Copolymer with surfactant blocks prepared by controlled free radical polymerisation

SURFACE-ACTIVATED BLOCK COPOLYMERS PREPARED BY CONTROLLED RADICAL POLYMERIZATION

The present invention relates to a surfactant block copolymer prepared by controlled radical polymerization, and a process for preparing said copolymers.

The subject of the present invention is therefore a block-surfactant copolymer comprising at least one hydrophilic block and at least one hydrophobic block and prepared by a so-called living preparation process using a transfer agent, said copolymer having:

a number-average molecular mass of between 1,000 and 50,000, preferably between 2,000 and 20,000, even more preferably between 4,000 and 16,000;

a glass transition temperature of the hydrophobic block of less than 30 ° C., preferably less than 25 ° C. and greater than -100 ° C., and a surface tension of less than 60 millinewtons per meter (mN / m), preferably less than at 50 mN / m, measured at a concentration in demineralized water less than or equal to 10^"4 mole / l, at 20 ° C and under an atmosphere.

Optionally, for certain applications of the copolymers, it is preferable to render the transfer agent located at one end of the molecule, chemically inert or to destroy said agent.

Other advantages and features of the present invention will emerge more clearly on reading the description and examples that follow.

According to the invention, block-surfactant copolymers comprising at least one hydrophilic block and at least one hydrophobic block, are prepared by a so-called living or controlled radical polymerization process involving the use of a transfer agent precisely for the purpose of controlling said radical polymerization.

In general, the preceding block copolymers can be obtained by any so-called living or controlled polymerization process such as, for example: xanthate-controlled radical polymerization according to the teaching of the application WO 98/58974,

the radical polymerization controlled by the dithioesters according to the teaching of the application WO 98/01478

the polymerization using nitroxide precursors according to the teaching of application WO 99/03894,

the radical polymerization controlled by dithiocarbamates according to the teaching of application WO 99/31144,

the atom transfer radical polymerization (ATRP) according to the teaching of the application WO 96/30421,

radical polymerization controlled by iniferters according to the teaching of Otu et al., Makromol. Chem. Rapid. Commun., 3, 127 (1982),

controlled radical polymerization by degenerative transfer of iodine according to the teaching of Tatemoto et al., Jap. 50, 127, 991 (1975), Daikin Kogyo Co. Itd Japan and atyjaszewski et al., Macromolecules, 28, 2093 (1995),

group transfer polymerization according to the Webster OW teaching "Group Transfer Polymerization", p. 580-588 of the "Encyclopedia of Polymer Science and Engineering", vol.7 and HF Mark, NM Bikales, CG Overberger and G. Menges, Eds., Wiley Interscience, New York, 1987,

radical polymerization controlled by the tetraphenylethane derivatives (D. Braun et al., Macromol.Symp.111,63 (1996)),

radical polymerization controlled by the organocobalt complexes (Wayland et al J.Am.Chem.Soc.Lu. 116,7973 (1994)). Preferred transfer agents for carrying out the controlled polymerization process are selected from dithioesters, thioethers-thiones, dithiocarbamates, and xanthates.

The preferred polymerization is live radical polymerization using xanthates. The invention further relates to a process for preparing these block polymers. This process consists of:

1- put in contact:

at least one ethylenically unsaturated monomer,

at least one source of free radicals, and at least one transfer agent of formula (I):

S \\

C - S - R1 (I)

/ R in which:

. R represents a group R2O-, R2R'2N- or R3- with:

R2 and R'2, identical or different, representing a group (i) alkyl, acyl, aryl, alkene or alkyne, or a ring (ii) carbon, saturated or unsaturated, optionally aromatic, or a heterocycle (iii), saturated or no, these groups and cycles (i), (ii) and (iii) may be substituted,

R3 representing H, Cl, an alkyl, aryl, alkene or alkyne group, a saturated or unsaturated (hetero) ring, optionally substituted, an alkylthio, alkoxycarbonyl, aryloxycarbonyl, carboxy, acyloxy, carbamoyl, cyano, dialkyl or diarylphosphonato group; , dialkyl- or diaryl-phosphinato, a polymer chain,

. R1 represents an optionally substituted (i) alkyl, acyl, aryl, alkene or alkyne group, or a saturated or unsaturated, optionally substituted or aromatic (ii) saturated or unsaturated carbon ring, or optionally saturated or unsaturated heterocycle (iii), or a polymer chain, and

Groups R1, R2, R'2 and R3 may be substituted with alkyl groups, substituted phenyls, substituted aromatic groups or groups: oxo, alkoxycarbonyl or aryloxycarbonyl (-COOR), carboxy (-COOH), acyloxy (-O2CR), carbamoyl (-CONR2), cyano (-CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, aryl alkyl, isocyanato, phthalimido, maleimido, succinimido, amidino, guanidino, hydroxy (-OH), amino (-NR2), halogen, allyl epoxy, alkoxy (-OR), S-alkyl, S-aryl, silyl, groups having a hydrophilic or ionic character, such as the alkaline salts of carboxylic acids, alkaline salts of sulfonic acid, polyalkylene oxide chains (POE, POP), cationic substituents (quaternary ammonium salts), R representing an alkyl or aryl group, and

2- repeat at least once the previous contacting using:

monomers different from the previous implementation, and

in the place of the precursor compound of formula (I), the polymer resulting from the preceding implementation, inerting the transfer agent at the end of the polymerization.

Preferably, the transfer agent of formula (I) is a dithiocarbonate chosen from the following compounds of formulas (IA), (IB) and (IC):

S \\

C - S - R¹ (IA)

/ O-R2

R^{2 '}- (~ o ​​- C - S - R¹) p (IB)

II S

R^{i "}(.. s - C - O - R²) p (IC) II S in which:

. R2 and R2 'represent a group (i) alkyl, acyl, aryl, alkene or alkyne, or a ring

(ii) carbonaceous, saturated or unsaturated, optionally aromatic, or a heterocycle (iii), saturated or unsaturated, these groups and cycles (i), (ϋ) and (iii) being able to be substituted,

. R1 and R1 'represent an optionally substituted (i) alkyl, acyl, aryl, alkene or alkyne group, or a saturated or unsaturated, optionally substituted or aromatic carbon (ii) ring, or a saturated or unsaturated heterocycle (iii), optionally substituted, a polymer chain,. p is between 2 and 10. During step 1, a first block of the polymer is synthesized of hydrophilic or hydrophobic nature depending on the nature and amount of the monomers used. In step 2, the other block of the polymer is synthesized.

The ethylenically unsaturated monomers are chosen from hydrophilic and hydrophobic monomers in proportions adapted to obtain a surfactant block copolymer whose blocks have the characteristics of the invention. According to this method, if all the successive polymerizations are carried out in the same reactor, it is generally preferable that all the monomers used in one step have been consumed before the polymerization of the next step begins, therefore before the new monomers are introduced. However, it may happen that the hydrophobic or hydrophilic monomers of the previous step are still present in the reactor during the polymerization of the next block. In this case, these monomers generally do not represent more than 5 mol% of all the monomers and they participate in the following polymerization by helping to introduce hydrophobic or hydrophilic units into the next block. Block-surfactant copolymers prepared according to this polymerization process may be simply di-blocks with a hydrophobic block and a hydrophilic block or else also triblocks with either a hydrophilic block surrounded by two hydrophobic blocks or a hydrophobic block surrounded by two blocks hydrophilic.

More particularly, the block-surfactant copolymer can be obtained by employing, as hydrophilic monomer in order to prepare the hydrophilic block, at least one ethylenically unsaturated monomer chosen from:

ethylenically unsaturated mono- and dicarboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid,

the mono-alkyl esters of the dicarboxylic acids of the type mentioned with the alkanols preferably containing 1 to 4 carbon atoms and their N-substituted derivatives, such as, for example, 2-hydroxyethyl acrylate or methacrylate,

amides of unsaturated carboxylic acids, such as acrylamide and methacrylamide,

ethylenic monomers containing a sulphonic acid group and its alkali or ammonium salts, for example vinylsulfonic acid, vinylbenzene sulphonic acid, alpha-acrylamido methylpropanesulfonic acid, 2-sulphoethylmethacrylate, the most preferred hydrophilic monomers are acrylic acid (AA), acrylamide (AM), 2-acrylamido-2-methyl-propanesulfonic acid (AMPS), and styrene sulfonate (SS).

By way of illustration of hydrophobic monomers that can be used to prepare the hydrophobic block, there may be mentioned in particular (meth) acrylic esters, vinyl esters and vinyl nitriles.

The term "(meth) acrylic esters" denotes the esters of acrylic acid and of methacrylic acid with C 1 -C 4 alcohols._π2 hydrogenated or fluorinated, preferably Ci-Ce- Among the compounds of this type, mention may be made of: methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate. The preferred monomers are esters of acrylic acid with linear or branched C 1 -C 4 alcohols such as methyl acrylate, ethyl acrylate, propyl acrylate and butyl acrylate. Vinyl nitriles include more particularly those having from 3 to 12 carbon atoms, such as, in particular, acrylonitrile and methacrylonitrile. The other ethylenically unsaturated monomers that can be used alone or in mixtures, or which can be copolymerized with the above monomers, are especially:

vinyl esters of carboxylic acid such as vinyl acetate, vinyl versatate, vinyl propionate,

vinyl halides,

the amides of vinylamine, in particular vinylformamide or vinylacetamide,

unsaturated ethylenic monomers containing a secondary, tertiary or quaternary amino group, or a nitrogen-containing heterocyclic group such as, for example, vinyipyridines, vinylimidazole, aminoalkyl (meth) acrylates and (meth) acrylamides; aminoalkyl such as dimethylaminoethyl acrylate or methacrylate, ditertiobutylaminoethyl acrylate or methacrylate, dimethylamino methyl acrylamide or methacrylamide.

It is of course possible to include in the composition of the block copolymers a certain proportion of hydrophobic monomers in the hydrophilic block and a certain proportion of hydrophilic monomers in the hydrophobic block, as long as the surfactant properties and the limits of the number of molecular masses, the glass transition temperature of the hydrophobic group and the surface tension remain verified. The polymerization of the copolymer may be carried out in an aqueous medium and / or an organic solvent such as tetrahydrofuran or a cyclic or branched dicyclic aliphatic alcohol such as methanol, ethanol or cyclohexanol, or a diol such as as ethylene glycol. An alcoholic solvent is more particularly recommended in the case where the hydrophilic monomers are acrylic acid (AA), acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and the sulfonate of styrene (SS) and the hydrophobic monomers are n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, t-butyl acrylate. At the end of the controlled polymerization step, the transfer agent located at one of the chain ends of the block-surfactant polymer can be rendered inert if desired for the end use of the copolymer. It is possible that the nature of the polymerization reaction medium (for example pH conditions, nature of the constituents of the reaction medium (monomers to be polymerized), is sufficient per se to inactivate the transfer agent at the end of polymerization. It is also possible that the medium to be treated in the final use of the copolymer inherently inactivates or neutralizes the transfer agent. It is recommended, if necessary for certain applications, to mask the active chemical functions of said agent by means of a suitable chemical masking agent, or to destroy the transfer agent by a hydrolysis, oxidation by metallic catalysis reaction. or by the use of primary radicals. In the case of xanthate as transfer agent, it is recommended to render it inert, if necessary, by treatment of the copolymer formed by means of a heat treatment for example in the temperature range 80 to 180 ° C. in the presence of an alkanolamine such as triethanolamine. The present invention also relates to obtaining block copolymers which, in addition to their surfactant properties and aqueous emulsion stabilizers, lower the surface tension of the water, cause the formation of micelles and / or small vesicles. suspension in water within which a chemical reaction can be carried out or can be encapsulated an active ingredient. The invention also relates to the use of the foregoing block copolymers as adhesion promoters. They can also be used as wetting agents or hydrophilizing agents for coating more or less hydrophobic surfaces with residual effect after rinsing. Preferably, the polymers may be used in an amount generally between 0.1% and 10% by weight relative to the aqueous medium. In particular, the block copolymers according to the invention have the advantage of improving the adhesion of paints to hydrophobic substrates such as substrates made of plastics material and of increasing the adhesion of fibers and plastic supports with compounds derived from aqueous dispersions (cement, mastics). In this particular application as an adhesion promoter, it is recommended to use from 0.1 to 10%, preferably from 0.5 to 5% by weight of copolymer relative to the total weight of the paint. In the application as wetting agent in aqueous solution, it is recommended to use an amount of 0.01 to 3%, preferably 0.1 to 1% by weight of copolymer relative to the total weight of said solution. The block copolymers according to the invention are also promoters of conventional detergent agents such as benzenesulphonate benzenes when they are used in combination with these at a dose preferably of between 0.5 and 5% by weight relative to the weight of the detergent. In the particular case of a butyl polyacrylate / acrylic polyacrylic block copolymer designated p (BA) -bp (AA) according to the invention, The following range of properties is varied by varying the p (BA) / p (AA) mass ratios as follows: surfactant and aqueous emulsion stabilizer properties: p (BA) / p (AA) between 10 / 90 and 40/60; vesicle formation: p (BA) / p (AA) between 70/30 and 80/20; and adhesion promoters and wetting agents: p (BA) / p (AA) between 70/30 and 40/60;

At the end of the controlled polymerization step, the transfer agent located at one of the chain ends of the block surfactant polymer can be rendered chemically inert by any suitable means. Inerting the transfer agent may be advantageous for some applications. It is then recommended to mask the active chemical functions of said agent by means of a suitable chemical masking agent, or to destroy the transfer agent by a hydrolysis reaction, by oxidation by metal catalysis or by the use of primary radicals. .

Concrete but non-limiting examples of the invention will now be presented. In the following examples:

Mn represents the number-average molecular mass Mn of the polymers, Mn is expressed in polystyrene equivalents (g / mol),

Mw represents the weight average molecular weight (g / mol),

Mw / Mn represents the polydispersity index,

the polymers, before hydrolysis, are analyzed by chromatography (GPC) with THF as elution solvent. The following examples illustrate the preparation of diblock surfactant copolymers according to the invention:

EXAMPLE 1 Preparation of a 50/50 Diblock Polymer by Weight p (BA) -bp (AA) (Butyl Polyacrylate-Acrylic Acid) Comprising a Reactive End of the Xanthate Type

The following mixture is introduced into a reactor equipped with a magnetic stirrer and a reflux column, and comprising 160 g of acetone: 3.04 g of S-ethylpropionyl O-ethyl dithiocarbonate (xanthate)

21.24 g of isopropanol, and

0.82 g of azobisisobutyronitrile (AIBN).

The mixture is then stirred and maintained at reflux at 70 ° C. 66 g of acrylic acid (AA) and 15 g of water are added gradually for 3 hours. 0.41 g of azobisobutyronitrile are then added after one hour of addition and then another 0.41 g of azobisisobutyronitrile are added after a second hour of addition. After the addition of acrylic acid is complete, the polymerization is allowed to continue for another hour. An amount of 0.20 g of reaction mixture is taken as a sample of PAA homopolymer.

The temperature is then lowered to 65 ° C. by the addition of 560 g of acetone. While maintaining the temperature at 65 ° C., 140 g of butyl acrylate (BA) are gradually added for 3 hours. 0.40 g of AIBN is added at the beginning of the BA addition. The reaction is allowed to continue for another 3 hours. The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The resulting residue is dispersed in water and lyophilized. The polymers are analyzed by carbon 13 nuclear magnetic resonance and by measuring their acid content. The number-average molecular weight of the copolymer is 15,000. The glass transition temperature of the hydrophobic block is -54 ° C. The surface tension is 55 mN / m at 10^"4 mol / l.

EXAMPLE 2 Preparation of a 70/30 Diblock Polymer by Weight p (BA) -bp (AA)

(butyl polyacrylate-acrylic acid) comprising a reactive end of the xanthate type:

The following mixture is introduced under a nitrogen atmosphere into a reactor equipped with a magnetic stirrer and a reflux column, and comprising 160 g of acetone:

0.61 g of S-ethylpropionyl O-ethyl dithiocarbonate (xanthate) - 4.25 g of isopropanol,

0.16 g of azobisisobutyronitrile

The mixture is then stirred and maintained at reflux at 70 ° C. 13.2 g of acrylic acid (AA) and 30.3 g of water are added gradually for 3 hours. Then 0.08 g of azobisobutyronitrile are added after one hour of addition and then another 0.08 g of azobisobutyronitrile are added after a second hour of addition. After the addition of acrylic acid is complete, the polymerization is allowed to continue for another hour. An amount of 4.1 g of reaction mixture is taken as a sample of PAA homopolymer. The temperature is then lowered to 65 ° C. by the addition of 112 g of acetone. While maintaining the temperature at 65 ° C., 28 g of butyl acrylate (BA) are added gradually for 3 hours. 0.08 g of AIBN is added at the beginning of the BA addition. The nitrogen purge is stopped and the reaction is allowed to continue for a further 12 hours. The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The resulting residue is dispersed in water and lyophilized. The polymers are analyzed by carbon 13 nuclear magnetic resonance and by measuring their acid content. The number-average molecular weight is 15,000. The glass transition temperature of the hydrophobic block is: -54 ° C. Surface tension is 52 mN / m at 10^"4 mol / l.

Example 3 Preparation of a 60/40 Diblock Polymer by Weight p (BA) -bp (AA) Comprising a Reactive End of the Xanthate Type: It Is Introduced in a Reactor Equipped with a Magnetic Agitator and a Reflux Column and comprising 160 g of acetone, the following mixture:

1. 53 g of S-ethylpropionyl O-ethyl dithiocarbonate (xanthate)

10.72 g of isopropanol, and

0.42 g of azobisisobutyronitrile (AIBN). The mixture is then stirred and maintained at reflux at 70 ° C. 44.0 g of acrylic acid (AA) and 75.4 g of water are added gradually for 3 hours. Then 0.21 g of azobisisobutyronitrile are added after one hour of addition and then another 0.21 g of azobisisobutyronitrile are added after a second hour of addition. After the addition of acrylic acid is complete, the polymerization is allowed to continue for another hour. An amount of 10.98 g of reaction mixture is taken as sample of PAA homopolymer.

The temperature is then lowered to 65 ° C. by addition of 280 g of acetone. While maintaining the temperature at 65 ° C, 60 g of butyl acrylate (BA) are gradually added for 3 hours. 0.20 g of AIBN is added at the beginning of the BA addition. The nitrogen purge is stopped and the reaction is allowed to continue for a further 12 hours. The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The resulting residue is dispersed in water and lyophilized. The polymers are analyzed by carbon 13 nuclear magnetic resonance and by measuring their acid content. The molecular weight of the copolymer in number is 15,000.

The glass transition temperature of the hydrophobic block PBA is -54 ° C. and 105 ° C. for the PAA block.

Surface tension is 58.8 mN / m at 10^"4 mol / l. EXAMPLE 4 Preparation of an 80/20 Diblock Polymer by Weight p (BA) -bp (AA) (Butyl Polyacrylate-Acrylic Polyacid) Comprising a Reactive End of the Xanthate Type: It Is Introduced in a Reactor Equipped with a Magnetic Agitator and a reflux column, and comprising 60 g of acetone, the following mixture:

0.61 g of S-ethylpropionyl O-ethyl dithiocarbonate (xanthate)

4.21 g of isopropanol, and

0.16 g of azobisisobutyronitrile (AIBN). The mixture is then stirred and maintained at reflux at 70 ° C. 8.80 g of acrylic acid (AA) and 30.35 g of water are added gradually for 3 hours. Then 0.08 g of azobis-isobutyronitrile are added after one hour of addition and then another 0.08 g of azobisisobutyronitrile are added after a second hour of addition. After the addition of acrylic acid is complete, the polymerization is allowed to continue for another hour. A quantity of 3.7 g of reaction mixture is taken as a sample of PAA homopolymer.

The temperature is then lowered to 65 ° C. by addition of 112 g of acetone. While maintaining the temperature at 65 ° C., 32 g of butyl acrylate (BA) are gradually added for 3 hours. 0.08 g AIBN is added at the beginning of the BA addition. The nitrogen purge is stopped and the reaction is allowed to continue for a further 12 hours. The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The resulting residue is dispersed in water and lyophilized. The polymers are analyzed by carbon 13 nuclear magnetic resonance and by measuring their acid content. The molecular weight of the copolymer in number is 15,000.

The glass transition temperature of the hydrophobic block PBA is -54 ° C. and 105 ° C. for the PAA block.

EXAMPLE 5 Preparation of a diblock polymer 55/45 by weight p (BA) -bp (AA) (butyl polyacrylate-acrylic polyacid) comprising a reactive end of the xanthate type:

The following mixture is introduced into a reactor equipped with a magnetic stirrer and a reflux column, and comprising 160 g of acetone:

0.61 g of S-ethylpropionyl O-ethyl dithiocarbonate (xanthate) - 4.31 g of isopropanol, and

0.17 g of azobisisobutyronitrile (AIBN).

The mixture is then stirred and maintained at reflux at 70 ° C. 19.80 g of acrylic acid (AA) and 30.31 g of water are added gradually for 3 hours. Then 0.08 g of azobis-isobutyronitrile are added after one hour of addition and then another 0.08 g of azobisisobutyronitrile are added after a second hour of addition. After the addition of acrylic acid is complete, the polymerization is allowed to continue for another hour. 4.76 g of reaction mixture is taken as sample of PAA homopolymer.

The temperature is then lowered to 65 ° C. by addition of 112 g of acetone. While maintaining the temperature at 65 ° C, 22 g of butyl acrylate (BA) are gradually added for 3 hours. 0.08 g AIBN is added at the beginning of the BA addition. The nitrogen purge is stopped and the reaction is allowed to continue for a further 12 hours. The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The resulting residue is dispersed in water and lyophilized. The polymers are analyzed by carbon 13 nuclear magnetic resonance and by measuring their acid content. The molecular weight of the copolymer in number is 15,000. The glass transition temperature of the hydrophobic block PBA is -54 ° C. and 105 ° C. for the PAA block. Surface tension is 58.0 mN / m at 10^"4 mol / l.

EXAMPLE 6 Preparation of a Diblock Polymer with a Weight Ratio p (BA) / p (AM): 60/40 μ (BA τnrrb-p (AM (butyl polyacrylate-polyacrylamide) comprising a reactive end of the xanthate type: 1 Step 1: Synthesis of the monoblock p (BA)₃₀₀oX (X≈xanthate) Composition of the reaction mixture:

Tetrahydrofuran 66.38 g. Butyl Acrylate 24.00 g.

S-ethylpropionyl (O-ethyldithiocarbonate) 1.664 g.

AIBN (Azo-bis-isobutyronitrile) 0.263 g.

The above ingredients are loaded into a 250 ml polymerization reactor equipped with a magnetic stirrer. The reaction is carried out under a dry nitrogen atmosphere for 20 minutes, the reaction mixture is then heated to 60 ° C. and maintained at this temperature for 20 hours. Small amounts of polymer samples are taken from time to time to control the conversion. The solids content is 28.09%.

2) Step 2: Synthesis of the diblock p (BA_{) 3}ooo-bp (AM)_{? 0}oo - X Composition of the reaction mixture:

Tetrahydrofuran 63.00 g.

Acrylamide 16.00 g.

AIBN (Azo-bis-isobutyronitrile) 0.263 g. The above ingredients are loaded in a dry container under a dry nitrogen atmosphere for 20 minutes and then transferred to the polymerization reactor using a 2-tip syringe. At the end of the transfer, the reaction mixture is then heated to 60 ° C. and maintained at this temperature for 20 hours. Small amounts of polymer samples are taken from time to time to control the conversion. The solids content is 24.59%.

The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The number-average molecular mass of the copolymer is 5,000. The glass transition temperature of the hydrophobic block PBA is: -54 ° C. and 165 ° C. for the PAM block. The surface tension is 58 mN / m.

Example 7: Preparation of a diblock polymer with a weight ratio p (BA) / p (AA): 80/20 p (BA) 4nnn-bp (AA)₁₀oo (butyl polyacrylate-acrylic polyacid) comprising a reactive end of the xanthate type in ethanol: 1) Step 1: Synthesis of the monoblock p (BA)₄₀oo (Composition of the reaction mixture:

Ethanol 79.00 g. Butyl acrylate 32.00 g.

S-ethylpropionyl (O-ethyldithiocarbonate) 1.664 g.

AIBN (Azo-bis-isobutyronitrile) 0.263 g.

The above ingredients are loaded into a 250 ml polymerization reactor equipped with a magnetic stirrer. The reaction is carried out under a dry nitrogen atmosphere for 20 minutes, the reaction mixture is then heated to 60 ° C. and maintained at this temperature for 20 hours. Small amounts of polymer samples are taken from time to time to control the conversion. The solids content is 30.04%.

2) Step 2: Synthesis of the diblock p (BA)₄ooo-bp (AA)₁₀₀o - X Composition of the reaction mixture:

Ethanol 19.00 g.

Acrylic acid 8.00 g.

AIBN (Azo-bis-isobutyronitrile) 0.066 g.

The above ingredients are loaded in a dry container under a dry nitrogen atmosphere for 20 minutes and then transferred to the polymerization reactor using a 2-tip syringe. At the end of the transfer, the reaction mixture is then heated to 60 ° C. and maintained at this temperature for 20 hours. Small amounts of polymer samples are taken from time to time to control the conversion. The solids content is 30%.

The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The number-average molecular weight of the copolymer is 5,000.

The glass transition temperature of the hydrophobic block pBA is -54 ° C. and 105 ° C. for the pAA block.

Example 8 Synthesis of the p diblock (BA)₇₅oo-bp (AA)₇₅oo - X with weight ratio P (BAVP (AA): (50/50)

A) Step 1: Synthesis of the monoblock p (BA)₇₅₀Composition of the reaction mixture:

Tetrahydrofuran 48.00 g.

Butyl acrylate 20.00 g. S-ethylpropionyl O-ethyldithiocarbonate 0.555 g.

AIBN (Azo-bis-isobutyronitrile) 0.088 g.

The above ingredients are loaded into a 250 ml polymerization reactor equipped with a magnetic stirrer. The reaction is carried out under a dry nitrogen atmosphere for 20 minutes, the reaction mixture is then heated to 60 ° C. and maintained at this temperature for 20 hours. Small amounts of polymer samples are taken from time to time to control the conversion. The solids content is 30.2%.

B)) Step 2: Synthesis of the diblock p (BA)₇₅₀OBP (AA)₇₅₀₀ X Composition of the reaction mixture: Tetrahydrofuran 47.00 g.

Acrylic acid 20.00 g.

AIBN (Azo-bis-isobutyronitrile) 0.088 g.

The above ingredients are loaded in a dry container under a dry nitrogen atmosphere for 20 minutes and then transferred to the polymerization reactor using a 2-tip syringe. At the end of the transfer, the reaction mixture is then heated to 60 ° C. and maintained at this temperature for 20 hours. Small amounts of polymer samples are taken from time to time to control the conversion. The solids content is 30%.

The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The number-average molecular weight of the copolymer is 15,000.

The glass transition temperature of the hydrophobic block p (BA) is -54 ° C. and 105 ° C. for the p (AA) block. The surface tension is 55 mN / m.

Example 9 Synthesis of the diblock p (BA)₁ooo-bp (AA)₄₀oo - X with a weight ratio p (BA) / p (AA): (20/80) A) Step 1: Synthesis of the monoblock p (BA)₁₀oo; X

The procedure of step A) of Example 8 is reproduced exactly except that the reaction mixture is used:

Tetrahydrofuran 23.00 g.

Butyl acrylate 8.00 g. S-ethylpropionyl O-ethyldithiocarbonate 1, 664 g.

AIBN (Azo-bis-isobutyronitrile) 0.263 g.

The solids content is 30.2%. B) Step 2: Synthesis of the diblock p (BA)₁ooo-bp (AA)₄₀oo - X

The procedure of step B) of Example 8 is reproduced exactly except that the reaction mixture is used:

Tetrahydrofuran 75.00 g.

Acrylic acid 32.00 g.

AIBN (Azo-bis-isobutyronitrile) 0.263 g.

The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The number-average molecular weight of the copolymer is 5,000.

The glass transition temperature of the hydrophobic block pBA is -54 ° C. and 105 ° C. for the pAA block.

The surface tension is 45.11 mN / m.

Example 10 Synthesis of the p (BA) 7ooo-bp (AM) Diblock₃ooo - X with weight ratio p (BA) / p (AM): (40/60)

A) Step 1: Synthesis of the monoblock p (BA)₁₀o_{0 =}X

The procedure of step A) of Example 8 is reproduced exactly except that the reaction mixture is used:

Tetrahydrofuran 30.00 g.

Butyl acrylate 16.00 g.

S-ethylpropionyl O-ethyldithiocarbonate 1.664 g.

AIBN (Azo-bis-isobutyronitrile) 0.263 g. The solids content is 37.4%.

B) Step 2: Synthesis of the diblock p (BA)₂ooo-bp (AM) arlen - X

The procedure of step B) of Example 8 is reproduced exactly except that the reaction mixture is used: Tetrahydrofuran 100.00 g.

Acrylamide 24.00 g.

AIBN (Azo-bis-isobutyronitrile) 0.263 g.

The reaction mixture is allowed to cool and the solvents are almost completely removed using a rotavapor (rotary evaporator). The number-average molecular weight of the copolymer is 5,000.

The glass transition temperature of the hydrophobic block p (BA) is -54 ° C. and 165 ° C. for the p (AM) block. The surface tension is 52 mN / m.

EXAMPLE 11 Step of decomposition of thiocarbonylthio (Di-thiocarbonate or Xanthate) at the end of the copolymer chain

This decomposition step is general and applies to all the copolymers of Examples 1 to 10: A solution of 6 g of a copolymer as obtained in any one of Examples 1 to 10 at 30% by weight in tetrahydrofuran, 0.09 g of triethanolamine is added to a sealed vessel equipped with a magnetic stirrer. The vessel is stirred and heated to 160 ° C in an oil bath for 16 hours. The inert polymer is characterized by¹³C-NMR. The ratio of C = S groups at 216 ppm to C = O groups in the 176 ppm polymer decreases with the reaction time. The C = S groups disappear at the end of the reaction.