FR2825365A1 - RADICAL POLYMERIZATION USING TRANSFER AGENTS CONTAINING PHOSPHORUS AND SULFUR - Google Patents

Abstract

The invention relates to a radical polymerization method wherein a compound of formula (I-a), (I-b), (I-c) is used as a transfer agent, wherein the symbols Z, Z' and Z'' are identical or different, each representing a group such that the radicals Z DEG , Z' DEG , Z'' DEG are stabilized radicals which can initiate radical polymerization, and the symbols R<1> and R<2>, are identical or different, each representing a radical or group such that the links P-R<1> and P-R<2> are stable (non reactive) in conditions of radical polymerization.

Description

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DESCRIPTION
The present invention relates to the field of radical polymerization and more particularly relates to that of radical polymerization of a living nature, this character being useful for the synthesis of copolymers with controlled architecture such as block, branched, star and / or graft copolymers. .

In Polymer International 27,359 (1992), Quirk and Lee described the living character of a polymerization and assigned the following criteria to it:
1. The polymerization can continue until the complete consumption of the monomer and the further addition of monomer allows the polymerization to continue.

2. The macromolecular chains are in constant concentration throughout the polymerization and all grow at the same speed; this results in a linear increase in molecular masses with conversion, as well as a tight distribution of these masses.

3. Molecular mass is linearly correlated to the monomer / chain precursor molar ratio.

4. Finally, in relation to the preceding criteria, the living character makes it possible to prepare copolymers with a complex architecture.

In the field of polymerization controlled by the RAFT (Radical Addition-Fragmentation Transfer) method, the use of sulfur-containing transfer agents of the dithioesters or dithiocarbamates type has already been described and their value in radical polymerization has been shown (patent applications WO 98 / 01478, FR 2 773 161, WO 98/58974 and WO 99/35177). However, the polymers obtained with the dithioesters are always colored (violet, purple). As for dithiocarbamates, although they control the polymerization of vinyl acetate well, they do not control that of other monomers such as, for example, methyl methacrylate.

It has now been found that these drawbacks can be overcome by using as transfer agent a compound containing phosphorus and sulfur, corresponding to one of the following general formulas:

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dans lesquelles les symboles Z, Z'et Z", identiques ou différents, représentent chacun un groupement tel que les radicaux Z', Z"et Z"* sont des radicaux stabilisés susceptibles d'amorcer une polymérisation radicalaire, et les symboles R1 et R2, identiques ou différents, représentent chacun un radical ou groupement tel que les liaisons P-R1 et P-R2 sont stables (non réactives) dans les conditions de polymérisation radicalaire.

in which the symbols Z, Z 'and Z ", which are identical or different, each represent a group such that the radicals Z', Z" and Z "* are stabilized radicals capable of initiating radical polymerization, and the symbols R1 and R2, which are identical or different, each represent a radical or group such that the P-R1 and P-R2 bonds are stable (non-reactive) under the conditions of radical polymerization.

The transfer agents of formula (Ia), (Ib) or (Ic) in fact lead to colorless polymers and make it possible to control the polymerization of other monomers other than vinyl acetate such as, for example, styrene and acrylic monomers.

A subject of the invention is therefore a radical polymerization process, characterized in that at least one compound of general formula (I-a), (I-b) or (I-c) is used as transfer agent.

les symboles R1 et R2 ayant les mêmes significations que précédemment. A subject of the invention is also (co) polymers characterized by the presence in their structure of at least one group of formula (II-a), (II-b) or (II-c):

the symbols R1 and R2 having the same meanings as above.

Those skilled in the art know that, by stabilized radicals, is meant species in which the atom carrying the free electron is in position a of a function

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known to stabilize radicals. As nonlimiting examples of Z *, Z '@ and Z "@ radicals, mention may be made of those of the following formulas:

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dans lesquelles : - n est égal à 1 ou 2, - X représente un atome d'hydrogène ou d'halogène ou un radical alkyle, halogénoalkyle ou alcoxy, ce radical pouvant être linéaire ou ramifié et contenir de 1 à 20 atomes de carbone, - Y représente un atome de chlore ou de fluor ou un groupe cyano,

4 - les symboles R3 et R4, identiques ou différents, représentent chacun un atome d'hydrogène ou un radical alkyle linéaire ou ramifié contenant de 1 à 20 atomes de carbone, - les symboles R5 et R5', identiques ou différents, représentent chacun un atome d'hydrogène ou un radical alkyle linéaire ou ramifié contenant de 1 à 20 atomes de carbone, éventuellement substitué par un atome d'halogène ou un groupement hydroxy, amino, alkylamino, dialkylamino ou ammonium quaternaire, ou R5 et R5'ensemble avec l'atome d'azote auxquels ils sont liés forment le reste d'un hétérocycle pouvant contenir d'autres hétéroatomes, et - les symboles R6 à R10 représentent chacun un atome d'hydrogène ou un radical alkyle linéaire ou ramifié contenant de 1 à 20 atomes de carbone, les symboles R7 et R10 pouvant aussi représenter ensemble un enchaînement bivalent tri méthylène.

in which: - n is equal to 1 or 2, - X represents a hydrogen or halogen atom or an alkyl, haloalkyl or alkoxy radical, this radical possibly being linear or branched and containing from 1 to 20 carbon atoms, - Y represents a chlorine or fluorine atom or a cyano group,

4 - the symbols R3 and R4, identical or different, each represent a hydrogen atom or a linear or branched alkyl radical containing from 1 to 20 carbon atoms, - the symbols R5 and R5 ', identical or different, each represent a hydrogen atom or a linear or branched alkyl radical containing from 1 to 20 carbon atoms, optionally substituted by a halogen atom or a hydroxy, amino, alkylamino, dialkylamino or quaternary ammonium group, or R5 and R5 'together with l the nitrogen atom to which they are attached form the remainder of a heterocycle which may contain other heteroatoms, and - the symbols R6 to R10 each represent a hydrogen atom or a linear or branched alkyl radical containing from 1 to 20 atoms carbon, the symbols R7 and R10 can also together represent a tri-methylene bivalent chain.

As nonlimiting examples of radicals or groups R1 and R2 leading to stable P-R1 and P-R2 bonds, mention may be made of alkyl, cycloalkyl, aryl or aralkyl radicals containing from 1 to 20 carbon atoms, amino groups disubstituted by alkyl, cycloalkyl, aryl or aralkyl radicals containing from 1 to 20 carbon atoms, and linear alkylthio groups containing from 1 to 20 carbon atoms. The radicals R1 and R2 of formulas (I-a) and (II-a) can also be linked to form, with the phosphorus atom, a heterocycle.

Certain transfer agents according to the invention are already described in the literature. This is the case: - bis (1-phenylethyl) methyltrithiophosphonate and bis (1-phenylethyl) phenyltrithiophosphonate described by B. Strijtveen et al. in Tetrahedron, Vol. 43, no l, pp. 123-130, and

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- 2-octyl diphenyldithiophosphinate described by 1. R. Hopkins et al. in J. A. C. S., Vol. 78, pp. 4447-4450.

The transfer agents according to the invention can be prepared by methods known per se, such as those described in the two aforementioned articles or also in US patents 3,162,570 and 3,705,216, as well as in the articles of: - M Grayson et al. in J. Org. Chem., Vol. 32,1967, pp. 236-238; - O. N. Grishina et al. in J. Gen. Chem. USSR, Vol. 37,1967, pp. 2276-2278; - L. V. Nesterov et al. in J. Gen. Chem. USSR, Vol. 40,1970, pp. 1237-1241; - V. S. Blagoveshchenskii et al. in J. Gen. Chem. USSR, Vol. 41,1971, pp. 1036-1037.

A general method for preparing the transfer agents according to the invention is described in US Pat. No. 3,705,216 and consists of reacting a phosphine with a disulfide.

The dithiophosphinates of formula (I-a) can advantageously be prepared by reaction of a Z-S2-Z disulfide with an RRPH phosphine under the conditions described by M. Grayson et al. in the aforementioned reference, or by reacting an alcohol or an alkene with a dithiophosphinic acid R1R2P (= S) SH under the conditions described by 1. R. Hopkins et al. in the aforementioned reference.

The trithiophosphonates (I-b) can be advantageously prepared by reaction of a thiophosphonic dichloride R1-P (= S) C! 2 with a Z-SH and / or Z'-SH mercaptan under the conditions described by B. Strijtveen et al. and by L. Nesterov et al. in the aforementioned references, or by reaction of elemental sulfur with a dithiophosphonite R1p (SZ) (SZ ') under the conditions described in US Pat. No. 3,162,570.

The tetrathiophosphates of formula (I-c) are advantageously prepared according to the process described by V. S. Blagoveshchenskii et al. in the aforementioned reference, which consists in reacting P2Ss with a Z-OH alcohol or a mixture of Z-OH, Z'OH, Z "-OH alcohols.

Among the transfer agents according to the invention, preferred are dithiophosphinates (I-a) and tetrathiophosphates () -c) and, among the latter, more particularly tris (1-phenylethyl) tetrathiophosphate.

For the implementation of the process according to the invention, one mixes, optionally in a solvent, at least one polymerizable monomer by the radical route with a radical polymerization initiator and a compound of general formula (Ia), (Ib) or (Ic ) and this mixture is reacted at a temperature chosen as a function of the decomposition temperature of the initiator used. The reaction temperature can thus range from 20 to 200 C, but is preferably between 50 and 150 C.

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If we denote by fA the functionality of the initiator (that is to say the number of moles of free radicals generated by each mole of initiator), by nA the number of moles of initiator, by fAG the functionality of the transfer agent (that is to say the number of RS groups that compound 1 comprises), and by nAG the number of moles of compound 1, the ratio of initiator to transfer agent, equal to fA. nA / fAG. nAG, can range from 0.001 to 5 and is preferably between 0.05 and 1. The initiator can be introduced in several fractions added semi-continuously.

If the number of moles of monomer is denoted by nM, the ratio of monomer to transfer agent, equal to nM / fAG. nAG, can range from 1 to 10,000 and is preferably between 10 and 5,000.

2, 2'-azobis [2-méthyl-N (1, 1) -bis (hydroxyméthyl) -2-hydroxyéthyl]propionamide, le 2, 2'azobis[2-méthyl-N (1, 1) -bis (2-méthyl-N-hydroxyéthyl]propionamide, le dichlorure de 2, 2' -azobis (diméthylèneisobutyramidine), le 2, 2'-azobis (N, N'-diméthylèneisobutyramide), les systèmes rédox, le peroxyde de lauroyle, l'hydroperoxyde de tert-butyle, l'hydroperoxyde de cumène, le t-butyl-peroxyacétate, le t-butylperoxybenzoate, le tbutylperoxyoctoate, le t-butylperoxynéodécanoate, le t-butylperoxyisobutyrate, le tamylperoxypivalate, le t-butylperoxypivalate, le peroxyde de dicumyle, le peroxyde de benzoyle, le persulfate de potassium ou le persulfate d'ammonium. The radical polymerization initiator can be chosen from all the initiators conventionally used in radical polymerization, in particular from organic peroxides, hydroperoxides and azo compounds. As examples of initiators which can be used, there may be mentioned more particularly 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2-butanenitrile), 4, 4'-azobis (4-pentanoic acid), 1,1'-azobis (cyclohexanecarbonitrile), 2- (t.butylazo) -2-cyanopropane,

2, 2'-azobis [2-methyl-N (1, 1) -bis (hydroxymethyl) -2-hydroxyethyl] propionamide, 2, 2'azobis [2-methyl-N (1, 1) -bis (2 -methyl-N-hydroxyethyl] propionamide, 2, 2 '-azobis (dimethyleneisobutyramidine) dichloride, 2, 2'-azobis (N, N'-dimethyleneisobutyramide), redox systems, lauroyl peroxide, hydroperoxide t-butyl, cumene hydroperoxide, t-butyl-peroxyacetate, t-butylperoxybenzoate, tbutylperoxyoctoate, t-butylperoxyneodecanoate, t-butylperoxyisobutyrate, tamylperoxypivalate, t-butylperoxypicumicumate, benzoyl peroxide, potassium persulfate or ammonium persulfate.

In the process according to the invention, any monomer which can be polymerized by the radical route can be used. The following are more particularly suitable: - styrene and its derivatives such as, for example, α-methylstyrene, vinyltoluene, mono-, di- or tri-halogenostyrenes, chloromethylstyrene, 2,4dimethylstyrene and vinylanthracene; - vinyl esters of carboxylic acids such as, for example, vinyl acetate; - (meth) acrylic esters of alcohols which may or may not be functionalized, such as, for example, methyl, ethyl, n-butyl, isobutyl, heptyl, octyl or isooctyl acrylates or methacrylates, 2-ethylhexyl, lauryl, stearyl, 2-hydroxyethyl, 2-hydroxypropyl, 2-methoxyethyl, 2-ethoxyethyl, butyldiglycol, 2,2, 2-trifluoroethyl, 2- (dimethylamino) ethyl , 2- (tert-butylamino) ethyl, allyl, isobornyl, 2- (dicyclopentenyl) oxyethyl, 2- (2oxoimidazolidin-1-yl) ethyl and ethylene glycol dimethacrylate;

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- C3 to C12 vinyl nitriles such as, for example, acrylonitrile and methacrylonitrile; - dienes such as butadiene, isoprene, 2, 3-dimethyl-1, 3-butadiene, piperylene and chloroprene; - vinyl chloride and vinylidene fluoride.

In the following examples which illustrate the invention without limiting it, the gel permeation chromatography (GPC) was carried out on a WATERS "apparatus (reference Alliance 2410) completed with an RI and UV detector, with used in series, STYRAGELO HR 3,4 and 5 columns, the eluent being tetrahydrofuran and the complete line being heated to 30 C.

EXAMPLE 1 Radical polymerization of styrene at 65 ° C. in the presence of tris (1-phenylethyl) tetrathiophosphate and of azobisisobutyronitrile in the absence of solvent.

60 ml of styrene were introduced into a 100 ml two-necked flask, surmounted by a condenser, and at room temperature and by means of a vacuum manifold, the styrene was deoxygenated by three vacuum-nitrogen cycles. To the styrene thus deoxygenated, 22 mg of tris (1-phenylethyl) tetrathiophosphate and 17.3 mg of azobisisobutyronitrile (AIBN) were added, then the reaction mixture was brought to 65 ° C. for 41 hours.

The course of the reaction was followed using samples which were analyzed by GPC and proton NMR in order to determine respectively the number-average molecular mass Mn, the polymolecularity index Ip and the conversion rate.

After 41 hours of reaction, a transparent and colorless solution was obtained. The results of the test are collated in the following table.

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<tb>

Time <SEP> Conversion <SEP> Mn <SEP> Ip
<tb> (in <SEP> hours) <SEP> (%) <SEP> (g / mol)
<tb> 4 <SEP> 2 <SEP> 161400 <SEP> 17
<tb> 16.5 <SEP> 5 <SEP> 184 <SEP> 500 <SEP> 1.6
<tb> 25 <SEP> 25 <SEP> 235 <SEP> 300 <SEP> 1.6
<tb> 41 <SEP> 42 <SEP> 287000 <SEP> 1.9
<tb>
Tris (1-phenylethyl) tetrathiophosphate of the formula:

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used in this example, was prepared as follows:
Into a 50 ml two-necked flask were introduced 1.53 g of phosphorus pentasulfide and 3.33 ml of dry-phenethyl alcohol, then the mixture was stirred until the evolution of hydrogen sulfide persisted. With stirring, 1.02 g of phosphorus pentasulfide was then added to the solution and the mixture was heated at 120 ° C. for 90 minutes. The temperature was then raised to 160 ° C., then, the heating being stopped, it was allowed to cool and extracted with 20 ml of carbon tetrachloride. 4.8 g of a crude precipitate of tris (1-phenylethyl) tetrathiophosphate were thus recovered, ie a crude molar yield of 88%.

By purifying 1.76 g of this crude precipitate on a silica column with a mixture of pentane and petroleum ether (34/1 by volume) as eluent, 0.63 g of pure compound 1d was obtained in the form of 'a white solid exhibiting, by proton, carbon and phosphorus NMR in CDCts,) the following characteristics:
1H NMR: 7.3 ppm (m, 5H), 4.5 ppm (m, 1H), 1.7 ppm (m, 3H)
C NMR: 128.6 ppm (m), 127.6 ppm (m), 50 ppm (m), 24 ppm (m)
31p NMR: 86.05 ppm (majority) and 85.84 ppm
EXAMPLE 2 (Comparative)
Example 1 was repeated, but without using tris (1phenylethyl) tetrathiophosphate and with a similar amount (18 mg) of AIBN.

After 15 hours of reaction at 65 ° C., the results summarized in the following table were obtained.

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Time <SEP> Conversion <SEP> Mn <SEP> Ip
<tb> (in <SEP> hours) <SEP> (%) <SEP> (glmol)
<tb> 1.50 <SEP> 2 <SEP> 245000 <SEP> 1.6
<tb> 2.25 <SEP> 11 <SEP> 231 <SEP> 000 <SEP> 1.6
<tb> 5.50 <SEP> 29 <SEP> 219 <SEP> 900 <SEP> 1.6
<tb> 14, <SEP> 25 <SEP> 63 <SEP> 221 <SEP> 800 <SEP> 1, <SEP> 5
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Comparison of these results with those of Example 1 shows the living character conferred by tris (1-phenylethyl) tetrathiophosphate.

EXAMPLE 3
The operation was carried out as in Example 1, but in a 50 ml two-necked flask with 10.5 ml of styrene, 40 mg of compound Id and 48 mg of AIBN.

After 8 hours of reaction at 65 ° C., the results collated in the following table were obtained.

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<tb>

Time <SEP> Conversion <SEP> Mn <SEP> Ip
<tb> (in <SEP> hours) <SEP> (%) <SEP> (gimol)
<tb> 4 <SEP> 28 <SEP> 55 <SEP> 800 <SEP> 1.45
<tb> 5 <SEP> 36 <SEP> 58 <SEP> 800 <SEP> 1.4
<tb> 6 <SEP> 52 <SEP> 61 <SEP> 200 <SEP> 1.4
<tb> 7, <SEP> 8 <SEP> 67 <SEP> 64 <SEP> 800 <SEP> 1, <SEP> 5
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EXAMPLE 4 (Comparative)
Example 3 was repeated, but without using compound Id with 96 mg of AIBN per 21 ml of styrene.

The following table summarizes the results obtained for 8 hours at 65 C.

Their comparison with the results of Example 3 again shows the living character conferred by tris (1-phenylethyl) tetrathiophosphate.

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<tb>

Time <SEP> Conversion <SEP> Mn <SEP> Ip
<tb> (in <SEP> hours) <SEP> (%) <SEP> (g / mol)
<tb> 1 <SEP> 5 <SEP> 50 <SEP> 300 <SEP> 1.6
<tb> 3 <SEP> 24 <SEP> 47 <SEP> 900 <SEP> 1.8
<tb> 5 <SEP> 41 <SEP> 50 <SEP> 000 <SEP> 1.8
<tb> 8 <SEP> 90 <SEP> 52 <SEP> 600 <SEP> 1, <SEP> 9
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EXAMPLE 5
The operation was carried out as in Example 1 with 21 ml of styrene, 41.3 mg of compound Id and 24 mg of AIBN.

After 22 hours at 65 ° C., the results collated in the following table were obtained.

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Time <SEP> Conversion <SEP> Mn <SEP> Ip
<tb> (in <SEP> hours) <SEP> (%) <SEP> (g / mol)
<tb> 5 <SEP> 19 <SEP> 70 <SEP> 200 <SEP> 1.5
<tb> 8 <SEP> 27 <SEP> 82 <SEP> 500 <SEP> 1, <SEP> 5
<tb> 22 <SEP> 72 <SEP> 112 <SEP> 400 <SEP> 2.1
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EXAMPLE 6 (Comparative)
Example 5 was repeated, but without using compound 1d. The results obtained for 8 hours at 65 ° C. are collated in the following table. Their

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comparison with the results of Example 5 still shows the living character conferred by tris (1-phenylethyl) tetrathiophosphate.

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Time <SEP> Conversion <SEP> Mn <SEP> Ip
<tb> (in <SEP> hours) <SEP> (%) <SEP> (gimol)
<tb> 1 <SEP> 4 <SEP> 72600 <SEP> 1.9
<tb> 3 <SEP> 12 <SEP> 67100 <SEP> 1.8
<tb> 5 <SEP> 62 <SEP> 68 <SEP> 200 <SEP> 1.8
<tb> 8 <SEP> 83 <SEP> 67 <SEP> 400 <SEP> 1.9
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EXAMPLE 7 Radical polymerization of vinyl acetate in the presence of compound I-d and of AIBN at 65 ° C. in the absence of solvent.

The procedure was as in Example 1, but in a 50 ml two-necked flask with 20 ml of vinyl acetate, 43.3 mg of compound 1-d and 24.4 mg of AIBN.

The reaction, followed for 2.5 hours, gave the results summarized in the following table.

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<tb>

Time <SEP> Conversion <SEP> Mn * <SEP> Ip
<tb> (in <SEP> minutes) <SEP> (%) <SEP> (g / mol)
<tb> 15 <SEP> 10 <SEP> 128 <SEP> 500 <SEP> 1.9
<tb> 30 <SEP> 14 <SEP> 204 <SEP> 300 <SEP> 1.9
<tb> 50 <SEP> 75 <SEP> 210600 <SEP> 2,3
<tb> 150 <SEP> 86 <SEP> 223000 <SEP> 3.0
<tb>
* calibration against standard polystyrenes
EXAMPLE 8 (Comparative)
Example 7 was repeated, but without using compound 1d. The results obtained are collated in the following table. As in the case of styrene, their comparison with the results of Example 7 shows the living character conferred by tris (1-phenylethyl) tetrathiophosphate.

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<tb>

Time <SEP> Conversion <SEP> Mn * <SEP> Ip
<tb> (in <SEP> minutes) <SEP> (%) <SEP> (g / mol)
<tb> 15 <SEP> 15 <SEP> 245600 <SEP> 1.8
<tb> 30 <SEP> 35 <SEP> 214 <SEP> 500 <SEP> 2, <SEP> 1
<tb> 50 <SEP> 54 <SEP> 236 <SEP> 600 <SEP> 2.1
<tb> 150 <SEP> 85 <SEP> 192 <SEP> 300 <SEP> 3, <SEP> 55
<tb>
* calibration against standard polystyrenes

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EXEMPLE 9
Le tableau suivant rassemble les résultats obtenus lorsqu'on reproduit l'exemple 7, mais en utilisant deux fois plus de composé l-d (89,8 mg au lieu de 43,3 mg). Leur comparaison avec les résultats de l'exemple 7 montre qu'à même taux de conversion l'emploi d'une quantité deux fois plus grande de composé I-d conduit à une importante diminution de la masse moléculaire en nombre.

EXAMPLE 9
The following table collates the results obtained when example 7 is reproduced, but using twice as much compound 1d (89.8 mg instead of 43.3 mg). Their comparison with the results of Example 7 shows that at the same conversion rate, the use of a twice as large amount of compound Id leads to a significant reduction in the molecular weight in number.

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<tb>

Time <SEP> Conversion <SEP> Mn * <SEP> Ip
<tb> (in <SEP> minutes) <SEP> (%) <SEP> (glmol)
<tb> 30 <SEP> 16 <SEP> 135 <SEP> 000 <SEP> 1.8
<tb> 45 <SEP> 24 <SEP> 144 <SEP> 000 <SEP> 1.9
<tb> 60 <SEP> 44 <SEP> 150 <SEP> 000 <SEP> 1.95
<tb>
* calibration against standard polystyrenes
EXAMPLE 10 Area radical polymerization of styrene at 65 ° C. in the presence of 1-phenylethyl diphenyldithiophosphinate and AIBN in the absence of solvent.

The operation was carried out as in Example 1, but in a 50 ml two-necked flask with 15 ml of styrene, 120.8 mg of 1-phenylethyl diphenyldithiophosphinate (compound l-e) and 28.3 mg of AIBN.

The reaction, followed for 25 and a half hours, gave the results summarized in the following table.

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<tb>

Time <SEP> Conversion <SEP> Mn <SEP> Ip
<tb> (in <SEP> hours) <SEP> (%) <SEP> (glmol)
<tb> 7.5 <SEP> 5 <SEP> 84 <SEP> 700 <SEP> 1.4
<tb> 20 <SEP> 63 <SEP> 100 <SEP> 700 <SEP> 1.6
<tb> 22, <SEP> 5 <SEP> 86 <SEP> 121 <SEP> 300 <SEP> 1, <SEP> 9
<tb>
1-Phenylethyl diphenyldithiophosphinate of the formula:

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utilisé dans cet exemple, a été préparé en deux étapes : synthèse de l'acide diphényidithiophosphinique, puis synthèse de son ester 1-phényléthylique. a) Synthèse de l'acide diphényidithiophosphinique ..........................................

used in this example, was prepared in two steps: synthesis of diphenyidithiophosphinic acid, then synthesis of its 1-phenylethyl ester. a) Synthesis of diphenyidithiophosphinic acid ..........................................

20 ml of benzene were introduced into a 100 ml three-necked flask, followed by 5 g of phosphorus pentasulfide. After complete solubilization of the latter, the reaction mixture was brought to 50 ° C. and 12.07 g of aluminum trichloride were introduced therein in portions and over 3 hours. After these three hours at 60-63OC, the reaction mixture was heated under reflux for 5 hours, then cooled to room temperature and then poured into 100 g of crushed ice.

To the mixture thus obtained (light green and precipitated solution), 50 ml of benzene were added, then the mixture was poured into a separating funnel and the organic phase extracted three times with 30 ml of distilled water.

b) Synthèse du composé l-e 50%. The organic phase thus recovered was then dried with anhydrous magnesium sulfate, then mixed with 100 ml of a 10% sodium hydroxide solution, and the aqueous phase obtained was washed with benzene (3 washes of 40 ml) and then acidified to pH below 3 with 35% hydrochloric acid. There was thus obtained a green organic phase which, after recovery and drying under reduced pressure, gave 6.96 g of green crystals which were recrystallized once from 60 ml of isopropanol. The final yield of diphenyldithiophosphi nic acid was

b) Synthesis of the compound 50%.

... S //? esec compose / -e
In a 50 ml flask topped with a condenser fitted with a Dean-stark to remove the water formed during the esterification, 2 g of the diphenyldithiophosphinic acid obtained previously were dissolved in 5 ml of dry alcohol. -phenethyl, then the solution was brought to 185 C for 4 hours and then allowed the mixture to return to room temperature. A white precipitate formed (mass = 2.42 g) which was purified on a silica column using a mixture of pentane and ethyl acetate (24/1 by volume) as eluent. 1.43 g of pure compound were thus obtained in the form of a white solid characterized by proton NMR of CDOs: 1H NMR: 7.8 ppm (m, 9H), 7.3 ppm (m, 6H), 4.7 ppm (m, 1H), 1.6 ppm (m, 3H).

EXAMPLE 11 Synthesis of a poly (styrene) -b- poly (vinyl acetate) block copolymer
5.1 g of the poly (styrene) of Example 5 (Mn = 112,400 after 22 h of reaction) and 20 ml of vinyl acetate were introduced into a 50 ml two-necked flask, surmounted by a condenser. , then, at ambient temperature and by means of an empty ramp,

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vinyl acetate was deoxygenated by three vacuum-nitrogen cycles. To the reaction mixture was then added 1.06 mg of AIBN before bringing it to 65 ° C. for 30 minutes.

The following table summarizes the results obtained during the reaction followed, as previously, using samples analyzed by GPC and proton NMR.

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Time <SEP> Conversion <SEP> Mn <SEP> Ip
<tb> (in <SEP> minutes) <SEP> (%) <SEP> (g / mol)
<tb> 0 <SEP> 0 <SEP> 112 <SEP> 400 <SEP> 2.1
<tb> 15 <SEP> 15 <SEP> 171 <SEP> 200 <SEP> 2.35
<tb> 30 <SEP> 39 <SEP> 182 <SEP> 400 <SEP> 2, <SEP> 3
<tb>

Claims (5)

1. Radical polymerization process characterized in that at least one compound of formula (I-a), (I-b) or (I-c) is used as transfer agent:

in which the symbols Z, Z 'and Z ", which are identical or different, each represent a group such that the radicals Z', Z '* and Z" @ are stabilized radicals capable of initiating radical polymerization, and the symbols R1 and R2, which are identical or different, each represent a radical or group such that the P-R1 and P-R2 bonds are stable (non-reactive) under the conditions of radical polymerization. 2. Process according to claim 1, in which the radical (s) Z, Z ′ and Z "are chosen from those of the formulas:

<Desc / Clms Page number 15> - the symbols R5 and R5 ', identical or different, each represent a hydrogen atom or a linear or branched alkyl radical containing from 1 to 20

3 4 - the symbols R3 and R4, identical or different, each represent a hydrogen atom or a linear or branched alkyl radical containing from 1 to 20 carbon atoms,

in which: - n is equal to 1 or 2, - X represents a hydrogen or halogen atom or an alkyl, haloalkyl or alkoxy radical, this radical possibly being linear or branched and containing from 1 to 20 carbon atoms, - Y represents a chlorine or fluorine atom or a cyano group,

<Desc / Clms Page number 16> carbon atoms, optionally substituted by a halogen atom or a hydroxy, amino, alkylamino, dialkylamino or quaternary ammonium group, or R5 and R5 'together with the nitrogen atom to which they are attached form the remainder of a heterocycle which may contain other heteroatoms, and - the symbols R6 to R10 each represent a hydrogen atom or a linear or branched alkyl radical containing from 1 to 20 carbon atoms, the symbols R7 and R10 also possibly representing together a bivalent trimethylene chain . 3. Method according to claim 1 or 2 wherein the radicals or groups R1 or R2 are chosen from alkyl, cycloalkyl, aryl or aralkyl radicals containing from 1 to 20 carbon atoms, amino groups disubstituted by alkyl, cycloalkyl radicals, aryl or aralkyl containing from 1 to 20 carbon atoms, and linear alkylthio groups containing from 1 to 20 carbon atoms. 4. Method according to one of claims 1 to 3 wherein the transfer agent is tris (1-phenylethyl) tetrathiophosphate. 5. Polymers and copolymers characterized by the presence in their structure of at least one group of formula (II-a), (II-b) and / or (l1-c):

the symbols R1 and R2 having the same meanings as in claim 1.