A method of removing dithiocarbonyl and dithiophosphoryl terminal groups from a polymer prepared by controlled radical polymerization by contacting it with a source of free radicals and an organic compound with a labile hydrogen atom

The present invention relates to a process for the radical reduction of dithiocarbonylated or dithiophosphorylated functions carried by a polymer resulting from a living radical polymerization, giving in particular access to polymers of controlled architecture, and in particular to block copolymers, not exhibiting such dithiocarbonylated or dithiophosphorylated functions.

In the present description, in the absence of any indication to the contrary, the term polymer will be used to denote, in the broad sense, both homopolymers and copolymers. The polymers can correspond to polymers (homopolymers) or copolymers (statistics, diblocks, triblocks, grafted or star-shaped, or hyperbranched)

More specifically, within the meaning of the invention, by polymer with controlled architecture is meant a polymer based on two or more monomers having a controlled arrangement of these different monomer units constituting it.

The term “block polymer” (or block copolymer) is understood to mean, according to the invention, a copolymer comprising at least two successive sequences (blocks) of monomer units of different chemical constitutions. Each of the blocks present can consist of a homopolymer or of a copolymer obtained from a mixture of ethylenically unsaturated monomers. In the second case, the block can in particular be a random copolymer. The block copolymers within the meaning of the invention can thus comprise two blocks each consisting of random copolymers. In this case, the ethylenically unsaturated monomers are such that the blocks obtained are of different natures. By blocks of different natures is meant either blocks made up of monomers of different types, or blocks made up of monomers of the same type but in different amounts.

Polymers with controlled architecture, such as block polymers, are usually prepared by ionic polymerization. However, this type of polymerization has the drawback of only allowing the polymerization of certain types of nonpolar monomers, such as styrene and butadiene. In addition, ionic polymerization generally requires severe implementation constraints, and in particular a reaction medium which is particularly free of impurities and processing temperatures often below ambient, so as to minimize the appearance of side reactions. .

Such constraints do not exist in the case of radical polymerization, which also has the advantage of being able to be implemented in the context of the polymerization of other types of monomers. As a result, we quickly became interested in radical polymerization in the context of the preparation of polymers with controlled architecture of the type of block copolymers.

However, during a conventional radical polymerization reaction, the growing macroradicals generally have non-selective reactivity and the chains generally terminate irreversibly by coupling or disproportionation. Consequently, in radical polymerization, it is generally very difficult to control the structure of the chains produced and it is in particular extremely difficult to produce polymers functionalized at the end of the chain, which limits, in the most general case, the possibilities of 'obtain block copolymers.

In order to overcome this type of difficulty, specific radical polymerization processes have recently been developed, in which the growing polymer chains as well as the chains produced in fine are functionalized by end groups capable of being reactivated in the form of free radicals. thanks to reactions of reversible terminations or transfers.

This type of specific radical polymerization is generally designated by the term of controlled or living radical polymerization. These names come from the fact that the presence of the reactivatable end groups described above induces the existence of equilibria between functionalized species (called dormant species) and active species (free radicals), which makes it possible both to control the growth of polymer chains (obtaining tight mass distributions and controlling the average molecular mass, in particular by adjusting the monomer / active chain precursor molar ratio) and to obtain functionalized polymers, called living polymers, that is to say capable of being used as reactivatable species in subsequent radical polymerization reactions , which proves to be particularly advantageous in the context of the preparation of block copolymers. For more details on this subject, reference may be made in particular to K. Matyjaszewski, Ed. Controlled Radical Polymerization, ACS Symposium Series 685, American Chemical Society Washington, DC, 1998 and ACS Symposium Series 768, 2001.

Living (or controlled) radical polymerization ideally presents the following distinctive aspects:

1. a fixed number of chains throughout the duration of the reaction;

2. a very tight growth rate around an average value, for all the growing polymer chains, and advantageously an identical growth rate for all the chains, which results in:

an increase in molecular masses with conversion, advantageously linearly; and

- a tight weight distribution;

3. a possibility of controlling the average molecular mass by the monomer / chain precursor molar ratio;

In this context, we have in particular developed multiple controlled polymerization processes (living), called by reversible chain transfer, implementing addition-fragmentation mechanisms. This particular polymer synthesis is carried out by carrying out a radical polymerization in the presence of reversible transfer agents and of a source of free radicals, generally thermally initiated, which leads to the production of functionalized polymers. This type of polymerization is one of the most suitable technologies for synthesizing block copolymers by the radical route.

For more information concerning this type of reversible transfer polymerization by addition-fragmentation, reference may be made, for example, to patent applications WO 98/01478 or WO 99/35178, which describe the use of reversible transfer agents of the type. RS (C = S) R 'type dithioesters for the synthesis of copolymers with controlled architecture. The use of dithiocarbamate transfer agents of RS (C = S) NR'R type to carry out the control of radical polymerizations has also been described in patent applications WO 99/35177 or WO 99/31144. Still with regard to this type of reversible transfer polymerization, a process for the preparation by radical polymerization under thermal activation of silicone / organic hybrid copolymers has also been described in French patent application FR 00/09722 filed by the Applicant on July 25. 2000. These hybrid copolymers consist of a silicone backbone and carry organic groups, they are prepared from a silicone precursor, at least one organic ethylenically unsaturated monomer and a radical polymerization initiator. In the context of living radical polymerization by thermal initiation, the xanthates of general formula RSC (= S) OR ', described for example in patent applications WO 98/58974, WO 00/75207 and WO 01/042312 are agents of reversible transfer particularly advantageous, which make it possible to control the radical polymerization of a good number of monomers such as styrenic, acrylic, acrylamides, vinyl esters and diene monomers.

Whatever the exact mode of carrying out a living radical polymerization reaction, the polymer chains obtained at the end of such a reaction are most often functionalized at the end of the chain. This functionalization generally gives them an effective living character, that is to say that they can play the role of reactivatable species in subsequent polymerization reactions, which is particularly advantageous for carrying out the synthesis of polymers with controlled architecture, and in particular block copolymers. However, as a general rule, the reactivatable functions present at the end of the chains on the polymers obtained at the end of a living radical polymerization are also fragile, and they are, for example, often hydrolyzable in a basic medium. These hydrolysis reactions are likely to release by-products of low molecular weight, malodorous and / or toxic for the environment and humans, such as for example carbonyl sulfide in the case of polymers having reactivatable functions. xanthate type.

One of the aims of the present invention is to provide a process making it possible to remove the reactive functions carried by certain polymers resulting from a living polymerization reaction.

The object of the invention is also to provide a process for preparing polymers having the advantages presented by polymers resulting from a living radical polymerization reaction, namely, in particular, a number-average molecular mass M_not well controlled and a tight mass distribution, but not having reactivatable functions at the end of the chains liable to lead to the aforementioned drawbacks.

These aims, and others which will become apparent from the description, 'are achieved by the present invention, which relates to a process for preparing a polymer, which comprises a step consisting in bringing into contact:

(A) at least one living organic polymer having at the end of the chain at least one reactivatable dithiocarbonyl or dithiophosphoryl function;

(B) at least one source of free radicals; and (C) at least one organic compound carrying a labile hydrogen atom.

This step makes it possible more particularly to proceed with a substitution of the dithiocarbonyl or dithiophosphoryl function present on said living organic polymer with a hydrogen atom.

By living organic polymer is meant, within the meaning of the present description, any polymer within the meaning of the invention, at least partially based on organic monomer units, and capable of being obtained according to a living radical polymerization process.

The living organic polymers which are used in the process of the invention can advantageously be copolymers with controlled architecture, and they can thus be, for example, block copolymers. Whatever their exact structure, these living organic polymers specifically exhibit, at the end of the chain, at least one reactivatable dithiocarbonyl or dithiophosphoryl function, that is to say a function of the -S (C = S) -R or -S type respectively. (P = S) -R, where R denotes any organic group.

Thus, the reactivatable dithiocarbonyl or dithiophosphorylated function present at the end of the chain on the polymer (A) used in the process of the invention can advantageously be an -S (C = S) -R or -S (P = S) function. ) -R, where R denotes;

(i) an alkyl, haloalkyl, perfluoroalkyl, alkenyl or alkynyl, acyl, aryl, arylalkyl, arylalkenyl, arylalkynyl group, or else a carbon ring or a heterocycle, or else a polymer chain;

(ii) an -OR radical^at, where R^at denotes a group chosen from:

an alkyl, haloalkyl, perfluoroalkyl, alkenyl, alkynyl, acyl, aryl, arylalkyl, arylalkenyl, arylalkynyl group, or else a carbon ring or a heterocycle, or else a polymer chain;

- a -CR group^bR^vsPO (OR^d)(GOLD^e), in which ;

- R^b and R^vs each represent, independently of one another, a hydrogen atom, a halogen atom, a perfluoroalkyl group, a carbon ring or a heterocycle, or alternatively a -NO2, -NCO, -CN group, or a group chosen from groups of the -R type^f, -SO3R^f, -GOLD^f, -SR^f, -NR^fR⁹, -OOCR^f, -CONR^fR⁹, or -SO₃R^f, in which R^f and R⁹ each denote, independently, an alkyl, alkenyl, alkynyl, aryl, aryl, arylalkyl, arylalkenyl, or arylalkynyl group;

or R^b and R^vs together with the carbon to which they are attached form a C = O or C = S group, or else a hydrocarbon ring or a heterocycle; and

- R^d and R^e each represent, independently of one another, a radical corresponding to one of the definitions given above for the group R^f ;

or R^d and R® together form a hydrocarbon chain comprising from 2 to 4 carbon atoms, optionally interrupted by an -O-, -S- or NR group^h-, where R^h meets one of the definitions given above for the group R^f;

(iii) an -NR'R group, where:

- R 'and R^j represent, independently of one another, a radical chosen from an alkyl, haloalkyl, alkenyl, alkynyl, acyl, ester, aryl, arylalkyl, arylalkenyl, arylalkynyl group, or a carbon ring; or

- R and R^J together form a hydrocarbon chain comprising from 2 to 4 carbon atoms, optionally interrupted by an -O-, -S-, or -NR group^H-, where R^H meets one of the definitions given above for the group R^f, said hydrocarbon chain advantageously forming a 5-membered ring with the nitrogen to which R^! and R^j, the radicals R¹ and R * preferably inducing an electron-withdrawing effect or a delocalization effect with respect to the electron density of the nitrogen atom to which they are linked.

Throughout the present description, the term “alkyl group” is intended to cover a saturated, linear or branched hydrocarbon radical, which may optionally include one or more saturated aliphatic ring (s). For the purposes of the invention, the alkyl groups may have up to 25 carbon atoms, and they preferably contain from 1 to 12 carbon atoms, and advantageously from 1 to 6 carbon atoms.

In particular, an alkyl group can also denote, within the meaning of the invention, a cycloalkyl group, that is to say a saturated cyclic hydrocarbon radical, preferably having from 3 to 10 carbon atoms.

For its part, an alkoxy group denotes, within the meaning of the invention, an —OAlk radical, where Alk denotes an alkyl group as defined above.

By haloalkyl group within the meaning of the invention, is meant an alkyl radical as defined above and substituted by at least one halogen atom, where the term halogen atom denotes here, as throughout the description, a fluorine, chlorine, bromine or iodine atom, preferably a fluorine or chlorine atom, and advantageously a fluorine atom. The haloalkyl groups of the invention can thus be, for example, perfluoroalkyl groups, that is to say, within the meaning of the invention, groups corresponding to the formula -CH₂VS_notF_{2n + 1}, where n represents an integer ranging from 1 to 20.

Moreover, an alkenyl group, in the sense in which it is used in the present description, denotes an unsaturated, linear or branched hydrocarbon radical, having at least one C = C double bond. The alkenyl groups of the invention can have up to 25 carbon atoms and preferably comprise from 2 to 12 carbon atoms, and advantageously from 2 to 6 carbon atoms.

Likewise, the term “alkynyl group” is understood to mean an unsaturated, linear or branched hydrocarbon-based radical having at least one C = C triple bond. The alkynyl groups of the invention generally have from 2 to 25 carbon atoms, and they preferably comprise from 2 to 15 carbon atoms, and advantageously from 2 to 6 carbon atoms.

For its part, an acyl group denotes, within the meaning of the invention, a group of formula -C (= O) -B, where B denotes a linear or branched, saturated or unsaturated hydrocarbon chain, and comprising from 1 to 25 carbon atoms. carbon, and which may in particular be an alkyl, alkenyl or alkynyl group as defined above.

For the purposes of the invention, the term “ester group” is understood to mean a -C (= O) -OB group, where B denotes a linear or branched, saturated or unsaturated hydrocarbon chain, and comprising from 1 to 25 carbon atoms, and which can in particular be an alkyl, alkenyl or alkynyl group as defined above.

For the purposes of the invention, a radical of carbon ring type denotes a saturated, unsaturated or aromatic cyclic group, in particular of cycloalkyl, cycloalkenyl or cycloalkynyl type, optionally substituted, and comprising from 3 to 20 carbon atoms. A heterocycle type radical denotes such a carbon ring interrupted by at least one heteroatom chosen for example from N, O or S.

For its part, an aryl group denotes, within the meaning of the invention, a mono- or polycyclic aromatic group generally having from 5 to 20 carbon atoms, and preferably from 6 to 10 carbon atoms. Thus, it may for example be a phenyl group, or else 1- or 2-naphthyl. According to a particular variant, an aryl group within the meaning of the invention can integrate one or more heteroatoms such as sulfur, oxygen or nitrogen. In this particular case, the aryl group within the meaning of the invention denotes a mono- or polycyclic heteroaromatic group.

The arylalkyl, aralkenyl and aralkynyl groups within the meaning of the invention are respectively alkyl, alkenyl and alkynyl chains substituted with an aryl group as defined above. In other words, the arylalkyl, aralkenyl and aralkynyl groups within the meaning of the invention are respectively groups of Ar-Ra- type, in which Ar- represents an aryl group and in which the groups of -Ra- type respectively represent an alkylene, alkenylene, or alkynylene chain.

The various radicals can optionally be interrupted by one or more heteroatoms chosen in particular from O, S, and N, Si, or by groups - (C = O) -, - (C = S) -, -SO₂-, -SO-, or secondary or tertiary amines, and they can be substituted by any type of group which is not capable of interfering with the polymerization reaction or of leading to side reactions between the compounds present, and in particular by one or several identical or different groups chosen from a halogen atom, a silyl group, an -OH, alkoxy, -SH, thioalkoxy, -NH group₂, mono- or di-alkylamino, -CN, -COOH, ester, amine, or perfluoroalkyl, said substituents possibly possibly being interrupted by heteroatoms. It is within the competence of those skilled in the art to choose the nature of the various groups and substituents present in the compounds used in order to avoid any undesirable side reaction.

Preferably, the living organic polymer (A) used in the process of the invention is a polymer resulting from a process implementing a living radical polymerization using reversible transfer agent by addition-fragmentation, of the dithioester type, xanthate, dithiocarbamate, thioether-thione, trithiocarbonate or dithiophosphoroester, and which has at least one end of its chain a reactivatable dithiocarbonyl or dithiophosphoryl part originating from these reversible transfer agents.

The living organic polymers (A) used in the process of the invention can be, for example, polymers resulting from a controlled radical polymerization process carried out by contacting one or more ethylenically unsaturated® monomer, at least a source of free radicals and at least one reversible transfer agent of the aforementioned type. More specifically, the living organic polymers used in the process of the invention can be block polymers resulting from a copolymerization process comprising N successive radical polymerization steps (N being greater than or equal to 2), the first of these stages being a controlled radical polymerization carried out by contacting one or more ethylenically unsaturated® monomer®, of at least one source of free radicals and of at least one reversible transfer agent of the aforementioned type, and the following (N-1) stages being controlled radical polymerizations carried out by contacting one or more ethylenically® monomer unsaturated® different from those of the previous step, of at least one source of free radicals and of the living polymer composition resulting from the previous step.

Thus, the living organic polymers (A) used in the process of the invention can advantageously be polymers resulting from a copolymerization process chosen, for example, from the processes described in patent applications WO 98/01478 and WO 99/35178. , which use reversible transfer agents of dithioesters or dithiocarbamates type, or among the processes of patent applications WO 98/58974, WO 00/75207 and WO 01/042312 using reversible transfer agents of xanthate type. They may also be polymers obtained according to one of the processes described in patent applications WO 99/35177 or WO 99/31144, which use reversible transfer agents of the dithiocarbamate type, or else according to the process described in patent application FR 2794464, which uses reversible transfer agents of the thioether-thione type.

According to a particular embodiment of the invention, the living organic polymers (A) used in the process of the invention can also be obtained from the process using reversible transfer agents of the dithiophosphoroester type of the type of that which has been used. described in French patent application No. 00/09952 filed on July 28, 2000 by the

Applicant, that is to say according to a process comprising at least one step of radical polymerization of a composition containing:

- at least one ethylenically unsaturated monomer

- a source of free radicals, and

- at least one compound of dithiophosphoroester type of general formula (F):

S

II

R₂-PS-Ri ^R3 (F) in which:

- R! represented :

•. an alkyl, acyl, aryl, aralkyl, alkene or alkyne group, preferably an alkyl group, advantageously substituted. a carbon ring or a heterocycle, saturated or not, aromatic and optionally substituted, •. a polymer chain, for example resulting from a radical or ionic polymerization or from a polycondensation,

- R₂ and R₃, identical or different, represent:

•. a hydrogen atom, •. -SR₄, where R₄ has one of the meanings given above for R_v •. an optionally substituted alkyl, acyl, aryl, aralkyl or alkyne radical, •. a carbon-based ring or a heterocycle, saturated or not, aromatic, optionally substituted;

or R₂ and R₃ together represent the atoms necessary to form a carbon ring or a heterocycle, saturated or not, aromatic, optionally substituted; and p is between 2 and 10, the groups R_not R₂ and R₃, which may be substituted, preferably by optionally substituted phenyl groups, optionally substituted aromatic groups, saturated or unsaturated carbon rings, saturated or unsaturated heterocycles, or alkoxycarbonyl or aryloxycarbonyl (-COOR), carboxy (COOH), acyloxy groups (-O2CR), carbamoyl (-CONR2), cyano (-CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxy (-OH), amino (-NR2), halogen, perfluoroalkyl C_notF_{2n + 1}, allyl, epoxy, alkoxy (-OR), S-alkyl, S-aryl, groups having a hydrophilic or ionic character such as alkali metal salts of carboxylic acids, alkali metal salts of sulphonic acid, poly (oxide alkylene) (of the poly (ethylene oxide) or poly (propylene oxide) type), the cationic substituents (quaternary ammonium salts), R representing an alkyl or aryl group, or a polymer chain.

The optionally substituted alkyl, acyl, aryl, aralkyl or alkyne groups present in the dithiophosphoroesters of formula (F) generally have from 1 to 20, advantageously from 1 to 12, and more preferably from 1 to 9 carbon atoms. They can be linear or branched. They can also be substituted by oxygen atoms, in particular in the form of esters, sulfur or nitrogen atoms.

Among the alkyl radicals which can be envisaged, mention may in particular be made of the methyl, ethyl, propyl, butyl, pentyl, isopropyl, tert-butyl, pentyl, hexyl, octyl, decyl or dodecyl radical.

Among the aryl radicals, mention may in particular be made of the phenyl radical, optionally substituted in particular by a nitro or hydroxyl function.

Among the aralkyl radicals, mention may in particular be made of the benzyl or phenethyl radical, optionally substituted, in particular by a nitro or hydroxyl function.

According to this specific embodiment, the dithiophosphoroester of formula (F) can advantageously be a compound in which the group

Rt is chosen from the following groups:

- CH₂VS₆H₅

- CH (CH3) (CO2Et)

- CH (CH3) (C6H₅)

- CH (CO2Et) 2

- C (CH3) (CO2Et) (S-C6H5)

- C (CH3) 2 (C₆H5)

- C (CH3) 2CN or

HOI II - c— C— Ph I

VY '- where the symbol Et represents an ethyl group and the symbol Ph represents a phenyl group.

Whatever their exact structure, the dithiophosphoroesters of formula (F) are easily accessible. They can thus in particular be obtained by reaction between P₄S₁₀, K₂CO₃ and a halogenated derivative according to a process described for example by Nizamov et al. in Phosphorous Sulfur and Silicon, vol. 132, 85100 (1998). Another route of access to the compounds of formula (F) consists in reacting an alkali metal salt of a dithiophosphonic acid with a halogenated derivative. On this subject, reference may be made to Mastryukova et al (Bull. Acad. Sci.

USSR. Div. Chem. Sci (Engl Transi), Vol. 27, 1917 (1978)).

According to another conceivable embodiment, the living organic polymers (A) used in the process of the invention can also be hybrid silicone / organic copolymers obtained by a preparation process by thermally activated radical polymerization of the type of those described in French patent application FR 00/09722 filed by the applicant on July 25, 2000, namely hybrid silicone / organic copolymers comprising (r) x (u) ySiO [4_ (_{x +}y)] / 2 in which:

- x is equal to 0, 1, 2 or 3, y is equal to 0, 1, 2 or 3 with 2 <(x + y) <3 and y is different from 0 for at least one of the units of the hybrid copolymer,

- the x groups (r), identical or different, each represent:

• a linear or branched alkyl radical containing 1 to 8 carbon atoms, optionally substituted by at least one halogen, preferably fluorine, the alkyl radicals preferably being methyl, ethyl, propyl, octyl and 3,3,3-trifiuoropropyl, • a cycloalkyl radical containing between 5 and 8 cyclic carbon atoms, optionally substituted,.

• an aryl radical containing between 6 and 12 carbon atoms which can be substituted, preferably phenyl or dichlorophenyl, • an aralkyl part having an alkyl part containing between 5 and 14 carbon atoms and an aryl part containing between 6 and 12 carbon atoms , optionally substituted on the aryl part by halogens, aikyls and / or alkoxyls containing 1 to 3 carbon atoms,

- the y groups (u), identical or different, each represent a group:

C — sjc— (CV = CV ')_at—CH₂j-Cr²r³—C — w — Sp— (U)_x—Z^Z [j (.

or :

- z, which may differ from one group (u) to another, represent a carbon, sulfur, oxygen, phosphorus, nitrogen and / or a free valence atom, and preferably a sulfur atom or oxygen;

- x '= 1,2,3 or 4 depending on the valence of z,

- each of the H groups, identical or different, represents:

- an optionally substituted alkyl, acyl, aryl, alkene or alkyne group, a carbon ring, saturated or not, optionally substituted and / or aromatic, and / or a heterocycle, saturated or not, optionally substituted, these groups and (hetero) rings which can be substituted by:

substituted phenyl groups, substituted aromatic groups, or groups: alkoxycarbonyl, aryloxycarbonyl (-COOr), carboxy (-COOH), acyloxy (-O2Cr⁵), carbamoyl (-CON (r⁵) 2), cyano (-CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxy (5 5

OH), amino (-N (r)₂), halogen, allyl, epoxy, alkoxy (-Or), S-alkyl,

S-aryl, groups having a hydrophilic or ionic character such as alkali salts of carboxylic acids, alkali salts of sulfonic acid, polyalkylene oxide chains (POE, POP), cationic substituents (ammonium salts quaternary), the 5 groups r, identical or different, representing an alkyl or aryl group, and / or a polymer chain,

- a group of formula -C_notF_{(2n + 1)} with n between 1 and 20,

- a group of formula:

r⁶ Gold⁸

<img file="FR2829138A1_D0001.tif" />

in which :

- Γθ, F, identical or not, are chosen from

- a halogen group, -NO2, -SC&gt; 3r¹⁰, -NCO, -CN, -Or¹⁰, -Sr¹⁰, N (r¹⁰) 2, -COOr¹⁰, -O2Cr¹⁰, -CON (r¹⁰) 2, -NCO (r¹⁰) 2 and -C_notF_{(2n + 1)} with n between 1 and 20, preferably equal to 1 and r¹⁰ representing a hydrogen atom or an alkyl, alkenyl, alkynyl, cycloacenyl, cycloalkynyl, alkaryl, aralkyl, heteroaryl or aryl radical optionally condensed to an aromatic or non-aromatic heterocycle; these radicals possibly being substituted by one or more identical or different groups, chosen from halogen atoms, = 0, = S, -OH, alkoxy, SH, thioalkoxy, NH2, mono or dialkylamino, CN, COOH, ester, amide, C_notF_{(2n + 1)} and / or optionally interrupted by one or more atoms chosen from O, S, N, P;

- a heterocyclic group optionally substituted with one or more groups as defined above;

or r⁶ and r⁷ together with the carbon atom to which they are attached, form a C = O, C = S group, a hydrocarbon ring or a heterocycle;

- and r⁸ and r⁹, identical or different, represent a group as defined above for r¹⁰; or together form a C2-C4 hydrocarbon chain, optionally interrupted by a heteroatom chosen from O, S and N;

- V and V, identical or different, represent: H, an alkyl group or a halogen,

- X and X ', identical or different, represent H, a halogen or a group R⁴, GOLD⁴, O2COR⁴, NHCOH, OH, NH2, NHR⁴, N (R⁴) 2, (R⁴) 2N⁺O-, NHCOR⁴, CO2H, CO2R⁴, CN, CONH2, CONHR⁴ or CONR⁴2, where R⁴ is chosen from alkyl, aryl, aralkyl, alkaryl, alkene or organosilyl groups, optionally perfluorinated and optionally substituted by one or more carboxyl, epoxy, hydroxyl, alkoxy, amino, halogen or sulfonic groups,

- r² and r³, identical or different, represent:

- a hydrogen atom

- an optionally substituted alkyl, acyl, aryl, alkene or alkyne group; a carbon-based ring, saturated or not, optionally substituted and / or aromatic; a heterocycle, saturated or not, optionally substituted, an alkoxycarbonyl, aryloxycarbonyl (-COOR), 5-carboxy (-COOH), acyloxy (-O) group₂CR), carbamoyl (-CONR ₂), cyano (CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, 5 guanidimo, hydroxy (-OH), amino (-NR ₂), halogen, allyl, epoxy, alkoxy (-OR), S-alkyl, S-aryl, groups having a hydrophilic or ionic character such as alkali salts of carboxylic acids, alkali salts of sulfonic acid, chains polyalkylene oxide), the cationic substituents (quaternary ammonium salts), R, identical or different, representing an alkyl or aryl group, and / or a polymer chain, these radicals and (hetero) rings possibly being substituted by: substituted phenyl groups, substituted aromatic groups, or groups: alkoxycarbonyl,

5 aryloxycarbonyl (-COOR), carboxy (-COOH), acyloxy (-O₂CR), carbamoyl (-CONR ₂), cyano (-CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxy (-OH), amino (2829138

5

NR 2), halogen, allyl, epoxy, alkoxy (-OR), S-alkyl, S-aryl, groups having a hydrophilic or ionic character such as alkali metal salts of carboxylic acids, alkali metal salts of sulphonic acid, alkylene polyoxide chains (POE, POP), 5 cationic substituents (quaternary ammonium salts), R, identical or different, representing an alkyl or aryl group, and / or a polymer chain,

- w, which may differ from one group (u) to another, represents a divalent radical chosen from -O-, -NR © -NH-, or -S-,

- Sp, which may differ from one group (u) to another, represents a divalent organic radical of formula - (CH₂)_X...- in which x 'is between 1 and 20, this radical possibly being substituted and / or containing at least one heteroatom,

- a = 0 or 1,

- m&gt; 1, and when m&gt; 1, the repeating unit units of index m are identical or different.

These particular polymers, which are advantageously in the form of a silicone / organic hybrid copolymer consisting of a linear silicone backbone comprising from 1 to 300 (preferably 1 to 200) units (r) x (u) ySiO [4_ (_x+ y)] / 2 ^and comprising in total from 1 to 50 u radicals, and preferably from 1 to 10 u radicals, can be obtained according to a process which consists in reacting a mixture comprising

- a radical polymerization initiator.

- at least one ethylenically unsaturated monomer of formula

CXX '(= CV - CV')_at = CH₂, and

- a precursor silicone compound comprising units, identical or different, of formula rxU'ySiO ^ x + y)] ^ in which

- r, x and y have the definitions given previously, and

- the y radicals u ', identical or different, are monovalent radicals of formula:

so 1

II n II

C — S — CW — C — w — Sp— (r¹)_x—Z^Z where r¹, x ', z, r², r³, w and Sp have the aforementioned definitions, the radicals u 'being and are preferably chosen from the following radicals:

<img file="FR2829138A1_D0002.tif" />

where R¹ represents a group corresponding to the definition of group r¹ defined above.

The precursor silicone compound used in the process for preparing hybrid copolymers can be obtained by reaction;

(i) a silicone comprising units of formula:

R_XUySiO [4- (_{X +}y)] / 2 where the monovalent radical U is according to the following formula:

L-CR2'R3- (C = O) -W-Sp-— in which:

- W and Sp have definitions identical to those given previously,

- L is an electrofuge group, for example: Br, CL, L, OTs;

OMs-, (C₆H₆) - (C = O) -O; (CH₃) - (C = O) -O-, (CF₃) - (C = O) -O-.

(ii) with a compound chosen from those of the following general formulas:

, M ²⁺ (X) c-sC-S-, (R¹) x '(IX)

CS (R¹) x '(M')_m (XI) in which:

- M '⁺ represents K⁺, N / A⁺, NR /, or PR / R being of similar definition to that given for R of formula (I),

- M²⁺ represents an alkaline earth metal such as Ca²⁺, Ba²⁺and Sr²⁴/

- M 'represents Ζη, Cd, m is equal to 1 or 2, n is equal to 1, 2, 3 or 4 and preferably m is equal to 1 and n is equal to 2.

This silicone of formula can be obtained in particular from (i) a silicone comprising units of formula: R_xU'ySiO [4- (x + y)] / 2 where the monovalent radical U 'is of the formula: -Sp-WH and (ii) of a compound of the formula:

ol

<img file="FR2829138A1_D0003.tif" />

H

According to yet another conceivable embodiment, the living organic polymers (A) used in the process of the invention can also be so-called star-shaped polymers such as those obtained by a process of the type of that described in the application. of French Patent No. 01 05144 filed on April 13, 2001 by the Applicant, namely a process which comprises a step of radical polymerization of a composition containing:

- a source of free radicals, and

- at least one polymer composition resulting from a living radical polymerization process and having at the end of the chain at least one reactivatable dithiocarbonyl or dithiophosphoryl function, and

- at least one crosslinking monomer, said crosslinking monomer being chosen from organic compounds known to be reactive by the radical route, and comprising between two and 10 ethylenic unsaturations, and preferably 2, this crosslinking monomer being able to be advantageously chosen from acrylic derivatives, methacrylics, acrylamido, methacrylamido, vinyl ester, vinyl ether, diene, styrene, alpha-methyl styrene and allylic.

Particularly preferably, the living organic polymers (A) used in the process of the invention are polymers resulting from a polymerization or copolymerization process comprising at least one step of controlled radical polymerization using a reversible transfer agent. by addition-fragmentation chosen from a xanthate, a dithiocarbamate or a dithioester. Advantageously, they are living polymers resulting from the use of transfer agents of xanthate type.

By source of free radicals within the meaning of the invention is meant, broadly, any compound or mixture of compounds capable of leading to the formation of radical species under suitable operating conditions (thermal activation, irradiation, etc. .), this compound or mixture of compounds being used under said required conditions. Preferably, the source of free radicals (B) used in the process of the present invention is a compound or a mixture of compounds leading to the formation of free radicals under the effect of a heat treatment. Thus, it may for example be a radical polymerization initiator of the usual type. The source of free radicals (B) used in the process of the invention can thus in particular be chosen from

- hydrogen peroxides, such as tertiary butyl hydroperoxide, cumene hydroperoxide, t-butyl-peroxyacetate, tbutylperoxybenzoate, t-butylperoxyoctoate, t-butylperoxyneodecanoate, tbutylperoxyisobutaroyl peroxide, t-amylperoxypivalte, tbutylperoxypivalate, dicumyl peroxide, benzoyl peroxide, potassium persulfate, or even ammonium persulfate;

- azo compounds such as: 2-2'-azobis (isobutyronitrile), 2,2'-azobis (2-butanenitrile), 4,4'-azobis (4-pentanoic acid), 1,1'azobis (cyclohexane-carbonitrile), 2- (t-butylazo) -2-cyanopropane, 2,2'azobis [2-methyl-N- (1,1) -bis (hydroxymethyl) -2-hydroxyethyl] propionamide, 2,2'azobis ( 2-methyl-N-hydroxyethyl] -propionamide, 2,2'-azobis dichloride (N, N'2829138 dimethyleneisobutyramidine), 2,2'-azobis (2-amidinopropane) dichloride, 2,2'- azobis (Ν, Ν'-dimethyleneisobutyramide), 2,2'-azobis (2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide), 2,2'-azobis (2-methyl-N- [1,1- bis (hydroxymethyl) ethyl] propionamide), 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], or alternatively 2,2'-azobis (isobutyramide) dihydrate; or

- redox systems comprising combinations such as, for example:

- mixtures of hydrogen peroxide, alkyl, peresters, percarbonates and the like and a compound selected from an iron salt, a titanium salt, zinc formaldehyde sulfoxylate or sodium formaldehyde sulfoxylate, and sugars reducers;

- alkali metal or ammonium persulphates, perborates or perchlorates, in combination with an alkali metal bisulphite, such as sodium metabisulphite, and reducing sugars;

- alkali metal persulphates in combination with an arylphosphinic acid, such as benzene phosphonic acid and the like, and reducing sugars

Preferably, the source of free radicals (B) of the invention comprises a peroxide, advantageously chosen, where appropriate, from the compounds corresponding to one of the following formulas (I) to (IV):

^R'—Oo—^R(l),

R '- [t— OO — q — R

OO

R'— O— | -j— OO — OR (II).

(III).

and

R'— Ό — jj — Ο-OR ⁰ (IV), in which the groups R ′ and R, which are identical or different, represent alkyl, linear or branched, aryl or aralkyl, optionally substituted.

Thus, as examples of peroxides which are particularly suitable as a source of free radicals (B) in the process of the invention, mention may in particular be made of diisobutyryl peroxide, cumyl peroxyneodecanoate, ter-amyl peroxyneodecanoate, di (2-ethylhexyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, dibutyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, tert-butyl peroxyneoheptanoate, tert-amyl peroxypivalate, didecanoyl peroxide, tert-amyl peroxy-2-ethylhexanoate, tertbutyl peroxyisobutyrate, 1,4-di (tert-butylperoxycarbo) cyclohexane, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, di-tert-amyl peroxide, tert-butyl cumyl peroxide, bis-tert-butyl, dicumyl peroxide, dilauroyl peroxide or di (4-tert-butylcyclohexyl) peroxydicarbonate.

Whatever its exact nature, the source of free radicals (B) implemented according to the process of the invention is used under conditions allowing the production of free radicals, which is generally carried out by thermal activation, that is to say ie by raising the temperature of the reaction medium, generally to a temperature of the order of ambient (approximately 20 ° C) to 200 ° C, preferably from 40 to 180 ° C, advantageously from 80 to 160 ° C.

The source of free radicals used can be introduced all at once into the reaction medium, but it can also be introduced gradually, where appropriate in portions or continuously.

The amount of the source of free radicals depends on its efficiency and its mode of introduction. Advantageously, the source of free radicals used is introduced in an amount such that the amount of free radicals that it is capable of releasing is between 50% and 200% by mole, and preferably between 100% and 150% by mole. , relative to the total molar quantity of dithiocarbonyl or dithiophosphoryl functions carried by all the living organic polymers present in the medium.

Another characteristic of the process of the invention is the specific use of an organic compound (C) carrying a labile hydrogen atom.

For the purposes of the invention, the term “labile hydrogen” will be understood to mean a hydrogen bonded to the organic compound via a sigma bond of sufficiently weak intensity for this bond to be able to lead to homolytic radical rupture.

Without wishing to be linked in any way to a particular theory, it seems to be able to be argued that, in the process of the invention, free radicals RL originating from the source of free radicals employed react with the dithiocarbonyl function -S (C = S) -R (or -S (P = S) -R) of the living organic polymer, to form radical species according to the following reaction scheme (Pol) -S (C = S) -R + RL · &lt;=&gt; ( Pol) · + RL-S (C = S) -R (where (Pol) denotes the polymer chain, the same reaction scheme could be presented with the -S (P = S) -) function.

It is assumed that the organic compound carrying a labile hydrogen atom used according to the invention (denoted Org-H) plays the role of hydrogen transfer agent and reacts with the radical of the (Pol) type. thus formed according to the reaction balance:

(Pol) + Org-H -&gt; (Pol) H + Org

In any event, whatever the exact mechanism used in the process of the invention, at the end of this process, a substitution of the dithiocarbonylated or dithiophosphorylated® function (or functions) is specifically obtained. initially present on the living organic polymer used by one (or more) atom® hydrogen®.

The organic compound (C) carrying a labile hydrogen atom which is used according to the invention is preferably chosen from:

- secondary alcohols of formula (HO) CH (R^I) (R),

-mercaptans of formula R'SH,

-the phosphites of formula (O =) PH (-OR^IV)(-GOLD^V),

-silanes of formula R^vlR^vR^vlSiH, or

-acetals of formula R^IXCH (OR^X)(GOLD^XI), where the groups R¹, R, R¹, R^IV, R^v, R^vj R^v, R^v', R'^x, R^x and R^XIeach independently represent an alkyl, cycloalkyl, alkoxy, alkene, acyl, aryl, aralkyl, aralkenyl or aralkynyl radical, it being possible for these radicals to be optionally substituted.

Preferably, R¹, R, R¹, R^IV, R^v, R^VI, R^v, R^VI , R^IX, R^x and R^XI are chosen from an alkyl radical from C1 to C8 and the phenyl radical.

Advantageously, this organic compound (C) carrying a labile hydrogen atom is chosen from 2-propanol, 2-butanol, 2-octanol, mercaptoethanol, diethyl phosphite, benzaldehyde dimethylacetate and dimethylphenylsilane. More particularly, this organic compound (C) is 2propanol.

Furthermore, the organic compound (C) carrying a labile hydrogen atom used according to the invention is generally an organic compound capable of fulfilling the role of solvent for the living polymer used, which presents at the end of the chain at the least one reactivatable dithiocarbonyl or dithiophosphoryl function. In this case, the amount of compound (C) used is generally between 1 and 50,000 molar equivalents, and preferably between 2 and 10,000 molar equivalents, relative to the polymer (A).

In the event that this compound is not able to perform this role, it is preferable to carry out the reaction in the presence of a co-solvent, chosen, where appropriate, in particular from water, ethanol, toluene. and tetrahyrofuran (THF). In this case, the amount of compound (C) used is most often between 1 and 200 molar equivalents, and advantageously between 20 and 100 molar equivalents, relative to the polymer (A).

In the most general case, the compound (C) is used in an amount of 1 to 50,000 molar equivalents, and preferably between 2 and 10,000 molar equivalents, relative to the polymer (A).

Furthermore, in the method of the invention, the step of bringing the living polymer (A), the source of free radicals (B) and the organic compound carrying labile hydrogen (C) into contact is generally carried out. at a temperature sufficient to allow effective initiation of the source of free radicals, but it is also most often preferred that this temperature is less than or equal to the boiling point of the various reagents used, otherwise, the process of the invention is carried out under pressure, which certainly does not compromise the effectiveness of the process in the general case, but is likely to be reflected in terms of increased implementation costs.

Thus, in the most general case, at atmospheric pressure, it is preferred that this step be carried out at a temperature between 0 ° C and 200 ° C. Preferably, this processing temperature is greater than 20 ° C, and it is advantageously less than 180 ° C. Thus, this temperature can typically be between 40 ° C and 160 ° C.

The non-limiting examples set out below illustrate the process of the invention.

EXAMPLES

Example 1:

- Synthesis of an O-ethyl xanthate terminated poly (acrylic acid):

7 g of acrylic acid, 28 g of ethanol, 2.02 g of S-ethylpropionyl O-ethyl xanthate and 0.48 g of azobisisobutyronitrile are introduced into a two-necked flask surmounted by a condenser. The mixture is brought to 70 ° C. for 4 hours. The polyacrylic acid obtained has the following characteristics: Mn = 2950 g / mol, Mw / Mn = 1.19.

Mn is the number average molar mass. It is measured by steric exclusion chromatography (CES) in water, with relative calibration by polyethylene oxide.

Mw / Mn is the polymolecularity index (given by CES). Mw is the weight average molar mass.

- Radical reduction of polyacrylic acid terminated O-ethyl xanthate:

To a 20 ml sample of the polyacrylic acid solution of Example 1, 27.8 g of 2-propanol are added. The mixture is then brought to 80 ° C. 0.37 g of dilauroyl peroxide are introduced every two hours for 14 hours. Then, the system is maintained at temperature for 3 additional hours. At the end of the reaction, the crude reaction product is analyzed by CES in water. By UV detection at 290 nm, wavelength at which the S (C = S) group of the xanthate absorbs very strongly, a total disappearance of the signal is observed. This is characteristic of the total reduction of the xanthate chain end.

Also, after purification of the sample by liquid-liquid extraction (hexane / ether), analysis of the polyacrylic acid purified by proton and carbon NMR shows the absence of the signals characteristic of the xanthate end.

Example 2:

- Radical reduction of polyacrylic acid terminated O-ethyl xanthate:

To a 20 ml sample of polyacrylic acid solution, the synthesis of which is described above, 27.8 g of 2-propanol are added. The mixture is then brought to 80 ° C. 3.7 of p-di-t-butylcyclohexyl percarbonate are then introduced, and the reaction is carried out at this temperature for five hours. At the end of the reaction, the crude reaction product is analyzed by CES in water. By UV detection at 290 nm, wavelength at which the S (C = S) group of the xanthate absorbs very strongly, a total disappearance of the signal is observed. This is characteristic of the total reduction of the xanthate chain end. Also, after purification of the sample by liquid-liquid extraction (hexane / ether), analysis of the polyacrylic acid purified by proton and carbon NMR shows the absence of the signals characteristic of the xanthate end.