FR2919296A1 - OPENING EPOXY CYCLES BY CARBENES. - Google Patents

Abstract

The present invention relates to the use of carbenes as epoxy ring-opening agents, especially for the polymerization of oxirane monomers. The invention relates in particular to various processes for the preparation of polyoxiranes using a carbene as a initiator and / or anionic polymerization catalyst.

Description

The present invention relates to the use of carbene epoxy rings.

  organic synthesis processes, especially macromolecular synthesis, using epoxy ring opening reactions.

  In particular, the invention relates to polymerization processes for oxirane monomers, such as ethylene oxide or propylene oxide, making it possible to access polymers of the poly (oxirane) type, more generally designated by the term polyethers, such as poly (ethylene oxide), poly (propylene oxide).

  By "oxirane" compound (or monomer) is meant, within the meaning of the present description, any organic compound bearing at least one epoxy ring, of formula: ## STR2 ## In an oxirane compound as defined herein, each of the compounds two carbon atoms of the ring is usually carrying two groups independently selected from H, an alkyl group (CH3 for example) or, more generally, a hydrocarbon chain, linear or branched, saturated or unsaturated, optionally cyclized in whole or in part , this chain can be interrupted by one or more heteroatoms.

  The epoxy cycle is a tense cycle that has been described in various modes of opening. The epoxy ring opening reactions contained in oxiranes are at the basis of multiple organic chemistry reactions, ranging from fine chemistry to polymer chemistry. An interesting application of the opening reaction of the epoxy rings is in particular the synthesis of polyoxirane type polymers (polyethers). By "polyoxirane" is meant here a polymer resulting from the polymerization of oxirane compounds of the aforementioned type and implementing the opening of the epoxy ring of the monomers. These polyoxirane polymers are generally obtained by an ionic polymerization (anionic in particular) or by a coordinated route. These polyoxiranes are also referred to as "poly (oxirane)" or "polyether". By way of example of polyoxiranes, poly (ethylene oxide) or poly (propylene oxide) can be mentioned. Usually, the polyoxiranes are synthesized by an anionic ring-opening polymerization, in which an alkali metal or alkaline earth metal alkoxide (BuOK for example) or a metal hydroxide (sodium hydroxide or potassium hydroxide in particular) is used as a polymerization initiator. .

  In this type of reaction, the alkoxide or hydroxide which is used as an initiator reacts on the epoxy ring of the oxirane monomers, according to the following schematic reaction: ## STR1 ## The ring opening thus obtained creates a new alkoxide species which, in turn, can react on an epoxy ring of another oxirane, which reaction then propagates and thus allows for growth of the polymer chain. Polymerization reactions of this type are well known and have been widely described. For more details on this subject, reference may in particular be made to Comprehensive Polymer Science, Third Edition, Allen G., Bevington JC Eds, Pergamon: Oxford (1985) or to the article by S Penczek et al., In Prog . Polym. Sci. , flight. 32, pp. 247, 282 (2007). The anionic ring-opening polymerization reactions of the above-mentioned type have the drawback of using metal ions (namely the counter-ions of the alkoxides employed), which generally remain in the polymer synthesis medium and which end up in the polymer synthesis medium. ultimately in the synthesized polyoxirane polymers.

  In many applications of polyoxiranes such as poly (ethylene oxide) and poly (propylene oxide), it is necessary to eliminate these metal cations, which implies an additional purification step, which makes the process more difficult. in particular, its cost and duration. Such additional purification steps are especially required when the polymer is intended for use in the biomedical field or even in that of microelectronics. To avoid having to carry out a purification step of the aforementioned type, it has been proposed, in particular in ACS Polymer Preprints, Div. Polym.

  Chem., Vol. 47 (2), p. 99-100 (2006), to use as a polymerization initiator, not a metal alkoxide, but an alcohol used in the presence of a carbene. In the aforementioned Polymer Preprints article, the use of an N-heterocyclic carbene (NHC) of the type described in Tetrahedron, vol. 55, pp. 14523-14534 (1999). In this process, carbene is used as an alcohol deprotonating agent, its reaction with alcohol leading to an alcoholate species associated with an imidazolium counter cation. Thus, schematically, an alcoholate initiator similar to those employed in the usual ring-opening anionic polymerization processes is obtained, except that this initiator does not contain a metal cation, which opens the way for a polymer synthesis without metal cations. Despite these advantages, the aforementioned method nevertheless systematically requires the use of an alcohol as an initiator, which affects the nature of the synthesized polymer chains, these chains systematically having at one of their ends a group corresponding to the alcohol. used in the initiation step of the reaction. However, if the presence of such a terminal group can be sought in some cases, there is another where it is preferred to obtain polyoxirannes free of this type of functionality at the end of the chain. On the other hand, it is sometimes desirable to obtain polyoxiranes with end-chain functionality, but this functionality is not dictated by the nature of an alcohol employed in the priming step.

  More generally, it is presently desirable to have an epoxy ring opening reaction which does not systematically require the use of an alcohol or an alcoholate. An object of the present invention is to provide a new method 5 for producing an epoxy ring opening which is particularly suitable for the preparation of polyoxirane-type polymer and which does not require the use of metal salts, or the implementation of an alcoholate or an alcohol. For this purpose, it is provided according to the invention a new opening path of an epoxy ring, in which a new epoxy ring opening agent is used. More specifically, according to the invention, a carbene is used as an opening agent for an epoxy ring. For the purposes of the present description, the term "carbene" refers to a chemical species, generally electrically neutral, comprising a divalent carbon which comprises two non-binding electrons, these two non-binding electrons being preferably in paired form (singlet), but which may be 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, as used herein, the term carbene also encompasses compounds of the aforementioned type where the divalent carbon carries an additional electron pair or is engaged in a delocalized bond and / or in which the divalent carbon is carrying an electric charge (typically a negative charge possibly delocalized). In the context of the present invention, the inventors have demonstrated that a carbene as defined above proves effective, on its own, to effect the opening of an epoxy ring. Unexpectedly, it turns out that the direct reaction of a carbene on an epoxy ring leads to an opening of the epoxy ring, without it being necessary to use an alcohol of the type of those described in the article. of Polymer Preprints supra. Without wishing to be bound by a particular theory, the work of the inventors makes it possible to state that, when placed in contact with an oxirane compound, a carbene induces an opening of the epoxy ring, according to the following schematic reaction: The opening of epoxy rings with a carbene according to the invention can, inter alia, be used to initiate a polymerization reaction of oxirane monomers, in particular the polymerization of ethylene oxide or propylene oxide. In this context, the carbene, acting as an epoxy ring-opening agent for oxirane compounds, leads to the formation of anionic species of alkoxide type, and thereby plays the role of initiating agent of the anionic polymerization. More precisely, in the polymerization reaction, by acting as an agent for opening epoxy rings, the carbene acts as an initiator and / or catalyst for the anionic polymerization. According to a particular aspect, the subject of the present invention is this specific use of a carbene as an initiator and / or anionic polymerization catalyst for the polymerization of oxirane monomers. For the sake of brevity, carbene will more simply be referred to hereinafter as a polymerization "initiator". This term initiator indicates that the carbene is an initiator and / or a catalyst of the polymerization reaction. Most often, according to the invention, only carbene (or possibly a mixture of several carbenes) is used as the only anionic polymerization initiator, without any other anionic polymerization initiator. It is certainly not excluded to use one or more other polymerization initiators together with carbene, but the implementation of such additional initiators is not required by the invention.

  In particular, in the context of the invention, there is no need to employ metal alcoholate initiators in addition to the carbene type initiator. More generally, the process of the invention does not require the use of compounds comprising metal cations, which makes it possible to dispense with the presence of metal ions in the synthesized polyoxiranes. In this regard, it should be noted that, when it is desired to overcome the presence of metal ions in the polymers synthesized according to the invention, it is preferable to use carbenes which are not bound or complexed with metal cations. In this context, it should be emphasized that many currently known carbenes are obtained according to methods of preparation leading to carbenes complexed with metal cations. It is preferable according to the invention not to use this type of carbene and to employ, on the contrary, carbenes free of metal cations such as those prepared, for example, according to the method described in the article by Otto, M. et al. in J. Am. Chem. Soc. , flight. 126, pp. 1016-1017 (2004). In addition, the use of an alcohol together with the carbene is not required to obtain the desired polymerization according to the invention.

  According to a more particular aspect, the subject of the invention is different processes for preparing polyoxiranes from oxirane polymers, employing a carbene as an initiator and / or anionic polymerization catalyst, which are defined below. In a first process (P1) for preparing polyoxiranes according to the invention, oxirane monomers are brought into contact with a carbene, in the absence of any alcohol capable of reacting with the carbene acting as an initiator and / or anionic polymerization catalyst. In this first process (PI), carbene is most often employed in the absence of any anionic polymerization initiator other than a carbene.

  In this process (P1), an alcohol is not used at any time during the polymerization reaction itself. At most, it may be possible to use an alcohol to stop the polymerization reaction (the use of an alcohol is not required for this purpose, other species can be used to stop the reaction of polymerization, for example water, or, more generally, any compound of formula Nu-H or Nu is a nucleophilic group). A second process (P2) for the preparation of polyoxiranes according to the invention comprises a first step (E1) in which oxirane monomers are brought into contact with a carbene, and a step (E2) in which an alcohol capable of reacting with the alcohol is added. carbene in the polymerization medium, the step (E2) being performed after or during step (E1). In general, the process (P2) has no pre-mixing step of alcohol and carbene. In the process (P2), step (E1) leads to epoxy ring opening reactions of the oxirane compounds by carbene. This step (E1) is advantageously carried out before step (E2), typically allowing the carbene and the monomers to react for at least one minute, preferably at least two minutes, and more preferably at least two minutes. for example for a period of 1 minute to 72 hours, in particular from 2 minutes to 48 hours before adding the alcohol. According to a particular embodiment, the step (E2) is carried out shortly after step (E1), typically allowing the carbene and the monomers to react for 1 to 15 minutes, typically between 2 and 10 minutes, beforehand. the implementation of step (E1). According to another embodiment, the carbene and the monomers are allowed to react longer before the implementation of step (E1), for example for 5 hours to 72 hours, for example between 10 hours and 48 hours, in particular for 20 to 30 hours before adding the alcohol. According to yet another embodiment, the carbene and the monomers are allowed to react for 30 minutes to 5 hours, for example between 1 hour and 3 hours, before adding the alcohol.

  Alternatively, the steps (E1) and (E2) of the process (P2) may optionally be carried out simultaneously, in which case the process (P2) may typically comprise a step (E) in which the oxirane monomers, the carbene, are simultaneously brought into contact with each other. and alcohol, for example by simultaneously introducing these compounds into a polymerization reactor.

  In a third process (P3) for preparing polyoxiranes according to the invention, oxirane monomers are brought into contact with a carbene and an alcohol, in a medium comprising a solvent chosen from DMSO (dimethylsulfoxide), THF ( tetrahydrofuran), and / or dioxane, and preferably in a medium comprising DMSO (for example a solvent medium consisting essentially of DMSO). In another process (P4) for the preparation of polyoxiranes possible according to the invention, oxirane monomers are brought into contact with a carbene and an alcohol, in the absence of any solvent. In this context, the process (P4) may in particular be carried out in the absence of any alcohol capable of reacting with the carbene acting as an initiator and / or anionic polymerization catalyst. Alternatively, the process (P4) can be carried out using the conditions of the process (P2), namely by implementing a first step (El ') in which oxirane monomers are brought into contact with a carbene, and a step (E2 ') in which an alcohol capable of reacting with the carbene in the polymerization medium is added, the step (E2') being carried out after or during the step (E1), said steps (E1 ') and ( E2 ') being conducted in the absence of solvent. Various specific aspects and preferred embodiments of the invention will now be described in more detail.

  The carbene useful according to the invention Whatever the method employed according to the invention, the carbene used as epoxy ring-opening agent (and generally as initiator of anionic polymerization) may vary in a fairly wide range. measured. Advantageously, the carbene used according to the invention comprises, in a of its divalent carbon, at least one heteroatom selected from N, S, P, Si and O. Advantageously, in this context, the carbene used corresponds to the general formula (I ) below: (I) 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 Rx and RY 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 preferably being: an alkyl group, alkenyl or alkynyl, optionally substituted linear or branched, 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 with 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 Rx carried by the heteroatom X and one of the groups RY borne by the heteroatom Y 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.

  Advantageously, the carbene used according to the invention 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 used is an NHC carbene of the aforementioned type corresponding to one of the general formulas (1-1) or (1-1 ') below: RI Ri / N`A Wherein Y is a heteroatom selected from N, S, P, Si and O, wherein R is a heteroatom selected from N, S, P, Si and O. R 1 (R Y) n y-2 1 (R Y) n y 2 Y being preferably a nitrogen atom; • ny and RY have the above definitions; and R1 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 a 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, wherein the aryl part is optionally substituted, for example by an alkyl or alkoxy group; A denotes a nitrogen atom or a CRlla group; B denotes a nitrogen atom or a CRIlla group; R and R111, and; where appropriate, Rua and Rllla, 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. In the case where R11 R "Rua or RIlla represents a hydrocarbon chain, this hydrocarbon chain preferably being: a linear or branched alkyl, alkenyl or alkynyl group

  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. According to an even more advantageous embodiment, the carbene used corresponds to one of the general formulas (1-1 a) or (I-1 a ') below: RI RI

  N Rna N ~~ ùRila: C: C \ N - B \ N ~ B ~ RuI I (1-1a) Rlv (I-1 a ') in which:

  • R1 R11 R11a, R1 and B are as defined above; and • Rlv 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 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 corresponds to the aforementioned formula (I-1a). Alternatively, according to another conceivable embodiment, the carbene employed according to the invention may be a compound chosen from the following compounds: phosphino (amino) carbenes of formula (II): RN • bisphosphinocarbenes of formula (III) : Carbodiphosphoranes corresponding to one of the following mesomeric formulas (IV) or (IV ') Rp1 Rp2 Rp1 Rp2 + / P rp / P rp: C: C + + / P r / P r Rp Rp4 Rp3 Rp4 where each of the groups R, Rp, Rp ', Rp2, Rp3, Rp4, RN and Rp1 represents, independently of the other groups, a linear or branched hydrocarbon-based chain, 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 with 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 R group and the RP group 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 comprises from 5 to 7 members). According to yet another possible embodiment, the carbene used according to the invention is a carbene with an alkylaminocyclic unit, or CAAC (for the English term "Cyclic AlkylAminoCarbene"), of the type of those described for example in the application WO 20061138166, where the mode of preparation of these compounds and described. In this context, the carbene advantageously corresponds to the formula (V) below: Ra N "C (V) where: - A represents a ring comprising from 4 to 7 atoms, of which at least one of the atoms is the atom nitrogen as shown, - 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. Rb and Rb, which may be identical or different, represent an alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, alkoxy, alkenyloxy, alkynyloxy or aryloxy group. alkoxycarbonyl, or Rb and Rc are bonded together to form a spirocycle, the bet of the ring carrying the two groups Rb and R, bonded to each other comprising from 3 to 12 atoms CAAC carbenes preferably used in the present invention answer formula (V) above in which A represents a ring of 5 or 6 atoms and L represents a divalent group comprising 2 or 3 atoms. In the compounds of formula (V), 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 atom, the available valences may be substituted. 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 (III-5), 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 the context of the present description, the term "alkyl", a linear or branched hydrocarbon chain C1-C15, preferably C1-C10.et more preferably C1-C4. 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 C2-C8, preferably C2-C6, double bond. and even more preferably C2-C4. 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 C2-C8, preferably C2-C6, and even more preferentially C2-C4, triple bond. 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 C3-C8, preferably a cyclopentyl or cyclohexyl or polycyclic (bicyclic or tricyclic) C4-C18, especially adamantyl or norbornyl. By "aryl" is meant an aromatic mono- or polycyclic group, preferably mono- or bicyclic C6-C20, 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 two by two by a bonds. Examples of (C6-C18) aryl groups 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 linear or branched hydrocarbon-based group carrying a C 7 -C 12 monocyclic aromatic ring, preferably benzyl: the aliphatic chain comprising 1 or 2 carbon atoms. Specific examples of carbenes of formula (V) are carbenes corresponding to formulas (Va) and (Vb) below: Rd. Re

  Wherein: Ra, Rb, Rc, have the meanings given for the general formula (III-5), Rd and Re, identical or different, represent an alkyl, alkenyl or alkynyl group; , cycloalkyl, aryl, aralkyl. Suitable CAAC carbenes are carbenes of the formula (Va) or (Vb) wherein: Ra is an alkyl group, an optionally substituted aryl group, preferably an optionally substituted phenyl group; Rb and Rc, identical or different, represent an alkyl group, an optionally substituted aryl group, preferably an optionally substituted phenyl group; or R1 and R2 are bonded together to form a cycloalkane; Rd and Re, identical or different, represent an alkyl group.

  Preferably, it is possible to use carbenes of formula (Va) or (Vb), 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, identical or different, represent a linear or branched alkyl group having 1 to 4 carbon atoms or a phenyl group, or RI and R2 are bonded together to form a cyclopentane or cyclohexane, - Rd and Re, identical or different, represent a linear or branched alkyl group having 1 to 4 carbon atoms. Rb Rc (Va) (Vb) Thus, as illustrative examples of CAAC carbenes of interest according to the invention, there may be mentioned the following compounds: Whatever its exact nature, the carbene used according to the invention may be a carbene which has been preformed in a step prior to the opening step of the epoxy ring, for example prior to the polymerization step in which it is carried out. In this context, it is a so-called "bare" carbene, which is generally stored under an inert and non-reactive atmosphere (generally anhydrous), before it is used according to the invention, typically under nitrogen or under argon. usually in a glove box, usually in a solvent medium such as toluene, for example. Alternatively, the carbene used according to the invention can be formed in situ from at least one precursor (PC) of said carbene ("masked" form of the carbene), in the medium where the carbene is used according to the invention, typically in the polymerization medium of the oxirane. In this case, the carbene precursor (PC) used may in particular be a carbene in dimerized form, which is cleaved into two carbenes in situ by thermal activation, this dimerized carbene advantageously satisfying the following formula (PCo):

  (Rx) nx-1X X (Rx) nx-1 (RY) nY-1Y Y (RY) nv-1 (PCD) wherein X, Y, nx, ny, Rx and RY are as defined above;

  According to a particular embodiment, the carbene used according to the invention may be an encapsulated carbene, namely physically mixed with a polymer serving as a protective matrix. Advantageously, the protective polymer used in this context is a silicone oil.

  In the context of the present invention, the oxirane monomers employed are advantageously chosen from compounds of the following formula (VI): ## STR2 ## in which each of the groups R 1, R 2, R 3 and R 4 represents independently of the other groups, a hydrogen atom, an alkyl group or a linear or branched, saturated or unsaturated hydrocarbon-based chain, optionally cyclized in whole or in part, this chain being interruptable by one or more heteroatoms. More preferably, each of the groups R 1, R 2, R 3 and R 4 represents, independently of the other groups, a hydrogen atom or a free alkyl group of 1 to 6 atoms, for example 1, 2, 3 or 4 atoms. According to an advantageous embodiment, the oxirane monomers which are used according to the invention are chosen from the compounds corresponding to the above-mentioned formula (VI) in which R 1 = R 2 = R 3 = H, and R 4 is a methyl or ethyl group. , n-propyl, isopropyl, n-butyl or t-butyl. Typically, the oxirane monomers used according to the invention may be chosen from ethylene oxide, propylene oxide and mixtures thereof. The alcohol used in processes (P2) and (P3)

  The alcohol that can be used in processes (P2) and (P3) according to the invention can vary to a large extent. This alcohol will preferably be chosen from the following alcohols of formula (VI):

R-OH (VI)

  where R is a linear or branched, saturated or unsaturated alkyl or hydrocarbon chain, optionally cyclized in whole or in part, and optionally interrupted by one or more heteroatoms, R being for example an alkyl, alkenyl or alkynyl group, optionally one or more other OH groups than that presented above (in which case the polymerization generally leads to polymers having a star structure).

  According to an advantageous embodiment, the alcohols used may be chosen from the following compounds: fatty alcohols, especially the alcohols of formula (V) above wherein R is an alkyl or alkenyl chain comprising from 6 to 18 carbon atoms; alcohols of formula (V) above wherein R is an unsaturated chain, such as, for example, undecylenol or allyl alcohol; diols and polyols, such as ethylene glycol or glycerol, or alternatively trimethylolpropane, pentaerythritol, polymers comprising a succession of units including a group OHOH.

  The parameters for implementing the polymerization processes according to the invention

  In the processes (PI), (P2), (P3) and (P4) above, whatever the nature of the carbene and the oxirane monomer used according to the invention, it is preferred to use these compounds with a molar ratio (carbene / epoxy). ), corresponding to the total number of moles of carbene (C :) relative to the total number of moles of epoxy functions carried by the oxirane monomers, of between 0.000001 and 0.1, especially in the case where it is sought to obtain polymers with a molar mass of between 500 and 500 000 g / mol. Advantageously, this molar ratio (carboxyl epoxy) is between 0.0001 and 0.1, for example between 0.001 and 0.01 if the carbene is used without alcohol. In the case where the carbene is used in combination with an alcohol, a molar ratio (carbenepoxy) of between 0.000001 and 0.01, for example between 0.00001 and 0.001, is preferably used. Furthermore, the processes (P1) and (P2) are most often carried out in a solvent medium, as is always the case for the process (P3). Where appropriate, the solvent is advantageously chosen from the advantageous solvents defined for the process (P3). In the case of the use of a solvent medium, the concentration of carbene in the solvent is advantageously between 0.01 g / l and 1 g / l, for example between 0.1 gl and 0.5 g / l. L. Alternatively, the processes (P1) and (P2) can be carried out without solvent, according to an embodiment similar to that of the method (P4).

  In the case of (P2), (P3) and (P4) processes, the alcohol, when present, is generally used at a carbon-metal molar ratio of 0.01 to 0.5, typically from 0.02 to 2. On the other hand, the processes (P1), (P2) and (P3) are advantageously carried out at a temperature of between 0.degree. C. and 120.degree. C., typically from 15 to 100.degree. C., for example from 25.degree. at 80 C. Preferably, the processes (P1), (P2) and (P3) are conducted at a pressure between 105 to 5106 Pa (namely between 1 and 50 bar), typically between 1.5 x 10 5 to 5 x 10 Pa (c). that is, between 1.5 and 5 bar).

  In the case of the processes of the invention, it may be advantageous, in certain cases, to add slowly or semi-continuously the monomers in a medium comprising carbene. According to another particular aspect, the subject of the present invention is the polymer compositions based on polyoxiranes as obtained according to the present invention, in particular the compositions based on polyoxiranes which can be obtained according to the processes (P1), (P2) , (P3) and (P4) above. In these specific polymer compositions, all or part of the polymer chains obtained carry specific groups at the end of the chain, which are characteristic of the use of a carbene as an anionic polymerization initiator. Most often, the polymer chains carry such specific groups. This is particularly the case for the compositions as obtained according to the process (P1). The polymer chains obtained at the end of the polymerization according to the method of the invention react with compounds of Nu-H type where the Nu group is a nucleophilic group. In particular, the polymers as obtained according to the processes of the invention react with water, whereby terminal ends of OH are obtained at the ends of the polymer chains. Most often, they react with any Nu-H compound, to lead to the formation of Nu-function at one end of the polymer chains and at other end -OH functions. As pointed out above in the present description, the polymer compositions obtained according to the invention may advantageously be free of metal cations. The polymer compositions obtained according to the invention can be used in many applications, for example as surface-active agents, dispersing agents, rheological property modifiers for liquid compositions or gels, and / or as a system for encapsulation (and generally issuance) of assets. More specifically, the polymer compositions obtained according to the invention which are free of metal cations can advantageously be used as an encapsulation and / or asset delivery system, reactive surfactants or for the constitution of films, or coatings, in particular in devices for biomedical use or in microelectronics. The polymers obtained according to the invention can also be used as polymerizable macromonomers. The polymers obtained according to the invention are also living polymers (reactivatable), which can be involved in subsequent polymerization reactions for the preparation of block polymers, for example by bringing the polymers from the processes into contact with oxirane monomers. For this purpose, the process of the invention may for example comprise, after a process (P1), (P2), (P3) or (P4) of the aforementioned type, one or more additional steps (E ') for contacting the polymers. obtained with a carbene oxirane monomers different from those used in the previous step. These different applications constitute, in another aspect, yet another object of the present invention. Various aspects and advantages of the invention will emerge even more in light of the illustrative examples set forth below.

  EXAMPLES In the examples which follow, poly (ethylene oxide) synthesis reactions were carried out using the process of the invention, and using 1, 3-di-tert-butylimidazole. 2-ylidene or 1,3-diisopropylimidazol-2-ylidene as carbene. The carbene used In the examples below, 1,3-di-tert-butylmidazol-2-ylidene and 1,3-di-isopropylimidazol-2-ylidene were used, which will be more simply referred to below. after carbene 1 and carbene 2, which respectively correspond to the following formulas: 24 i 2 These carbenes were 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 in an inert atmosphere) The glassware used was dried by heating under vacuum before use .The various solvents employed were dried, then distilled, before use). The synthesis of carbene 1 is described below in detail. The carbene 2 was synthesized according to a similar mode of synthesis (except that at the end of the synthesis, a solid product is obtained for the carbene 1 which is purified by sublimation, whereas the carbene 2 obtained at liquid state, is purified by distillation).

  Synthesis of carbene 1 Synthesis of the precursor 1,3-diterbutylimidazolium chloride: 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 (200 mmol) tertbutylamine were added dropwise into the medium stirred at 0 ° C, and 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. with stirring. The medium was then allowed to evolve under these conditions for 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 11.5 ml of glyoxal was added dropwise in the form of a 40% solution. 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 tert-butylammonium chloride), having the following characteristics: 1H NMR (CDCl3), δ (ppm): 10.49 (tr, 1H, J = 1.7 Hz); 7.45 (d, 2H, J = 1.7 Hz); 1.73 (s, 18H). Synthesis of the carbene from the precursor: 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 were introduced. (THF).

  The reaction medium was then brought to -78 ° C., and then 8.7 ml of a solution of 1.6M n-BuLi in hexane (ie 13.8 mmol) were introduced dropwise at this temperature. n-BuLi). The reaction medium was stirred at -78 ° C. for 30 minutes and then allowed to warm to room temperature (20 ° C.). The medium was then allowed to stir at room temperature for 2 hours until the evolution of gas had ceased. The medium was 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: 1H NMR (C6D6), (ppm): 6.77 (s, 2H, CH); 1.51 (s, 18H, t-Bu). 13 C NMR (C6 D6), 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.

  The carbene thus obtained was used for the preparation of poly (ethylene oxide) from ethylene oxide (referred to as EO) under the conditions set out below. In all the examples, the polymerization reactions of ethylene oxide (EO) were carried out under slight vacuum in Schlenk-type glass apparatus immersed in an oil bath preheated to 40 ° C. in a polymerization solvent. which is dimethylsulfoxide (DMSO). This solvent was previously dried over calcium hydride, distilled under vacuum and stored under an inert atmosphere of nitrogen in a graduated tube equipped with Teflon tap. The EO monomer was introduced into a three-necked flask containing sodium pieces where it was dried for three hours at -30 ° C. The monomer was then distilled off into a sealed graduated tube equipped with Teflon valves. Carbenes 1 and 2, respectively in the form of a sublimated solid and a distilled liquid, were stored under an inert atmosphere of argon and removed in a glove box before each polymerization. In some examples, an alcohol is used, in which case the alcohol is previously dried over magnesium sulphate (MgSO4); after filtration, it is distilled on molecular sieve. Samples of the various reagents were taken by weighing or using a precision syringe. Prior to each polymerization reaction, the Schlenk type glass apparatus was dried under vacuum at the flame of the torch and transferred to a glove box. The required amount of carbene was removed in a glove box and the Schlenk-type apparatus was removed and connected to a vacuum / nitrogen line.

  The appropriate amounts of DMSO solvent and then of monomer (EO) are introduced under vacuum using the graduated tubes described above. The reaction mixture was then placed in a preheated oil bath at 40 ° C. for 4 days. A few drops of degassed methanol were then added to stop the reaction (the water contained in the methanol being responsible at least in part for chain termination reactions leading to the cessation of the polymerization). Monomer conversion was calculated gravimetrically after precipitation of the polymer in ether. The average molar masses Mn (in g.mor1) are expressed in polyethylene oxide (PEO) equivalents. The molar mass distribution is evaluated by the polymolecularity index (lp) corresponding to the ratio of the mass-average molar mass and the number-average molar mass (Ip = Mw / Mn). The 1 H NMR spectra of the polymers were obtained with a 400 MHz (Bruker AC400) apparatus using DMSO-d6 as the solvent.

  EXAMPLE 1 Polymerisation of EO in the Presence of Carbene 1 45 mg (2.5) (10 -4 moles) of carbene 1 and 10 ml of DMSO were introduced into a Schlenk-type apparatus equipped with a magnetized bar according to the procedure described upper. After homogenization of the medium, 1 mL (0.02 mol) of EO was added. After polymerization, a polymer having a molecular weight Mn = 5000 g / mol and a polarity index of lp = 1.5 was recovered. In 1H NMR, characteristic peaks are observed at 4.6 ppm corresponding to the proton of the hydroxyl functions (CH 2 OH) and at 3.5 ppm corresponding to the OCH 2 CH 2 of the PEO repeating unit. EXAMPLE 2 Polymerisation of EO in the Presence of Carbene 1 45 mg (2.5 × 10 -4 moles) of carbene 1 and 20 ml of DMSO were introduced into a Schlenk-type apparatus equipped with a magnetized bar according to the procedure described above. After homogenization of the medium, 0.5 ml (0.01 mol) of EO was added After polymerization, a polymer with a molar mass Mn = 2000 g.mol-1 and a polydispersity index of lp = 1 was recovered. 1H NMR shows characteristic peaks: at 4.6 ppm corresponding to the proton of the hydroxyl functions (CH 2 OH) and at 3.5 ppm corresponding to the OCH 2 CH 2 of the repeating unit of PEO Example 3 EO polymerization in presence of carbene 2 80 mg (5.3x10-4 moles) of carbene 2 and 20 ml of DMSO were introduced into a Schlenk-type apparatus equipped with a magnetized bar according to the procedure described above. added 2 mL (0.04 mole) of EO.

  After polymerization, a polymer with a molar mass Mn = 3000 g.mor1 and a polydispersity index lp = 1.4 was recovered. In 1H NMR, characteristic peaks are observed at 4.6 ppm corresponding to the proton of the hydroxyl functions (CH 2 OH) and at 3.5 ppm corresponding to the OCH 2 CH 2 of the PEO repeating unit. EXAMPLE 4 Polymerization of EO in the Presence of Carbene 1 and Benzyl Alcohol 18 mg (10 -4 moles) of carbol, 0.1 ml (10.3 moles) of benzyl alcohol and 15 ml of DMSO were introduced into a machine. Schlenk type equipped with a magnetic bar according to the procedure described above. After homogenization of the medium, 2 mL (0.04 mol) of EO was added. After polymerization, a polymer having a molar mass M n = 1500 g / mol -1 and a polydispersity index ρ = 1.26 was recovered. In 1H NMR, characteristic peaks are observed at 4.6 ppm corresponding to the proton of the hydroxyl functions (CH 2 OH) and at 3.5 ppm corresponding to the OCH 2 CH 2 of the PEO repeating unit. EXAMPLE 5 Polymerization of EO in the Presence of Carbene 1 and Benzyl Alcohol 18mg (104 moles) of carbene 1, 0.1mL (10-3 moles) of benzyl alcohol and 15mL of DMSO were introduced into a machine. Schlenk type equipped with a magnetic bar according to the procedure described above. After homogenization of the medium, 4 mL (0.04 mol) of EO was added. After polymerization, a polymer with a molar mass Mn = 4000 g.mor1 and a polydispersity index lp = 1.13 was recovered. In 1 H NMR, characteristic peaks are observed at 4.6 ppm corresponding to the proton of the hydroxyl functions (CH 2 OH) and at 3.5 ppm corresponding to the OCH 2 CH 2 of the PEO repeating unit.

Claims (27)

  Use of a carbene as an opening agent of an epoxy ring.   2. Use according to claim 1, wherein the carbene is used as an initiator and / or anionic polymerization catalyst for the polymerization of oxirane monomers.   3. Process (P1) for preparing a polyoxirane, employing a carbene as an initiator and / or anionic polymerization catalyst, in which oxirane monomers are brought into contact with a carbene, in the absence of any alcohol susceptible to react with the carbene acting as an initiator and / or anionic polymerization catalyst.   4. Process (P2) for the preparation of a polyoxirane, employing a carbene as an initiator and / or anionic polymerization catalyst, comprising a first step (E1) in which oxirane monomers are brought into contact with a carbene, and a step (E2) where an alcohol reactive with the carbene is added to the polymerization medium, the step (E2) being carried out after or during step (E1).   5. The method of claim 4, wherein step (E1) is conducted prior to step (E2), preferably allowing the carbene and the monomers to react for 1 minute to 72 hours before adding the alcohol. 20   6. The method of claim 4, wherein the steps (E1) and (E2) of the process (P2) are conducted simultaneously, the process then comprising a step (E) in which the oxirane monomers, the carbene and the alcohol.   7. Process (P3) for preparing a polyoxirane, employing a carbene as initiator and / or anionic polymerization catalyst, wherein oxirane monomers are contacted with a carbene and an alcohol, within a medium comprising a solvent selected from DMSO, THF, and / or dioxane, preferably in a medium comprising DMSO.   8. Process (P4) for the preparation of a polyoxirane, employing a carbene as an initiator and / or anionic polymerization catalyst, in which oxirane monomers are brought into contact with a carbene and an alcohol, in the absence of any solvent.   9. Method according to one of claims 3 to 8, wherein the carbene used has the general formula (I) below: X (Rx) n 1: C \ Y (RY) ny-1 (1) 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 Rx and RY 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 preferably being: an alkyl group, alkenyl or alkynyl, optionally substituted linear or branched, 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 with 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 Rx carried by the heteroatom X and one of the groups RY borne by the heteroatom Y may optionally be bonded together to form a heterocycle with X and Y heteroatoms and divalent carbon bearing two non-binding electrons.   The process of claim 9 wherein X denotes a nitrogen atom.   The process according to claim 10, wherein the carbon has one of the following general formulas (1-1) or (1-1 '): R1 R1 / N, A, R11 / N-, A • Wherein Y is a heteroatom selected from N, S, P, Si, wherein Y is a heteroatom selected from N, S, P, Si and O, Y being preferably a nitrogen atom; • ny and RY are as defined in claim 3; and R1 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 a 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, wherein the aryl part is optionally substituted, for example by an alkyl or alkoxy group; A denotes a nitrogen atom or a CRlla group; B denotes a nitrogen atom or a CR1a group; R and RE, and; where appropriate, Rila and R 1, 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: 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 with 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 10, wherein the carbene corresponds to the general formula (1-1a) or (1-1a ') below: ## STR2 ## Wherein R 1, R 1, R 1, R 1, R 1, and B are as defined in claim 5; and R 1v 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.   The process of claim 12, wherein the carbene has the general formula (1-1a). 20   14. Process according to one of claims 3 to 8, wherein the carbene is a compound chosen from the following compounds: phosphino (amino) carbenes of formula (II): (I-1 a ') 10 15RN • bisphosphinocarbenes of Formula (III): ## STR2 ## carbodiphosphoranes corresponding to one of the following mesomeric formulas (IV) or (IV '): ## STR1 ## Wherein each of the groups R, RP, RP1, RP2, RP3, RP4, RN, and Rpl 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 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 at least one alkyl or alkoxy group, it being understood that, in each of the formulas (II), (III), (IV) and (IV '), the R group and the RP group may optionally be bonded together to form a heterocycle with the two hetero atoms to which they are bonded and the divalent carbon, the heterocycle thus formed having, if appropriate, preferably from 5 to 7 members.   15. Method according to one of claims 3 to 8, wherein the carbene is an alkylaminocyclic carbene CAAC corresponding to formula (V) below: (L) Ra (V) where: - A represents a ring comprising 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 atom of oxygen, nitrogen or silicon, the available valencies may be substituted, - Ra represents an alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl group, - Rb and Rb, identical or different, represent an alkyl, alkenyl or alkynyl group; , cycloalkyl, aryl, aralkyl, alkoxy, alkenyloxy, alkynyloxy, aryloxy, alkoxycarbonyl, or Rb and R, are bonded together to form a spirocycle, the bet of the ring bearing the two groups Rb and Rb bonded together comprising from 3 to 12 atoms.   16. A process according to any one of claims 3 to 15, wherein the carbene used is a carbene which is preformed in a step prior to the polymerization step in which it is carried out.   17. Process according to any one of claims 3 to 15, in which the carbene used is formed in situ, from at least one precursor (PC) of said carbene, said precursor being a carbene in dimerized form, which is cleaved. in two carbenes in situ by thermal activation, this dimerized carbene advantageously corresponding to the following formula (PCD): (Rx) nx-1X (RY) ny-tY (PCD) where X, Y, nx, ny, Rx and RY are as defined in claim 3.   18. The process as claimed in claim 3, in which the carbene is an encapsulated carbene physically mixed with a polymer serving as a protective matrix.   19. Process according to any one of Claims 3 to 18, in which the oxirane monomers employed are chosen from compounds of the following formula (VI): ## STR3 ## in which each of the groups R 1, R 2 and R 3 and R4 represents, independently of the other groups, a hydrogen atom or a free alkyl group of 1 to 6 atoms.   20. The method of claim 19, wherein the oxirane monomers employed are selected from ethylene oxide, propylene oxide and mixtures thereof.   21. Process according to one of claims 3 to 20, in which the carbene and the oxirane monomers are employed with a molar ratio (carbene / epoxy) of between 0.000001 and 0.1.   22. A polyoxirane-based polymer composition obtainable according to the method of one of claims 3 to 21.   23. The polymer composition of claim 22 which is free of metal cations.   24. Use of a composition according to claim 22 or 23 as surfactants, dispersing agents, rheological properties modifiers of liquid compositions or gels, and / or encapsulation system (and generally of issue) of assets.   25. Use of a composition according to claim 22 or 23 as polymerizable macromonomers.   26. Use of a composition according to claim 22 or 23 as living polymers for the preparation of block polymers.   27. Use of a composition according to claim 23, as a system for encapsulation and or delivery of active agents, reactive surfactants or for the constitution of films or coatings in devices for biomedical or microelectronic use. .