WO2008068348A1 - Controlled polymerization of monomers bearing an alpha,beta-unsaturated group in the presence of a carbene - Google Patents

Abstract

The present invention relates to a process enabling the controlled polymerization of monomers comprising an a,ß-unsaturated carbonyl sequence C=C-C=O or copolymers, comprising a step of polymerization (P) in which the following are brought into contact: (A) said monomers comprising an a,ß-unsaturated carbonyl sequence C=C-C=O; (B) a silyl-based polymerization initiator; and (C) at least one carbene. The invention also relates to the use of this process for preparing polymers with controlled structure.

Description

 Controlled polymerization of monomers carrying an unsaturated α-β group in the presence of a carbene

The present invention relates to a new method for the controlled polymerization of monomers bearing an unsaturated α-β carbonyl group C = C-C = O, which is particularly suitable for the controlled polymerization of acrylate and methacrylate monomers. Various controlled polymerization methods of monomers bearing unsaturated α-β carbonyl groups are known at the present time.

In this context, it has been proposed in particular in the early 1980s techniques called "group transfer polymerization" (also referred to as "Group Transfer Polymerization"). The GTP polymerization has in particular been described for the polymerization of monomers of (meth) acrylate and maleimide type. The GTP polymerization techniques generally consist in using the monomers bearing a C = C-C = O group in the presence of:

(i) a silyl acetals initiator of dimethylketene (such as 1-methoxy-2-methyl-1-trimethylsiloxypropene, so-called MTS); and

(ii) an ionic or Lewis acid compound acting as catalyst or co-initiator.

For the GTP polymerization of monomers of the methacrylic type, a nucleophilic catalyst is generally used in combination with the initiator, the "GTP" type polymerization reaction then being most often an anionic chain polymerization. The best results are obtained with catalysts which are anions associated with congested countercitations, in particular fluoride (F ^" ) or bifluoride (HF ₂ ^" ) anions derived from soluble salts such as tris (dimethylamino) sulfonium bifluoride, [ (CH ₃ ) ₃ N] ₃ S ⁺ , HF ₂ ^" and tetrabutylammonium fluoride, (nC ₄ H ₉ ) N ⁺ , F ^~ . GTP polymerization of acrylic monomers can not be carried out with Initiator / catalyst system of the aforementioned type, used with methacrylic monomers For the GTP polymerization of acrylic monomers, it has been proposed to use, in combination with the initiator, not nucleophilic species, but Lewis, such as zinc halides or a dialkylaluminum chloride (AI (Alkyl) ₂ CI) In this case, it appears that the reaction involves a mechanism distinct from the case of methacrylates, which presumably implements an activation of the acrylic monomer by the Lewis acid, the latter then acting as co-initiator (consumed by the reaction) and not that of catalyst. GTP polymerization techniques of the aforementioned type are in particular the subject of US Pat. Nos. 4, 414, 372, US 4, 524, 196, US 4,581,428, which describe the polymerization of methacrylic type monomers in the presence of an initiator. silyl acetal type dimethylketene such as methyl-1-trimethylsiloxypropene (said MTS) and a fluoride-type catalyst associated with a congested counterfeit or even US Patent 5, 162, 467, which relates to the polymerization of monomers type in the presence of MTS type initiators and zeolite Lewis acids as a co-initiator for GTP of the acrylic monomers.

The abovementioned GTP polymerization processes are certainly advantageous, especially insofar as they allow controlled polymerizations with, in particular, a control of the molecular mass (which can be modulated by the ratio of the initial concentrations of monomers and initiators) and a low polydispersity index, and this at temperatures close to room temperature, typically between 20 and 60 ⁰ C, with further experimental conditions generally simple to implement. In addition, polymerization by GTP leads to the production of living polymers, namely reactivatable in subsequent polymerizations, thus allowing the synthesis of controlled architecture copolymers, especially diblock, triblock or multiblock block copolymers or star polymers. .

However, apart from these advantages, the GTP polymerization processes which have been described up to now have the disadvantage of requiring an adaptation of the polymerization system used as a function of the nature of the monomers subjected to the polymerization. In addition, the currently known GTP polymerization processes have another disadvantage, namely that they can generally be conducted in a polar medium, particularly given the ionic nature of the catalysts or co-initiators used. An object of the present invention is to provide a polymerization process having the advantages of GTP polymerization processes currently known, particularly in terms of controlling the polymerization at low temperature, but which make it possible to avoid the aforementioned problems. In this context, the invention aims in particular to provide a GTP polymerization system which is suitable for the polymerization of most ethylenically unsaturated monomers carrying α-β unsaturated carbonyl groups, and which is particularly suitable for the polymerization of methacrylic as well as acrylic monomers. The invention also aims to provide a a process which opens the way, at least in some cases, to GTP polymerization in an apolar medium.

These various objectives, and others, are achieved by the present invention which relates to a method for preparing a polymer, comprising a polymerization step (P) in which is brought into contact with:

(A) monomers having an unsaturated α-β carbonyl linkage C = C-C = O;

(B) a silylated polymerization initiator; and

(C) at least one carbene. Schematically, the process of the invention can be considered as a polymerization process similar to the currently known GTP methods, in which the generally used anion or Lewis acid catalyst or co-initiator is replaced by a carbene. For the purposes of the present description, the term "carbene" means a chemical species, generally electrically neutral, comprising a divalent carbon which comprises two non-binding electrons, these two non-binding electrons preferably being in paired form (singlet), but also be in unmatched form (triplet). Most often, a carbene within the meaning of the invention is a carbene in the most usual sense of the term, namely a species comprising 6 valence electrons, and not electrically charged. However, in the sense that it is used here, the notion of carbene also includes compounds of the aforementioned type where the divalent carbon carries an additional electronic doublet or is engaged in a delocalized bond and / or in which the divalent carbon is carrying an electrical charge (typically a negative charge possibly delocalized). The work of the inventors has now made it possible to demonstrate that a controlled polymerization of monomers carrying an unsaturated α-β carbonyl chain C = CC = O (in particular methacrylic or acrylic monomers) can be carried out by placing them in the presence of one another. of a polymerization system comprising a silyl polymerization initiator and a carbene of the aforementioned type. In particular, the control of the reaction obtained makes it possible to control the molecular mass, which can be modulated by the ratio of the initial concentrations of monomers and initiators, as well as a low polydispersity index. Furthermore, the polymerization carried out is generally of a "living" nature, that is to say that the polymer chains formed are most often reactivatable, that is to say that they can be used in subsequent polymerization reactions in contact with monomers, which allows the synthesis of copolymers with controlled architecture, in particular diblock, triblock or multiblock block copolymers or even star polymers.

In addition, quite surprisingly, the inventors have demonstrated that the implementation of a carbene in a GTP-type polymerization makes it possible to carry out a controlled polymerization of methacrylic or maleimide-type monomers as well as acrylic type monomers. Without wishing to be bound to a particular theory, it seems possible to be argued that, in step (P) of the process of the invention, the carbene is most likely to act as a catalyst for the polymerization reaction. A plausible explanation would be that, in particular because of its nucleophilic character which is variable over a wide range, a carbene is able to ensure both (1) a role similar to that of the catalysts of the type of bulky fluoride salts with bulky countercurrent for the polymerization of methacrylates, and (2) a role substantially identical to that of a Lewis acid for the polymerization of an acrylate. In the most general case, it also seems to be possible to claim that step (P) of the process of the invention is most often an anionic chain polymerization.

Most carbenes make it possible to obtain the aforementioned results. However, advantageously, the carbene (C) used in step (P) of the process of the invention has at least one of the preferred characteristics described below.

Preferably, the carbene (C) used in step (P) comprises, in α of its divalent carbon, a heteroatom selected from N, S, P, Si and O. Advantageously, in this context, carbene (C) corresponds to the general formula (I) below:

' ^Y < ^RY ) ny-1 _(|) wherein

X and Y, identical or different, are heteroatoms selected from N, S, P, Si and O;

Nx and ny are two integers, respectively equal to the valency of the heteroatom X and the valency of the heteroatom Y (ie 2 when the heteroatom is S or O; 3 when the heteroatom is N or P; and 4 when the heteroatom is Si);

Each of the groups R ^x and R ^γ linked to the heteroatoms X and Y represents, independently of the other groups, a hydrocarbon chain, linear or branched, optionally cyclized in whole or in part, and optionally substituted, this chain being preferably: a linear or branched, optionally substituted alkyl, alkenyl or alkynyl group, for example by at least one perfluoroalkyl group, a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example by at least one alkyl or alkoxy group; an aryl group optionally substituted, for example by at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, for example by at least one alkyl or alkoxy group, it being understood that one of the groups R ^x borne by the heteroatom X and one of the groups R ^γ carried by the Y heteroatom may optionally be bonded together to form a heterocycle with X and Y heteroatoms and divalent carbon bearing two non-binding electrons. In this case, the heterocycle thus formed preferably comprises from 5 to 7 members.

In the context of the present description, the term "alkyl" is intended to mean a linear or branched hydrocarbon-based chain of C ₁ -C _5, preferably of C ₁ -C 10 and even more preferentially of C ₁ -C ₄ . Examples of preferred alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl and t-butyl.

By "alkoxy" is meant an alkyl-O- group in which the term alkyl has the meaning given above. Preferred examples of alkoxy groups are methoxy or ethoxy.

By "alkoxycarbonyl" is meant the alkoxy-C (O) - group in which the alkoxy group has the definition given above.

By "alkenyl" is meant a linear or branched hydrocarbon chain comprising a C ₂ -C _8, preferably C ₂ -C _6, double bond. and even more preferably C ₂ -C ₄ . Examples of preferred alkenyl groups include vinyl, 1-propenyl, 2-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl and isobutenyl.

By "alkynyl" is meant a linear or branched hydrocarbon chain comprising a C ₂ -C _8, preferably C ₂ -C _6, triple bond. and even more preferably C ₂ -C ₄ . Examples of preferred alkynyl groups include ethynyl, 1-propynyl, 1-butynyl, 2-butenyl.

By "alkenyloxy" and "alkynyloxy" is meant respectively an alkenyl-O- and alkynyl-O- group in which the terms alkenyl and alkynyl have the meanings given above.

By "cycloalkyl" is meant a cyclic hydrocarbon group, monocyclic C ₃ -C ₈ , preferably a cyclopentyl or cyclohexyl or polycyclic (bicyclic or tricyclic) C ₄ -C ₈ , in particular adamantyl or norbornyl.

By "aryl" is meant an aromatic mono- or polycyclic group, preferably mono- or bicyclic C ₆ -C ₂ O, preferably phenyl or naphthyl. When the group is polycyclic, that is to say that it comprises more than one ring nucleus, the ring nuclei can be condensed two by two or attached in pairs by bonds σ. Examples of groups (C ₆ -C ₈₎ aryl include phenyl, naphthyl.

By "aryloxy" is meant an aryl-O- group in which the aryl group has the meaning given above.

By "arylalkyl" is meant a hydrocarbon group, linear or branched bearer of a monocyclic aromatic ring C ₇ -C _2, preferably benzyl: the aliphatic chain contains 1 or 2 carbon atoms.

Advantageously, the carbene (C) used in step (P) is a carbene corresponding to the general formula (I) above, where X denotes a nitrogen atom. The carbene used is then a carbene said NHC (N-heterocyclic carbene).

According to a particularly interesting embodiment, the carbene (C) is an NHC carbene of the aforementioned type corresponding to one of the general formulas (1-1) or (1-1 ') below:

R ¹ R ¹

') dans lesquelles

') in which

Y is a heteroatom selected from N, S, P, Si and O, Y being preferably a nitrogen atom • ny and R ^γ are as defined above; and R ¹ denotes a linear or branched hydrocarbon-based chain, optionally cyclized in whole or in part, and optionally substituted, this chain preferably being: a linear or branched, optionally substituted alkyl, alkenyl or alkynyl group, for example by at least one group; perfluoroalkyl, a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example by at least one alkyl or alkoxy group; an aryl group optionally substituted, for example with at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, for example by an alkyl or alkoxy group

A denotes a nitrogen atom or a group CR ^lla , B denotes a nitrogen atom or a group CR ^IIIa ,

R "and R ¹ ", and; where appropriate, R ^11a and R ^11a , identical or different, each denote a hydrogen atom, or a hydrocarbon chain, linear or branched, optionally cyclized in whole or in part, and optionally substituted. In the case where R ", R ¹ ", R ^11a or R ^11a represents a hydrocarbon-based chain, this hydrocarbon-based chain preferably being: an alkyl, alkenyl or alkynyl group, linear or branched, optionally substituted, for example by at least one perfluoroalkyl group a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example with at least one alkyl or alkoxy group; an aryl group optionally substituted, for example by at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, in particular by at least one alkyl or alkoxy group.

According to an even more advantageous embodiment, the carbene (C) employed corresponds to one of the general formulas (1-1 a) or (1-1 a ') below: R ¹ R ¹

dans lesquelles :

in which :

R ¹ , R ", R" ^a , R ^m and B are as previously defined; and • R ^ιv denotes a linear or branched hydrocarbon-based chain, optionally cyclized in whole or in part, and optionally substituted, this chain preferably being: an alkyl, alkenyl or alkynyl group, linear or branched, optionally substituted, for example by at least one perfluoroalkyl group; a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example by at least one alkyl or alkoxy group; an aryl group optionally substituted, for example by at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, in particular by at least one alkyl or alkoxy group.

In a particularly advantageous manner, the carbene (C) has the formula (1-1 a) above. Alternatively, according to another conceivable embodiment, the carbene (C) may be a compound chosen from the following compounds:

les bisphosphinocarbènes de formule (III) :Alkylaminocyclic carbenes, termed CAACs (for the English term "Cyclic AlkylAminoCarbene"), or an example of the type of those described, for example, in the application WO 2006/138166, where the method of preparation of these compounds and describes, phosphino (amino) carbenes of formula (II):

bisphosphinocarbenes of formula (III):

Carbodiphosphoranes corresponding to one of the following mesomeric formulas (IV) or (IV)

(IV) (IV) wherein each of the groups R, R _P , R _P ¹ , R _P ² , R _P ³ , R _P ⁴ , R _N , and R _P 1 represents, independently of the other groups, a linear hydrocarbon chain or branched, optionally cyclized in whole or in part, and optionally substituted, this chain being preferably: an alkyl, alkenyl or alkynyl group, linear or branched optionally substituted, for example by at least one perfluoroalkyl group, - a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example by at least one alkyl or alkoxy group; an aryl group optionally substituted, for example by at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, for example by at least one alkyl or alkoxy group, it being understood that, in each of the formulas (II), (III), (IV) and (IV), the group R and the group R ^p may optionally be bonded together to form a heterocycle with the two heteroatoms to which they are bonded and the divalent carbon (where appropriate, the heterocycle thus formed preferably has from 5 to 7 members).

The carbenes of the CAAC type can in particular be carbenes corresponding to the formula (X) below:

(X) where:

A represents a ring comprising from 4 to 7 atoms, of which at least one of the atoms is the nitrogen atom as represented,

L is a divalent group comprising from 1 to 4 carbon atoms, one or more atoms of which may be substituted by an oxygen, nitrogen or silicon atom, the available valences may be substituted,

Ra represents an alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group;

- R _b and R _c , identical or different, represent an alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, alkoxy, alkenyloxy, alkynyloxy, aryloxy, alkoxycarbonyl, or R _b and R _c are linked together to form a spirocycle , the bet of the ring bearing the two groups Rb and R _c linked together comprising from 3 to 12 atoms.

In the compounds of formula (X), since one of the groups Ra, Rb, or Rc comprises a ring, it may be substituted by one or more, for example by two substituents. The nature of the substituent can be any as long as this group does not interfere with the level of the reaction catalysed by the carbene. Furthermore, L is a divalent group comprising from 1 to 4 atoms, one or more atoms of which may be substituted by an oxygen, nitrogen or silicon, the available valences being substitutable. By this is meant that a hydrogen atom present on an atom may be replaced by a substituent.

As preferred examples of substituents on the groups L, Ra, Rb or Rc of the formula (Ic) or (IIc), mention may be made especially of alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, amino and amino groups substituted by alkyl groups, cycloalkyl, a nitrile group, haloalkyl preferably perfluoromethyl.

In particular, carbenes of the CAAC type can be used, corresponding to formulas (X ') and (X ") below:

où :

or :

Ra, Rb, Rc, have the meanings given for the general formula (II),

Rd and Re, which may be identical or different, represent an alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group.

In particular, it is possible to use carbenes corresponding to one of the abovementioned formulas (X ') or (X "), where:

Ra represents a tert-butyl group, a phenyl group, a phenyl group substituted with one to three alkyl groups having from 1 to 4 carbon atoms,

Rb and Rc, which may be identical or different, represent a linear or branched alkyl group having from 1 to 4 carbon atoms or a phenyl group, or else R ₁ and R ₂ are linked together to form a cyclopentane or a cyclohexane,

- Rd and Re, identical or different, represent a linear or branched alkyl group having 1 to 4 carbon atoms.

It may especially be the carbene of formula (X '") below:

Quelle que soit sa nature exacte, le carbène (C) utilisé dans le procédé de l'invention peut être un carbène qui a été préformé dans une étape préalable à l'étape de polymérisation (P). Il s'agit dans ce cadre d'un carbène dit "nu", qui est généralement conservé sous atmosphère inerte et non réactive (généralement anhydre), préalablement à la mise en œuvre de l'étape (P), typiquement sous azote ou sous argon, généralement en boite à gants, le plus souvent dans un milieu solvant tel que le toluène, par exemple.

Whatever its exact nature, the carbene (C) used in the process of the invention may be a carbene which has been preformed in a step prior to the polymerization step (P). In this context, it is a so-called "bare" carbene, which is generally stored under an inert and non-reactive atmosphere (generally anhydrous), prior to the implementation of step (P), typically under nitrogen or under nitrogen. argon, usually in a glove box, usually in a solvent medium such as toluene, for example.

Alternatively, the carbene (C) can be formed in situ in the middle of the polymerization step (P), from at least one precursor (PC) of said carbene ("masked" form of the carbene). In this case, the carbene precursor employed can be chosen from at least one of the following precursors:

a carbene in dimerized form, which is cleaved into two carbenes in situ by thermal activation, this dimerised carbene advantageously satisfying the following formula (PC ₀ ):

où X, Y, nx, ny, R^x et R^γ ont les définitions précitées ;

where X, Y, nx, ny, R ^x and R ^γ have the above definitions;

an imidazolium salt, which forms a carbene in situ by reaction with a base. The base used may in particular be a tertiary amine (such as triethylamine for example) or an alcoholate (tBuOK in particular) or an alkyl lithium (such as BuLi). The imidazolium salts used as carbene precursors according to the invention advantageously correspond to one of the following formulas (PC _S ) or (PC _S '):

dans lesquelles

in which

B, R ¹ , R ", R ¹ " and R ^ιv are as defined above; and An ^" is an anion derived from a Bronsted acid, preferably a carboxylate, sulfate, hydrogenosulphate, sulfonate, phosphate, hydrogenophosphate, halide, perchlorate or borate anion;

- An adduct of carbene and alcohol, which releases in situ the carbene when it is heat treated.

According to a particular embodiment, the carbene used can be an encapsulated carbene, that is to say physically mixed with a polymer serving as a protective matrix. Advantageously, the protective polymer used in this context is a silicone oil. Whatever the nature of the carbene employed in step (P), the stability of this carbene is generally liable to be questioned in the presence of protic compounds. In this context, it is therefore most often preferred that the monomers (A) are non-protic monomers, ie non-bearing labile protons, such as those of methacrylic acid or 2-hydroxyethyl methacrylate. The process of the invention may advantageously be used to polymerize monomers (A) which are methacrylates or acrylates. The process of the invention can be used more widely for the polymerization of other types of monomers carrying a C = CC = O chain, such as, for example, maleimides. According to a particular embodiment, the monomers (A) used according to the process of the invention are methacrylates, preferably non-protic, these methacrylates preferably having the following formula (V):

COOR ' _(V)

In which R 'is a linear or branched hydrocarbon-based chain, optionally cyclized in whole or in part, optionally interrupted by one or more heteroatoms, in particular O or S, and optionally substituted, this chain preferably being: an alkyl, alkenyl or alkynyl, linear or branched, optionally substituted; an optionally substituted cycloalkyl group; an optionally substituted aryl, alkylaryl or arylalkyl group. According to another embodiment, the monomers (A) are acrylates, preferably non-protic. Typically, it may be acrylate monomers corresponding to the following formula (Va)

CH 2 = CH-COOR "(Va) where R" has the meaning given for R 'in the compounds of formula (V) above.

Moreover, in the process of the invention, whatever the nature of the monomers (A) and of the carbene (C), the polymerization initiator (B) used in step (P) is generally a silylated compound capable of generating in the polymerization medium nucleophilic species capable of initiating the polymerization reaction. Most often, it is a silyl acetal ketene or a trimethylsilyl cyanide.

According to a particular embodiment, the polymerization initiator (B) comprises (or consists of) a compound of formula (VI) below:

dans laquelle :

in which :

Ra and Rb, which may be identical or different, are alkyl, alkenyl or alkynyl, cycloalkyl, aryl, alkylaryl or arylalkyl groups, Ra and Rb preferably being alkyl groups, for example methyl or ethyl groups. Rc is an alkyl group or else alkenyl or alkynyl, cycloalkyl, aryl, alkylaryl or arylalkyl, Rc typically being a methyl or ethyl group

Rd, Re and Rf, identical or different (generally identical) each denote an alkyl group, for example a methyl or ethyl group.

According to a particular embodiment, the polymerization initiator (B) is 1-methoxy-2-methyl-1-trimethylsiloxypropene (MTS) corresponding to the following formula (VIa):

In general, regardless of the nature of the compounds (A), (B) and (C) used in the polymerization step (P), the molar ratio (C) / (B) of the amount of catalyst ( C) introduced relative to the amount of polymerization initiator introduced is most often between 0.1 and 10%, preferably between 0.5 and 8%, especially between 1 and 5%, for example between 2 and 4%, it is generally possible to influence the speed of the polymerization in playing on this ratio, the speed of the polymerization generally increasing with the molar ratio (C) / (B). Moreover, in the polymerization step (P), the molar ratio (A) / (B) of the quantity of monomers (A) introduced introduced relative to the amount of polymerization initiator (B) is between 5 and 1000, for example between 10 and 300. The value of this ratio makes it possible to control the degree of polymerization of the polymer obtained in step (P), the degree of polymerization tending to increase when this ratio increases. The polymerization step (P) of the process of the invention has the advantage of being able to be conducted at a low temperature, for example close to room temperature, which constitutes one of the advantages of the invention both in terms of convenience and reduced costs. Most often, the step (P) is conducted at a temperature below 70 ⁰ C, typically between 15 and 60 ⁰ C, for example between 20 and 50 ° C. More generally, as emphasized above in the present description, it should be noted that the polymerization step (P) can most often be carried out in a polar and nonpolar solvent medium, and in particular in an apolar medium which is a specificity of the process of the invention compared to other GTP polymerization processes, which generally require the systematic use of a polar solvent. With regard to the solvent employed in step (P), it should furthermore be noted that it is preferably aprotic.

The process of the invention, which leads to controlled and living polymerization, has a large number of practical applications. In particular, it can be implemented for the synthesis of block polymers, especially diblock or triblock, and / or controlled architecture. This particular use of the process of the invention constitutes a particular object of the invention.

The polymer compositions as obtained at the end of step (P) of the controlled polymerization process of the invention are specific compositions, which generally comprise polymer chains carrying reactive end groups of the type conventionally obtained. in GTP type polymerization, for example of the type described in US Pat. Nos. 4,524,196 or US 4,581,428.

The polymeric compositions as obtained at the end of step (P) of the controlled polymerization process of the invention have a reactivatable (living) character enabling them to be used in subsequent polymerization reactions with other monomers , the invention thus making it possible to obtain polymers with a controlled architecture. Thus, according to a particular embodiment, the process of the invention may for example be used for the preparation of diblock block copolymers. In this context, the process of the invention advantageously comprises, at the end of the polymerization step (P), a new polymerization step (P ¹ ) in which the polymer is brought into contact as obtained with the the result of step (P) with monomers comprising an unsaturated α-β carbonyl chain C = CC = O different from those used in stage (P), in the presence of the carbene employed in the polymerization stage previous.

The diblock copolymers thus obtained also have a reactivatable nature and can then be used in a new polymerization step for the constitution of triblock polymers, typically by implementing at the end of step (P ¹ ) a new step (P ² ) in which the polymer as obtained at the end of step (P ¹ ) is brought into contact with monomers comprising an unsaturated α-β carbonyl chain C = CC = O different from those used in the process. step (P ¹ ) in the presence of the carbene employed in the preceding polymerization step.

More generally, the process of the invention can be implemented for the preparation of multiblock copolymers comprising N blocks, where N is an integer at least equal to 3, the process then comprising, at the end of step (P ) a succession of (N-1) polymerization steps (P ¹ ) to (P ^{N "1} ), wherein in each of these polymerization steps, the polymer is contacted as obtained at the end of the preceding polymerization step with monomers comprising an unsaturated α-β carbonyl chain C = CC = O different from those used in the preceding step, in the presence of the carbene employed in the preceding polymerization step. this frame, each step (P ¹ ) to (P ^N ) is a polymerization step similar to step (P) of the process of the invention wherein the reactivatable polymer introduced into the polymerization medium acts as an initiator of polymerization and anchor point of the new shea polymerization.

According to another particular embodiment, the process of the invention may advantageously be used for the preparation of convergent star copolymers (star-type "arm-first" copolymers). In this context, the process of the invention advantageously comprises a polymerization step (P ^* _af ) in which the polymer obtained at the end of step (P) is brought into contact, or alternatively a sequenced polymer such as obtained after a subsequent polymerization step of the type (P ¹ ), (P ² ) or (P ^N ) mentioned above, with bi- or polyethylenically unsaturated monomers (optionally mixtures of such polyethylenically unsaturated monomers), these monomers bi- or polyethylenically unsaturated having advantageously a unsaturated α-β carbonyl linkage C = CC = O, in the presence of the carbene employed in the preceding polymerization step.

According to yet another embodiment, the process of the invention can be used for the preparation of copolymer nanogels. In this context, step (P) of the process of the invention advantageously employs, as monomers comprising an unsaturated α-β carbonyl chain C = CC = O, a mixture comprising (i) monoethylenically unsaturated monomers and (ii) bi- or polyethylenically unsaturated monomers (optionally mixtures of such polyethylenically unsaturated monomers). The copolymer nanogels obtained according to this specific variant of the process of the invention can in particular be used for the preparation of divergent star-shaped polymers ("core-first" star copolymers). In this context, the process of the invention preferably comprises a polymerization step (P ^* _cf ) in which the copolymer nanogel obtained at the end of step (P) is brought into contact with monoethylenically unsaturated monomers ( optionally mixtures of such monoethylenically unsaturated monomers), these monoethylenically unsaturated monomers advantageously comprising a C = C-C = O unsaturated α-β carbonyl linkage in the presence of the carbene employed in the preceding polymerization step.

The polymer and copolymer compositions as obtained according to the invention have multiple applications. They may for example be used for the formation of coatings or else as dispersing agents for pigments or fillers, wetting agents or surface modifiers, rheology modifying agents, or else additives in thermoplastic mixtures or thermosetting resins. Certain block copolymers, in particular diblock or triblock copolymers of which one block is hard (high Tg monomers such as MMA) and one block is flexible (low Tg monomers such as Butyl Acrylate), for example triblocks whose blocks are outer are hard, can be used especially as thermoplastic elastomers. These applications constitute yet another particular object of the present invention. The polymers of the invention may especially be used in cosmetic compositions, in coatings such as paints, in compositions of plastic materials, in ink compositions, in fluids used in the course of oil exploitation or of gas, in household care compositions.

Various aspects and advantages of the invention will emerge even more in light of the illustrative examples set forth below. EXAMPLES

In the examples below, polymerization reactions according to the invention were carried out using 1-methoxy-2-methyl-1-trimethylsiloxypropene (MTS) as initiator, and various carbenes.

The carbenes used are: - Carbene 1: 1, 3-di-tert-butylimidazol-2-ylidene - Carbene 2: 1, 3-di-isopropylimidazol-2-ylidene

Carbene 1

The 1,3-di-tert-butylimidazol-2-ylidene (Carbene 1) used in the examples below has the following formula:

This carbene was obtained according to the protocol described in the Journal of Organometallic Chemistry, vol. 617-618, pp. 242-253 (2001), starting from a 1,3-diterbutylimidazolium chloride as obtained according to the protocol described in the Journal of the American Chemical Society, vol. 127, pp. 3516-3526 (2005). More specifically, the carbene was prepared according to the protocol below (implemented in a Schlenk tube while working under an inert atmosphere) The glassware used was dried by heating under vacuum before use .The various solvents employed were dried, then distilled, before use):

Synthesis of the 1,3-diterbutylimidazolium chloride precursor:

3 g (100 mmol) of paraformaldehyde and 100 ml of toluene were introduced into a flask which was placed at 0 ^° C. 21.2 ml (or 200 mmol) of terbutylamine were added dropwise to the medium maintained. with stirring at 0 ⁰ C, then stirring was continued for 10 minutes.

25 ml of a solution of 4N hydrochloric acid in dioxane were then added dropwise and very slowly, still keeping the medium at 0 ^° C. and stirring. The medium was then allowed to evolve under these conditions during

30 minutes.

After these 30 minutes of stirring at 0 ° C., the temperature of the reaction medium was raised to room temperature (25 ° C.), then 0.1 ml of glyoxal in the form of a solution was added dropwise. 40% in water (ie 100 mmol of glyoxal) in the medium always kept stirring. The medium was allowed to stir for 16 hours.

The water was then removed by Dean Stark, and the volatile solvents were removed under reduced pressure.

There was thus obtained 15 g of a brown solid (1,3-diterbutylimidazolium chloride including traces of tertbutylammonium chloride), having the following characteristics:

¹ H NMR (CDCl ₃ ) δ (ppm): 10.49 (tr, 1H, J = 1.7 Hz);

7.45 (d, 2H, J = 1.7 Hz); 1.73 (s, 18H).

^"Synthesis of carbene precursor from:

In a Schlenk tube, 2 g (ie 9.22 mmol) of the precursor prepared in the previous step (1,3-diterbutylimidazolium chloride) and then 15 ml of tetrahydrofuran (THF) were introduced. The reaction medium was then brought to -78 ° C., and 8.7 ml of a solution of 1.6M n-BuLi in hexane were introduced dropwise at this temperature.

(ie 13.8 mmol of n-BuLi).

The reaction medium was stirred at -78 ° C. for 30 minutes and then allowed to rise to room temperature (20 ^° C.). The medium was then left stirring at room temperature for 2 hours until the end of gas evolution.

The medium is then placed under vacuum to remove volatile compounds, and the carbene was purified by sublimation, whereby 1.4 g of a white crystalline powder (yield: 84%) was obtained, having the above characteristics. below:

¹ H NMR (C ₆ D ₆ ), δ (ppm): 6.77 (s, 2H, CH); 1, 51 (s, 18H, t-Bu).

¹³ C NMR (C ₆ D ₆ ), δ (ppm): 212.2 (carbene); 11, 47; 55.5 31, 1. After synthesis, the carbene was stored in a glove box under an inert atmosphere.

Carbene 2

The 1,3-diisopropylimidazol-2-ylidene (Carbene 2) used in the examples below has the following formula:

This carbene was obtained according to the protocol adapted from the protocol described in the Journal of the American Chemical Society, 1992, 14, 5530-5534. To adapt the di-isoproyl-limidazolium salt was deprotonated with NaH starting from a 1,3-diisopropyl-imidazolium chloride.

Example 1 Polymerization of Methyl Methacrylate (MMA)

Various MMA polymerization reactions were carried out using the aforementioned MTS initiator and carbene 1, 3-di-tert-butylimidazol-2-ylidene (Carbene 1). These different reactions were carried out in a THF (tetrahydrofuran) solvent medium, under a slight static vacuum in a Schlenk tube immersed in a preheated oil bath and maintained at 25 ^° C.

Before each of the polymerization reactions carried out, the MMA monomer, the MTS initiator and the THF solvent used were predried on CaH ₂ and distilled under reduced pressure. The equipment was previously dried with the flame of a torch, then transferred in glove box to take the carbene.

In each case, the polymerization reaction was conducted as follows.

A certain quantity of carbene was introduced into the Schlenk tube, then the

Schlenk has been connected on a line of vacuum and nitrogen. We then introduced into the

Schlenk 20 ml THF, then a determined amount of initiator MTS, then finally 13 ml.

(ie 12.17 grams, i.e. 0.1125 moles) of MMA monomer.

The medium was then allowed to evolve at 25 ° C. for a given polymerization time, at which time the polymerization was stopped by the addition of degassed methanol.

Several polymerization reactions have thus been carried out, by modifying the amounts of carbene and initiator, as well as the polymerization times.

For comparison, a reference reaction was carried out using only the initiator without using carbene.

The different conditions of the polymerizations employed are reported in the

Table 1 below, which also shows the degree of polymerization D _p referred to in each case. This degree of theoretical polymerization D _p is calculated by the ratio of the amount of MMA monomer introduced relative to the amount of MTS supplied.

Table 1: Polymerization conditions

For each of the polymerizations, it was determined:

the number-average molecular weight of the polymer obtained, this number-average molar mass (M _n ), expressed in grams per mole, was determined by size exclusion chromatography (SEC) in THF. This average mass in number is expressed in polystyrene equivalent. 99

The conversion rate of monomer to polymer this conversion rate (Tc) was evaluated gravimetrically. From this conversion, the theoretically expected average number molecular weight for the polymer M _n ^theoπque , calculated by the following ratio:

^ theoretical _ ^^ / ^ _{5 χ convers} j _{on χ} | y | _MMA

_MMA represents the initial amount of introduced MMA monomer MTI _MT S represents the initial amount of MTS introduced M _MMA rest the molar mass of the MMA monomer (ie 100.12 g / mol) - Polymolecularity index of the polymer obtained

This index (l _p ), equal to the ratio of the mass average molecular weight to the number average molar mass (l _p = MJM _n ).

The results obtained are reported in Table 2 below, which shows that the polymerization conditions of the invention lead to a controlled polymerization, with a number average molar M _n poly (methyl methacrylate)

(PMMA) obtained very close to the theoretical molar mass M _n ^theoπque and a polydispersity index l _p very low, less than 1, 5, and most often 1, 3. Moreover, the conversion rates are very high under the conditions of the invention, much more than in the case of the control where only a 6% conversion is observed.

Table 2: Results Achieved

Example 2

Polymerization of tert-butyl acrylate (ATB) A tert-butyl acrylate polymerization according to the invention was carried out using the conditions of Example 1, but employing tert-butyl acrylate instead of MMA.

In this context, 9.8 g (ie 5.5 × 10 ^-5 mol) of carbene, 20 ml of THF solvent, 0.238 g (ie 1.36 × 10 ^-3 mol) of MTS initiator and 8.75 g ( or 0.0682 moles) of ATB monomer, corresponding to an expected degree of polymerization of 50. The polymerization reaction was conducted for a reaction time of 16 hours at 25 ° C. There was thus obtained a polymer of average molar mass M _n equal to 4480 g / mol, with a conversion rate of 86%, corresponding to an average molar mass M _n ^theoπque of 6400, close to the experimental value. The polydispersity index of the polymer obtained is 1.31. Thus, again, controlled polymerization was obtained.

Example 3 Polymerization of methyl methacrylate (MMA)

Various MMA polymerization reactions were carried out using the MTS initiator and the carbenes 1, 3-di-tert-butylimidazol-2-ylidene (carbene 1) and 1,3-diisopropylimidazol-2-ylidene (carbene 2). ) above.

These different reactions were carried out in a THF (tetrahydrofuran) or toluene solvent medium under a slight static vacuum in a Schlenk tube immersed in a preheated oil bath and maintained at 25 ^° C.

Before each of the polymerization reactions carried out, the MMA monomer and the MTS initiator employed were predried on CaH ₂ and distilled under reduced pressure. THF and toluene were dried on CaH ₂ , then on Na / Benzophenone and PS-Li respectively.

The equipment was previously dried with the flame of a torch, then transferred in glove box to take the carbene.

In each case, the polymerization reaction was conducted as follows.

A determined quantity of carbene (determined volume of mother solution and corresponding carbene mass in the case of quantities which are too difficult to measure directly) and MTS initiator were introduced into the Schlenk tube, and then the Schlenk was connected to a line empty. 20 ml of THF were then added to the Schlenk. Finally, a volume of MMA monomer was introduced dropwise into the reaction medium. The medium was then allowed to evolve at 25 ° C. for a given polymerization time, at which time the polymerization was stopped by the addition of degassed methanol.

Several polymerization reactions have thus been carried out, by modifying the amounts of carbene and initiator, as well as the monomer / initiator ratios.

The different polymerization conditions used are reported in Table 3 below, which also shows the degree of polymerization D _p referred to in each case. This degree of theoretical polymerization D _p is calculated by the ratio of the amount of MMA monomer introduced relative to the amount of MTS supplied.

Table 3: MMA Polymerization Conditions

For each of the polymerizations, it was determined: the number-average molecular weight of the polymer obtained, this number-average molar mass (M _n ), expressed in grams per mole, was determined by size exclusion chromatography (SEC) in the THF. This average mass in number is expressed in polystyrene equivalent.

The conversion rate of monomer to polymer this conversion rate (Tc) was evaluated gravimetrically. From this conversion, we calculated the average molar mass theoretically expected number for the polymer _Mn ^theoπque calculated by the following ratio: M _n th ^β oπquθ _ i _{ΠMMA ΠMTS lay χ} j _is M _{x MMA}

Π _MMA represents the initial quantity of MMA monomer introduced ΓI _MTS represents the initial quantity of MTS introduced

M _MMA remains the molar mass of the monomer MMA (ie 100.12 g / mol).

the polymolecularity index of the polymer obtained

This index (l _p ), equal to the ratio of the mass average molecular weight to the number average molar mass (l _p = M _w / M _n ).

The results obtained are reported in Table 4 below, which shows that the polymerization conditions of the invention lead to controlled polymerization, with a number average molar mass M _n of poly (methyl methacrylate) (PMMA). ) obtained very close to the theoretical molar mass M _n ^theoπque and a polydispersity index l _p very low, less than 1, 3, and usually 1, 2. In addition, the conversion is complete in all the added examples.

Table 4: Results of PMMA obtained

Example 4

Polymerization of tert-butyl acrylate (ATB)

A tert-butyl acrylate polymerization according to the invention was carried out using the conditions of Example 3, but employing tert-butyl acrylate instead of MMA.

The results are summarized in Table 5: Table 5: ATB Polymerization Conditions

Thus, again, controlled polymerization was obtained.

To calculate, simply replace the MMA data with that of the ATB.

Example 5

Preparation of Block Copolymer by Sequential Polymerization of Methyl Methacrylate (MMA) and Ferf-Butyl Acrylate (ATB)

Copolymerizations of methyl methacrylate and tert-butyl acrylate were carried out by the sequential monomer addition method according to the present invention to obtain a PMMA-b-PATP-b-PMMA triblock copolymer. Thus, during a first sequence, MMA is polymerized to obtain a first so-called hard block of PMMA of known molar mass. Then during a second sequence polymerizes on the first block of ATB, to form a flexible block of PATB, mass molar equivalent to the first block, in a diblock copolymer, PM MA-b-PAT B. Finally, in a third block, MMA is polymerized on the diblock copolymer, to form a block of PMMA in a triblock copolymer PMMA-b-PATB -b-PMMA. and finally a last hard block (PMMA: sequence 3, synthesis of the PMMA-b-PATB-b-PMMA triblocks). It should be noted that the molar mass of this last block corresponds to the sum of the masses of the first two blocks for reasons of detection by steric exclusion chromatography (SEC) of a significant increase in molar mass.

The experiments are summarized in Table 7

Table 7: Copolymerization conditions

The samples to determine the masses were carried out under vacuum and the conversion was determined gravimetrically based on the mass concentration of monomer in the reaction medium: the sample has a given mass of which a precise percentage corresponds to the monomer ( and therefore to the polymer after reaction).

The calculations were performed in the same manner as for Example 3 for each block of the copolymer.

The results are shown in Table 8: Table 8: Results of the triblock obtained

Example 7

Polymerization of n-butyl acrylate (ABU)

N-butyl acrylate polymerizations according to the present invention were carried out in order to obtain PABU.

The experiments are summarized in Table 9:

Table 9: Polymerization conditions

The calculations were performed in the same way as in Example 3. The results are shown in Table 10:

Table 10: Results of PABUs obtained

Claims

Process for the preparation of a polymer, comprising a polymerization step (P) in which: (A) monomers having an unsaturated α-β carbonyl linkage C = C-C = O; (B) a silylated polymerization initiator; and (C) at least one carbene. 2. Method according to claim 1, wherein the carbene (C) used comprises, in α of its divalent carbon, a heteroatom selected from N, S, P, Si and O. 3. Process according to claim 2, in which the carbene (C) corresponds to the general formula (I) below:

in which : X and Y, identical or different, are heteroatoms selected from N, S, P, Si and O; Nx and ny are two integers, respectively equal to the valency of the heteroatom X and the valency of the heteroatom Y; Each of the groups R ^x and R ^γ linked to the heteroatoms X and Y represents, independently of the other groups, a hydrocarbon chain, linear or branched, optionally cyclized in whole or in part, and optionally substituted, this chain being preferably: a group alkyl, alkenyl or alkynyl, linear or branched optionally substituted, for example by at least one perfluoroalkyl group, a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example by at least one alkyl or alkoxy group; an aryl group optionally substituted, for example by at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, for example by at least one alkyl or alkoxy group, it being understood that one of the groups R ^x borne by the heteroatom X and one of the groups R ^γ carried by the Y heteroatom may optionally be bonded together to form a heterocycle with X and Y heteroatoms and divalent carbon bearing two non-binding electrons. 4. The process according to claim 3, wherein X is a nitrogen atom. 5. The process according to claim 4, wherein the carbene (C) corresponds to one of the general formulas (1-1) or (1-1 ') below: R ¹ R ¹

^(RY) ny-2 J Ji _-1 ^(RY) ny-2 ^ _-1, j in which: • Y is a heteroatom selected from N, S, P, Si and O, Y is preferably a nitrogen atom ; Ny and R ^γ are as defined in claim 3; and R ¹ denotes a linear or branched hydrocarbon-based chain, optionally cyclized in whole or in part, and optionally substituted, this chain preferably being: a linear or branched, optionally substituted alkyl, alkenyl or alkynyl group, for example by at least one group; perfluoroalkyl, a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example with at least one alkyl or alkoxy group; an aryl group optionally substituted, for example by at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, for example by an alkyl or alkoxy group • A denotes a nitrogen atom or a group CR ^lla,, B denotes a nitrogen atom or a group CR ^IIIa , R "and R ¹ ", and; where appropriate, R ^11a and R ^11a , which are identical or different, each denote a hydrogen atom, or a linear or branched hydrocarbon-based chain, optionally cyclized in whole or in part, and optionally substituted, this hydrocarbon-based chain preferably being: a linear or branched, optionally substituted alkyl, alkenyl or alkynyl group, for example by at least one perfluoroalkyl group, a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example with at least one alkyl or alkoxy group; an aryl group optionally substituted, for example by at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, in particular by at least one alkyl or alkoxy group. The process according to claim 4, wherein the carbene (C) is of the general formula (1-1a) or (1-1a ') below: R ¹ R ¹

in which : R ¹ , R ", R" ^a , R ^m and B are as defined in claim 5; and • R ^ιv denotes a hydrocarbon chain, linear or branched, optionally cyclized in whole or in part, and optionally substituted, this chain preferably being: a linear or branched, optionally substituted alkyl, alkenyl or alkynyl group, for example by at least one group perfluoroalkyl, a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example with at least one alkyl or alkoxy group; an aryl group optionally substituted, for example by at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, in particular by at least one alkyl or alkoxy group. The process of claim 6, wherein the carbene (C) has the general formula (1-1a). The process according to claim 2, wherein the carbene (C) is a compound selected from the following compounds: Alkylaminocyclic carbenes, Phosphino (amino) carbenes of formula (II):

Bisphosphinocarbenes of formula (III):

Carbodiphosphoranes corresponding to one of the following mesomeric formulas (IV) or (IV)

(IV) (IV) where each of the groups R, R _P , R _P ¹ , R _P ² , R _P ³ , R _P ⁴ , R _N , and R _P 1 represents, independently of the other groups, a hydrocarbon chain, linear or branched, optionally cyclized into all or part, and optionally substituted, this chain being preferably: - an optionally substituted linear or branched alkyl, alkenyl or alkynyl group, for example by at least one perfluoroalkyl group, a perfluoroalkyl group, linear or branched; a cycloalkyl group, optionally substituted, for example by at least one alkyl or alkoxy group; an aryl group optionally substituted, for example by at least one alkyl or alkoxy group; an alkylaryl or arylalkyl group, where the aryl part is optionally substituted, for example by at least one alkyl or alkoxy group, it being understood that, in each of the formulas (II), (III), (IV) and (IV), the group R and the group R ^p may optionally be bonded together to form a heterocycle with the two heteroatoms to which they are bonded and the divalent carbon, the heterocycle thus formed having, if appropriate, preferably from 5 to 7 members. 9. Process according to any one of claims 1 to 8, wherein the carbene (C) used is a carbene which has been preformed in a step prior to the polymerization step (P). 10. Process according to any one of claims 1 to 8, wherein the carbene (C) is formed in situ in the middle of the polymerization step (P), from at least one precursor (PC) of said carbene, said precursor being: a carbene in dimerized form, which is cleaved into two carbenes in situ by thermal activation, this dimerized carbene advantageously satisfying the formula (PC ₀ ) next:

where X, Y, nx, ny, R ^x and R ^γ are as defined in claim 3; or an imidazolium salt, which forms a carbene in situ by reaction with a base, this imidazolium salt advantageously corresponding to one of the following formulas (PCs) or (PCs'):

or : B, R ¹ , R ", R ¹ " and R ^ιv are as defined in claim 6; and An- is an anion derived from a Bronsted acid, preferably a carboxylate, sulfate, hydrogen sulphate, sulphonate, phosphate, hydrogen phosphate, halide, perchlorate or borate anion; - An adduct of carbene and alcohol, which releases in situ the carbene when it is heat treated. 11. Process according to any one of claims 1 to 9, in which the carbene (C) is an encapsulated carbene, physically mixed with a polymer serving as a protective matrix. The process according to any of claims 1 to 11, wherein the monomers (A) are non-protic monomers. 13. Method according to one of claims 1 to 12, wherein the monomers (A) are methacrylates. The process according to claim 13, wherein the monomers (A) have the following formula (V):

COOR ' _(V) In which R 'is a hydrocarbon chain, linear or branched, optionally cyclized in whole or in part, optionally interrupted by one or a plurality of heteroatoms, in particular O or S, and optionally substituted, this chain preferably being: an optionally substituted linear or branched alkyl, alkenyl or alkynyl group; an optionally substituted cycloalkyl group; an optionally substituted aryl, alkylaryl or arylalkyl group. Process according to one of claims 1 to 12, wherein the monomers (A) are acrylates. The process according to claim 15, wherein the monomers (A) having the following formula (Va) Where R "has the meaning given for R 'in the compounds of formula (V) of claim 14. 17. A process according to any one of claims 1 to 16, wherein the polymerization initiator (B) is a silyl acetal of ketene, or a trimethylsilyl cyanide. 18. The method of claim 17, wherein the polymerization initiator (B) comprises a compound of formula (VI) below:

in which: Ra and Rb, which may be identical or different, are alkyl, alkenyl or alkynyl, cycloalkyl, aryl, alkylaryl or arylalkyl groups, Ra and Rb preferably being alkyl groups, for example methyl or ethyl groups; Rc is an alkyl group; or alternatively alkenyl or alkynyl, cycloalkyl, aryl, alkylaryl or arylalkyl, Rc being typically methyl or ethyl groups Rd, Re and Rf, which may be identical or different, each denote an alkyl group, for example a methyl or ethyl group. The process according to claim 18, wherein the polymerization initiator (B) is 1-methoxy-2-methyl-1-trimethylsiloxypropene (MTS) having the following formula (VIa):

20. Process according to any one of claims 1 to 19, wherein, in the polymerization step (P), the molar ratio (C) / (B) of the amount of catalyst (C) introduced relative to the amount introduced polymerization initiator is between 0.1 and 10%. 21. A process according to any one of claims 1 to 20, wherein, in the polymerization step (P), the molar ratio (A) / (B) of the amount of monomer (A) introduced relative to the amount polymerization initiator (B) introduced is between 5 and 1000. 22. Process according to any one of claims 1 to 21, wherein the polymerization step (P) is conducted at a temperature below 70 ⁰ C, for example between 15 and 60 ⁰ C. 23. A process according to any one of claims 1 to 22, wherein the polymerization step (P) is conducted in an apolar solvent medium. 24. Process according to any one of claims 1 to 23, for the preparation of a diblock block copolymer, said process comprising, at the end of the polymerization step (P), a new polymerization step (P ¹ ) in which the polymer as obtained at the end of step (P) is brought into contact with monomers comprising an unsaturated α-β carbonyl chain C = CC = O different from those used in the stage (P), in the presence of the carbene employed in the preceding polymerization step. 25. Process according to any one of claims 1 to 23, for the preparation of a block copolymer comprising N blocks, where N is an integer at least equal to 3, said process comprising, at the end of step (P), a succession of (N-1) polymerization steps (P ¹ ) to (P ^{N "1} ), where in each of these polymerization steps, it is possible to contacting the polymer as obtained at the end of the preceding polymerization step with monomers comprising an unsaturated α-β carbonyl chain C = CC = O different from those used in the previous step, in the presence of carbene used in the previous polymerization step. 26. Process according to any one of claims 1 to 23, for the preparation of convergent star copolymers, said process comprising a polymerization step (P ^* _af ) in which the polymer obtained at the end is contacted. of step (P), or a block polymer as obtained after a polymerization step (P ¹ ), (P ² ) or (P ^N ) as defined in claims 24 and 25, with bi monomers or polyethylenically unsaturated, in the presence of the carbene employed in the preceding polymerization step. 27. Process according to any one of claims 1 to 23, for the preparation of copolymer nanogels, in which, in step (P), is implemented, as monomers comprising an unsaturated α-β carbonyl linkage. C = CC = O, a mixture comprising (i) monoethylenically unsaturated monomers and (ii) bi- or polyethylenically unsaturated monomers. 28. Process according to any one of claims 1 to 23, for the preparation of divergent star polymer, where: in step (P), a monomer containing an unsaturated α-β carbonyl chain C = CC = O is used, a mixture comprising (i) monoethylenically unsaturated monomers and (ii) bi- or polyethylenically monomers; unsaturated, whereby a nanogel of copolymers is obtained; and the process comprises a polymerization stage (P ^* _cf ) in which the copolymer nanogel obtained at the end of stage (P) is brought into contact with monoethylenically unsaturated monomers, in the presence of the carbene employed in the stage previous polymerization. 29. A polymer or copolymer composition obtainable by the method according to any one of claims 1 to 28. 30. Use of a composition according to claim 29, for the constitution of coatings, as dispersing agents for pigments or filler, wetting agents or surface modifiers, rheology modifying agents, or additives in thermoplastic mixtures or thermosetting resins.