EP1115767A1 - Method for making copolymers with controlled architecture and resulting copolymers - Google Patents

Abstract

The invention concerns a method for making bi-sequence, tri-sequence or multi-sequence copolymers, characterised in that it comprises: a first step which consists in radical telomerisation or polymerisation in the presence of a specific transfer agent to form a telomer or a polymer comprising at least a terminal group capable of initiating a controlled atom transfer radical polymerisation; and at least a second step which consists in using said telomer or said polymer as mono-or multi-functional macro-initiator for controlled radical polymerisation by transfer of one or several monomer atoms. In the first step the method consists in using as telogen or as specific transfer agent a compound X-Y whereof at least one of the groups X and Y is active in atom transfer radical polymerisation (ATRP), Y representing a hydrogen, chlorine, bromine or iodine atom, and X being: either a CZZVVW3-Z-V type group comprising at least a chlorine, bromine or iodine atom, wherein Z is a hydrogen, chlorine, bromine or iodine atom, a phenyl group, CN, CO2R or any other electron-attracting group or stabilising by resonance, V and W can each be a hydrogen or halogen atom or an alkyl group; or a CnF2n+1 group.

Description

PROCESS FOR PRODUCING COPOLY ERES WITH CONTROLLED ARCHITECTURE AND COPOLY ERES OBTAINED

The present invention relates to a process for the manufacture of diblock, triblock or multiblock copolymers (and co-oligomers) including a first step of radical telomerization or of radical polymerization with a functional transfer agent, and one or more second step (s) ( s) radical polymerization by atom transfer (PRTA). The diblock, triblock or multiblock copolymers obtained can be made up of blocks with a homopolymer structure, random copolymer or gradient copolymer. The manufacturing process can be developed in bulk, in solution, or in a dispersed medium.

STATE OF THE ART

The use of controlled radical polymerization (PRC) makes it possible, thanks to the living nature of the active species, the synthesis of homopolymers or copolymers having a very wide variety of molecular architectures (blocks, multiblocks, grafted, branched, hyperbranched, in stars ...), well defined in terms of compositions and functionalities, on the one hand, and in terms of molar mass and polymolecularity index, on the other hand.

Compared to other methods where the polymerization has a living character (anionic, cationic or with specific priming and catalysis systems), PRC offers the advantage of being applicable to a wide range of commercially available monomers, including a large many cannot be polymerized according to non-radical processes, and it makes it possible to use processes in mass, in solution or in dispersed phase, well mastered in the industrial field. Three approaches allowing polymerization according to a controlled radical process have been described (Gresta et al., Macromolecules, 27,638 (1994). The first approach is based on a mechanism in which the growing radical reacts reversibly with another radical compound or radical generator to form a covalent species. The second approach relies on a mechanism in which the growing radical reacts reversibly with a covalent compound to lead to a persistent radical species. The third approach involves a mechanism in which the radical in growth participates in a degenerative transfer reaction making it possible to restore a radical species of the same type.

Based on a principle consistent with the first approach cited, radical polymerization controlled by atom transfer (PRTA) has already been the subject of numerous works which have placed it as one of the richest ways of PRC (K. Matyjaszewski and JS. Wang, Macromolecules, 28.7901 (1995) - K. Matyjaszewski, T. Patten, J. Xia and T. Abernathy, Science, 272.866 (1996) - US Patents 5763548, 5789487 and 5807937. More specifically, PRTA is based on the reversible activation and deactivation of a compound containing an atom or a group transferable by radicals to allow the generation of an active radical (R ^* ), this process being governed by a redox exchange between the radical R "and a transition metal complex (Mt ^{n + 1} ) comprising an atom or a group (X) transferable by radical means.

The overall mechanism of PRTA is represented by the following diagram:

R - X + M _t ⁿ / ligand ligand

R - R

in which R-X denotes a compound comprising an atom or a group transferable by radical route, Mt7ligand denotes a transition metal complex, R "denotes the active radical,

XMt ^{n + 1} / ligand denotes a transition metal complex with a higher degree of oxidation, M denotes a monomer, and RR denotes a compound resulting from termination by coupling.

PRTA is initiated by the use or the formation of a compound of the R-X type comprising an atom or a group (X) transferable by radical route. R-X is most often an alkyl halide, the group R generally having a chemical structure making it possible to stabilize the radical R "formed, X then corresponding to a bromine, chlorine or iodine atom.

PRTA generally involves metallic salts with a low degree of oxidation:

Cu (l), Fe (ll), etc., capable of homolytically fixing an atom or a group X which makes it possible to initiate the polymerization from the compound RX and to maintain the redox cycle during the polymerization .

The deactivation of the growing polymer chain by reaction with the metal salt at its higher degree of oxidation brings about the reversion of the equilibrium which regenerates the metal salt at its lower degree of oxidation and the polymer chain protected by the atom or group X. This redox exchange process is repeated to prime the polymer chain and allow the degree of polymerization to be increased. After numerous repetitions of the redox exchange, polymers of high molar mass are obtained with DP _n = Δ [M] / [l] ₀ and Mp / Mn <1.5, Δ [M] and [l] ₀ being respectively the amount of monomer consumed and the initial concentration of initiator compound. According to this specific mechanism, PRTA has thus been used to synthesize a large number of homopolymers or copolymers having a wide range of mass average molar associated with reduced polymolecularity indices, generally less than 1.5.

One of the aspects, more particularly advantageous in the context of the present invention, is the obtaining of diblock, triblock or multiblock copolymers of which at least one of the blocks concerned can be obtained according to the principle of PRTA.

As a general definition of diblock, triblock or multiblock copolymers, it is understood here that a first block with homopolymer or copolymer structure (statistical, gradient) is formed in a first step, and that the second or other blocks, with homopolymer structure or copolymer, is or are formed during subsequent steps, specifically by reactions involving functional groups present at the ends of existing blocks to produce a final macromolecular chain with a linear structure.

The approach consisting in preparing at least one of the blocks of a diblock, triblock or multiblock copolymer via PRTA has already been described in a certain number of documents. Outside the framework of the PRTA, the concept allowing to associate different polymerization technologies to lead to copolymer structures comprising several blocks has moreover already been used in a significant number of previous works, generally based on the initial preparation of a macro -functional initiator obtained from a first monomer, which was, for example, capable of initiating radical thermal or photochemical polymerization of a second monomer: - Harabaglu, Makromol. Chem. Rapid Commun. 11, 4331 (1990)

- Bamford, New trends in photochemistry of polymers, Elsevier Applied Science Publishers London (1985)

- Yagci, Polymer Commun. 31, 7 (1990).

The advantage brought by the approach integrating one or more stages of PRTA lies however in the possibility of controlling the composition, the molar mass and the polymolecularity index of one or more blocks of the copolymer.

Document WO 97/18247 thus presents the general principle of the use of an acro-initiator comprising one or more functional groups within the meaning of PRTA, this macro-initiator being obtainable by radical polymerization, anionic polymerization, cationic polymerization or by metathesis, to then lead, by PRTA, from the functional group or groups to copolymers with a block, graft or comb structure. No example precisely associating a polymerization technology different from PRTA in a first step and PRTA in a second step is however described. On the other hand, the preparation of PMA-PSt diblock or PSt-PMA-PSt and PMA-PSt-PMA (St = styrene, MA = methyl acrylate) copolymers where all the blocks are obtained via a PRTA step leading to groups reactive terminals is well exemplified. US Pat. No. 5,789,487 also sets out the very general principle of the use of functional macro-initiators prepared by living cationic polymerization, by living radical polymerization or by a new polymerization route, which then makes it possible to produce block structure copolymers by PRTA. More precisely, a synthesis scheme is presented with a first step of living cationic polymerization leading to a polystyrene carrying a terminal chlorine atom, which is used to initiate in a second step a PRTA of styrene, of acrylate of methyl or methyl methacrylate (MMA) to obtain diblock copolymers with PSt-PSt, PSt-PMA or PSt-PMMA structure. It is also presented, for isobutene (IB), a similar synthetic scheme comprising a first step of living cationic polymerization leading to a polyisobutene (PIB) carrying a chlorine atom at each of its chain ends, which ends initiate in a second stage a PRTA of styrene to form a triblock copolymer PSt-PIB-PSt (ABA structure), with the possibility of further developing, from the chlorinated end groups present on the PSt blocks, a third stage of PRTA of styrene , methyl acrylate or methyl methacrylate. The examples describe, according to the approach described above, the preparation of PSt-PSt, PSt-PMA, PSt-PMMA diblock copolymers and present analytical elements making it possible to confirm the controlled nature of the formation of the second block.

In the same document, it is also mentioned the principle of obtaining a macro-initiator active in PRTA by polycondensation of a diol and a diacid in the presence of an acid or a monofunctional acid chloride containing an activated halogen. In this case, the acid compound or acid chloride acts as an end-of-chain agent to introduce at each end of the polycondensate a group carrying an activated halogen.

However, in the particular case of the monomers which, such as for example vinylidene fluoride (VDF), are not or hardly polymerisable by anionic, cationic or polycondensation route to form a chain of determined molar mass and comprising terminal groups active in PRTA, associated with the particular case where these same monomers are not or hardly polymerisable via a PRTA type process, no access route to copolymers with diblock, triblock or multiblock structures of which at least one of the blocks results from a PRTA is not explicitly proposed and described in previous works.

Furthermore, in the particular case where synthesis technologies perfectly mastered on an industrial scale (for example, radical polymerization in emulsion or in suspension, the advantages of which in terms of thermal control, viscosity of the reaction medium, purification of the product or suitability for application are well known) are necessary to produce a copolymer with a diblock, triblock or multiblock structure, one of which at fewer blocks result from a PRTA, no manufacturing process is precisely described in the aforementioned works.

To overcome these drawbacks of the prior art, the present invention now relates to a process for the manufacture of diblock, triblock or multiblock copolymers, characterized in that it comprises:

a first telomerization or radical polymerization step in the presence of a specific transfer agent to form a telomer or a polymer comprising at least one terminal group capable of initiating a radical polymerization reaction controlled by atom transfer, and - at least a second step using this telomer or this polymer as a mono- or polyfunctional macro-initiator for radical polymerization controlled by atom transfer from one or more monomers.

DESCRIPTION OF THE INVENTION

The first step of the process according to the present invention consists in the synthesis of a telomer T by telomerization or of a polymer P by radical polymerization in the presence of a specific transfer agent, the telomer T or the polymer P comprising one or two end groups capable of initiating a PRTA and the telomer T or the polymer P may result from the reaction of a monomer or of several comonomers.

To form the telomer T or the polymer P in accordance with the present invention, a compound XY of which at least one of the groups X and Y is active in PRTA is used as telogen or as specific transfer agent, Y represents an atom of hydrogen, chlorine, bromine or iodine, and X is: - either a group of the type CZ _Z V _V W _3-ZV comprising at least one atom of chlorine, bromine or iodine, in which Z is a hydrogen, chlorine, bromine or iodine atom, a phenyl group, CN, CO ₂ R or any other electron-withdrawing or resonance stabilizing group which may contain chlorine, bromine or iodine atoms, and V and W, which may be identical or different, may each be a hydrogen or halogen atom (chlorine, bromine, iodine, fluorine) or an alkyl group,

- or a group of the type C _n F _{2n + 1} .

The second stage of the process according to the present invention is based on the use of the telomer T or of the polymer P, resulting from the first stage, as a mono- or bifunctional macro-initiator of the PRTA of a single monomer which allows to access AB or BAB block structure copolymers or PRTA of a mixture of comonomers, which gives access to block / statistical or block / gradient copolymers. This second step can be repeated several times to lead to multiblock copolymers. The general principle of two-stage synthesis according to the invention is illustrated, in the case of a telomer T or of a polymer P, by the following diagrams in which the terms p and p 'signify that the blocks resulting from the propagation of the monomer M ² on either side of the block of monomer M ¹ do not have the same DP _n , due to the possible difference in reactivity of the initiator groups XM ¹ and M ¹ Y.

First step: Telomerization or polymerization of the monomer M ¹ . Telomerization of the monomer M ¹

l ₂ or Δ or hv

X -Y + g M ¹ _→ X _ (_ M ¹ -) _g - Y (T) or redox

where I = radical initiator Δ = thermal initiation hv = photochemical initiation

XY = telogen (X and Y as defined above)

OR

. Polymerization of the monomer M ¹ or copolymerization of M ¹ and M ¹ '

X - Y + n M ¹ / -or hv> X - (- M ¹ -) _n - Y (P)

X - Y + m M ¹ + m 'M ¹ ' ^{h or hv} > x _ (_ M ¹ - M ¹ '-) _{m + rn} .- Y (P) statistic or gradient

Second stage: PRTA of the monomer M ² initiated by T or P • 1st case: Only X is active in PRTA

Mt ^{n +} / ligand

TT + pp MM ²² X '_ (_ M -) _p -Q _ (- M ¹ -) _g -Y or or

PX '_ (_ M ² -) _p -Q - (- M ¹ -) _n -Y or

X '- (- M ² -) _p -Q - (- M ¹ - M ¹ ' -) _{m + m} - Y

where Mt ^{n +} = transition metal with a lower degree of oxidation, and Q = X minus X 'with X' = Cl, Br or I • 2nd case: X and Y are both active in PRTA

Mt ^{n +} / ligand T + (p + p ') M ² .. X' _ (_ M ² -) _p -Q - (- M ¹ -) _g - (- M ² -) _p. -Y 'OR OR

PX '- (- M ² -) _p -Q - (- M ¹ -) _n - (- M ² -) _p . -Y 'or X' - (- M ² -) _p -Q - (- M ¹ - M ¹ '-) _{m + m} .- (- M ² -) _p -Y'

where Mt ^{n +} = transition metal with a lower degree of oxidation,

Q = X minus X 'with X' = Cl, Br or I, and Y '= Cl, Br or I

Prior to the PRTA reaction, a bistelomerization reaction can also be envisaged as described in the following diagram. The resulting bistelomer (BT) is then used as a mono- or bifunctional macro-initiator depending on the ability of the groups X'M ¹ 'and M ¹ Y to effectively prime PRTA.

First step: Bistelomerization of the monomers M 1 e „.t n“ 1>

l ₂ or Δ or hv

X -Y + g M ¹ _→ X - (- M ¹ -) _g - Y (T) or redox

l ₂ or Δ or hv

T + h M ¹ '-, X' - (- M ¹ '-) _h - Q - (- M ¹ -) _g - Y (BT) or redox where I = radical initiator Δ = thermal initiation hv = photochemical initiation

XY = telogen (X and Y as defined above)

Second stage: PRTA of the monomer M ² initiated by BT

• 1st case: Only X 'is active in PRTA Mt ^{π +} / ligand BT + i M ² _→ X "- (_ M ² -) i- Q '- (- M ¹ ' -) _h - Q - (- M ¹ -) g- Y

where Mt ^{n +} = transition metal with a lower degree of oxidation, and Q '= X' minus X "with X" = Cl, Br or I.

• 2nd case: X 'and Y are both active in PRTA

Mt ^{n +} / ligand BT + (i + i ') M ² X "- (- M ² -) i-Q' - (- M ¹ '-) _h - Q - (- M ¹ -) _g - (- M ² -) ι-Y '

When the first step according to the invention is a radical telomerization reaction between a telogenic agent XY and a monomer M ¹ [CM. Starks, Free Radical Telomerization, Académie Press, NY and London (1974); B. Boutevin and Y. Pietrasanta, "Telomerization" in Comprehensive Polymer Science, Pergamon Press, Oxford, vol.3, chap. 14, p.185 (1989)], this reaction can be initiated thermally, by a free radical generator I2 (AIBN, benzoyl peroxide, etc.), photochemically or catalyzed redox. This method has generally been used to synthesize compounds of low molar mass, and often monoaddition products [this borderline case of the telomerization reaction has been the subject of numerous studies listed under various names: Kharasch reaction (MS Kharasch, Jensen and WH Urry, Science, Washington DC, 102.128 (1945) or radical addition by atom transfer (DP Curran, Synthesis, 489 (1989)). For the monoaddition reaction catalyzed by the redox route, the terminologies will be retained. :

- "radical addition catalyzed by redox route" [M. Asscher, D. Vofsi, J. Chem. Soc, 1887 and 3921 (1963) and D. Bellus, Pure and Applied Chem. 57, 12, 1827 (1985)]

- "radical addition by atom transfer catalyzed by redox route" (D.P. Curran, Synthesis, 489 (1989), or simply

- "redox telomerization" [CM. Starks, Free Radical Telomerization, Académie Press, Ν.Y. and London (1974); B. Boutevin and Y. Pietrasanta, "Telomerization" in Comprehensive Polymer Science, Pergamon Press, Oxford, vol.3, chap. 14, p.185 (1989)].

For certain Monomer / Telogen pairs (in radical telomerization) or certain Monomer / Telogen / Metal complex systems (in redox telomerization) and for adequate initial temperature and concentration conditions, high DP _n values

(up to about 100) have been obtained while retaining an excellent degree of purity of structure X- (M ¹ ) gY. As an example, we can cite the VAC / HCCI3 couple ⁱⁿ radical telomerization (synthesis of telomeres with CCI3 structure - (CH2CHOAc) _n - H with DP _n = 50 with a structure purity greater than 90% (B. Boutevin, M. Macret, O Maubert, Y. Pietrasanta, M. Tanesie, Tetrahedron Letters, 33, 3019 (1978) or the CCl4 / Fe (ll) / ethyl acrylate system or acid in redox telomerization (20 <DP _n <120: telomeres with CCl3 structure (CH2CHC02) _n -CI (B. Boutevin et al., J. Polym.Sci., Polym.Chem.Ed., 19, 2, 499 ( With regard to bistelomerization, mention may be made of the synthesis of structures PVAc-b-ethyl polyacrylate with CCI4 as telogenic agent (OH. Bamford, XZ. Han. Polym. Commun., 22, 1299 (1981) , or the synthesis of block structures with CBr4 (M. Destarac, Doctoral thesis, Montpellier (October 1997).

In telomerization, the efficiency of the telogen with respect to the transfer reaction is governed by two main factors: - the type of atom transferred (energy of dissociation of the CY bond) - the other substituents of the telogen which stabilize the resulting telogen radical.

For the transferred atom, the normal reactivity scale is as follows: l>Br> CI ~ H. However, reactivity inversions can take place, particularly between H and Cl and between H and Br. For polychloroalkanes, the atoms transferred can be chlorine or hydrogen, depending on the most stable resulting radical. Of course, only one chlorine atom can be transferred when using CCI4, CCI3CN, CICN ... as a telogen agent, since it is the only transferable one. The transfer of a chlorine atom also takes place for CCI3CO2CH3, CCI3CH3 and similar compounds. With compounds such as HCCI3, CH ₂ Cl2, CH3CCI2H, CI2CHCO2CH3 or CICH2CO2H, the abstraction of a hydrogen atom is preferred, allowing the chlorine atoms to further stabilize the telogen radical. For brominated telogens, a bromine atom stabilizes a telogen radical roughly equivalent to a chlorine atom. On the other hand, the dissociation energies of the C-Br bonds are lower than those of the chlorinated analogs. Consequently, the use of (poly) bromoalkanes such as CHBr3 or BrCH2CO2CH3 leads almost exclusively to a transfer of bromine atom, unlike chlorinated analogs. In redox telomerization, a halogen atom will be transferred by the metallic species in its highest oxidation state (or in minimal proportions via the telogen agent).

In Table A below are listed some examples of telogen / monomer pairs leading to telomeres comprising PRTA initiator groups. In this table, the abbreviations have the following meanings: VAc = vinyl acetate; VDF = vinylidene fluoride; VC = vinyl chloride; CTFE = trifluoromonochloroethylene; TFE = tetrafluoroethylene; CV2 = vinylidene chloride; IB = isobutylene; MAN = methacrylonitrile; MAM = methyl methacrylate; AN = acrylonitrile; AE = ethyl acrylate. Table A

Synthesis of initiating telomeres for a PRTA reaction

(references on the next page)

REFERENCES

1) B. Boutevin, M. Macret, O Maubert, Y. Pietrasanta, M. Tanesie, Tetrahedron

Letters, 33, 3019 (1978)

2) M. Duc, Doctoral thesis, Montpellier (November 1997)

3) Englin et al., Izv. Akad. Nauk. SSSR, Ser Khim (12), 2542 (1971)

4) Clarke, Howard, Makromol. Chem. 44/46, 427 (1961) 5) Englin et al. Izv Akad. Nauk. SSSR, Ser Khim, 425 (1965)

6) Englin et al., Ibid, 2712 (1968)

7) L. O. Moore, J. Phys. Chem. 75, 2075 (1971)

8) K. Nakagawa, T. Nakata, (Shionogi Co. Ltd), U.S. Patent 3,429,934 (1969)

9) Kharasch et al. J.Am. Chem. Soc, 67, 1626 (1945) 10) Terent'ev et al., Izv. Akad. Nauk. SSSR, Ser Khim, 73 (1971)

11) Englin et al., Ibid. 1568 (1972)

12) Bobinova et al., Zh. Org. Khim. 5.216 (1969)

13) Platt and Tittle, J. Chem. Soc, C, 150 (1967)

14) Bogomolova et al., Tr. Inst. Nefti, Akad. Nauk. SSSR, 8, 176 (1956) 15) J.E. Fields (Monsanto Chemicals Co), US Patent 2837559 (1972)

16) Barson et al., Trans. Faraday Soc, 68, 1666 (1972)

17) Vidotto et al., Makromol. Chem., 140, 263 (1970)

18) E.C. Ladd (US Rubber Co), US patent 2615915 (1952)

19) B. Boutevin et al., J. Polym. Sci., Polym. Chem. Ed., 19, 2, 499 (1981) 20) M. Oka, M. Tatemoto, Contemp. Topics Polym. Sci., 4, 763

21) C. Vergé, Thesis of the University of Montpellier II (1991)

When the first step according to the invention is a radical polymerization reaction with a specific transfer agent XY, the initiation of the reaction can be carried out by photochemical route or catalyzed by redox route and, in many industrial manufacturing processes, rests on the use of free radical generators, such as azo derivatives, peroxides, percarbonates or persulfates.

In most cases, this method is used to synthesize compounds of high molar mass, typically corresponding to PD _n between 50 and several tens of thousands (sometimes up to 100,000), with polymolecularity indices generally greater than 1 , 5. The proportion of transfer agent in contact with the monomer is much lower than that of a telogen and this proportion is adjusted, in a manner known per se to those skilled in the art, to limit the molar mass of the polymer. formed to determine its rheological, physico-chemical or thermomechanical properties. Those skilled in the art will understand that, in the case of radical polymerization using a specific XY transfer agent as in the case of certain telomerizations, the majority but not all of the macromolecular chains have two ends corresponding to fragments X or Y of the transfer agent. Certain chain ends in fact correspond to products derived from the free radical generator used for initiation or result from secondary transfer reactions, or even termination reactions of different types.

In radical polymerization, the efficiency of transfer agents is governed by factors analogous to those previously commented on for telogen compounds. The differences from telomerization sometimes appear in terms of kinetic characteristics and distribution of average molecular weights mainly due to the contribution of secondary transfer reactions or termination reactions. In dispersed phase processes, such as emulsion or suspension polymerizations, predicting the effect of the transfer agent is moreover complicated by its uneven distribution between the different phases present. The range of monomers which can be used, alone or as mixtures, in radical polymerization processes with specific transfer agents is very wide. In the context of the present invention, a non-limiting list grouping together three main families of monomers can be proposed. a) A first family brings together compounds of general formula (I) which lead to fluoropolymers:

in which L, L ′ and L ″ may be independently of each other a hydrogen atom, a fluorine atom or a electron-withdrawing group such as a fluoroalkyl group (for example trifluoromethyl or pentafluoroethyl) or even a group nitrile. Preferably, at least one of L, L 'and L "is a fluorine.

As examples of such monomers, mention may be made more particularly of vinylidene fluoride (VDF), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), trifluoroethylene, 1-hydro-pentafluoropropene and 2-hydro-pentafluoropropene. They can be used alone, mixed with each other, or mixed with other olefinic unsaturated monomers such as chlorotrifluoroethylene (CTFE), 1, 1-dichlorofluoroethylene, dichlorodifluoroethylene, 2-chloropentafluoropropene, perfluoroalkylated vinyl ethers such as CF ₃ -O-CF = CF ₂ or CF ₃ - CF ₂ -O-CF = CF ₂ , perfluoro-1, 3-dioxoles such as those described in US Patent 4,558,142, and olefinic unsaturated monomers containing no fluorine such as ethylene, propylene, butylene and higher counterparts. b) A second family consists of fluorinated diolefins such as perfluorodiallyl ether and perfluoro-1, 3-butadiene. c) A third family brings together compounds of general formula (II) which lead to polyvinyl acetates or to polyvinyl acrylates:

in which L ¹ , L ² and L ³ are independently a hydrogen atom, a halogen, a hydrocarbon group of 1 to 20 carbon atoms (preferably from 1 to 6) with a linear or branched structure, and L ⁴ is a substituent of the type -CO-OL ⁵ or -O-CO-L ⁵ , L ⁵ being a hydrocarbon group of 1 to 20 carbon atoms (preferably from 1 to 6) with a linear or branched structure or a hydrocarbon group with a structure linear, cyclic or aromatic, containing one or more ethylenic or acetylenic bonds and possibly including one or more halogen and / or heteroatom atoms. More specifically, the monomers, polymerized alone or as a mixture, preferred for the present invention are vinylidene fluoride (VDF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), vinyl acetate (VAc), vinyl choroacétate, and acrylates or methacrylates having linear or branched hydrocarbon ester groups to C _20. The standard procedures for the radical polymerization of these various monomers by bulk, solution or dispersed phase processes (for example, emulsion or suspension) have been very widely described in the literature:

- Principles of Polymerization, Third edition, G. Odian, Wiley-lnterscience Publication, John Wiley and Sons, 1991 - Emulsion Polymerization and Emulsion Polymers, edited by P.A. Lovell, M. S. El-Aasser,

Edition John Wiley and Sons (Chichester), 1997. During a solution polymerization, the solvent can act as a transfer agent generating terminal groups active in PRTA if its transfer constant is suitable.

Depending on the chemical structure of the monomer (s) involved, the polymerization process will be chosen and optimized to produce a homopolymer or copolymer (statistical or gradient) of well-defined composition and average molar mass.

During the second step of the process according to the invention, the telomer T (or bistelomer BT) or the polymer P are used to initiate the PRTA of a monomer M ² or of a mixture of comonomers M ² to form a diblock copolymer or triblock, and possibly multiblock via subsequent stages of PRTA. Thus, for example, starting from a diblock structure, a subsequent step of PRTA with a monomer M ³ leads to a triblock structure according to the following scheme:

X - (- M ² -) _p -Q - (- M ¹ -) _n -Y + i M ₃ → X " ¹ - (- M ³ -) t - X" - (- M ₂ -) _P -Q - (- M ¹ -) _n -Y

For the second step (s), it is possible to use all of the radical polymerizable monomers such as those defined in US Pat. No. 5,789,487 (column 7, line 28 to column 9, line 12) of which the content is incorporated herein by reference, as well as the styrenic or acrylic monomers carrying carboxylic or sulfonic acid functions.

Any transition metal derivative which can participate in the redox exchange described above can be used in the second stage (s) of PRTA according to the present invention.

As nonlimiting examples of such derivatives, mention may be made more particularly of the compounds Mt ^{n +} A _n in which Mt ^{n +} is chosen from the group consisting of the Cu ⁺ cations,

Cu ²⁺ , Fe ²⁺ , Fe ³⁺ , Ru ²⁺ , Ru ³⁺ , Cr ^{2 *} , Cr ³⁺ , Mo ⁺ , Mo ²⁺ , Mo ³⁺ , W ²⁺ , W ³⁺ , Rh ³⁺ , Rh ⁴⁺ , Co \ Co ²⁺ , Re ²⁺ ,

Re ³⁺ , Ni \ Mn ³⁺ , Mn ⁴⁺ , v ²⁺ , v ³⁺ , Zn \ Zn ²⁺ , Au \ Au ²⁺ , Ag ⁺ , Ag ² \ and the anion A is chosen from the group consisting of halide, alkoxylate anions in CC ₂₀ , (SO ₄ ) _{1 2} , (PO ₄ ) ι ₃ and (HPO ₄ ) ι ₂ .

For the second stage (s) of PRTA according to the present invention, it is possible to use as ligands all the compounds mentioned in US Pat. No. 5,789,487 (column 10, line 65 to column 12, line 31) . However, bipyridine and its derivatives, bis-triphenylphosphine and its derivatives, tertiary polyamines and their derivatives are preferred.

The molar ratios between the active terminal groups of the macroinitiator, the transition metal derivative and the ligand are in a range between 1 / 0.01 / 0.01 and 1/4/12, preferably in a range between 1 / 0.1 / 0.1 and 1/2/6.

According to a conventional approach, the PRTA stage (or the subsequent PRTA stages) can be carried out in bulk or in solution. In the case of the solution process, the macroinitiator (T telomer, BT bistelomer or P polymer) will either be dissolved if it comes from a first step mass reaction, either used in its first stage synthesis solvent, or isolated in dry form in the case of a first stage synthesis solvent not compatible with the PRTA process.

Solvents compatible with PRTA include all those mentioned in US Pat. No. 5,789,487 (column 12, line 51 to column 13, line 13).

In accordance with a preferred embodiment of the PRTA step or steps according to the invention, the components of the initiator system (macro-initiator, metal derivative and ligand) are introduced into the reactor, degassed under vacuum and placed under a d atmosphere. an inert gas such as argon. The order of introduction of the components of the initiator system is not important. The preferred polymerization temperature is between 0 and 150 ° C and is advantageously lower than the boiling point of the monomer.

According to an approach in certain cases more advantageous for the manufacture of product on an industrial scale, the PRTA stage (or the subsequent PRTA stages) can be carried out in a dispersed medium, preferably in emulsion or in suspension, and more particularly with an aqueous continuous phase. In the context of the present invention, the PRTA stage has thus been able to be carried out from a mixture of aqueous emulsions (coemulsion) of the telomer or of the macro-initiator polymer and of the reactive monomer (or comonomers) in PRTA. In this case, the telomer or the macro-initiator polymer can be either emulsified in the presence or not of a compatible solvent by the PRTA process, or previously prepared according to an aqueous emulsion manufacturing process, this type of process being perfectly described and known for a large number of polymers for commercial use.

The coemulsion comprising the macro-initiator and the reactive PRTA monomer can be formed and initially stabilized by the addition of one or more suitable surfactants. All the surfactants suitable for the formation of an emulsion or a suspension of polymers or for carrying out an emulsion or suspension polymerization are capable of being used, provided that they are compatible with the process of PRTA (and possibly with the surfactant (s) used during a first stage of emulsion synthesis).

To promote the advancement of the PRTA reaction, a surfactant of the nonionic type will preferably be incorporated. Among the range of non-ionic surfactants, polyethoxyalkylphenols, alkylated polyethoxy, polyethoxy alcohols, polyethoxy mercaptans, polyethoxypropoxyglycols and, preferably, alkylated polyglucosides are recommended because of their effectiveness and their commercial availability. .

A standard protocol for implementing the PRTA step from a co-emulsion in aqueous phase of a macro-initiator polymer and a reactive monomer in PRTA is as follows:

- The macro-initiator compound is prepared by radical polymerization in aqueous emulsion of a monomer M ¹ in the presence of a specific transfer agent and therefore occurs in the form of a latex, the dry extract of which is between 0.1 and 50% by weight, preferably between 5 and 30% by weight.

- This latex is subjected to a partial vacuum of between 10 and 500 mm Hg at a temperature between 30 and 80 ° C for 2 to 24 hours so as to remove the residual specific transfer agent and complete the decomposition of the radical initiator used in the first step.

- A nonionic surfactant (either a polyethoxyalkylphenol or an alkylated polyglucoside) is added to the latex with stirring and under scanning of an inert gas, preferably argon, in a proportion of between 0.1 and 12% by weight of the reactive PRTA monomer added subsequently, preferably between 0.4 and 5% by weight; the dissolution conditions (duration and temperature) depend on the chemical structure of the surfactant.

- At the same time, a metallic PRTA catalyst, for example a nickel dichloride associated with the bis-triphenylphosphine ligand or an iron dichloride associated with the tris-triphenylphosphite ligand (molar catalyst / ligand ratio preferably between 1 and 3) is dispersed with stirring and under scanning of an inert gas, preferably argon, in the monomer M ² active in PRTA or dispersed in water in the presence of a nonionic surfactant such as those defined above. The quantity of catalyst is fixed in molar proportion relative to the ends of the active chain of the macro-initiator. The molar ratio of catalyst to active chain ends is preferably between 2 and 0.1. The weight of monomer M ² incorporated determines the weight composition of M ¹ and M ² of the final product. For low proportions of monomer M ² , a co-solvent of the hexadecane or cetyl alcohol type can be added to facilitate the dispersion of the catalyst. This dispersion of catalyst associated with the ligand in the monomer M ² is then emulsified with vigorous stirring in the macro-initiator latex additive with the nonionic surfactant. This operation is carried out at a temperature between 5 and 95 ° C, preferably between 10 and 30 ° C. In the case where the PRTA catalyst has been separately dispersed in water with a nonionic surfactant, its introduction into the latex will be carried out under the same conditions as the previous operation. A co-emulsion is then formed and stored with stirring and under scanning of inert gas for a period of between 0.1 and 24 hours. The co-emulsion is then heated to a temperature between 30 and 95 ° C, preferably between 70 and 90 ° C, for 4 to 48 hours, preferably 6 to 10 hours to allow maximum consumption of M ² .

Depending on the amount of catalyst incorporated in the reaction, the nature of the latex formed from M ¹ and the nature of the monomer M ² , the final reaction medium is either in the form of a dispersion formed of grains of several tens of microns in average diameter which are directly filterable, either in the form of a stable emulsion which can be used as such or treated to isolate a dry product. The appearance of the final product in dispersion or in emulsion will be advantageously exploited depending on the intended field of application.

The whole of the protocol previously described, including the prior step of radical emulsion polymerization of the macroinitiator, or even the subsequent PRTA steps, can be carried out in the same reactor, which considerably simplifies the process for obtaining diblock copolymers, triblocks or multiblocks.

Experimental part

The following exemplary embodiments illustrate the invention without limiting it. The CES analysis was carried out with WATERS equipment (Injector 717, Pump 600 E, Refractometer R410) equipped with μ STYRAGEL columns 10 ³ + 10 ⁴ +10 ⁵ Â (L = 300 mm) regulated at 30 ° C with DMF as eluent (flow rate: 1 ml / min). PS or PMMA standards are products of Polymer Laboratories. The NMR analysis was carried out with a BRUKER DRX 400 AVANCE spectrometer at 330 ° K with dissolution of the samples in DMSO-d6.

Example 1: Synthesis of polyvinyl acetate-b-polystyrene copolymers; obtaining amphiphilic polyvinyl alcohol-b-polystyrene copolymers by hydrolysis of the PVAc block.

Step 1. Telomerization of vinyl acetate with chloroform, initiated by di-t-butylcyclohexyl percarbonate or benzoyl peroxide (obtaining the T telomer).

The required quantities of vinyl acetate (freshly distilled), chloroform, initiator and solvent if necessary are introduced into a 100 to 500 ml two-necked flask surmounted by a condenser and placed under argon. The reaction mixture is initially purged by a stream of argon for 15 minutes. It is then placed in a thermostate oil bath at 60 ° C. Samples are then made at regular time intervals and analyzed by NMR ^"Η. The reaction is stopped when about 90% conversion is achieved. The residual monomer, chloroform, and the solvent is then evaporated. The polymer is taken up xylene and the solution is brought to 90 ° C. overnight in order to decompose all of the residual initiator. The solvent is then evaporated and the product dried under vacuum at 60 ° C. to constant mass. initial molar ratio R ₀ = (HCCl3) ₀ / (M) ₀ , a viscous gel (R ₀ = 10) or a yellow solid (R ₀ = 0.5) is obtained.

In the following table are reported the results obtained. Table B: Synthesis of polyvinyl acetate telomeres

Determined by NMR ^" Η at 90% conversion Priming with di-t-butylcyclohexyl percarbonate Priming with benzoyl peroxide

Step 2. PRTA of styrene primed by T and catalyzed by CuCl / 2,2'-bipyridine.

In a previously degassed Schlenk tube are introduced the catalyst, the solvent

(volume ratio monomer / xylene = 0.33), the monomer, as well as the macroinitiator (T). The system is then degassed by three "freeze / vacuum / return to ambient" cycles, then placed under argon in a thermostate oil bath at 130 ° C. At the end of the reaction, the system is cooled to room temperature.

A pure PVAc-b-PS copolymer was obtained in the following manner: the reaction crude is filtered through a frit covered with a thin layer of alumina to remove the copper salts. In order to remove the 2,2'-bipyridine, the solution is then washed with an acidic aqueous solution (10% HCl), then rinsed with water until neutral pH. The xylene is then evaporated under vacuum. A first boiling cyclohexane extraction makes it possible to separate the traces of homopolystyrene. A second methanol extraction makes it possible to eliminate the small amounts of homoPVAc present in the medium. Finally, by precipitation in hexane, the pure PVAc-b-PS diblock copolymer is recovered in the form of a pale yellow powder.

The results obtained are reported in Table C below: Table C: Synthesis of PVAc-b-PS diblock copolymers

[Styrene] ₀ / [T] ₀ variable; [T] ₀ = [CuCI] ₀ = ϋP ^. _; τ = 130 ° C; solvent: xylene

a) DPn th (PS) = ([styrene] ₀ / [T] ₀ ) ^* α _m b) 0.9 <α _m = conversion to monomer <1 c) yield obtained by the relation p = m (pure copolymer) / [m ₀ (T) + m ₀ (styrene)]

The CES analysis of the products corresponding to inputs 1 and 2 shows a CES peak shifted towards high molar masses in comparison with the peak of the initial telomer.

Step 3. Hydrolysis of the PVAc block of PVAc-b-PS synthesized with CuCI / 2BPy Mild hydrolysis with K2CO3 was carried out according to the method described by Tezuka et al. in Makromol. Chem., 186, 685 (1985) and the purification of the copolymer according to the work of Imoto et al. reported in Makromol. Chem., 36, 193 (1960).

In a 500 ml two-necked flask fitted with a dropping funnel, 2 g of potassium carbonate K2CO3 are dissolved in 500 ml of methanol and the mixture is brought to reflux (60 ° C.) so that it becomes clear. The PVAc-b-PS copolymer (entry 1 of table b) is diluted in THF and the mixture is then poured dropwise through the dropping funnel. A white precipitate forms as the reaction takes place. After two hours of reaction, the reaction mixture is filtered. After evaporation of the solvents under vacuum and drying of the product under vacuum to constant mass, the polyvinyl alcohol-b-polystyrene (PVOH-b-PS) copolymer is obtained in the form of a pale yellow powder, insoluble in the usual solvents.

Example 2: Synthesis of polyvinyl acetate-b-PMMA copolymers; obtaining polyvinyl alcohol-b-PMMA copolymers by hydrolysis of the PVAc block.

Step 1. Same as in Example 1. Step 2. PRTA of MM A initiated by T and catalyzed by CuCl / 2,2'-bipyridine.

In a Carius tube are added consecutively the catalyst, the monomer, the solvent (xylene) and the initiator (T of DP _n = 25) (in respective molar proportions:

T / CuCI / Bpy / MMA = 1/1/3/200). The tube is then degassed and sealed under vacuum. It is then placed in an oil bath brought to 110 ° C for 4 hours. At the end of the reaction, the tube is opened and the resulting polymer characterized by CES A mass M _n equal to 18000 g / mol is obtained (Ip = 1, 4). CES analysis shows a displacement of the chromatogram towards high masses, in comparison with the initial peak of T.

Step 3. Same as step 1.

Example 3: Synthesis of PVDF-b-PS block oligomers.

Step 1. Telomerization of vinylidene fluoride with chloroform. The reaction is carried out in a Hastelloy type "batch" high pressure reactor of

1 litre. The procedure is as follows: after introduction of 1.8 g (0.012 mole) of di-t-butyl peroxide and 298.3 g of chloroform (2.5 mole), the autoclave is sealed. After having tested the tightness of the reactor under 10 bar of nitrogen and purged the content of the residual air by expansion to the atmosphere, the reactor is immersed in an acetone / liquid nitrogen mixture at approximately -90 ° C. 80 g (1.25 mole) of VF2 are then introduced through the inlet valve. The mass of VDF introduced is evaluated by multiple weighings at this temperature. The system is then brought to 141 ° C for 5 hours. The medium is agitated by a system of superimposed blades actuated by an electric motor. After reaction, the reactor is cooled in an ice bath and the residual vinylidene fluoride is released under an extractor hood. 1 H NMR analysis of the synthesized telomer made it possible to confirm its structure and to calculate the value of DP _n (equal to 4.5) (note: presence of traces of secondary distributions and of additions qq):

CCI3— CH2— CF2— (- CH2— CF2—) 2.5— CH2— CF ₂ H

¹ H NMR: (acetone d- @): δ: 1, 8 (t, t, - CF2CF2CH3, 3H, traces of secondary products), 2.3 (m, - CF2— CH ₂ CH2 CH2— CF2—, 2H) ; 2.9 (m, - CF ₂ CH ₂ CF2—, 2H); 3.3 (t, d, CCI3-- CH2— CF ₂ H, monoaduct, 2H); 3.7 (t, CCI3CH2CF2—, 2H); 6.2 (t, t - CH ₂ CF ₂ H, 1 H).

Step 2. PRTA of styrene initiated by T (telomer of VF2) and catalyzed by CuCl / Bpy. Into a previously degassed Schlenk tube are successively introduced

0.086 g (8.73.10 ^"4 mole) CuCI, 410 mg (2.62.10 ^'3 mole) 2,2'-bipyridine, 4.576 g (4.38.10 ^"

2 moles) of styrene, 8.608 g of anhydrous p-xylene and 0.346 g of the telomer T (8.62.10 "4 moles). The system is then degassed by three cycles" freezing / vacuum / return to ambient "then placed under argon in a thermostatted oil bath at 130 ° C. After 20 hours of reaction, the system is cooled to room temperature. After a purification identical to those previously described (Example 1, step 2), the polymer (white powder) is analyzed by CES. Its number average mass Mn is equal to 5800 g / mole (Ip = 1.7). The comparison of the chromatograms of the initial T telomer and of the final polymer makes it possible to conclude that the total consumption of the T telomer by its trichloromethyl end during the second step, to lead to the final copolymer of theoretical structure (PVDF) 4 5 - b - (PS ) 5 _Q -

Example 4: Synthesis of PVDF-PMMA block copolymer in solution using the CuCl / 2,2'-bipyridine catalyst.

Step 1. Polymerization of vinylidene fluoride with transfer to chloroform.

Into a 3-liter high-pressure reactor, 1.8 I of water, 2.4 g of emulsifier (C ₇ Fι ₅ COONH) are introduced. After having tested the tightness of the reactor with 10 bars of nitrogen, it is put under vacuum, then under 5 bars of vinylidene fluoride (VDF), brought back to atmospheric pressure and put back under vacuum. 41.2 ml of chloroform are then introduced before heating the reactor to 80 ° C., and introducing VDF until a pressure of 65 bars is obtained. Once these conditions have been reached, 0.09 g of ammonium persulfate are introduced, and VDF is injected to maintain the pressure at 65 bars. After 2 h, 0.09 g of ammonium persulfate are added. The polymerization is stopped after 6 hours so as to obtain a dry extract of approximately 15%. The latex is dried at 100 ° C for 8 hours.

NMR analysis made it possible to identify and measure the chain ends; the results are reported in the following table:

Table D: NMR characterization of the PVDF transferred with CHCI ₃ (acetone-d6)

CES analysis of the product with a PS calibration gives the following results Mn = 37,000 Mp = 55,000 Ip = 1.48 Step 2: PRTA of MAM in solution, initiated by PVDF transferred to CHCI ₃ and catalyzed by CuCI / 2, 2 '-bipyridine.

Initially, the ortho-xylene and the MAM are degassed by bubbling with argon for 4 hours, and the CuCl, the bipyridine and the PVDF are dried under vacuum for 4 hours.

50 g of ortho-xylene are introduced into a 1 liter jacketed reactor surmounted by a condenser and continuously swept by a low flow of argon, then successively, with stirring, 0.5 g of CuCl and 1, 57g of 2,2'-bipyridine, 50g of MAM, and finally 45g of PVDF transferred to chloroform (step 1). The reactor is heated at 100 ° C for 6 hours. At the end of polymerization, the residual monomer and the solvent are evaporated under vacuum at 80 ° C for 6 hours using a rotary evaporator. After dissolving in 800 ml of acetone, the polymer is isolated by precipitation with stirring in 2.5 liters of water, filtration and drying under vacuum at 60 ° C for 8 hours.

The apparent conversion rate of MMA, calculated after evaporation under vacuum at 80 ° C. for 6 hours from the reaction medium at the end of the reaction, is 95%.

CES analysis of the final product shows a total disappearance of the characteristic peak of PVDF and the appearance of a peak corresponding to the diblock copolymer PVDF-b-PMMA (Ip = 1.29 in PMMA calibration).

Characterization by ¹ H and ¹⁹ F NMR (DMSO-d6) of the final product demonstrates total consumption of the terminal groups of structure -CF ₂ -CH ₂ -CCI ₃ on the PVDF macro-initiator.

Example 5: Synthesis of a PVDF-PMMA block copolymer in solution using the NiCI ₂ / bis-triphenylphosphine catalyst.

Step 1: identical to that of Example 4

Step 2: PRTA of MAM in solution, initiated by PVDF transferred to CHCI ₃ and catalyzed by NiCI ₂ / bis-triphenylphosphine.

Initially, the ethylbenzene and the MMA are degassed by bubbling with argon for 4 hours, and the NiCI ₂ / bis-triphenylphosphine complex and the PVDF are dried under vacuum for 4 hours. 50 g of ethylbenzene are introduced into a 1 liter jacketed reactor surmounted by a condenser and continuously swept by a low flow of argon, then successively, with stirring, 3.71 g of NiCl ₂ / bis-triphenylphosphine, 50 g of MAM, and finally 45 g of PVDF transferred to chloroform (step 1). The reactor is heated at 100 ° C for 6 hours. Finally polymerization, the residual monomer and the solvent are evaporated under vacuum at 80 ° C for 6 hours using a rotary evaporator. After dissolving in 800 ml of acetone, the polymer is isolated by precipitation with stirring in 2.5 liters of water, filtration and drying under vacuum at 60 ° C for 8 hours.

The apparent conversion rate of MMA, calculated after evaporation under vacuum at 80 ° C for 6 hours from the reaction medium at the end of the reaction, is 90%.

CES analysis of the final product shows a total disappearance of the characteristic peak of PVDF and the appearance of a peak corresponding to the diblock copolymer PVDF-b-PMMA (Ip = 1.28 in PMMA calibration).

Example 6: Synthesis of a VDF / HFP-PMMA block copolymer in solution using the CuCl / 2,2'-bipyridine catalyst.

Step 1: Polymerization of vinylidene fluoride and hexafluoropropene with transfer to chloroform. 1.8 I of water, 2.4 g of emulsifier are introduced into a 3-liter high-pressure reactor

(CF ₁₅ COONH). After having tested the tightness of the reactor with 10 bars of nitrogen, it is put under vacuum, then under 5 bars of 80/20 by weight of vinylidene fluoride (VDF) and hexafluoropropene (HFP), brought back to atmospheric pressure and returned to vacuum. 41.2 ml of chloroform are then introduced before heating the reactor to 80 ° C., and introducing VDF / HFP mixture until a pressure of 65 bars is obtained. Once these conditions have been reached, 0.09 g of ammonium persulfate are introduced, and VDF / HFP mixture is injected to maintain the pressure at 65 bars. After 1 hour, 0.09 g of ammonium persulfate are added. The polymerization is stopped after 6 hours so as to obtain a dry extract of approximately 10%. The latex is dried at 100 ° C for 8 hours. CES analysis of the product with a PS calibration gives the following results:

Mn = 48,000 Mp = 73,300 Ip = 1.53

Step 2: PRTA of MAM in solution, initiated by the VDF / HFP copolymer transferred to CHCI ₃ and catalyzed by CuCI / '2, 2' -bipyridine.

Initially, the ortho-xylene and the MAM are degassed by bubbling with argon for 4 hours, and the CuCl, the bipyridine and the VDF / HFP copolymer are dried under vacuum for 4 hours. 50 g of ortho-xylene are introduced into a 1 liter double-jacketed reactor surmounted by a condenser and continuously swept by a low flow of argon, then successively, with stirring, 0.5 g of CuCl and 1.56 g of 2,2'-bipyridine, 50 g of MAM, and finally 52.5 g of VDF / HFP copolymer transferred to chloroform (step 1). The reactor is heated to 100 ° C for 6 hours. At the end of polymerization, the residual monomer and the solvent are evaporated under vacuum at 80 ° C for 6 hours using a rotary evaporator. After dissolving in 800 ml of acetone, the polymer is isolated by precipitation with stirring in 2.5 liters of water, filtration and drying under vacuum at 60 ° C for 8 hours. The apparent conversion rate of MMA, calculated after evaporation under vacuum at 80 ° C for 6 hours from the reaction medium at the end of the reaction, is 76%.

CES analysis of the final product shows a total disappearance of the peak characteristic of the VDF / HFP copolymer and the appearance of a peak corresponding to the diblock copolymer (VDF / HFP) -b-PMMA (Ip = 1.27 in PMMA calibration ).

Example 7: Synthesis of a VDF / HFP-PMMA block copolymer in dispersed phase using the NiCI ₂ / bis-triphenylphosphine catalyst.

Step 1: Polymerization of vinylidene fluoride with transfer to chloroform. 1.8 I of water, 2.4 g of emulsifier are introduced into a 3-liter high-pressure reactor

(C ₇ Fι ₅ COONH ₄ ). After having tested the tightness of the reactor with 10 bars of nitrogen, it is put under vacuum, then under 5 bars of vinylidene fluoride (VDF), brought back to atmospheric pressure and put back under vacuum. 41.2 ml of chloroform are then introduced before heating the reactor to 80 ° C., and introducing VDF until a pressure of 65 bars is obtained. Once these conditions have been reached, 0.09 g of ammonium persulfate are introduced, and VDF is injected to maintain the pressure at 65 bars. After 2 hours, 0.09 g of ammonium persulfate are added. The polymerization is stopped after 5 hours so as to obtain a dry extract of approximately 10%. The polymer is kept in the form of latex.

CES analysis of the product with a PS calibration gives the following results: Mn = 39,000

Mp = 60,400 Ip = 1.55

Step 2: PRTA of the dispersed phase MAM, initiated by PVDF latex transferred to CHCI ₃ and catalyzed by. NiCI _∑ / bis-triphenylphosphine.

Firstly, the latex and the PVDF are evaporated under 300 mbar for 12 hours at 50 ° C, to remove the residual chloroform and decompose the remaining persulfate, and the NiCI ₂ / bis-triphenylphosphine complex is dried under vacuum for 1 hour .

In a 500 ml glass bottle, 2.2 g of SIMULSOL SL 10 surfactant from SEPPIC (alkylated polyglucoside) are mixed with 425 g of PVDF latex. The whole is stirred and degassed by bubbling with argon for 4 hours.

3.50 g of NiCI ₂ / bis-triphenylphosphine are added to 50 g of MMA in a 125 ml glass bottle. The whole is stirred and degassed by bubbling with argon for 4 hours. In a jacketed 1 liter reactor surmounted by a condenser and continuously swept by a low flow of argon, the latex / surfactant mixture is introduced, then the MMA / catalyst mixture is dripped with strong stirring to form a co -emulsion. The reaction medium is left under stirring for 1 hour at room temperature, then the reactor is heated to 80 ° C for 6 hours. At the end of polymerization, the product obtained in the form of a dispersion can be filtered under vacuum. It is then washed 4 times with 100 ml of water and dried under vacuum at 60 ° C for 8 hours.

The apparent conversion rate of MMA, calculated after filtration and drying under vacuum at 80 ° C. for 6 hours from the reaction medium at the end of the reaction, is 70%. The CES chromatogram of the product shows a new peak corresponding to the PVDF-b-PMMA diblock copolymer (Ip = 1.3 in PMMA calibration).

Example 8: Synthesis of a VDF / HFP-PMMA block copolymer in dispersed phase using the NiCI ₂ / bis-triphenylphosphine catalyst. Step 1: Polymerization of vinylidene fluoride and hexafluoropropene with transfer to chloroform.

1.8 l of water, 2.4 g of emulsifier (CF ₁₅ COONH ₄ ) are introduced into a 3 liter high-pressure reactor. After having tested the tightness of the reactor with 10 bars of nitrogen, it is placed under vacuum, then under 5 bars of an 80/20 mixture by weight of vinylidene fluoride (VDF) and hexafluoropropene (HFP), brought back at atmospheric pressure and returned to vacuum. 41.2 ml of chloroform are then introduced before heating the reactor to 80 ° C., and introducing VDF / HFP mixture until a pressure of 65 bars is obtained. Once these conditions have been reached, 0.09 g of ammonium persulfate are introduced, and VDF / HFP mixture is injected to maintain the pressure at 65 bars. After 1 hour, 0.09 g of ammonium persulfate are added. The polymerization is stopped after 6 hours so as to obtain a dry extract of approximately 12%. The copolymer is stored in the form of latex.

CES analysis of the product with a PS calibration gives the following results: Mn = 48,000 Mp = 78,300 Ip = 1.63

Step 2: PRTA of the MMA in dispersed phase, initiated by the VDF / HFP copolymer transferred to CHCI ₃ and catalyzed by. NiCI ₂ / bis-triphenylphosphine

Firstly, the VDF / HFP copolymer latex is evaporated under 300 mbar for 12 hours at 50 ° C to remove the residual chloroform and decompose the remaining persulfate, and the NiCI ₂ / bis-triphenylphosphine complex is dried under vacuum for 1 hour . In a 500 ml glass bottle, 2.2 g of SIMULSOL SL 10 surfactant from SEPPIC (alkylated polyglucoside) are mixed with 425 g of VDF / HFP copolymer latex. The whole is stirred and degassed by bubbling with argon for 4 hours.

In a 125 ml glass bottle, 3.72 g of NiCI ₂ / bis-triphenylphosphine are added to 50 g of MMA. The whole is stirred and degassed by bubbling with argon for 4 hours.

In a jacketed 1 liter reactor surmounted by a condenser and continuously swept by a low flow of argon, the latex / surfactant mixture is introduced, then the MMA / catalyst mixture is dripped with strong stirring to form a co -emulsion. The reaction medium is left under stirring for 6 hours. At the end of polymerization, the product obtained in the form of a dispersion can be filtered under vacuum. It is then washed 4 times with 100 ml of water and dried under vacuum at 60 ° C for 8 hours.

The apparent conversion rate of the MMA obtained by filtration and drying under vacuum at 80 ° C. for 6 hours from the reaction medium at the end of the reaction is 70%.

The CES chromatogram of the product shows a new peak corresponding to the poly (VDF / HFP) -b-PMMA diblock copolymer (Ip = 1.6 in PMMA calibration).

Example 9 Synthesis of a PVDF-PMMA block copolymer in a dispersed phase using little NiCI ₂ / bis-triphenylphosphine catalyst. Step 1: identical to that of Example 7

Step 2: PRTA of the dispersed phase MAM, initiated by the PVDF latex transferred to CHCI ₃ and catalyzed by very little NiCI _∑ / bis-triphenylphosphine complex

First, the PVDF latex is evaporated under 300 mbar for 12 hours at 50 ° C to remove the residual chloroform and decompose the remaining persulfate, and the NiCI ₂ / bis-triphenylphosphine complex is dried under vacuum for 1 hour.

In a 500 ml glass bottle, 2.2 g of SIMULSOL SL 10 surfactant from SEPPIC (alkylated polyglucoside) are mixed with 425 g of PVDF latex. The whole is stirred and degassed by bubbling with argon for 4 hours. 0.38 g of NiCI ₂ / bis-triphenylphosphine complex is added to 50 g of MMA in a 125 ml glass bottle. The whole is stirred and degassed by bubbling with argon for 4 hours.

In a jacketed 1 liter reactor surmounted by a condenser and continuously swept by a low flow of argon, the latex / surfactant mixture is introduced, then the MMA / catalyst mixture is dripped with strong stirring to form a co -emulsion. The reaction medium is left under stirring for 1 hour at room temperature, then the reactor is heated to 80 ° C for 6 hours. At the end of polymerization, the reaction mixture occurs and is a stable emulsion which is coagulated with a few drops of acid. hydrochloric, then filtered under vacuum and washed 4 times with 100 ml of water on filter. The copolymer is then dried under vacuum at 60 ° C for 8 hours.

The apparent conversion rate of MMA, calculated after filtration and drying under vacuum at 80 ° C. for 6 hours from the reaction medium at the end of the reaction, is 80%.

The CES chromatogram of the product shows a new peak corresponding to the PVDF-b-PMMA diblock copolymer (Ip = 1.8 in PMMA calibration).

Claims

1. Process for the manufacture of diblock, triblock or multiblock copolymers, characterized in that it comprises: - a first step of telomerization or of radical polymerization in the presence of a specific transfer agent to form a telomer or a polymer comprising at least a terminal group capable of initiating a radical polymerization reaction controlled by atom transfer, and

at least a second stage using this telomer or this polymer as a mono- or polyfunctional macro-initiator for radical polymerization controlled by atom transfer from one or more monomers.

2. Method according to claim 1, characterized in that, starting from a monomer M ¹ and a telogen XY of which at least one of the groups X and Y is active in PRTA, Y representing a hydrogen atom , chlorine, bromine or iodine, and X being:

- or a group of the type CZ _Z V _V W ₃ . _ZV comprising at least one chlorine, bromine or iodine atom, in which Z is a hydrogen, chlorine, bromine or iodine atom, a phenyl group, CN, CO ₂ R or any other electron-withdrawing group or resonance stabilizer which may contain chlorine, bromine or iodine atoms, and V and W, which may be identical or different, may each be a hydrogen or halogen atom (chlorine, bromine, iodine, fluorine) or a alkylated group,

- or a group of the type C _n F _{2n + 1} , a telomer of the formula is formed in the first step:

X- < ¹ ) ' _α gY (T)

and this telomer T is used as a mono- or bifunctional macro-initiator of radical polymerization controlled by atom transfer for the production of diblock or triblock copolymers of formula:

XM ² ) _Q- (M ¹ ) _g -Y or χ ._ (M ² ) _p -CM ¹ ) _g -O '- (M ² -Y'

in which Q is equal to X minus X ', Q' is equal to Y minus Y ', the symbols X' and Y 'each being a chlorine, bromine or iodine atom, and M ² are units of identical or different monomers.

3. Method according to claim 1, characterized in that, starting from an XY telogen as defined in claim 2 and from monomers M ¹ and M ^{1 ′} , a bistelomer of formula is formed in the first step:

XM) _h - Q- (M ¹ ) _q -Y (BT)

and this BT bistelomer is used as a mono- or bifunctional macro-initiator of radical polymerization controlled by atom transfer for the production of copolymers of formulas:

X "_ (_ ² -) i- Q '- (- M ¹ ' -) _h - Q - (- M ¹ -) _g - Y

X "- (- M ² -) i-Q '- (- M ¹ ' -) _h - Q - (- M ¹ -) _g - (- M ² -) _r -Y '

in which:

Q = X minus X 'with X' = Cl, Br or I, Q '= X' minus X "with X" = Cl, Br or I, Y = CI, Br or I, and Y '= CI, Br or l.

4. Method according to claim 2 or 3 wherein the telogen XY is chosen from chloroform, methyl or ethyl dichloroacetate, methyl trichloroacetate, bromotrichioromethane, tetrachloride or carbon tetrabromide, dibromoacetronitrile and iodides of perfluoroalkyl.

5. Method according to one of claims 2 to 4 wherein the monomer or monomers used for telomerization are chosen from olefins optionally substituted by one or more halogen atoms, vinyl monomers and acrylic monomers.

6. The method of claim 5 wherein the monomer used for telomerization is vinyl acetate.

7. The method of claim 6 wherein the copolymer is subjected to hydrolysis.

8. The method of claim 5 wherein the monomer used for telomerization is vinylidene fluoride.

9. Method according to claim 1, characterized in that, starting from a monomer M ¹ and a transfer agent XY (X and Y being as defined in claim 2), a first stage is formed. polymer of formula:

X - (- M ¹ -) _n - Y or χ _ ₍ _ M ¹ - M ¹ '-) _{m + m} .- Y

and this polymer P is used as a macro-initiator of radical polymerization controlled by atom transfer for the production of copolymers of formula:

XM M ² ) _p -Q- (M ¹ ) _n -Y or

X '- (- M ² -) _p -Q - (- M ¹ - M ¹ ' -) _{m + m} - Y or X '- (- M ² -) _p -Q - (- M ¹ -) _n - (- M ² -) or _ (_ M ² -) _p -Q - (- M ¹ - M ¹ '-) _{m + m} .- (- M ² -) _p -Y'

in which Q is equal to X minus X ', the symbols X' and Y 'each being a chlorine, bromine or iodine atom, and M ¹ and M ² are units of identical or different monomers.

10. The method of claim 9 wherein the transfer agent is chosen from chloroform, methyl or ethyl dichloroacetate, methyl trichloroacetate, bromotrichloromethane, tetrachloride or carbon tetrabromide, dibromoacetronitrile and iodides of perfluoroalkyl.

11. The method of claim 9 wherein the transfer agent is chloroform.

12. Method according to one of claims 9 to 10 in which the monomer or monomers used in the first step are chosen from the monomers of formula:

The

\

C = C H)

/ \ in which L, L 'and L "may be independently of each other a hydrogen atom, a fluorine atom, a fluoroalkyl group or a nitrile group, at least one of L, L and L" preferably being a fluorine.

13. Method according to one of claims 9 to 10 in which the monomer or monomers used in the first step are chosen from the monomers of formula:

in which L ¹ , L ² and L ³ are independently a hydrogen atom, a halogen, a hydrocarbon group of 1 to 20 carbon atoms (preferably from 1 to 6) with a linear or branched structure, and L ⁴ is a substituent of the type -CO-OL ⁵ or -O-CO-L ⁵ , L ⁵ being a hydrocarbon group of 1 to 20 carbon atoms (preferably from 1 to 6) with a linear or branched structure or a hydrocarbon group with a structure linear, cyclic or aromatic, containing one or more ethylenic or acetylenic bonds and possibly including one or more halogen atoms or heteroatoms.

14. Method according to one of claims 9 to 12 wherein the step of radical polymerization controlled by atom transfer is carried out in dispersed phase.

15. The method of claim 14 wherein the telomer or macroinitiator polymer is in emulsion or aqueous suspension.

16. The process as claimed in claim 15, in which the monomer M ² is added to the emulsion or to the suspension of the macro-initiator to form an aqueous emulsion or suspension stabilized by a nonionic surfactant, preferably an alkylated polyglucoside. .

17. Method according to one of claims 9 to 16 in which the monomer used for the radical polymerization step controlled by atom transfer is chosen from vinyl monomers (preferably vinyl aromatic) and acrylic monomers such as (meth) alkyl acrylates and (meth) acrylonitriles.

18. The method of claim 17 wherein the monomer used for the radical polymerization step controlled by atom transfer is styrene or methyl methacrylate.

19. Copolymers as prepared by a process according to one of claims 1 to 18.