Diblock polymer consisting of a polystyrene block and a statistical copolymer block of a branched diene and ethylene, and bearing a silanol or alkoxysilane function

Abstract

The invention relates to a diblock polymer of formula A-B in which the symbol A represents a polystyrene block, the symbol B represents a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, the diblock polymer bearing at the chain end a functional group containing a silanol or alkoxysilane function, the styrene units of the block A being present in the diblock in a molar content of less than 15% of the repeating units constituting the diblock polymer, and the diblock polymer having a Mooney viscosity ML (1+4) at 100°C greater than 30. The invention also relates to a method for synthesizing a polymer of this kind, and to a rubber composition containing same and intended to be used in particular in a tyre.

Description

[0001] Diblock polymer formed from a polystyrene block and a statistical copolymer block of a branched diene and ethylene and bearing a silanol or alkoxysilane function.

[0002] The field of the present invention is that of copolymers containing units of a branched 1,3-diene and ethylene units.

[0003] The Applicant described statistical copolymers of ethylene and a branched 1,3-diene such as myrcene or P-famesene in patent applications WO 2019180356 Al and WO 2020074804 Al, as well as copolymers of ethylene and 1,3-butadiene for example in patent application WO 2014114607 AL. The former, which differ from the latter by the branched structure of the 1,3-diene, may prove more suitable in certain applications due to their lower stiffness.

[0004] These copolymers, both the first and second types, are prepared by polymerizing a mixture of ethylene and a 1,3-diene. The 1,3-diene is a branched 1,3-diene for the first type and 1,3-butadiene for the second. They can also be functionalized at the chain ends by reaction with a modifying agent containing an alkoxysilane group, such as those described in patent applications WO 2021053294 Al, WO 2018224774 Al, and WO 2024088776 AL. Once synthesized, the copolymers undergo a series of operations, after which they are generally baled. These operations include finishing steps such as spinning and drying the copolymers.The spinning of copolymers, which aims to remove most of the water from the copolymers, is generally carried out in an extrusion machine called an "expeller"; the drying of the copolymers, which allows the copolymers to be recovered with an even lower moisture content and in accordance with specifications, takes place in another extrusion machine called an "expander".

[0005] The Applicant observed that the finishing steps were more challenging for the first copolymers than for the second, potentially resulting in decreased productivity. The Applicant attributes the difficulties encountered in the finishing steps of the first copolymers to their excessively low Mooney viscosity values. Therefore, there is a need to increase the Mooney viscosity of the first copolymers.

[0006] The inventors discovered that replacing a statistical copolymer of ethylene and a branched 1,3-diene with a diblock polymer formed of a polystyrene block and a statistical copolymer block of a branched diene and ethylene and bearing a silanol or alkoxysilane function solves the aforementioned problem.

[0007] The inventors also discovered that replacing a statistical copolymer of ethylene and a branched 1,3-diene with a diblock polymer according to the invention in a rubber composition comprising a reinforcing filler and a crosslinking system leads to a very significant increase in the high-temperature hysteresis (100°C) of the rubber composition. Substituting elastomers in the rubber composition is beneficial for improving the dry grip of a tire incorporating the rubber composition in its tread.

[0008] Thus, a first object of the invention is a diblock polymer of formula AB in which the symbol A represents a polystyrene block, the symbol B represents a random copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, the diblock polymer bearing at the end of the chain a

[0009] 2023PAT00317WO functional group containing a silanol or alkoxysilane function, , the styrene units of block A being present in the dibloc in a molar content of less than 15% of the repeat motifs constituting the dibloc polymer, the dibloc polymer having a Mooney viscosity ML(l+4) at 100°C greater than 30.

[0010] A second object of the invention is a rubber composition comprising a dibloc polymer according to the invention, a reinforcing filler and a crosslinking system.

[0011] A third object of the invention is a tire which includes a tread, which tire includes a rubber composition according to the invention, preferably in its tread.

[0012] Another object of the invention is a method for synthesizing a diblock polymer according to the invention, which polymer is a diblock polymer of formula AB bearing at the end of the chain a functional group containing a silanol or alkoxysilane function, A representing a polystyrene block, B representing a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, which method comprises, in the presence of a catalytic system based at least on a metallocene of formula (I) and an organomagnesium compound of formula (II), the statistical copolymerization of a monomer mixture of ethylene and the branched 1,3-diene, followed by the reaction with a modifying agent bearing an alkoxysilane function, and then, if necessary, the hydrolysis of the alkoxysilane function to the silanol function,

[0013] P(Cp 1 CP 2 ) Nd(BH4)(i +v ) Li y(THF)x (I)

[0014] R-Mg-A (II)

[0015] CP 1 and Cp 2 , identical or different, being chosen from the group consisting of cyclopentadienyl groups and fluorenyl groups, the groups being substituted or not, P being a group bridging the two Cp groups 1 and Cp 2 and representing a ZR'R group 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, preferably a methyl, y, an integer, being equal to or greater than 0, x, an integer or not, being equal to or greater than 0,

[0016] R comprising a benzene ring of which two carbon atoms are substituted, one of the two is substituted by a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in ortho position with respect to each of said two carbon atoms, the symbol A in formula (II) representing the polystyrene block constituting the dibloc polymer according to the invention, in other words a polystyrene chain identical to the polystyrene block, block A, of formula AB.

[0017] Detailed description:

[0018] Any range of values ​​designated by the expression "between a and b" represents the range of values ​​greater than "a" and less than "b" (i.e., bounds a and b excluded) while any range of values ​​designated by the expression "from a to b" means the range of values ​​from "a" to "b" (i.e., including the strict bounds a and b).

[0019] 2023PAT00317WO The compounds mentioned in the description may be of fossil origin or bio-based. 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 previously used materials; that is, they may be partially or totally derived from a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0020] The polymer according to the invention is a diblock polymer whose essential characteristic is having a Mooney viscosity ML(1+4) at 100°C greater than 30. Below a Mooney viscosity value of 30 or less, the finishing steps become difficult, as previously mentioned. Preferably, the diblock polymer has a Mooney viscosity ML(1+4) at 100°C greater than or equal to 40. A viscosity ML(1+4) at 100°C greater than 40 further facilitates the finishing steps. The viscosity ML(1+4) at 100°C of the diblock polymer is advantageously less than 70. If the viscosity ML(1+4) at 100°C is greater than or equal to 70, the polymer may overheat during the finishing steps, and this overheating may result in partial degradation of the polymer.

[0021] The block represented by the symbol B in the formula AB and hereafter referred to as "block B" is a statistical copolymer of ethylene and a branched 1,3-diene, which means that the monomer units constituting block B are statistically distributed in block B.

[0022] An ethylene unit is understood to be a unit whose repeating unit is -(CH2-CH2)-. The ethylene units of block B, referred to as the central block, preferably represent more than 50% by mole of the repeating units constituting block B. In the present application, the proportion of ethylene units in block B, that is, the number of moles of ethylene units in block B, is expressed as a mole percentage relative to the number of repeating units constituting block B. More preferably, the ethylene units of block B represent more than 60% by mole of the repeating units constituting block B. Even more preferably, the ethylene units of block B represent at least 70% by mole of the repeating units constituting block B.

[0023] According to a particular embodiment of the invention, the ethylene units in block B represent less than 90% by mole of the units that constitute block B, in which case block B contains less than 90% by mole of ethylene units.

[0024] According to another particular embodiment of the invention, the ethylene units in block B represent at most 85% by mole of the units that constitute block B, in which case block B contains at most 85% by mole of ethylene units.

[0025] According to the invention, "a branched 1,3-diene" means one or more branched 1,3-dienes. Suitable branched 1,3-dienes include, for example, myrcene, P-famesene, or a mixture thereof. The branched 1,3-diene is preferably myrcene, P-famesene, or a mixture of myrcene and P-famesene. Preferably, the expression "a branched 1,3-diene" refers to a single compound, that is, a single branched 1,3-diene. The branched 1,3-diene is more preferably myrcene.

[0026] Since the branched 1,3-diene useful for the purposes of the invention is a substituted 1,3-diene, the 1,3-diene can give rise to monomeric units of configuration 1,2 represented by formula (1), of configuration 3,4 represented by formula (2), and of configuration 1,4 whose trans form is represented below by formula (3). Preferably, the units of branched 1,3-diene in configuration 1,2 and the units of 1,3-diene in configuration 3,4 represent more than 50% by mole

[0027] 2023PAT00317WO of the 1,3-diene units. When block B contains branched 1,3-diene units that are more than 50% by mole of 1,2 or 3,4 configuration units, the complement to 100% of the branched 1,3-diene units is preferentially 1,4-trans configuration units.

[0028] According to the invention, block B is a statistical copolymer of ethylene and branched 1,3-diene, in which case the monomer units of block B are those resulting from the copolymerization of the only two monomers, namely ethylene and branched 1,3-diene, and are statistically distributed in block B.

[0029] Block B has a glass transition temperature (Tg) preferentially between -90°C and -40°C, and more preferably between -70°C and -50°C. It is known that the glass transition temperature of block B can be adjusted, for example, by the chemical structure of the branched 1,3-diene, specifically the respective proportions of ethylene units and branched 1,3-diene units in block B.

[0030] Block B has a number-average molar mass, Mn, preferably greater than 100,000 g / mol. Block B has a number-average molar mass preferably less than 300,000 g / mol.

[0031] Advantageously, block B has a number-average molar mass ranging from over 100,000 g / mol to under 300,000 g / mol.

[0032] The block represented by the symbol A in formula AB and hereafter referred to as block A has the essential characteristic of being polystyrene. One end of block A is connected to one end of block B.

[0033] Preferably, block A represents linear polystyrene. Preferably, block A is atactic polystyrene.

[0034] The A-block styrene units are present in Dibloc at a molar content of less than 15% of the repeating units constituting the Dibloc polymer. With a molar content of A-block styrene units below 15%, the Dibloc polymer exhibits elastomeric properties. Above 15%, the polymer begins to lose its elastomeric properties, and the finishing processes become problematic. The A-block styrene units are present in Dibloc at a molar content preferably greater than 2% of the repeating units constituting the Dibloc polymer.

[0035] Preferably, block A has a number-average molar mass greater than 3,000 g / mol and less than or equal to 30,000 g / mol.

[0036] The diblock polymer according to the invention is a functionalized diblock polymer, since it carries at the end of its chain a functional group of the formula Si(OR 3 )3- n (R 4)n or formula -CLfi- CH(CH3)-COOZ', the symbols R 3 , identical or different, representing an alkyl or a hydrogen atom, the symbols R 4 , identical or different, representing a hydrogen atom, a chain

[0037] 2023PAT00317WO hydrocarbon or a hydrocarbon chain substituted by a tertiary amine function, n being an integer from 0 to 2 when R 3 is alkyl, n being an integer equal to 2 when R 3 is a hydrogen atom,

[0038] Z' representing an alkyl substituted by a function of the formula Si(OR 5 )3- m (R 6 )m, the R symbols 5 , identical or different, representing an alkyl or a hydrogen atom, the symbols R 6 , identical or different, representing a hydrogen atom, a hydrocarbon chain, m being an integer from 0 to 2 when R 5is alkyl, m being an integer equal to 2 when R 5 is a hydrogen atom.

[0039] According to a first variant of the invention, the functional group carried at the end of the chain by the copolymer has the formula (Ill-a)

[0040] If (OR 3 )3.n(R 4 )n (III-a) the R symbols 3 , identical or different, representing an alkyl, the symbols R 4 , identical or different, representing a hydrogen atom, a hydrocarbon chain or a hydrocarbon chain substituted by a tertiary amine function, n being an integer from 0 to 2.

[0041] According to a second variant of the invention, the functional group carried at the end of the chain by the copolymer has the formula (Ill-b)

[0042] Si(OH)(R 4 )2(Ill-b) the R symbols 4, identical or different, representing a hydrogen atom, a hydrocarbon chain or a hydrocarbon chain substituted by a tertiary amine function.

[0043] Among the hydrocarbon chains represented by the symbols R 4 In formulas (Ill-a) and (Ill-b), we can mention alkyls, especially those having 1 to 6 carbon atoms, preferentially methyl or ethyl, more preferentially methyl.

[0044] Among the hydrocarbon chains substituted by a tertiary amine function represented by the symbols R 4In formulas (Ill-a) and (Ill-b), we can cite the alkanediyl chains, in particular those with at most 6 carbon atoms, especially the 1,3-propanediyl group, the alkanediyl group bearing the tertiary amine function, in other words, one valence of the alkanediyl chain for the tertiary amine function, the other valence for the silicon atom of the silanol or alkoxysilane function.

[0045] Preferably, the R symbols 4 , identical or different, each represent an alkyl having at most 6 carbon atoms or an alkanediyl chain having at most 6 carbon atoms and substituted by a tertiary amine function in formulas (Ill-a) and (Ill-b).

[0046] In formula (Ill-a), the symbols R 3 are preferentially an alkyl having at most 6 carbon atoms, more preferentially methyl or ethyl, and even more preferentially methyl. If 3-y is greater than 1, the symbols R 3are advantageously identical, in particular methyl or ethyl, more particularly methyl.

[0047] As a functional group of formula (Ill-a), we can cite the groups dimethoxymethylsilyl, dimethoxyethylsilyl, diethoxymethysilyl, diethoxyethysilyl, 3-(N,N-dimethylamino)propyldimethoxysilyl, 3-(N,N-dimethylamino)propyldiethoxysilyl, methoxydimethylsilyl, methoxydiethylsilyl, ethoxydimethysilyl, ethoxydiethysilyl, 3-(N,N-dimethylamino)propylmethoxymethylsilyl, 3-(N,N-dimethylamino)propylmethoxyethylsilyl, 3-(N,N-dimethylamino)propylethoxymethylsilyl, 3-(N,N-dimethylamino)propylethoxymethylsilyl, 3-(N,N-dimethylamino)propylethoxyethylsilyl.

[0048] 2023PAT00317WO As a functional group with formula (III-b), we can also mention the silanol form of the previously cited functional groups that contain one and only one ethoxy or methoxy function, the silanol form being obtained by hydrolysis of the ethoxy or methoxy function. Suitable examples include dimethylsilanol, diethylsilanol, 3-(N,N-dimethylamino)propylmethylsilanol, and 3-(N,N-dimethylamino)propylethylsilanol.

[0049] In formula (Ill-a), f is preferably equal to 1. For this preferred variant, groups for which R are particularly suitable 1 is a methyl or ethyl group, such as dimethoxymethylsilyl, dimethoxyethylsilyl, diethoxymethysilyl, diethoxyethysilyl, 3-(N,N-dimethylamino)propyldimethoxysilyl, 3-(N,N-dimethylamino)propyldiethoxysilyl. More preferably in formula (Ill-a), f is 1 and R 1is methyl. For this more preferred variant, dimethoxymethylsilyl, dimethoxyethylsilyl, 3-(N,N-dimethylamino)propyldimethoxysilyl groups are particularly suitable.

[0050] According to a third variant of the invention, the functional group carried at the end of the chain by the copolymer has the formula (III-c) -CH2-CH(CH3)-COOZ' (III-C)

[0051] Z' representing an alkyl substituted by a function of the formula Si(OR 5 )3- m (R 6 )m, the R symbols 5 , identical or different, representing an alkyl, the symbols R 6 , identical or different, representing a hydrogen atom or a hydrocarbon chain, m being an integer from 0 to 2.

[0052] According to a fourth variant of the invention, the functional group carried at the end of the chain by the copolymer has the formula (Ill-d) -CH2-CH(CH3)-COOZ' (Ill-d)

[0053] Z' representing an alkyl substituted by a function of formula Si(OH) (R 6 )2, the R symbols 6 , identical or different, representing a hydrogen atom or a hydrocarbon chain.

[0054] Among the alkyls substituted by a function of formula Si(OR 5 ) 3.m (R 6 )m in formula (III-c) and alkyls substituted by a function of formula Si(OH) (R 6 )2 in the formula (Ill-d), we can mention alkyls having at most 6 carbon atoms, more preferentially methyl, ethyl and propyl. Among the hydrocarbon chains represented by the symbols R 6 in formula (III-c) and in formula (III-d), we can mention alkyls, preferably alkyls having at most 6 carbon atoms, more preferably methyl or ethyl, better methyl.

[0055] As Z' in the third variant, we can cite methoxydimethylsilyl, methoxydiethylsilyl, ethoxydimethylsilyl, ethoxydiethylsilyl, dimethoxymethylsilyl, diethoxymethylsilyl, dimethoxyethysilyl, diethoxyethylsilyl, trimethoxysilyl, triethoxysilyl, preferably methoxydimethylsilylpropyl, ethoxydimethylsilylpropyl, diethoxymethylsilylpropyl, trimethoxysilylmethyl, 3-trimethoxysilylpropyl.

[0056] As Z' in the fourth variant, we can cite hydroxydimethylsilyl, hydroxydiethylsilyl, preferably hydroxydimethylsilylpropyl.

[0057] According to a particularly preferred embodiment, the functional group is carried at the end of the chain of block B. In other words, according to this embodiment, block B has one of its chain ends which is directly connected to the functional group, the other end of block B being connected to block A.

[0058] 2023PAT00317WO The dibloc polymer according to the invention can be prepared according to a process, which includes the statistical copolymerization of a monomer mixture of ethylene and branched 1,3-diene in the presence of a catalytic system, followed by the chain-end functionalization reaction of the dibloc.

[0059] The catalytic system (or catalytic composition) used in the statistical copolymerization of the monomer mixture is based on at least one metallocene of formula (I) and one organomagnesium compound of formula (II)

[0060] P(Cp 1 CP 2 ) Nd(BH4)(i +v ) Liy (THF)x (I)

[0061] R-Mg-A (II)

[0062] CP 1 and Cp 2 , identical or different, being chosen from the group consisting of cyclopentadienyl groups and fluorenyl groups, the groups being substituted or not, P being a group bridging the two Cp groups 1 and Cp 2 and representing a ZR'R group 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, preferably a methyl group, y, an integer, being equal to or greater than 0, x, an integer or not, being equal to or greater than 0

[0063] R comprising a benzene nucleus of which two carbon atoms are substituted, one of the two is substituted by a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in ortho position with respect to each of said two carbon atoms.

[0064] The symbol A in formula (II) represents the polystyrene block constituting the dibloc polymer according to the invention, in other words a polystyrene chain identical to the polystyrene block, block A, of formula AB.

[0065] In formula (I), the neodymium atom is linked to a ligand molecule consisting of the two Cp groups 1 and Cp 2 connected to each other by bridge P. Preferably, the symbol P, designated as bridge, corresponds to the formula ZR'R 2 , Z representing a silicon atom, R 1 and R2 , identical or different, representing an alkyl group comprising from 1 to 20 carbon atoms. More preferably, the P bridge has the formula SiR'R 2 , R 1 and R 2 , being identical and as defined previously. Even more preferably, P satisfies the formula SiMe2.

[0066] Examples of substituted cyclopentadienyl and fluorenyl groups include those substituted with alkyl groups having 1 to 6 carbon atoms, aryl groups having 6 to 12 carbon atoms, or trialkylsilyl groups such as SiMcs. The choice among alkyl, aryl, and trialkylsilyl groups is also influenced by the availability of the corresponding molecules, namely the substituted cyclopentadienes and fluorenes, because these are either commercially available or easily synthesized.

[0067] Examples of substituted cyclopentadienyl groups include those substituted at both position 2 (or 5) and position 3 (or 4), particularly those substituted at position 2, more specifically the tetramethylcyclopentadienyl group. In the present application, in the case of the cyclopentadienyl group, position 2 (or 5) refers to the position of the carbon atom that is adjacent to

[0068] 2023PAT00317WO the carbon atom to which the P bridge is attached, as shown in the diagram below.

[0069] Examples of substituted fluorenyl groups include those substituted at positions 2,7, 3, or 6, particularly the 2,7-ditertiobutyl-fluorenyl and 3,6-ditertiobutyl-fluorenyl groups. Positions 2, 3, 6, and 7 respectively designate the positions of the carbon atoms in the rings, as shown in the diagram below, with position 9 corresponding to the carbon atom to which the P-bridge is attached.

[0070] Preferably, Cp 1 and Cp 2 are identical and are chosen from the group consisting of substituted fluorenyl groups and the fluorenyl group. Advantageously, in formula (I) Cp 1 and Cp 2 Each represents a substituted fluorenyl group or a fluorenyl group, preferably a fluorenyl group. The fluorenyl group has the formula CisHs. Preferably, the metallocene has the formula (la), (Ib), (le), (Id), or (le), in which the symbol Flu represents the fluorenyl group of formula CisHs.

[0071] The metallocene used to prepare the catalytic system can be in the form of a crystalline or non-crystalline powder, or as single crystals. The metallocene can be monomeric or dimeric, depending on the method of preparation, as described, for example, in patent application WO 2007054224. The metallocene can be prepared conventionally by a process analogous to that described in patent application WO 2007054224, specifically by reacting the salt of an alkali metal of the ligand with a rare-earth borohydride under inert and anhydrous conditions in a suitable solvent, such as an ether like diethyl ether or tetrahydrofirane, or any other solvent known to those skilled in the art. After the reaction, the metallocene is separated from the reaction byproducts by techniques known to those skilled in the art, such as filtration or precipitation in a second solvent.The metallocene is ultimately dried and insulated in solid form.

[0072] Like all syntheses carried out in the presence of organometallic compounds, the synthesis of metallocene takes place under anhydrous conditions in an inert atmosphere. Typically, the reactions are conducted using solvents and anhydrous compounds under anhydrous nitrogen or argon.

[0073] 2023PAT00317WO The organomagnesium compound of formula (II) is used in the catalytic system as a co-catalyst. Preferably, the two substituents of the two carbon atoms with respect to which the magnesium atom is in the ortho position are identical. More preferably, they are methyl or ethyl. Advantageously, they are methyl.

[0074] Preferably, the organomagnesium compound of formula (II) corresponds to formula (II-1) in which A represents the polystyrene chain, Ri and R5, identical or different, represent a methyl or ethyl group, and R2, R3, and R4, identical or different, represent a hydrogen atom or an alkyl group. Preferably, Ri and R5 represent a methyl group. Preferably, R2 and R4 represent a hydrogen atom.

[0075] According to a preferred variant, Ri, R3, and R5 are identical. According to a more preferred variant, R2 and R4 represent a hydrogen atom, and Ri, R3, and R5 are identical. In a further preferred variant, R2 and R4 represent a hydrogen atom, and Ri, R3, and R5 represent a methyl group.

[0076] The organomagnesium compound of formula (II) can be prepared by a process that includes the reaction of a living anionic polystyrene ALi with a halide of an organomagnesium compound of formula R-Mg-X, where R is defined as in formula (II), A represents the polystyrene block, X is a halogen atom, preferably a chlorine or bromine atom, more preferably a bromine atom, and the symbol Li represents, in a well-known manner, the lithium atom. Anionic polystyrene is understood to be a polystyrene prepared by anionic polymerization. Also in a well-known manner, living polystyrene is understood to be a polystyrene whose polymer chains possess a reactive center with respect to polymerization, typically a carbon-lithium bond, particularly at the end of the polymer chain.

[0077] Living anionic polystyrene is conventionally obtained by the anionic polymerization of styrene in a solvent, known as the polymerization solvent. The polymerization solvent can be any hydrocarbon solvent known to be used in the polymerization of styrene. Preferably, the polymerization solvent is a hydrocarbon solvent, most preferably cyclohexane, methylcyclohexane, or toluene.

[0078] The ratio of solvent to styrene required for the formation of living anionic polystyrene is determined by a person skilled in the art based on the desired viscosity of the living polystyrene polymer solution. This viscosity depends not only on the concentration of the polymer solution but also on numerous other factors, such as the length of the polymer chains, the intermolecular interactions between the living polystyrene chains, the complexing power of the solvent, and the temperature of the polymer solution. Therefore, a person skilled in the art adjusts the amount of solvent on a case-by-case basis.

[0079] To initiate the polymerization of styrene, compounds well known to those skilled in the art as initiators of the anionic polymerization of styrene can be used. The initiator is, for example, a compound that contains a carbon-lithium bond. Examples of initiators include...

[0080] 2023PAT00317WO organolithium compounds, such as n-butyllithium, sec-butyllithium, and tert-butyllithium. The initiator is used at a rate chosen according to the desired chain length of the living polystyrene.

[0081] The polymerization temperature for forming living polystyrene can vary widely. Traditionally, it ranges from -20 to 100°C, preferably from 20 to 70°C.

[0082] To prepare an organomagnesium compound of formula (II), the reaction of anionic living polystyrene with the halide of an organomagnesium compound can be carried out by adding a solution of the anionic living polystyrene to a solution of the halide of an organomagnesium compound R-Mg-X, but it is preferably carried out by adding a solution of the halide of an organomagnesium compound R-Mg-X to a solution of the anionic living polystyrene. The solution of the anionic living polystyrene is generally a solution in a hydrocarbon solvent, preferably the polymerization solvent used for the synthesis of the anionic living polystyrene. The solution of the halide of an organomagnesium compound R-Mg-X is generally a solution in an ether, preferably diethyl ether or dibutyl ether. The concentration of living anionic polystyrene is preferentially from 0.01 to 1 mole of lithium equivalent (eq) / L, more preferably from 0.05 to 0.2 mole of lithium equivalent / L, that of the R-Mg-X organomagnesium solution preferably from 1 to 5 mol / L, more preferably from 2 to 3 mol / L.

[0083] The reaction between living anionic polystyrene and the organomagnesium halide R-Mg-X is typically carried out at a temperature ranging from 0°C to 60°C. Contact is preferably made at a temperature between 0°C and 23°C.

[0084] As with any synthesis involving organometallic compounds, the contact and reaction take place under anhydrous conditions in an inert atmosphere. Typically, solvents and solutions are used under anhydrous nitrogen or argon. The various steps of the process are generally carried out with stirring.

[0085] Once Torganomagnesian of formula (II) is formed, the solution of Torganomagnesian of formula (II) is typically stored prior to its use as a co-catalyst of the catalytic system in airtight containers, for example capped bottles, at a temperature between -25°C and 23°C, under an inert and anhydrous atmosphere.

[0086] The catalytic system can be prepared conventionally by a process analogous to that described in patent applications WO 2007054224 or WO 2007054223. For example, the co-catalyst and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20 to 80°C for a duration of 5 to 60 minutes. The amounts of co-catalyst and metallocene reacted are such that the ratio of the number of moles of Mg in the co-catalyst to the number of moles of rare-earth metal in the metallocene is preferably from 1 to 100, and more preferably from 1 to less than 10. The range of values ​​from 1 to less than 10 is particularly favorable for obtaining polymers with high molar masses. The catalytic system is generally prepared in a hydrocarbon solvent, either aliphatic such as methylcyclohexane or aromatic such as toluene.Generally, after its synthesis, the catalytic system is used as is in the polymer synthesis process according to the invention.

[0087] The catalytic system is generally in the form of a solution in a hydrocarbon solvent. The hydrocarbon solvent can be aliphatic, such as methylcyclohexane, or aromatic, such as toluene. The hydrocarbon solvent is preferably aliphatic, and more specifically, methylcyclohexane. Generally, the catalytic system is stored as a solution in the hydrocarbon solvent before being used in polymerization. We can speak

[0088] 2023PAT00317WO is a catalytic solution comprising the catalytic system and the hydrocarbon solvent. The concentration of the catalytic solution is typically 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.

[0089] As with any synthesis carried out in the presence of organometallic compounds, the synthesis of the catalytic system takes place under anhydrous conditions in an inert atmosphere. Typically, the reactions are conducted using solvents and anhydrous compounds under anhydrous nitrogen or argon.

[0090] The copolymerization of the monomer mixture is preferably carried out in solution, either continuously or batchwise, in a suitably stirred reactor. The polymerization solvent may be a hydrocarbon, aromatic, or aliphatic solvent. Examples of polymerization solvents include toluene and methylcyclohexane.

[0091] The catalytic system is typically introduced into the reactor containing the polymerization solvent and the monomer mixture containing ethylene and a 1,3-diene. To achieve the desired macrostructure of the core block, those skilled in the art adjust the polymerization conditions, particularly the molar ratio of the organomagnesium compound to the Nd metal that constitutes the metallocene. The molar ratio can reach 100, although a molar ratio below 10 is more favorable for obtaining polymers with high molar masses.

[0092] Block B is prepared by the statistical copolymerization of a mixture of ethylene monomer and branched 1,3-diene. Preferably, a continuous addition of ethylene and branched 1,3-diene is carried out in the polymerization reactor, in which case the polymerization reactor is a fed reactor. This embodiment is particularly suitable for the statistical incorporation of ethylene and branched 1,3-diene.

[0093] The polymerization temperature generally varies from 30 to 160°C, preferably from 30 to 120°C. During the preparation of block B, the temperature of the reaction medium is advantageously kept constant during copolymerization, and the total pressure in the reactor is also advantageously kept constant. The preparation of block B is completed by stopping the monomer supply, notably by dropping the reactor pressure, preferably to about 0.1 bar, and the chain end of the diblock polymer is then functionalized by reaction with a modifying agent.

[0094] According to a first variant of the process according to the invention, the modifying agent is a compound of formula (IV),

[0095] If(Fc 1 ) 4.g (Rc 2 ) g (IV) the Fc symbols 1, identical or different, representing an alkoxy group or a halogen atom, the symbols Rc 2 , identical or different, representing a hydrogen atom, a hydrocarbon chain or a hydrocarbon chain substituted by a tertiary amine function, g being an integer from 0 to 2.

[0096] When the Fc symbol 1 represents an alkoxy group; the alkoxy group is preferably methoxy or ethoxy. When the symbol Fc 1 represents a halogen atom, the halogen atom is preferably chlorine.

[0097] Among the hydrocarbon chains represented by the symbols Rc 2 in formulas (IV), we can mention alkyls, preferably alkyls having at most 6 carbon atoms, more preferably methyl or ethyl, better methyl.

[0098] Among the hydrocarbon chains substituted by a chemical function Fc 2 which are represented by the symbols Rc2 In formula (IV), we can mention the alkanediyl chains, preferably those

[0099] 2023PAT00317WO comprising at most 6 carbon atoms, more preferably the 1,3-propanediyl group, the alkanediyl group bearing a tertiary amine function, in other words, one valence of the alkanediyl chain for the tertiary amine function, the other valence for the silicon atom. g is preferably not equal to 0, which implies that the functionalizing agent includes at least one Si-Rc bond 2 .

[0100] Examples of modifying agents for the first variant of the process include dimethoxydimethylsilane, diethoxydimethylsilane, dimethoxydiethylsilane, diethoxydiethylsilane, (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)methyldiethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldiethoxysilane, trimethoxymethylsilane, triethoxymethylsilane, trimethoxyethylsilane, triethoxyethylsilane, (N,N-dimethylaminopropyl)trimethoxysilane, (N,N-dimethylaminopropyl)triethoxysilane, preferably dimethoxydimethylsilane, dimethoxydiethylsilane, (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane, (N,N-dimethyl-3-aminopropyl)ethyldimethoxysilane, trimethoxyethylsilane, (N,N-dimethylaminopropyl)trimethoxysilane, more preferably trimethoxymethylsilane, trimethoxyethylsilane, (N,N-dimethylaminopropyl)trimethoxysilane.

[0101] According to a second embodiment of the process according to the invention, the modifying agent is a compound of formula (V), CH2=CCH3COOZ”, Z”, representing an alkyl group substituted by a functional group of formula Si(OR 5 )3- m (R 6 )m, the R symbols 5 , identical or different, representing an alkyl, the symbols R 6 , identical or different, representing a hydrogen atom or a hydrocarbon chain, m being an integer from 0 to 2.

[0102] Alkyl groups represented by the symbols R 5 are preferentially methyl or ethyl, more preferentially methyl.

[0103] Among the alkyls substituted by a function of formula Si(OR 5 )3- m (R 6 )m, we can mention alkyls having at most 6 carbon atoms, more preferentially methyl, ethyl and propyl.

[0104] Among the hydrocarbon chains represented by the symbols R 6in formula (V), we can mention alkyls, preferably alkyls having at most 6 carbon atoms, more preferably methyl or ethyl, better methyl.

[0105] As modifying agents for the second variant of the process, the following compounds may be mentioned: methoxydimethylsilylmethyl methacrylate, ethoxydimethylsilylmethyl methacrylate, methoxydimethylsilylpropyl methacrylate, ethoxydimethylsilylpropyl methacrylate, dimethoxymethylsilylmethyl methacrylate, diethoxymethylsilylethyl methacrylate, dimethoxymethylsilylpropyl methacrylate, diethoxymethylsilylpropyl methacrylate, trimethoxysilylethyl methacrylate, 3-(trimethoxysilyl)propyl methacrylate, preferably trimethoxysilylmethyl methacrylate, 3-(trimethoxysilyl)propyl methacrylate.

[0106] The modifying agent is typically added to the polymerization medium at a monomer conversion rate chosen by a person skilled in the art according to the desired macrostructure of the polymer. The modifying agent is added under inert and anhydrous conditions to the polymerization medium, which is maintained at the polymerization temperature. The molar ratio of the number of moles of modifying agent to the number of moles of neodymium and magnesium is preferably greater than 1, and more preferably greater than or equal to 2. The molar ratio of the number of moles of modifying agent to the number of moles of neodymium and magnesium is preferably from 2 to 50, and more preferably greater than 1.

[0107] 2023PAT00317WO preferably from 2 to 10. The modifying agent is brought into contact with the polymerization medium for a sufficient time to allow the functionalization reaction. This contact time is judiciously chosen by those skilled in the art, depending on the concentration of the reaction medium, the temperature of the reaction medium, and the structure of the modifying agent. Typically, the functionalization reaction is carried out under stirring, at a temperature ranging from 17 to 80°C, for 0.01 to 24 hours. A diblock polymer bearing an alkoxysilane group at the end of its chain is then obtained.

[0108] Once the chain end of the diblock polymer is functionalized, a chain termination reaction is generally carried out to deactivate any remaining reactive sites in the reaction medium. This chain termination reaction is typically implemented by adding a terminating agent to the reaction medium containing the functionalized diblock polymer or by pouring the reaction medium onto a solution containing the terminating agent. The terminating agent is usually added in excess of the number of carbon-metal bonds, such as C-Mg and C-Nd, present in the reaction medium. The terminating agent is typically a protic compound, meaning a compound with a relatively acidic proton.Examples of terminating agents include water, carboxylic acids, particularly fatty acids such as acetic acid and stearic acid, aliphatic or aromatic alcohols such as methanol, ethanol, and isopropanol, and phenolic antioxidants.

[0109] The use of a formula-modifying agent (IV) according to the first variant of the process allows the preparation of a diblock polymer bearing an alkoxysilane group at its chain end, an alkoxysilane group of formula (Ill-a). The use of a formula-modifying agent (V) according to the second variant of the process also allows the preparation of a diblock polymer bearing an alkoxysilane group at its chain end, an alkoxysilane group of formula (Ill-d).

[0110] When the process is used to prepare a diblock polymer bearing a silanol function at the chain end, the process includes, after the functionalization reaction, a hydrolysis reaction of the alkoxysilane function to the silanol function and allows the preparation of diblock polymers bearing a silanol function at the chain end, in particular a silanol function of formula (III-b) or (III-d) using formula modifying agents (IV) or (V) respectively.

[0111] The hydrolysis of the alkoxysilane group to the silanol group can be carried out by acid treatment of a highly saturated diene telatomer obtained after reaction with the modifying agent bearing an alkoxysilane group. The acid treatment is typically performed in solution in the presence of aqueous hydrochloric acid, followed by stripping, for example, according to the conditions described in patent application EP 2 266 819 AL

[0112] The functionalized dibloc 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 steam stripping.

[0113] Alternatively, the functionalized dibloc polymer can be prepared by another process which differs from that described in that the co-catalyst is not the organomagnesium of formula (II), but the living anionic polystyrene ALi and the molar ratio between the number of moles of living polymer and the number of moles of Nd atoms in the metallocene varies in a range of 0.8 to 1.2.

[0114] The functionalized dibloc polymer is typically an elastomer and can be used in a rubber composition, another object of the invention.

[0115] 2023PAT00317WO The rubber compound may include any type of reinforcing filler, known for its ability to strengthen a rubber compound suitable for tire manufacturing. Examples include an organic filler such as carbon black, an inorganic reinforcing filler such as silica combined with a known coupling agent, or a mixture of both types of filler. Such a reinforcing filler typically consists of nanoparticles with an average size (by mass) of less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, and particularly and preferably between 20 and 150 nm. The reinforcing filler content is adjusted by a person skilled in the art according to the intended use of the rubber compound.

[0116] The crosslinking system can be based on sulfur, sulfur donors, peroxides, bismaleimides, or mixtures thereof. The crosslinking system is preferably a vulcanization system, that is, a system based on sulfur (or a sulfur-donating agent) and a primary vulcanization accelerator. Various known secondary accelerators or vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, guanidine derivatives (particularly diphenylguanidine), or known vulcanization retarders, can be added to this basic vulcanization system.

[0117] The rubber composition may also contain other additives known to be used in tire rubber compositions, such as plasticizers, anti-ozonants, and antioxidants.

[0118] The rubber composition according to the invention is typically manufactured in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first thermomechanical working or mixing phase (the so-called "non-productive" phase) at high temperature of the ingredients of the rubber composition, with the exception of the crosslinking system, up to a maximum temperature between 130°C and 200°C, followed by a second mechanical working phase (the so-called "productive" phase) down to a lower temperature, typically below 110°C, for example between 40°C and 100°C, a finishing phase during which the crosslinking system is incorporated.

[0119] After the incorporation of all the ingredients of the rubber composition, the final composition thus obtained can be calendered, for example in the form of a sheet or plate, in particular for characterization in the laboratory, or extraneous, to form for example a rubber profile used as a rubber component or semi-finished product, in particular for the manufacture of a tire.

[0120] Thus, according to a particular embodiment of the invention, the rubber composition according to the invention, which can be either in the raw state (before crosslinking or vulcanization) or in the cooked state (after crosslinking or vulcanization), is in a tire, for example in a tire tread.

[0121] Crosslinking (or curing), where applicable vulcanization, is carried out in a known manner at a temperature generally between 130°C and 200°C, for a sufficient time which can vary for example between 5 and 120 min depending in particular on the curing temperature, the crosslinking system adopted and the crosslinking kinetics of the composition considered.

[0122] The rubber composition according to the invention, which can be either in the raw state (before crosslinking or vulcanization) or in the cured state (after crosslinking or vulcanization), can be used in a semi-finished article for pneumatics.

[0123] 2023PAT00317WO The tire, another object of the invention, which includes a tread, comprises the rubber composition according to the invention defined under any one of the embodiments of the invention, preferably in its tread.

[0124] In the present invention, the term "pneumatic" (in English, "tire") refers to a pneumatic or non-pneumatic tire. A pneumatic tire typically comprises two beads for contact with a rim, a crown consisting of at least one crown reinforcement and a tread, and two sidewalls. The tire is reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic tire, on the other hand, typically comprises a base, designed, for example, for mounting on a rigid rim, a crown reinforcement connecting to a tread, and a deformable structure, such as spokes, ribs, or dimples, this structure being arranged between the base and the crown. Such non-pneumatic tires do not necessarily include sidewalls. Non-pneumatic tires are described, for example, in documents WO 03 / 018332 and FR2898077.According to any one of the embodiments of the invention, the tire according to the invention is preferably a pneumatic tire.

[0125] In summary, the invention is preferably implemented according to any one of the following embodiments 1 to 28:

[0126] Mode 1: Diblock polymer of formula AB in which the symbol A represents a polystyrene block, the symbol B represents a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, the diblock polymer bearing at the end of the chain a functional group containing a silanol or alkoxysilane function, the styrene units of block A being present in the diblock in a molar content of less than 15% of the repeating motifs constituting the diblock polymer, the diblock polymer having a Mooney ME(l+4) viscosity at 100°C greater than 30.

[0127] Mode 2: Diblock polymer according to mode 1 in which the ethylene units of block B represent more than 50% by mole of the repeating motifs constituting block B.

[0128] Mode 3: Diblock polymer according to any one of modes 1 to 2 in which the ethylene units of block B represent more than 60% by mole of the repeating motifs constituting block B.

[0129] Mode 4: Diblock polymer according to any one of modes 1 to 3 in which the ethylene units of block B represent at least 70% by mole of the repeating motifs constituting block B.

[0130] Mode 5: Diblock polymer according to any one of modes 1 to 4 in which the ethylene units of block B represent at most 85% by mole of the repeating motifs constituting block B.

[0131] Mode 6: Diblock polymer according to any one of modes 1 to 5 in which the functional group is carried at the end of the chain of block B.

[0132] Mode 7: Diblock polymer according to any one of modes 1 to 6 in which block B has a glass transition temperature between -90°C and -40°C, preferably between -70°C and -50°C.

[0133] Mode 8: Diblock polymer according to any one of modes 1 to 7 in which the branched 1,3-diene is myrcene or P-famesene or a mixture of myrcene and -famesene, preferably myrcene.

[0134] 2023PAT00317WO Mode 9: Diblock polymer according to any one of modes 1 to 8 in which block A has a number-average molar mass greater than 3,000 g / mol and less than or equal to 30,000 g / mol.

[0135] Mode 10: Diblock polymer according to any one of modes 1 to 9 in which block B has a number-average molar mass greater than 100,000 g / mol.

[0136] Mode 11: Diblock polymer according to mode 10 in which block B has a number-average molar mass of less than 300,000 g / mol.

[0137] Mode 12: Diblock polymer according to any one of modes 1 to 11 in which the functional group has the formula Si(OR 3 )3- n (R 4 )n or of the formula -CH2-CH(CH3)-COOZ', the symbols R 3 , identical or different, representing an alkyl or a hydrogen atom, the symbols R 4 , identical or different, representing a hydrogen atom, a hydrocarbon chain, or a hydrocarbon chain substituted by a tertiary amine function, n being an integer from 0 to 2 when R 3 is alkyl, n being an integer equal to 2 when R 3 is a hydrogen atom,

[0138] Z' representing an alkyl substituted by a function of the formula Si(OR 5 )3- m (R 6 )m, the R symbols 5 , identical or different, representing an alkyl or a hydrogen atom, the symbols R 6, identical or different, representing a hydrogen atom, a hydrocarbon chain, m being an integer from 0 to 2 when R 5 is alkyl, m being an integer equal to 2 when R 5 is a hydrogen atom.

[0139] Mode 13: Polymer according to any one of modes 1 to 12 in which the functional group carried at the end of the chain by the copolymer has the formula (Ill-a)

[0140] If (OR 3 )3.n(R 4 )n (III-a) the R symbols 3 , identical or different, representing an alkyl, the symbols R 4 , identical or different, representing a hydrogen atom, a hydrocarbon chain or a hydrocarbon chain substituted by a tertiary amine function, n being an integer from 0 to 2.

[0141] Mode 14: Polymer according to any one of modes 1 to 12 in which the functional group carried at the end of the chain by the copolymer has the formula (Ill-b)Si(OH)(R 4 )2(Ill-b) the R symbols 4 , identical or different, representing a hydrogen atom, a hydrocarbon chain or a hydrocarbon chain substituted by a tertiary amine function.

[0142] Mode 15: Polymer according to mode 13 or 14 in which the hydrocarbon chain is represented by the symbols R 4 in formulas (Ill-a) and (Ill-b) are methyl or ethyl.

[0143] Mode 16: Polymer according to mode 13 or 14 in which the hydrocarbon chain is substituted by a tertiary amine function and represented by the symbols R 4 in formulas (Ill-a) and (Ill-b) is the 1,3-propanediyl group substituted by a tertiary amine function.

[0144] Mode 17: Polymer according to mode 13 or according to any of modes 15 or 16 in which the symbols R 3 are methyl or ethyl.

[0145] Mode 18: Polymer according to any one of modes 1 to 12 in which the functional group carried at the end of the chain by the copolymer has the formula (III-c)-CH2-CH(CH3)-COOZ' (III-C)

[0146] Z' representing an alkyl substituted by a function of the formula Si(OR 5 )3- m (R 6 )m,

[0147] 2023PAT00317WO the R symbols 5 , identical or different, representing an alkyl, the symbols R 6 , identical or different, representing a hydrogen atom or a hydrocarbon chain, m being an integer from 0 to 2.

[0148] Mode 19: Polymer according to any one of modes 1 to 12 in which the functional group carried at the end of the chain by the copolymer has the formula (Ill-d) -CH2-CH(CH3)-COOZ' (Ill-d)

[0149] Z' representing an alkyl substituted by a function of formula Si(OH) (R 6 )2, the R symbols 6 , identical or different, representing a hydrogen atom or a hydrocarbon chain.

[0150] Mode 20: Polymer according to mode 18 or 19 in which the alkyl is substituted by a function of formula Si(OR 5 ) 3 m (R 6 )m and the alkyl substituted by a function of formula Si(OH) (R 6 )2 are methyl, ethyl or propyl.

[0151] Mode 21: Polymer according to any one of modes 18 to 20 in which the hydrocarbon chain is represented by the symbol R 6 is methyl or ethyl.

[0152] Mode 22: Rubber composition comprising a dibloc polymer defined according to any one of modes 1 to 21, a reinforcing filler and a crosslinking system.

[0153] Mode 23: A tire which includes a tread, which tire includes a rubber composition defined in mode 22, preferably in its tread.

[0154] Mode 24: A process for synthesizing a polymer defined in any one of modes 1 to 21, which polymer is a diblock polymer of formula AB bearing at the end of the chain a functional group containing a silanol or alkoxysilane function,

[0155] A representing a polystyrene block,

[0156] B representing a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R 1representing a hydrocarbon chain having 3 to 20 carbon atoms, which process comprises, in the presence of a catalytic system based on at least one metallocene of formula (I) and one organomagnesium compound of formula (II), the statistical copolymerization of a monomer mixture of ethylene and branched 1,3-diene, followed by the reaction with a modifying agent bearing an alkoxysilane function, and then, if necessary, the hydrolysis of the alkoxysilane function to the silanol function,

[0157] P(Cp 1 CP 2 ) Nd(BH4)(i + v) Li v (THF)x (I)

[0158] R-Mg-A (II)

[0159] CP 1 and Cp 2 , identical or different, being chosen from the group consisting of cyclopentadienyl groups and fluorenyl groups, the groups being substituted or not, P being a group bridging the two Cp groups 1 and Cp 2 and representing a ZR'R group 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, preferably a methyl, y, an integer, being equal to or greater than 0, x, an integer or not, being equal to or greater than 0,

[0160] R comprising a benzene ring in which two carbon atoms are substituted, one of the two is substituted by a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is

[0161] 2023PAT00317WO its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in ortho position with respect to each of said two carbon atoms, the symbol A in formula (II) representing the polystyrene block constituting the dibloc polymer.

[0162] Mode 25: Process according to mode 24 in which the organomagnesium compound of formula (II) corresponds to formula (II-1) in which A represents the polystyrene block, Ri and Rs, identical or different, represent a methyl or an ethyl, and R2, R3 and R4, identical or different, represent a hydrogen atom or an alkyl.

[0163] Mode 26: Process according to mode 25 in which Ri and R5 represent a methyl.

[0164] Mode 27: Process according to mode 25 or 26 in which R2 and R4 represent a hydrogen atom.

[0165] Mode 28: A method according to any one of modes 25 to 27 in which Ri, R3 and R5 are identical.

[0166] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of several examples of embodiments of the invention, given by way of illustration and not limitation.

[0167] Examples

[0168] The name EMR is used to designate a statistical copolymer of ethylene and myrcene; the name PS is used to designate a homopolymer of styrene; the name Mes is used to designate the mesityl group.

[0169] All reagents are commercially obtained except for the metallocene of formula [{Me2SiFlu2Nd(p- BH4)2Li(THF)}2] which is prepared according to the procedure described in document WO 2007054224. The styrene (Sigmal-Aldrich) is dried for 24 h on CaFL and then distilled under vacuum.

[0170] The ethylene, of N35 grade, comes from the company Air Liquide and is used without prior purification.

[0171] The myrcene, with a purity of 92.5% by weight, comes from the company DRT and is purified on an alumina column.

[0172] 2-mesitylmagnesium bromide, at 1 mol / L in THF, comes from Sigma-Aldrich (2-mesityhnagnesium bromide).

[0173] "-butyl lithium (1.6 M in hexane, Sigma-Aldrich) is used as received.

[0174] Also from Sigma-Aldrich come 4-vinylpyridine and sec-BuLi at 1.4M in cyclohexane.

[0175] Butyloctyhnagnesium BOMAG (20% by mass in heptane, C = 0.88 mol L⁻¹) 1 ) comes from Lanxess and is stored in a metal cylinder under an inert atmosphere.

[0176] (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane is obtained from ABCR and is used without prior purification.

[0177] The purified polymerization solvents (toluene, methylcyclohexane, cyclohexane) are purified through three alumina columns. The methylcyclohexane solvent from BioSolve is dried and purified on alumina columns in a solvent fountain from mBraun and

[0178] 2023PAT00317WO used in inert atmosphere.

[0179] All reactions are carried out in an inert atmosphere (argon) in Steinie bottles and sealed, inert reactors.

[0180] Mooney viscosity measurement:

[0181] To measure Mooney viscosity, an oscillating consistometer as described in ASTM D1646-2007 (Reapproved 2012) is used. The measurement of Mooney viscosity is performed according to the following principle: The telastomer is molded in a cylindrical chamber heated to 100°C under pressure. After a one-minute preheating period, the rotor rotates within the specimen at 2 revolutions per minute, and the torque required to maintain this rotation is measured after 4 minutes of 8 rotations. The Mooney viscosity (ML 1+4) is expressed in "Mooney units" (MU, with 1 MU = 0.83 Newton-meters).

[0182] Nuclear magnetic resonance (NMR):

[0183] Spectra were acquired on a Brüker Avance III 500 MHz spectrometer equipped with a 5 mm BBIz-grad "broadband" cryo-probe. Samples were solubilized in CDCL chloroform. Calibration was performed using the protonated impurity of deuterated chloroform at 7.26 ppm by ¹H NMR. The quantitative ¹H NMR experiment used a single 30° pulse sequence with a 5-second repetition delay between each acquisition.

[0184] Nuclear magnetic resonance (NMR) (block polymer synthesis):

[0185] Block polymers are solubilized in CDCL chloroform. Calibration is performed using the protonated impurity of deuterated chloroform at 7.26 ppm by ¹H NMR. The quantitative ¹H NMR experiment uses a single 30° pulse sequence and a 5-second repetition delay between each acquisition. 64 to 256 accumulations are performed. Two-dimensional ¹H / ¹³C experiments are used to determine the unit structure of the polymers. The ¹H-¹³C HMBC (heteronuclear multiple bond correlation) experiment detects long-range correlations via J-coupling between protons and carbon-13 nuclei. The ¹H NMR spectra and the edited ¹H / ¹³C IJ HSQC 2D NMR correlation spectrum allow for the determination of the block polymer microstructure and the proportion of each block in the sample.

[0186] Determination of the percentage of block polymer by DOSY:

[0187] The DOSY experiment, an NMR method, allows for the analysis of complex mixtures and the detection of trace elements. The aim of this experiment is to demonstrate that the block polymer constitutes the majority of the sample and that the presence of homopolymer is very low.

[0188] DOSY NMR analysis allows the separation of species present, particularly polymer matrices, by analyzing their diffusion coefficient in solution. The principle of the technique is as follows: The DOSY experiment consists of recording proton spectra while varying the applied gradient strength (G) and thus the diffusion strength. A linear increase in the gradient intensity will lead to an exponential decrease in the NMR signal intensity. The DOSY experiment will produce a two-dimensional map.

[0189] The second dimension F2 of the DOSY corresponds, after processing by the Fourier transform, to the dimension 1H. The first dimension Fl corresponds to the decay of the NMR signal as a function of the applied gradient force. After processing the dimension F2, the diffusion coefficient is extracted from equation (1), and a DOSY map is obtained.

[0190] I = I0.exp(-Dy) 2 G 2 oh 2 (A-ô / 3)) (1)

[0191] If the two matrices have the same diffusion coefficient, this means that the two matrices have the same hydrodynamic radius and are therefore grafted. Conversely, if the two matrices have different diffusion coefficients, this means that they are free from each other.

[0192] The equation that describes the diffusion coefficient is as follows:

[0193] 2023PAT00317WO

[0194] The experiment was conducted on samples of non-functional and functional poly(styrene-b-poly(ethylene-co-myrcene) synthesized according to the process according to the invention.

[0195] Recording two 1H ID NMR spectra with a scattering filter, one with a magnetic field gradient set at 90% of the maximum power of the gradient amplifier and the other at 1% of this value, allows, by comparison with the 1H NMR spectrum, observation of the signal loss due to spatial scattering of molecules and magnetization relaxation. The signal loss due to scattering is then attributed to "small molecules" not bound to the polymer matrix (reagents, antioxidants, solvents, etc.).

[0196] High-temperature size exclusion chromatography (SEC-3D):

[0197] The number-average molar mass (Mn), weight-average molar mass (Mw), and polydispersity index of the prepared polymers (hereafter referred to as the sample) are determined absolutely by triple-detection size exclusion chromatography (SEC-3D). Triple-detection size exclusion chromatography has the advantage of directly measuring average molar masses without calibration. SEC / 3D analyses are performed on a WATERS system equipped with three mixed-BLS columns and Wyatt refractometric, differential viscometric, and light-scattering detectors. Samples are prepared at a concentration of 5 g / L. 1 in tetrahydrofiirane and the analyses are carried out in tetrahydrofiirane (THF) at 35°C at a flow rate of 1 mL min 1The mobile phase flow rate is 1 L / min. Data are acquired and processed using ASTRA software, and the dn / dc of ethylene-based copolymers is assumed to be 0.1000 by default.

[0198] Differential scanning calorimetry (DSC):

[0199] The glass transition temperature (Tg) of the polymers is determined by differential scanning calorimetry (DSC). DSC analyses are performed on a DSC 3+ instrument (Mettler Toledo) with sealed aluminum crucibles (40 pL) and under a nitrogen flow (20 mL min⁻¹). 1 The thermograms of the homopolymers and diblock copolymers are obtained according to the following program repeated 3 times: ramp from +180 °C to -80 °C at 10 °C min 1 5-minute isothermal test at -80 °C, ramp from -80 °C to +180 °C at 10 °C minimum 1 , isothermal for 5 minutes at +180 °C.

[0200] Dynamic properties:

[0201] Dynamic properties are measured according to ASTM D 5992-96 and ASTM D 1349-99. The tan(φ) values, denoted "tan(φ) 0 °C" and "tan(φ) 100 °C", are taken from a temperature sweep at 0.7 MPa at 0 °C and 100 °C, respectively. They indicate wet surface grip performance and dry surface grip performance, respectively: the higher the tan(φ) value, the better the corresponding grip performance.

[0202] Polymer synthesis:

[0203] Example 1: Synthesis of an unfunctionalized EMR polymer (block B):

[0204] In an 80 L reactor, 53 L of methylcyclohexane and 450 mL of a BOMAG solution in methylcyclohexane at a concentration of 0.0134 mol / L are added. The temperature in the reactor is raised to 80°C and the myrcene and ethylene monomers are injected at a controlled rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor.

[0205] 2023PAT00317WO The catalytic system (6.3 mmol of Nd) is injected into the reactor ca t, or 4g of Nd cat) to a concentration of 0.0062 mol / L in methylcyclohexane to initiate the polymerization reaction of ethylene and myrcene. The polymerization temperature is regulated at 80°C, and the pressure in the reactor is increased to 8 bar. The pressure in the reactor is maintained constant at 8 bar by feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97.

[0206] The conversion of the polymerization reaction is measured by dry extract, and when a mass of 5.3 kg of polymer is reached after 70 min of polymerization, the injection of monomers into the reactor is stopped. The weighed mass of copolymer, 5.3 kg after 70 min, allows the determination of the average catalytic activity of the catalytic system, expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol·h), as 726 kg / mol·h.

[0207] 550 mL of 1 mol / L ethanol is injected to stop polymerization. 226 mL of an antioxidant, Irganox 1520L at 218 g / L, is injected into the reactor. The reactor contents are transferred to another reactor, called a "stripping reactor," to remove the solvent by steam distillation while maintaining a temperature of 100°C. The copolymer is collected and then dried for 48 hours in an oven at 60°C under vacuum and nitrogen purging.

[0208] The molar contents of ethylene and myrcene in block B are 74% and 26% respectively, percentages calculated in relation to the number of constituent motifs of block B.

[0209] The microstructure and macrostructure characteristics of the polymer are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of ethylene and myrcene units.

[0210] Example 2: Synthesis of a functionalized EMR copolymer (block B)

[0211] In an 80 L reactor, 53 L of methylcyclohexane and 450 mL of a BOMAG solution in methylcyclohexane at a concentration of 0.0134 mol / L are added. The temperature in the reactor is raised to 80°C and the myrcene and ethylene monomers are injected at a controlled rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor.

[0212] The catalytic system (6.3 mmol of Nd) is injected into the reactor ca t, or 4g of Nd cat) to a concentration of 0.0062 mol / L in methylcyclohexane to initiate the polymerization reaction of ethylene and myrcene. The polymerization temperature is regulated at 80°C, and the pressure in the reactor is increased to 8 bar. The pressure in the reactor is maintained constant at 8 bar by feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97.

[0213] The conversion of the polymerization reaction is measured by dry extract, and when a mass of 5.3 kg of polymer is reached after 70 min of polymerization, the injection of monomers into the reactor is stopped. The weighed mass of copolymer, 5.3 kg after 70 min, allows the determination of the average catalytic activity of the catalytic system, expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol·h), as 960 kg / mol·h.

[0214] The (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane (64 mmol, 4 eq / Mg) in solution in methylcyclohexane at a concentration of 0.4 mol / L is then transferred by overpressure into the reactor.

[0215] 2023PAT00317WO The functionalization reaction, at 80°C, is maintained for 15 min, then 550 mL of 1 mol / L ethanol is injected to stop the functionalization reaction. 226 mL of an antioxidant, Irganox 1520L at 218 g / L, is injected into the reactor. The reactor contents are transferred to another reactor, called the "stripping reactor," to remove the solvent by steam distillation while maintaining a temperature of 100°C. The copolymer is recovered and then dried for 48 hours in an oven at 60°C under vacuum and nitrogen purging.

[0216] The molar contents of ethylene and myrcene in block B are 74% and 26% respectively, percentages calculated in relation to the number of constituent motifs of block B.

[0217] The microstructure and macrostructure characteristics of the polymer are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of ethylene and myrcene units.

[0218] Example 3: Synthesis of an unfunctionalized PS-6-EMR diblock polymer (diblock of formula AB) ere Step: Synthesis of the first block (block A) and transmetallation reaction:

[0219] In an 80 L reactor containing 11.5 L of cyclohexane and heated to 40°C, 1.2 L of styrene (10.6 mol) is introduced. Polymerization of the styrene is initiated by a 0.5 L solution of sec-butyllithium (55 mmol) at a concentration of 0.11 mol / L in methylcyclohexane. The conversion of styrene is monitored by dry extract analysis, and 100% conversion is achieved after 37 min, yielding 1.1 kg of polystyrene.

[0220] Once the living polystyrene (PSLi) is formed, a transmetallation reaction is carried out to form the PSMgMes species. For this, 2-mesitylmagnesium bromide in toluene solution at a concentration of 0.1 mol / L (1 eq / L, 550 mL) is injected into the 80 L reactor at a temperature of 40°C. The temperature in the reactor is maintained at 40°C for 10 min.

[0221] Next, 39. 1 L of cyclohexane is introduced into the polymerization reactor and the polymer solution is brought to 80°C in the reactor.

[0222] 2 eme Step: Synthesis of the second block (block B):

[0223] During the temperature rise of the polymer solution (up to 80°C), the myrcene and ethylene monomers are injected at a controlled rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor.

[0224] The metallocene {Me2Si(Ci3Hs)2Nd(BEL)2Li(TEIF)}2 (Nd ca t) (6.3 mmol of Nd, i.e., 4 g of Nd) in solution in 500 mL of cyclohexane. The polymerization temperature is regulated at 80°C, and the pressure in the reactor is increased to 8 bar. The pressure in the reactor is maintained constant at 8 bar by feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97.

[0225] The conversion of the polymerization reaction is measured by dry extract, and when the mass of 4.2 Kg corresponding to the formation of the second block is reached after 52 min of polymerization of ethylene and myrcene, the injection of monomers into the reactor is stopped.

[0226] The mass weighed corresponding to the formation of the second block, 4.2 kg, allows the determination of the average catalytic activity of the catalytic system, expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol.h), as 794 kg / mol.h. The molar contents of ethylene and myrcene in block B are 74% and 26% respectively, percentages calculated in relation to the number of constituent units of block B.

[0227] 550 mL of 1 mol / L ethanol is injected to stop the polymerization reaction. 226 mL of an antioxidant, Irganox 1520L at 218 g / L, is injected into the reactor. The reactor contents are transferred to another reactor, called a "stripping reactor," to remove the solvent by steam distillation while maintaining a temperature of 100°C. The copolymer is recovered and then dried on

[0228] 2023PAT00317WO an extrusion line.

[0229] The weighed mass of the resulting PS-6-EMR dibloc is 5.3 kg.

[0230] The microstructure and macrostructure characteristics of the diblock are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of styrene, ethylene and myrcene units.

[0231] Example 4: Synthesis of a functionalized PS-6-EMR diblock polymer ere Step: Synthesis of the first block (block A) and transmetallation reaction: In an 80 L reactor containing cyclohexane (11.5 L) and heated to 40°C, 1.2 L of styrene (10.6 mol) is introduced. The polymerization of styrene is initiated by a solution of sec-butyllithium (55 mmol, 0.5 L) at a concentration of 0.11 mol / L in methylcyclohexane. The conversion of styrene is monitored by dry extract, and 100% conversion is achieved after 37 min, yielding 1.1 kg of polystyrene.

[0232] Once the living polystyrene (PSLi) is formed, a transmetallation reaction is carried out to form the PSMgMes species. For this, 2-mesitylmagnesium bromide in toluene solution at a concentration of 0.1 mol / L (1 eq / Li, 550 mL) is injected into the 80 L reactor at a temperature of 40°C. The temperature in the reactor is maintained at 40°C for 10 min.

[0233] Next, 39.1 L of cyclohexane is introduced into the polymerization reactor and the polymer solution is heated to 80°C in the reactor.

[0234] 2 eme Step: Synthesis of the second block (block B):

[0235] During the temperature rise of the polymer solution (up to 80°C), the myrcene and ethylene monomers are injected at a controlled rate into the reactor, respecting a mass ratio (g / g) myrcene / ethylene = 3.97, until a pressure of 6 bars is obtained in the reactor.

[0236] The metallocene {Me2Si(Ci3Hs)2Nd(BEL)2Li(TEIF)}2 (Nd ca t) (6.3 mmol of Nd, i.e., 4 g of Nd) in solution in 500 mL of cyclohexane. The polymerization temperature is regulated at 80°C, and the pressure in the reactor is increased to 8 bar. The pressure in the reactor is maintained constant at 8 bar by feeding myrcene and ethylene throughout the polymerization reaction at a myrcene / ethylene mass ratio of 3.97.

[0237] The conversion of the polymerization reaction is measured by dry extract, and when the mass of 4.2 Kg corresponding to the formation of the second block is reached after 52 min of polymerization of ethylene and myrcene, the injection of monomers into the reactor is stopped.

[0238] The weighed mass corresponding to the formation of the second block, 4.2 kg, allows the determination of the average catalytic activity of the catalytic system, expressed in kilograms of polymer synthesized per mole of neodymium metal per hour (kg / mol.h), as 959 kg / mol.h. The molar contents of ethylene and myrcene in block B are 74% and 26% respectively, percentages calculated in relation to the number of constituent units of block B.

[0239] The (N,N-dimethyl-3-aminopropyl)methyldimethoxysilane (64 mmol, 4 eq / Mg) in solution in methylcyclohexane at a concentration of 0.4 mol / L is then transferred by overpressure into the reactor.

[0240] The functionalization reaction, at 80°C, is maintained for 15 min, then 550 mL of 1 mol / L ethanol is injected to stop the functionalization reaction. 226 mL of an antioxidant, Irganox 1520L at 218 g / L, is injected into the reactor. The reactor contents are transferred to another reactor, called the "stripping reactor," to remove the solvent by steam distillation while maintaining a temperature of 100°C. The copolymer is recovered and then dried for 48 hours in an oven at 60°C under vacuum and nitrogen purging.

[0241] The weighed mass of the resulting PS-6-EMR dibloc is 4.5 kg.

[0242] 2023PAT00317WO The microstructure and macrostructure characteristics of the diblock are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of styrene, ethylene and myrcene units.

[0243] The microstructure and macrostructure characteristics of the diblock are shown in Table 1. The rate of units is expressed as a mole percentage calculated relative to the total number of moles of styrene, ethylene and myrcene units.

[0244] Table 1:

[0245] The EMR elastomer, a random copolymer of ethylene and branched 1,3-diene, from Example 1, has a Mooney viscosity well below 30, suggesting difficulties in the elastomer's finishing steps. Example 2, which differs from Example 1 by the presence of a silanol group at the end of the EMR elastomer and by a higher Mn value, shows that chain-end functionalization has no effect on the Mooney viscosity and that a 30% increase in Mn has no effect on the elastomer's Mooney viscosity. The results of Example 4 show that introducing a polystyrene block and a silanol group into an EMR polymer significantly increases the Mooney viscosity, from 16 to 37.This increase in Mooney viscosity to values ​​above 30, which facilitates the polymer finishing steps, is achieved without significantly altering the glass transition temperature and the dispersity of the elastomer.

[0246] 2023PAT00317WO Example 3 shows that the introduction of a polystyrene block into the EMR elastomer also increases the Mooney viscosity, but not as much as in the case of example 4. The Mooney viscosity in example 4 is unexpectedly higher than that in example 3, even though the Mn of the diblock polymer in example 4 is slightly lower than that of the diblock polymer in example 3.

[0247] Preparation of rubber compounds:

[0248] Rubber compositions are prepared according to the following procedure:

[0249] Rubber compositions, whose formulation expressed in parts per hundred parts of elastomer (pce) is shown in Tables 2 and 3, were prepared in an internal mixer. The copolymer, reinforcing filler, and various other ingredients, with the exception of the vulcanizing system, were introduced sequentially. A single-stage thermomechanical process (non-productive phase) was then carried out, lasting approximately 5 minutes, until a maximum "drop" temperature of 160°C was reached. The resulting mixture was collected, cooled, and then sulfur and an accelerator were incorporated in a mixer (homogenizer) at 40°C, where the mixture was blended for about ten minutes (productive phase). The compositions thus obtained were then calendered into either sheets (2 to 3 mm thick) or thin rubber sheets for the measurement of their physical and mechanical properties after vulcanization at 160°C.The applied crosslinking time, T(99), is the time required for the torque of the compositions of the invention to reach 99% of the maximum torque of these compositions, i.e. 20 minutes.

[0250] (1) Polymer of example 2

[0251] (2) Polymer of example 3

[0252] (3) Polymer of example 4

[0253] (4) “Zeosil 1165 MP” from Solvay-Rhodia in the form of microbeads, CTAB 160 m 2 / g, precipitated silica

[0254] (5) ASTM N234 Grade Carbon Black

[0255] (6) “Su-640” resin from Kolon Industries (Tg= 83°C, 100% aliphatic, Mn 398 g / mol).

[0256] (7) Liquid silane triethoxysilylpropyltetrasulfide (TESPT) “Si69” from the Evonik company

[0257] (8) N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine “Santaflex 6PPD” from the company Flexys

[0258] (9) Diphenylguanidine “Perkacit DPG” from the company Flexsys

[0259] (10) Stearic acid “Pristerene 4931” from the company Uniqema

[0260] (11) Industrial grade zinc oxide from Umicore

[0261] (12) N-cyclohexyl-2-benzothiazol-sulfenamide “Santicure CBS” from Flexsys

[0262] Only compositions C3 and C6 which contain a block polymer according to the invention, in this case P3, are compositions according to the invention.

[0263] Table 2:

[0264] 2023PAT00317WO

[0265] Table 3:

[0266] 2023PAT00317WO

Claims

Tl Demands 1. Diblock polymer of formula AB in which the symbol A represents a polystyrene block, the symbol B represents a statistical copolymer block of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R' representing a hydrocarbon chain having 3 to 20 carbon atoms, the diblock polymer bearing at the end of the chain a functional group containing a silanol or alkoxysilane function, the styrene units of block A being present in the diblock in a molar content of less than 15% of the repeating motifs constituting the diblock polymer, the diblock polymer having a Mooney viscosity ML(l+4) at 100°C greater than 30.

2. Diblock polymer according to claim 1 in which the ethylene units of block B represent more than 50% by mole of the repeating motifs constituting block B.

3. Diblock polymer according to any one of claims 1 to 2 wherein the ethylene units of block B represent more than 60% by mole of the repeating motifs constituting block B, preferably at least 70% by mole of the repeating motifs constituting block B.

4. Diblock polymer according to any one of claims 1 to 3 wherein the ethylene units of block B represent at most 85% by mole of the repeating motifs constituting block B.

5. Diblock polymer according to any one of claims 1 to 4 in which the functional group is carried at the end of the chain of block B.

6. Diblock polymer according to any one of claims 1 to 5 wherein block B has a glass transition temperature between -90°C and -40°C, preferably between -70°C and -50°C.

7. Diblock polymer according to any one of claims 1 to 6 wherein the branched 1,3-diene is myrcene or P-famesene or a mixture of myrcene and P-famesene, preferably myrcene.

8. Diblock polymer according to any one of claims 1 to 7 wherein block A has a number-average molar mass greater than 3,000 g / mol and less than or equal to 30,000 g / mol.

9. Diblock polymer according to any one of claims 1 to 8 wherein block B has a number-average molar mass greater than 100,000 g / mol and preferably less than 300,000 g / mol.

10. A diblock polymer according to any one of claims 1 to 9, wherein the functional group has the formula Si(OR 3 )3- n (R 4 )n or of the formula -CH2-CH(CH3)-COOZ', the symbols R 3 , identical or different, representing an alkyl or a hydrogen atom, the symbols R 4, identical or different, representing a hydrogen atom, a hydrocarbon chain, or a hydrocarbon chain substituted by a tertiary amine function, n being an integer from 0 to 2 when R 3 is alkyl, n being an integer equal to 2 when R 3 is a hydrogen atom, Z' representing an alkyl substituted by a function of the formula Si(OR 5 )3- m (R 6 )m, the R symbols 5 , identical or different, representing an alkyl or a hydrogen atom, the symbols R 6 , identical or different, representing a hydrogen atom, a hydrocarbon chain, m being an integer from 0 to 2 when R 5 is alkyl, m being an integer equal to 2 when R 5 is a hydrogen atom.

11. Rubber composition comprising a dibloc polymer as defined according to any one of claims 1 to 10, a reinforcing filler and a crosslinking system. 2023PAT00317WO 12. Tire comprising a tread, which tire comprises a rubber composition defined in claim 11, preferably in its tread.

13. A process for synthesizing a polymer as defined in any one of claims 1 to 10, which polymer is a diblock polymer of formula AB bearing at the end of the chain a functional group containing a silanol or alkoxysilane function, A representing a polystyrene block, B represents a block copolymer of ethylene and a branched 1,3-diene of formula CH2=CR'-CH=CH2, the symbol R 1representing a hydrocarbon chain having 3 to 20 carbon atoms, which process comprises, in the presence of a catalytic system based on at least one metallocene of formula (I) and one organomagnesium compound of formula (II), the statistical copolymerization of a monomer mixture of ethylene and branched 1,3-diene, followed by the reaction with a modifying agent bearing an alkoxysilane function, and then, if necessary, the hydrolysis of the alkoxysilane function to the silanol function, P(Cp 1 CP 2 ) Nd(BH4)(i +v ) Li v (THF)x (I) R-Mg-A (II) CP 1 and Cp 2 , identical or different, being chosen from the group consisting of cyclopentadienyl groups and fluorenyl groups, the groups being substituted or not, P being a group bridging the two Cp groups 1 and Cp 2 and representing a ZR'R group 2 Z represents a silicon or carbon atom, R1 and R 2 , identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl, y, an integer, being equal to or greater than 0, x, an integer or not, being equal to or greater than 0, R comprising a benzene ring of which two carbon atoms are substituted, one of the two is substituted by a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in ortho position with respect to each of said two carbon atoms, the symbol A in formula (II) representing the polystyrene block constituting the dibloc polymer. 2023PAT00317WO

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