses were distilled over sodium / benzophenone. Inerting was carried out using 3 vacuum / argon cycles.

[0068] Synthesis of 2-mesitylmagnesium bromide:4.15 g (170 mmol, 3.4 equivalents) of magnesium are inerted in a 250 mL flask fitted with a magnetic olive and topped with a 10 mL dropping funnel. A 10 mg iodine bead is introduced onto the magnesium. 47.5 mL of MeTHF are introduced into the flask with stirring and 2.5 mL are introduced into the dropping funnel. 7.65 mL of 2-bromomesitylene (50 mmol, 1 equivalent) degassed and dried over activated molecular sieve are introduced into the dropping funnel. The flask is heated to 60 °C and the 2-bromomesitylene is poured dropwise onto the magnesium for 1 h. Stirring is maintained for 3 h at 60 °C then 12 h at 20 °C.

[0069] Aliquot of concentrated oil in Young's tube: 1< H NMR (C 6 D 6 - 400 MHz - 298 K) δ: ppm = 7.01 (s, "a"), 2.74 (s, "b"), 2.36 (s, "c") Synthesis of 1,5-di(magnesium bromide)-pentanediyl:6.17 g (250 mmol, 10 equivalents) of magnesium are inerted in a 250 mL flask equipped with a magnetic olive and topped with a 50 mL dropping funnel. A 10 mg diiodine bead is introduced onto the magnesium. 10 mL of MeTHF are introduced into the flask under stirring and 40 mL are introduced into the dropping funnel. 3.41 mL of 1,5-dibromopentane (25 mmol, 1 equivalent) degassed and dried over activated molecular sieve are introduced into the dropping funnel. The haloalkane solution is poured dropwise onto the magnesium for 1 h. Stirring is maintained for 12 h at 20 °C.

[0070] Aliquot of concentrated oil in Young's tube: 1< H NMR (C 6 D 6 - 400 MHz - 298 K) δ: ppm = 2.06 (quin, J = 7.6 Hz, "b"), 1.80 (quin, J = 7.4 Hz, "c"), -0.05 (t, J = 7.7 Hz, "a"); quin for quintuplet.

[0071] Synthesis of 1,5-di(mesitylmagnesium)-pentanediyl:The previous solution of 2-mesitylmagnesium bromide is cannulated, i.e. transferred via a cannula, onto the 1,5-di(magnesium bromide)-pentanediyl solution. 20 mL of MeTHF and 10.3 mL of 1,4-dioxane (120 mmol, 1.2 equivalents / Mg) are introduced into the dropping funnel. This solution is poured into the flask dropwise over 1 h with vigorous stirring. Stirring is maintained for 20 h at 20 °C. Stirring is stopped and the flask is set aside for 24 h to allow the MgBr 2 salts to completely settle. The supernatant is transferred to the filter cannula in an inert Schlenk tube, which is equipped with a frit on which 1 cm of calcined celite has been placed, in order to be filtered. Once the salts have been eliminated, the yellow solution obtained is concentrated under vacuum until an oil of mass 17.88 g is obtained (23 mmol in pentanediyl group according to estimates made by 1< H NMR).15.75 mL of toluene is added to 9.1 g (11.7 mmol) of the oil with stirring to obtain a dilute solution with a concentration of 0.45 mol L -1< in pentanediyl group. The density of the concentrated oil was estimated at 1 g mL -1< .

[0072] Aliquot of concentrated oil: 1< H NMR (C 6 D 6 - 500 MHz - 340 K) δ: ppm = 6.90 (s, “d”), 2.54 (s, “e”), 2.29 (s, “f”), 2.20 (quin, J = 6.5 Hz, “b”), 1.82 (quin, J = 6.0 Hz, “ c"), 0.10 (t, J = 7.2 Hz, "a") 13< C NMR (C 6 D 6 - 500 MHz - 340 K) δ: ppm = 161.00 ("g"), 148.30 ("h"), 135.18 ("i"), 125.74 ("d"), 28.53 ("b"), 28.53 (" c"), 28.11 ("e "), 21.46 ("f"), 10.22 ("a")

[0073] High-resolution NMR spectroscopy of organometallic compounds and their precursors was performed on a Bruker 400 Avance III spectrometer operating at 400 MHz equipped with a 5 mm BBFO probe or on a Bruker 500 Avance III spectrometer operating at 500 MHz equipped with a 5 mm BBFO probe. Acquisitions were made at 298 K or 340 K in deuterated benzene (C 6 D 6 ). Samples were analyzed at a concentration of 5% by mass. Chemical shifts are given in ppm, relative to the proton signal of C 6 D 5 H set at 7.16 ppm and the carbon signal of C 6 D 6 set at 128.06 ppm. The structure of diorganomagnesium compounds is characterized by 1D NMR 1< H, 1< H- 13< C HSQC (Heteronuclear Single Quantum Coherence), 1< H- 13< C HMBC (Heteronuclear Multiple-Bond Correlation) and NOESY. The diorganomagnesium compound is analyzed with its synthesis solvent and deuterated benzene (C 6 D 6 ) is added to the solution to achieve the NMR “lock”. Example 2: Preparation of a reference co-catalyst, 1,5-di(magnesium bromide)-pentanediyl (DBMP).

[0074] 9.72 g of magnesium (400 mmol, 10 equivalents), 80 mL of MeTHF (including 64 mL in the dropping funnel), 60 mg of iodine (0.23 mmol, 0.006 equivalents) and 5.45 mL of 1,5-dibromopentane (40 mmol, 1 equivalent) were used during the synthesis. The glassware used consists of a 200 mL round-bottomed flask and a 100 mL dropping funnel. Once the synthesis of the Grignard reagent is complete, the solution is cannulated with a filter cannula into a second inerted 200 mL round-bottomed flask. This solution is concentrated under vacuum and then diluted in 55 mL of toluene. The concentration of pentanediyl group is estimated at 0.43 mol L -1< . This oil is immiscible in methylcyclohexane. Aliquot of concentrated oil: 1< H NMR (Toluene-D 8 - 500 MHz - 298 K) δ: ppm = 2.21 (quin, J = 7.2 Hz, "b"), 1.88 (quin, J = 7.0 Hz, "c"), 0.11 (t, J = 7.4 Hz, "a") Synthesis of telechelic and functional polymers :

[0075] Ethylene homopolymers and ethylene-butadiene copolymers were prepared from the complex {(Me 2 Si(C 13 H 8 ) 2 )Nd(-BH 4 )[(-BH 4 )Li(THF)]} 2 and the cocatalyst di(mesitylmagnesium) pentanediyl (DMMP) prepared according to the procedure described above. Polymers were also synthesized using a catalytic system not in accordance with the invention which comprises as cocatalyst 1,5-di(magnesium bromide)-pentanediyl (DBMP) of Example 2. The polymers were characterized with the methods described below.

[0076] High-temperature size exclusion chromatography (HT-SEC). High-temperature size exclusion chromatography (HT-SEC) analyses were performed using a Viscotek instrument (Malvern Instruments) equipped with 3 columns (PLgel Olexis 300 mm x 7 mm ID from Agilent Technologies) and 3 detectors (differential refractometer and viscometer, and light scattering). 200 µL of a sample solution at a concentration of 3 mg mL -1< was eluted in 1,2,4-trichlorobenzene using a flow rate of 1 mL min -1< at 150 °C. The mobile phase was stabilized with 2,6-di(tert-butyl)-4-methylphenol (400 mg L -1< ). OmniSEC software was used for data acquisition and analysis. The number-average (Mn) and mass-average (Mw) molar masses of the synthesized polyethylenes are calculated using a calibration curve obtained from standard polyethylenes ( Mp: 338, 507, 770, 1890, 17,000, 27,300, 43,400, 53,100, 65,700, 78,400 g.mol -1< ) ​​from Polymer Standard Service (Mainz). The number-average (Mn) and mass-average (Mw) molar masses of the synthesized ethylene-butadiene copolymers are calculated using a universal calibration curve calibrated from standard polystyrenes (Peak molar masses M p: 672 to 12,000,000 g mol -1< ) ​​from Polymer Standard Service (Mainz) using refractometric and viscometric detectors.

[0077] THF size exclusion chromatography (SEC-THF). Size exclusion chromatography analyses were performed using a Viscotek instrument (Malvern Instruments). This instrument is equipped with 3 columns (SDVB, 5 µm, 300 x 7.5 mm of Polymer Standard Service), a guard column and 3 detectors (differential refractometer and viscometer, and light scattering). 3 mL of a sample solution of concentration 3 mg mL -1< in THF was filtered through a 0.45 µm PTFE membrane. 100 µL of this solution was eluted in THF using a flow rate of 1 mL min -1< at a temperature of 35 °C. OmniSEC software was used for data acquisition and analysis. The molar masses of the synthesized ethylene and butadiene copolymers are calculated using a universal calibration curve obtained from standard polystyrenes ( M p: 1,306 to 2,520,000 g mol -1< ) ​​from Polymer Standard Service (Mainz).

[0078] Nuclear Magnetic Resonance (NMR). High-resolution NMR spectroscopy of polymers was performed on a Bruker 400 Avance III spectrometer operating at 400 MHz equipped with a 5 mm BBFO probe for the proton and on a Bruker 400 Avance II spectrometer operating at 400 MHz equipped with a 10 mm PSEX 13< C probe for carbon. Acquisitions were made at 363 K. A mixture of tetrachloroethylene (TCE) and deuterated benzene (C 6 D 6 ) (2 / 1 v / v) was used as solvent. Samples were analyzed at a concentration of 1% by mass for the proton and 5% by mass for carbon. Chemical shifts are given in ppm, relative to the proton signal of deuterated benzene set at 7.16 ppm and the carbon signal of TCE set at 120.65 ppm. The sequence used for the acquisition of a 13< C spectrum of a polymer is: “Power gate decoupling” (proton decoupled spectrum with NOE) with a pulse angle of 70 °, TD = 64 K and a delay between pulses of 4.5 s.The number of acquisitions is set at 5120. Synthesis of telechelic and functional polyethylenes : Example PE1:

[0079] 200 mL of sodium / benzophenone distilled toluene are introduced into an inerted 250 mL flask equipped with a magnetic olive.

[0080] 2.0 mL (0.90 mmol) of 1,5-di(mesitylmagnesium)-pentanediyl prepared according to Example 1 (0.45 mol L -1< in toluene) are introduced into the flask with stirring. 8.0 mg (12.5 µmol in neodymium) of {(Me 2 Si(C 13 H 8 ) 2 )Nd(-BH 4 )[(-BH 4 )Li(THF)]} 2 are then introduced into the flask.

[0081] The catalytic solution is cannulated into a 250 mL reactor under an inert atmosphere. The argon overpressure in the reactor is reduced to 0.5 bar, then the reactor is pressurized to 4 bar of ethylene and the temperature is simultaneously brought to 70 °C. The pressure is kept constant in the reactor using a tank containing ethylene.

[0082] When the desired amount of ethylene has been consumed, here after 19 min, the reactor is degassed and the temperature is brought back to 20 °C. 20% of the polymer solution is cannulated out of the reactor, then the polymer contained in this 20% is precipitated in methanol with stirring. 5.86 g (23 mmol, 16 equivalents / Mg) of iodine dissolved in 30 mL of toluene are added to the polymer solution remaining in the reactor. After 3 h of stirring, the polymer solution is poured onto methanol with stirring to precipitate the polymer.

[0083] The polymer recovered after reaction with the modifying agent (PE1F) is filtered, washed with methanol, then dried and characterized. It is designated PE1F.

[0084] The polymer precipitated in methanol before the addition of the modifying agent is also recovered by filtration, then dried before being characterized as non-functional polymer (PE1NF).

[0085] 1.13 g of PE1F polymer of formula I-(CH 2 -CH 2 ) n -(CH 2 ) 5 -(CH 2 -CH 2 ) n -I and 0.25 g of PE1NF polymer of formula H-(CH 2 -CH 2 ) n -(CH 2 ) 5 -(CH 2 -CH 2 ) n -H are recovered.

[0086] The proton NMR spectrum of the PE1F polymer (TCE / C 6 D 6 2 / 1 v / v, 400 MHz, 363 K) allows the observation of methylene in the α position of iodine at δ = 2.95 ppm (triplet, (CH 2 CH 2 ) n -C H 2 I). The functional rate in the PE1F polymer is calculated by determining the rate of non-functionalized chains in the polymer. The rate of non-functionalized chains in PE1F is determined by normalizing the integrals of the (CH 2 CH 2 ) n signals of the two 1< H NMR spectra to 100, then dividing the integral of the CH 3 signals of the PE1F polymer by that of the CH 3 signals of the PE1NF polymer. Thus in PE1F, 13% of the polymer chain ends are non-functional, and therefore 87% of the polymer chain ends have been functionalized with an iodine atom. Example PE2

[0087] The synthesis of the telechelic polymer is similar to that carried out in the previous example PE1 except that 4.0 mL (1.80 mmol) of 1,5-di(mesitylmagnesium)-pentanediyl prepared according to example 1 (0.45 mol L -1< in toluene) and 10.0 mg (15.6 µmol of neodymium) of {(Me 2 Si(C 13 H 8 ) 2 )Nd(-BH 4 )[(-BH 4 )Li(THF)]} 2 are used to prepare the catalytic solution.

[0088] When the desired amount of ethylene has been consumed, here after 46 min, the reactor is degassed and the temperature is brought back to 20 °C. 50% of the polymer solution is cannulated out of the reactor, then the polymer (PE2NF) contained in this 50% is precipitated in methanol with stirring.

[0089] 2.0 mL (44 mmol, 11 equivalents / Mg) of deuterated methanol diluted in 5 mL of toluene is added to the polymer solution remaining in the reactor. After 1 h of stirring, the polymer solution is poured onto methanol with stirring to precipitate the PE2M polymer.

[0090] Each precipitated polymer is filtered, washed with methanol and then dried. 1.03 g of PE2M polymer: D-(CH 2 -CH 2 ) n -(CH 2 ) 5 -(CH 2 -CH 2 ) n -D and 1.00 g of PE2NF polymer: H-(CH 2 -CH 2 ) n -(CH 2 ) 5 -(CH 2 -CH 2 ) n -H are recovered.

[0091] The proton NMR spectrum of the PE2M polymer (TCE / C 6 D 6 2 / 1 v / v, 400 MHz, 363 K) allows the observation of methylene in the α position of deuterium at δ = 0.83 (broad, -C H 2 D)).

[0092] The labeling rate in the PE2M polymer is calculated by determining the rate of unlabeled chains in the polymer. The rate of unlabeled chains in PE2M is determined by normalizing the integrals of the (CH 2 CH 2 ) n signals of the two 13< C NMR spectra to 100 and then dividing the integral of the CH 3 signals of the PE2M polymer by that of the CH 3 signals of the PE2NF polymer. Thus in PE2M, 9% of the polymer chain ends are unlabeled, and therefore 91% of the polymer chain ends have been labeled with a deuterium atom. Example PE3:

[0093] The synthesis of the telechelic polymer is similar to that carried out in the previous example PE2 except that 3.0 mL (1.35 mmol) of 1,5-di(magnesium bromide)-pentanediyl prepared according to example 2 (0.45 mol L -1< in toluene) and 10.0 mg (15.6 µmol of neodymium) of {(Me 2 Si(C 13 H 8 ) 2 )Nd(-BH 4 )[(-BH 4 )Li(THF)]} 2 are used to prepare the catalytic solution. The catalytic system is a catalytic system not in accordance with the invention.

[0094] When the desired amount of ethylene has been consumed, here after 49 min, the reactor is degassed and the temperature is brought back to 20 °C. 40% of the polymer solution is cannulated out of the reactor, then the polymer contained in this 40% is precipitated in methanol with stirring.

[0095] 2.0 mL (44 mmol, 15 equivalents / Mg) of deuterated methanol diluted in 5 mL of toluene is added to the polymer solution remaining in the reactor. After 1 h of stirring, the polymer solution is poured onto methanol with stirring to precipitate the polymer.

[0096] Each polymer is filtered, washed with methanol and then dried. 1.14 g of PE3M polymer: D-(CH 2 -CH 2 ) n -(CH 2 ) 5 -(CH 2 -CH 2 ) n -D and 0.70 g of PE3NF polymer: H-(CH 2 -CH 2 ) n -(CH 2 ) 5 -(CH 2 -CH 2 ) n -H are recovered. The proton NMR spectrum of the PE3M polymer (TCE / C 6 D 6 2 / 1 v / v, 400 MHz, 363 K) allows the observation of methylene in the α position of deuterium at δ = 0.83 (broad, -C H 2 D)).

[0097] The labeling rate in the PE3M polymer is calculated by determining the rate of unlabeled chains in the polymer. The rate of unlabeled chains in PE3M is determined by normalizing the integrals of the (CH 2 CH 2 ) n signals of the two 13< C NMR spectra to 100 and then dividing the integral of the CH 3 signals of the PE3M polymer by that of the CH 3 signals of the PE3NF polymer. Thus in PE3M, 11% of the polymer chain ends are unlabeled, and therefore 89% of the polymer chain ends have been labeled with a deuterium atom.

[0098] The conditions for the polymerization of ethylene are reported in Table 1. Table 1 also shows for each example the catalytic activity calculated over the entire duration of the polymerization and expressed in Kg mol -1< h -1< . The characteristics of the synthesized polyethylene polymers are shown in Table 2. The SEC-HT method was used.

[0099] Synthesis of telechelic and functional ethylene and 1,3-butadiene copolymers: Example EBR1:

[0100] 200 mL of toluene purified on an activated alumina column (also called a solvent fountain) are introduced into a 250 mL inerted flask equipped with a magnetic olive. 2.2 mL (1.0 mmol) of 1,5-di(mesitylmagnesium)pentanediyl prepared according to Example 1 (0.45 mol L -1< in toluene) are introduced into the flask with stirring. 32.0 mg (50 µmol in neodymium) of {(Me 2 Si(C 13 H 8 ) 2 )Nd(-BH 4 )[(-BH 4 )Li(THF)]} 2 are then introduced into the flask.

[0101] The catalytic solution is cannulated into a 250 mL reactor under an inert atmosphere. The argon overpressure in the reactor is reduced to 0.5 bar, then the reactor is pressurized to 4 bar with an 80 / 20 molar ethylene / butadiene mixture and the temperature is simultaneously brought to 70 °C. The pressure is kept constant in the reactor using a tank containing an 80 / 20 molar ethylene / butadiene gas mixture.

[0102] The reactor is degassed when 10 g of target monomers are consumed, here after 145 min, the temperature is brought back to 20 °C.

[0103] To determine the microstructure and macrostructure of the telechelic polymer, the polymer solution is poured onto methanol with stirring to precipitate the polymer. The polymer is washed with methanol and then dried. 10.50 g of polymer are recovered. Example EBR2:

[0104] The synthesis of the telechelic polymer is similar to that carried out in the previous example EBR1 except that 1.1 mL (0.5 mmol) of 1,5-di(mesitylmagnesium)pentanediyl prepared according to example 1 (0.45 mol L -1< in toluene) are used to prepare the catalytic solution. 10 g of the target monomers are consumed after 112 min of polymerization. 10.33 g of polymer are actually recovered. Example EBR3:

[0105] The synthesis of the telechelic polymer is similar to that carried out in the previous example EBR1 except that 0.55 mL (0.25 mmol) of 1,5-di(mesitylmagnesium)pentanediyl prepared according to example 1 (0.45 mol L -1< in toluene) is used to prepare the catalytic solution. 10 g of target monomers are consumed after 86 min of polymerization. 10.66 g of polymer are actually recovered. Example EBR4:

[0106] The synthesis of the telechelic polymer is similar to that carried out in the previous example EBR1 except that 2.3 mL (1.0 mmol) of 1,5-di(magnesium bromide)pentanediyl prepared according to example 2 (0.43 mol L -1< in toluene) are used as co-catalyst to prepare the catalytic solution. The catalytic system is a catalytic system not in accordance with the invention. 10 g of target monomers are consumed after 175 min of polymerization. 10.57 g of polymer are recovered. Example EBR5:

[0107] The synthesis of the telechelic polymer is similar to that carried out in the previous example EBR4 except that 1.15 mL (0.5 mmol) of 1,5-di(magnesium bromide)pentanediyl prepared according to example 2 (0.43 mol L -1< in toluene) are used as co-catalyst to prepare the catalytic solution. The catalytic system is a catalytic system not in accordance with the invention. 10 g of targeted monomers are consumed after 129 min of polymerization. 9.50 g of polymer are actually recovered. Example EBR6:

[0108] The synthesis of the telechelic polymer is similar to that carried out in the previous example EBR4 except that 0.58 mL (0.25 mmol) of 1,5-di(magnesium bromide)pentanediyl prepared according to example 2 (0.43 mol L -1< in toluene) is used as co-catalyst to prepare the catalytic solution. The catalytic system is a catalytic system not in accordance with the invention. 10 g of targeted monomers are consumed after 105 min of polymerization. 10.06 g of polymer are actually recovered.

[0109] The copolymerization conditions of ethylene and 1,3-butadiene are reported in Table 3. The catalytic activity expressed in Kg mol -1< h -1< is measured for each example at 80 minutes of polymerization and is shown in Table 3. The characteristics of the synthesized copolymers are shown in Table 4 and Table 5. The SEC-THF method was used for polymers EBR1 to EBR3; the SEC-HT method was used for polymers EBR4 to EBR6. The microstructure of the polymers was determined by NMR. The ethylene unit content, the 1,3-butadiene unit content in the 1,2 configuration (1,2 unit), in the 1,4 configuration (1,4 unit) and the 1,2-cyclohexane unit content (cycle unit) are expressed as molar percentage relative to all the monomer units of the polymer. Results :

[0110] The polymers of examples PE1, PE2, EBR1 and EBR2 are synthesized according to a process in accordance with the invention, the catalytic system being in accordance with the invention. The polymers of examples PE3, EBR3, EBR4 and EBR5 are synthesized according to a process not in accordance with the invention, the catalytic system not being in accordance with the invention.

[0111] The results show that the use of a catalytic system according to the invention allows the synthesis of telechelic polymers by polymerization of an olefin such as ethylene or a 1,3-diene such as 1,3-butadiene, as well as by their copolymerization. The telechelic character is shown in particular on the one hand by labeling the ends of the polymer by reaction with deuterated methanol (PE2M), on the other hand by functionalizing them with iodine (PE1F). The telechelic character is high, if we consider the rates of functions after reaction with diiodine (87%) and if we consider the rate of labeled polymer (table 2, labeling rate: 91%) and the average number of deuterated ends per polymer chain (table 2, labeled end per chain: 1.8 for a theoretical value of 2).

[0112] Furthermore, both for the synthesis of homopolymers and for the synthesis of copolymers, a catalytic activity of the catalytic system is noted which is much higher with the use of a catalytic system in accordance with the invention than with the use of a non-compliant catalytic system. Table 1 Polymer Co-catalyst Mg / Nd molar ratio Modifying agent or protic compound Duration (min) Activity (Kg mol -1< h -1< ) PE1F DMMP 144 iodine 19 315 PE1NF DMMP 144 MeOH 19 315 PE2M DMMP 231 MeOD 46 172 PE2NF DMMP 231 MeOH 46 172 PE3M DBMP 173 MeOD 49 118 PE3NF DBMP 173 MeOH 49 118 Table 2 Polymer M n NMR (g mol -1< ) M n SEC (g mol -1< ) Ð (Mw / Mn) Chain end Function rate or marking (%) End marked by chain PE1F 1740 1640 1,48 I 87 PE1NF 1400 1440 1,62 H - PE2M 1250 940 1,45 D 91 1,82 PE2NF 1250 940 1,44 H - PE3M 1630 1480 1,14 D 89 1,78 PE3NF 1630 1530 1,14 H - Table 3 Polymer Co-catalyst Mg / Nd molar ratio Protic compound Duration (min) Activity (Kg mol -1< h -1< ) EBR1 DMMP 40 MeOH 145 94 EBR2 DMMP 20 MeOH 112 134 EBR3 DMMP 10 MeOH 86 193 EBR4 DBMP 40 MeOH 175 64 EBR5 DBMP 20 MeOH 129 101 EBR6 DBMP 10 MeOH 105 153 Table 4 Polymer M n SEC (g mol -1< ) Ð Chain end EBR1 9800 1,29 H EBR2 18000 1,23 H EBR3 33100 1,29 H EBR4 13600 1,37 H EBR5 20000 1,44 H EBR6 35620 1,65 H Table 5 Polymer Ethylene unit Unit 1,2 Unit 1.4 Cycle Unit EBR1 75,3 9,4 5,6 9,7 EBR2 73,8 10,8 6,1 9,3 EBR3 73,4 11,0 6,3 9,3 EBR4 75,9 8,5 5,0 10,6 EBR5 75,9 8,8 5,2 10,1 EBR6 76,0 8,9 5,3 9,8

Claims

1. Catalytic system based at least: on a metallocene of formula (Ia) or (Ib), on an organomagnesium reagent as co-catalyst,         {P(Cp1)(Cp2)Y}     (Ia)         Cp3Cp4Y     (Ib) Y denoting a group including a rare-earth metal atom, Cp1, Cp2, Cp3 and Cp4, which are identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, P being a group bridging the two groups Cp1 and Cp2 and comprising a silicon or carbon atom, the organomagnesium reagent being a compound of formula (II)         RB-(Mg-RA)m-Mg-RB     (II) RB being different from RA, RB comprising a benzene nucleus substituted with the magnesium atom, one of the carbon atoms of the benzene nucleus ortho to the magnesium being substituted with a methyl, an ethyl, an isopropyl or forming a ring with the carbon atom which is its closest neighbour and which is meta to the magnesium, the other carbon atom of the benzene nucleus ortho to the magnesium being substituted with a methyl, an ethyl or an isopropyl, RA being a divalent aliphatic hydrocarbon-based chain, interrupted or not with one or more oxygen or sulfur atoms or with one or more arylene groups, m being a number greater than or equal to 1 and preferably equal to 1.

2. Catalytic system according to Claim 1, in which Cp1 and Cp2 are identical and are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C13H8, and each preferably represent an unsubstituted fluorenyl group of formula C13H8.

3. Catalytic system according to either of Claims 1 and 2, in which the symbol Y represents the group Met-G, with Met denoting the rare-earth metal atom and G denoting a group comprising the borohydride BH4 unit or denoting a halogen atom chosen from the group consisting of chlorine, fluorine, bromine and iodine.

4. Catalytic system according to Claim 3, in which G denotes a chlorine atom or the group of formula (III)         (BH4)(1+y)-Ly-Nx     (III) in which L represents an alkali metal chosen from the group consisting of lithium, sodium and potassium, N represents a molecule of an ether, preferably diethyl ether or tetrahydrofuran, x, which may or may not be an integer, is greater than or equal to 0, y, which is an integer, is greater than or equal to 0.

5. Catalytic system according to any one of Claims 1 to 4, in which the rare-earth metal is a lanthanide, the atomic number of which ranges from 57 to 71, preferably neodymium.

6. Catalytic system according to any one of Claims 1 to 5, in which the bridge P corresponds to the formula ZR1R2, Z representing a silicon or carbon atom and R1 and R2, which are identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl.

7. Catalytic system according to any one of Claims 1 to 6, in which the metallocene is of formula (III-1), (III-2), (III-3), (III-4) or (III-5):         [Me2Si(Flu)2Nd(µ-BH4)2Li(THF)]     (III-1)         [{Me2SiFlu2Nd(µ-BH4)2Li(THF)}2]     (III-2)         [Me2SiFlu2Nd(µ-BH4)(THF)]     (III-3)         [{Me2SiFlu2Nd(µ-BH4)(THF)}2]     (III-4)         [Me2SiFlu2Nd(µ-BH4)]     (III-5) Flu representing the C13H8 group.

8. Catalytic system according to any one of Claims 1 to 7, in which, if one of the two carbon atoms of the benzene nucleus of RB ortho to the magnesium is substituted with an isopropyl, the second carbon atom of the benzene nucleus of RB ortho to the magnesium is not substituted with an isopropyl.

9. Catalytic system according to any one of Claims 1 to 8, in which the carbon atoms of the benzene nucleus of RB ortho to the magnesium are substituted with a methyl or an ethyl, preferably a methyl.

10. Catalytic system according to any one of Claims 1 to 9, in which the organomagnesium reagent is of formula (IV-m) R1 and R5, which are identical or different, represent a methyl or an ethyl, preferably a methyl, R2, R3 and R4, which are identical or different, being a hydrogen atom or an alkyl, RA being a divalent aliphatic hydrocarbon-based chain, interrupted or not with one or more oxygen or sulfur atoms or with one or more arylene groups, m being a number greater than or equal to 1 and preferably equal to 1.

11. Catalytic system according to any one of Claims 1 to 10, in which RA is a branched or linear alkanediyl, cycloalkanediyl or xylenediyl radical, preferably an alkanediyl.

12. Process for preparing a first telechelic polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in any one of Claims 1 to 11, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.

13. Process for preparing a second telechelic polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in any one of Claims 1 to 11, this polymerization step being followed by a step of functionalization with a modifying agent, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.

14. Process for preparing a polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in any one of Claims 1 to 11 and a termination reaction with a protic compound, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.

15. Telechelic polymer of formula (V)         RB-Mg-poly-RA-poly-Mg-RB     (V) RA and RB being defined according to Claim 1 or any one of Claims 8 to 11, the name "poly" denoting a polymer chain of a 1,3-diene, of ethylene or of an α-monoolefin, or mixtures thereof, preferably a polymer chain of ethylene or a polymer chain of a 1,3-diene and ethylene or a polymer chain of a 1,3-diene, ethylene and an α-monoolefin.