WO2008129213A1 - Method for preparing an amphiphilic two-block or three-block copolymer having a hydrophilic block and one or two hydrophobic blocks, method for preparing an organic mesoporous material using this copolymer, and material thus prepared - Google Patents

Abstract

The invention relates to a method for the preparation of a diblock copolymer comprising a hydrophilic block (B) and a hydrophobic block (A), or of a triblock copolymer having a hydrophilic block (B), a hydrophobic block (A) and a second hydrophobic block (A'), said method comprising the following steps: a) an addition step 1,2 on an ethylene terminal group, or two terminal ethylene terminal groups, of a hydrophilic polymer, of an alkoxyamine having the following formula (I): in which: * R <SUB>1</SUB> and R <SUB>3</SUB>, identical or different, representing an alkyl group, linear or branched, having a number of carbon atoms comprised between 1 and 3; * R <SUB>2</SUB> represents a hydrogen atom, an alkaline metal, such as Li, Na, K, an ammonium ion such as NH<SUB> 4</SUB>+, NBu <SUB>4</SUB>+, NHBu <SUB>3</SUB>+, an alkyl group, linear or branched, having between 1 and 8 carbon atoms, a phenyl group; b) a step of contacting with the medium from step a) of one or more precursor monomers of a hydrophobic block for a sufficient amount of time to obtain the hydrophilic diblock copolymer (B)-b-block hydrophobic (A) in the case the addition step a) occurred on only one of the terminal ethylene group of the hydrophilic polymer; or to obtain the hydrophilic triblock copolymer (A)-b- block hydrophilic (B)-b-second block hydrophobic (A') in the case the addition reaction a) took place on both\terminal ethylene groups of the hydrophilic polymer. Use of the copolymers thus obtained as structural agents of mesoporous material, such as silica having pores greater than 15 nm in size.

Description

 PROCESS FOR PREPARING AN AMPHIPHILIC COPOLYMER

DIBLOC OR TRIBLOC COMPRISING A HYDROPHILIC BLOCK AND A

OR TWO HYDROPHOBIC BLOCKS, PROCESS FOR PREPARING A

MESOPOROUS ORGANIC MATERIAL USING THE COPOLYMER, AND MATERIAL THUS PREPARED

The invention relates to a process for preparing a diblock or triblock amphiphilic copolymer, comprising a hydrophilic block, and one or two hydrophobic blocks by controlled radical polymerization using a particular alkoxyam.

The diblock or tibblock copolymers thus prepared can find, in particular, their application as a structuring agent in a process for the preparation of a mesoporous inorganic material such as mesoporous silica.

The invention therefore also relates to a method for preparing mesoporous inorganic materials using a structuring agent comprising said amphiphilic diblock or triblock polymer having a hydrophilic block and one or two hydrophobic blocks.

More specifically, the invention relates to a method for preparing mesoporous inorganic materials from an inorganic precursor and a structuring agent comprising said diblock or triblock amphiphilic copolymer.

STATE OF THE PRIOR ART

Block copolymers comprising a hydrophilic block, and one or two hydrophobic blocks have been essentially prepared so far by ionic polymerization, such as cationic and / or amonic polymerization.

The amonic polymerization is described in particular in documents FR-A-2 762 604, FR-A-2 761 997 and FR-A-2 761 995.

Processes, based on ionic polymerization (cationic and / or amonic) have a number of disadvantages, in that they are very sensitive to traces of impurities in solvents and especially traces of water. Moreover, they do not provide control of the polymerization reactions of a wide range of monomers.

These polymers can also be prepared by the controlled radical polymerization technique which comprises several variants depending on the nature of the control agent that is used.

SFRP (Stable Free Radical Polymerization), which uses nitroxides T as a control agent and can be initiated by alkoxyamines, ATRP (Atom Transfer Radical Polymeπzation) which uses metal complexes as a control agent and which is initiated by halogenated agents, RAFT (Reversible Addition Fragmentation Transfer) makes use of sulfur-containing products such as dithioesters, thiocarbonates, xanthates or dithiocarbamates. Reference can be made to the general review Matyjaszewski, K. (Ed.), ACS Symposium Series (2003), 854 (Advances in Controlled / Living Radical Polymerization) and the following documents for more details on polymerization techniques controlled radicals which may be used: FR-A-2 825 365, FR-A-2 863 618, FR-A-2 802 208, FR-A-2 812 293, FR-A-2 752 238, FR-A- 2,752,845, US-A-5,763,548 and US-A-5,789,487. For obtaining a triblock copolymer

ABA 'using the controlled radical polymerization technique, it is advantageous to use a difunctional alkoxyamine of formula T-Z-T. We begin by preparing the central block B by polymerizing with the alkoxyamine the monomer mixture leading to the central block. The polymerization takes place with or without a solvent or in a dispersed medium. The mixture is heated to a temperature above the activation temperature of the alkoxyamine. When the central block B is obtained, the monomer (s) leading to the side blocks is added. It is possible that at the end of the preparation of the central block, there remain monomers not completely consumed that we can choose to eliminate or not before the preparation of the side blocks. The removal may for example consist of precipitating in a non-solvent, recovering and drying the central block. If one chooses not to remove the monomers not entirely consumed, they can polymerize with the monomers introduced to prepare the side blocks. WO-A-2006/053984 or WO-A-03/062293 disclose examples of the preparation of block copolymers by controlled radical polymerization.

However, most of the radical polymerization processes described in the documents cited above involve initiators, or control agents requiring binding operating conditions.

There is therefore a real need for a process for preparing a diblock or tπbloc amphiphilic copolymer comprising a hydrophilic block and one or two hydrophobic blocks allowing control of the polymerization of each of the blocks and, moreover, not requiring operating conditions. as demanding as the ionic polymerization or the radical polymerization with an initiator or a control agent of the type defined above.

A first object of the present invention is, according to a first object thereof, to provide a process for the preparation of these copolymers which, among other things, meets this need.

A first object of the present invention is still to provide a process for the preparation of such copolymers which do not have the drawbacks, defects, limitations and disadvantages of the processes for preparing these copolymers described in the prior art and which solve the problems posed by the preparation processes of the prior art.

Moreover, it has been seen above that the diblock or tibblock copolymers prepared by the process according to the invention find particular application as a structuring agent during the preparation of a mesoporous material.

These mesoporous inorganic materials find particular application in the synthesis of nanoparticles. The field of application of the invention can also be defined as that of mesoporous materials, in particular mesoporous inorganic materials.

Recall that the mesoporous materials have pores whose size generally defined by their diameter is generally 1.5 to 15 nm.

These mesoporous materials are formed by assembling a mineral phase around an organic phase of micelles of structuring agent molecules. The latter is then removed in order to obtain the porous matrix. Compared with microporous zeolites, they not only have larger pores but their diameter can be adjusted between 1.5 and 5 nm, which is impossible in the case of zeolites that have pores limited to sizes at most equal to 1, 3 nm. These materials can have very large areas, specific surfaces, up to 1000 m ² . g ^'1 . In addition, they can be easily functionalized either by organic groups linked to the surface of the pores or by nanoparticles incorporated into the cavities.

Indeed, it is known that the synthesis of nanoparticles with a dimension of less than 100 nm benefits from an important industrial interest because of the physical or physicochemical properties of these nanoparticles which have significantly different from those of the bulk material.

In all the studies concerning these nanoparticles, two problems remain: (1) the first concerns the difficulty to control the size and the size distribution of the nanoparticles during the synthesis generally carried out in the liquid phase, (ii) the second, of a technological nature, relates to the difficult integration of particles in solution.

In order to remedy these two problems, one of the ideas developed at present is to use a mesoporous starting matrix for the incorporation of nanoparticles. In fact, mesoporous materials with homogeneously sized and homogeneously distributed pores are perfect candidates for nanoparticle synthesis because the use of pores as a chemical nanoreactor makes it possible simultaneously to control the growth of particles and the distance between particles. The materials thus obtained are called nanocomposites. It is therefore important to be able to easily modulate the pore size of these mesoporous materials.

Mesoporous materials have a potentially wide range of applications, particularly in areas such as catalysis, chemical or biological sensors, materials for optics and electronics.

Finally, the physical and physicochemical properties of nanostructured materials are often correlated to the value of specific surface area, pore size and organization.

The mechanism of synthesis of mesoporous materials depends on two essential actors: the inorganic species or precursors that condense to form a polymeric network and the structuring agent molecules or "templates" that allow the network structuring at the nanoscale. Indeed, the structuring agents are not simple entities, they are amphiphilic molecules that are organized in solution to form micelles and liquid crystal phases.

Two mechanisms are generally proposed to explain the formation of mesoporous silica (scheme 1).

Ph

structurantElimination of the agent

structuring

Matrix of

Silica gel

Diagram 1

The first considers (route A) that the silica is formed between the micelles constituting the liquid crystal, which already exists before the introduction of silica precursors. The second mechanism (path B) consists of the self-assembly of the silicate species with the structuring agent molecules. In the latter case, the liquid crystal phase is not present in solution before the addition of the silica precursor. In both cases, after removal of the structuring agent, either by calcination or by extraction, a mesoporous silica matrix is obtained.

The inorganic matrix The amorphous inorganic network is prepared according to the sol-gel process by hydrolysis / condensation of inorganic precursors in solution. These precursors are most often silicon alkoxides (Si (OR) ₄ ) which hydrolyze and condense in the presence of water to form a gel.

The hydrolysis reaction is as follows:

≡Si-OR + H ₂ O * ~ ≡SiOH + ROH

The condensation reactions are as follows:

= Si - OR + HO- Si≡≡ *> ≡Si - O- Si≡≡ + ROH (elimination of alcohol)

≡Si - OH + HO- Si≡≡ * - ≡Si-0- Si ^ ≡ + H ₂ O (removal of water)

The polymerization can be catalyzed in acidic or basic medium. Basic catalysis promotes crosslinking while acid catalysis promotes condensation at the end of chains. Thus, in basic medium the condensation leads to small dense and highly branched silica entities, while in acidic medium it leads to the formation of species polymeπques low density. Basic catalysis is thus well adapted to the synthesis of colloids; acid catalysis is suitable for the preparation of polymeques gels and thin films. The structuring agents

The structuring agent molecules are generally amphiphilic molecules that organize in solution (above a concentration called critical micellar concentration -c.rn.c-) to form micelles to minimize interactions with the aqueous phase. . As the concentration of structuring agent increases, the distance between the micelles decreases and they form lyotropic liquid crystal phases.

The various lyotropic liquid crystal phases that exist in solution can be separated into four categories (FIG. 1): the direct phases consisting of structuring agent micelles in the solvent (FIG. 1- (A and B)), the indirect phases ( FIG. 1 (D)) consisting of solvent vesicles in the structuring agent, the bicontinuous phases (FIG. 1- (E)) and the lamellar phase

(Figure 1- (C)). The most interesting phases for forming structured mesoporous materials are the direct and bicontinuous phases.

Two types of structuring agents, forming lyotropic liquid crystal phases in solution, have been used for the synthesis of mesoporous silicas leading to very varied pore sizes and organization: surfactants and block copolymers.

Surfactants Two types of surfactants were mainly used for silica synthesis mesoporous: cationic surfactants and neutrals.

Cationic surfactants make it possible to form very ordered materials. Depending on their geometry, they lead to different porous structures. The formation of the mesoporous material is carried out according to route B of scheme 1 above. The surfactants most often used are alkyltrimethylammonium halides such as CTAB (alkyltrimethylammonium bromide). These surfactants most often lead to tubular hexagonal structures of the MCM-41 type. The pore size can be adjusted continuously between 1.8 and 3.7 nm by changing the length of the alkyl chain. Using cetyltπethylammonium bromide, a cubic micellar phase was obtained called SBA-I.

To increase the pore size obtained with this type of surfactants, organic additives such as tetramethylbenzene (TMB) have been used. They fit in the heart of the micelle which allows to obtain an increase in the volume of it. Thus pores up to 10 nm in diameter have been obtained. However, these materials are generally less well organized (D. Zhao, J. Feng, Q. Huo, N. Melosh, G.H. Fredπckson, B. F. Chmelka and G. D. Stucky, Science, vol 279, 1998).

Two types of neutral surfactants have mainly been used. Commercial alkyl poly (ethylene oxide) (C _x EO _y ) surfactants known as Bπj have resulted in pore sizes between 2 to 4 nm. Surfactants made of primary amine were used to synthesize mesoporous silicas whose pore size varies according to the amine used: 1.6 nm with octylamine and 3.1 nm with octadecylamine. Thus, in the case where surfactants are used as structuring agents, the maximum pore size is 10 nm.

Block copolymers Block copolymers are linear or radial molecules consisting of an alternation of long homogeneous sequences, they can be diblock, triblock or multiblock.

The copolymers most used for structuring porous silicas are diblock or triblock nonionic amphiphilic copolymers. The mesoporous materials obtained using these block copolymers are formed according to Route A of Scheme 1. The hydrophobic blocks generally used are either poly (propylene oxide), polystyrene or polybutadiene. With respect to the hydrophilic block, poly (ethylene oxide) is the most common.

The most used triblock copolymer, sold under the name Pluronic from BASF, is of the ABA type. It comprises two hydrophilic blocks POE (A) and a hydrophobic block PPO (poly (propylene oxide)) (B). The influence of synthesis conditions and chain length has been studied by Zhao and his collaborators (D. Zhao, J. Feng, Q. Huo, Melosh N., GH Fredrickson, Chmelka BF and GD Stucky, Science, vol 279, 1998).

Organized silica mesoporous matrices having pore sizes between 4.5 and 10 nm and wall thicknesses between 3 and 5 nm were obtained. The phases of mesoporous silica structured by these most common copolymers are: (i) SBA-15, hexagonal tubular phase (structuring agent P123 (OE ₂ oPθ7oOE ₂ o)), (ϋ) SBA-I 6, cubic phase centered (structuring agent F127 (OE ₁₀ 6Pθ7oOE ₁₀ 6)). As in the case of cationic surfactants, it is possible to add an organic additive in solution as swelling agent (tπmethylbenzene (TMB)). Studies on mesoporous silica prepared with Pluronic P123 have shown that it is possible to increase the pore size by 10 nm (without TMB).

The triblock copolymers of the ABA type have been very little used for the synthesis of mesoporous silica, a copolymer of PPO-i-POE-i-PPO type.

(PO ₁ 9OE33PO ₁ 9) was used and the resulting mesoporous matrix has 5 nm pores. Recently, a triblock copolymer of PMA-23-POE-23-PMA type (PMA: polyacrylate of methyl) has made it possible to obtain silica matrices having pores of 7 to 15 nm by varying the length of the hydrophobic blocks (MA _{33 at} 70 EO ₇₇ MA _33-70 ) (CF Lin, HP Lm, CY Mou and ST Liu, Microporous and Mesoporous Materials, 91, 151, 2006). In parallel, research teams developed mesoporous materials using new diblock copolymers. Thus, Goltner and his collaborators have worked on diblock copolymers of PS-23-POE type (commercial) (CG Goltner, S. Henke, MC Weissenberger and M. Antonietti, Angew Chem Int.Ed, 37, 613, 1998, CG Goltner, B. Smarsly, B. Berton and M. Antonietti, Chem Mater, 13, 1617, 2001) and of type PB - & - POE (CG Goltner, B. Berton, E. Kramer and M. Antonietti, Adv Mater, 11, No. 5, 1999).

With the diblock copolymers, PS-ώ-POE, symmetrical in mass, the pore size of the silica matrices obtained is 4 to 8 nm, with regard to the diblock copolymers PB-1? -POE the pore size is about 14 nm.

Thus, the use of block copolymers makes it possible to modulate the pore size from 2 to 15 nm, (without addition of blowing agent), by varying the chemical nature and the length of the hydrophilic and hydrophobic blocks.

In order to obtain pore diameters greater than 15 nm, it is necessary to increase the size of the micelles while maintaining their organization, and this has not been possible until now.

It follows from the foregoing, that currently the controlled development of mesoporous materials, especially mesoporous silica, having dimensions, pore diameters greater than 15 nm is extremely difficult or impossible, that the structuring agent used for the synthesis of mesoporous material is a surfactant or a block copolymer. However, the development of such materials with large pore sizes is necessary for the development of nanocomposites.

There is therefore a need for a process for preparing a mesoporous material, such as a mesoporous silica, which makes it possible to obtain a mesoporous material whose pore diameter dimensions are greater than 15 nm.

There is still a need for a process for preparing a mesoporous material such as a mesoporous silica, which does not require the addition of a blowing agent such as trialkylbenzene to achieve pore sizes greater than 15 nm.

Finally, there is a need for such a method that is simple, reliable, and has a limited number of steps.

The second object of the present invention is therefore according to a second object of the invention to provide a process for preparing a mesoporous material, such as mesoporous silica that meets the needs listed above, among others.

The object of the present invention is again according to this second object of providing a method of manufacturing a mesoporous material which does not have the disadvantages, limitations, defects and disadvantages of the methods of preparation of mesoporous materials described above, which solves the problems. of these methods, and which allows in particular the preparation of a mesoporous material having a size, pore diameter greater than 15 nm. The invention thus relates, according to a first object, to a process for preparing a diblock copolymer comprising a hydrophilic block (B) and a hydrophobic block (A), or a triblock copolymer comprising a hydrophilic block (B ), a hydrophobic block (A) and a second hydrophobic block (A '), said process comprising the following steps: a) a 1,2-addition step on an ethylenic terminal group or on two ethylenic end groups of a polymer hydrophilic compound of an alkoxyamine corresponding to the following formula (I):

R ₁ (CH ₃ ) ₃

R ₃ -CON CH-C (CH ₃ ) ₃

C (O) OR ₂ P (O) (OEt) ₂

(D) wherein: R 1 and R ₃ , which may be identical or different, represent a linear or branched alkyl group having a number of carbon atoms ranging from 1 to 3;

R 2 represents a hydrogen atom, an alkali metal, such as Li, Na, K, an ammonium ion such as NH ₄ ⁺ , NBu ₄ ⁺ , NHBu ₃ ⁺ , a linear or branched alkyl group having a number of carbon atoms ranging from

1-8, a phenyl group; b) a step of bringing into contact with the medium resulting from step a) of one or more precursor monomers of a hydrophobic block for a sufficient time to obtain the hydrophilic block copolymer (B) -jb-hydrophobic block ( A) in the case where the addition step a) has occurred on a single ethylenic end group of the hydrophilic polymer; or for obtaining the hydrophilic block triblock copolymer (A) -b-hydrophilic block (B) -b-second hydrophobic block (A ') in the case where the addition step a) has occurred on two ethylenic end groups of the polymer hydrophilic. The invention will now be described in detail in the following description, which is illustrative and not restrictive, with reference to the accompanying drawing in which:

FIG. 1 (A, B, C, D, E) schematically represents the various lyotropic liquid crystal phases that exist in solution.

Before going into more detail in the description, it is specified that for the precursor monomer of the hydrophobic block (A) and for the precursor monomer of the second hydrophobic block (A ') are meant the monomers which, after polymerization, constitute respectively the repeating units of the hydrophobic block (A) and the second hydrophobic block (A ').

The hydrophobic blocks (A) and (A ') may be the same or different.

By different, it is generally understood that these blocks are of the same nature as for the monomers that constitute them but may be of different lengths. It is specified that Et denotes an ethyl group and Bu, a butyl group, which can exist under its different isomers.

T ₅ denotes the glass transition temperature of a polymer measured by DSC according to ASTM E1356. We also speak of the T ₅ of a monomer to designate the T _g of the homopolymer having a mass number average molecular weight M _n of at least 10000 g / mol, obtained by radical polymerization of said monomer. Thus, it will be said that styrene has a T _g of 100 ° C because the homopolystyrene has a T _g of 100 ° C. All percentages are by weight unless otherwise indicated.

The innovative nature of the process for obtaining the copolymers lies particularly in: the 1,2 addition of the alkoxyamine to a terminal ethylenic group or to two terminal ethylenic groups of a hydrophilic polymer intended to constitute the hydrophilic block (B ); the resumption of the controlled radical polymerization from the hydrophilic polymer activated by a group derived from the alkoxyamine, this recovery of polymerization making it possible to obtain the hydrophobic block (A) and optionally the hydrophobic blocks (A ') covalently attached to the hydrophilic block (B); the controlled nature of the polymerization steps; the fact that no stress is induced by the alkoxyamine of formula (I) unlike other known initiators.

In addition, the controlled radical polymerization with a control by nitroxides T which is the technique used to obtain the block copolymer of the invention does not require working under conditions as severe as the anionic polymerization (c '). that is, absence humidity, temperature <100 ⁰ C). It also makes it possible to polymerize a wide range of monomers. It can be conducted under various conditions, for example by mass, solvent or in a dispersed medium. The nitroxide T is a stable free radical having a group = NO "that is to say a group on which is present a single electron.

The term "stable free radical" denotes a radical that is so persistent and non-reactive with respect to air and moisture in the ambient air that it can be handled and stored for a much longer period than the majority free radicals (see Accounts of Chemical Research 1976, 9, 13-19). The stable free radical thus differs from free radicals whose lifetime is ephemeral (from a few milliseconds to a few seconds) such as free radicals from conventional polymerization initiators such as peroxides, hydroperoxides or azo initiators. Free radicals initiating polymerization tend to accelerate polymerization whereas stable free radicals generally tend to slow it down. It can be said that a free radical is stable within the meaning of the present invention if it is not a polymerization initiator and if, under the usual conditions of the invention, the average lifetime of the radical is at least one minute .

A reaction scheme will be explained above starting from a specific example. In step a) of the process for obtaining the diblock or triblock copolymers, it is in contact with a hydrophilic polymer with an alkoxyamine of formula (I), this alkoxyamine being able to react with an ethylenic end group, or with two ethylenic end groups, of the polymer according to an addition reaction 1,2.

The hydrophilic polymer may be linear or branched.

The hydrophilic polymer comprising an ethylenic end group or two ethylenic end groups may be chosen in particular from semi-crystalline and / or hydrolysable polymers.

Thus, the hydrophilic polymer comprising an ethylenic end group or two ethylenic end groups may be: a non-hydrolyzable semi-crystalline polymer, such as polyethylene, polypropylene, polyethylene oxide and polyamides;

a hydrolyzable semi-crystalline polymer, such as the polymers resulting from a polycondensation reaction, such as polycaprolactones, L-polylactide and poly (L-lactide-co-glycolic acid) copolymers; a hydrolyzable non-semicrystalline polymer, such as DL-polylactide and poly (DL-lactide-co-glycolic acid) copolymers; a polymer having functional groups selected from carboxylic acid, anhydride and acrylamide functions; a copolymer of methyl methacrylate and at least one hydrophilic monomer. By way of example of hydrophilic monomer, mention may be made of acrylic or methacrylic acid, amides derived from these acids, such as, for example, dimethyl acrylamide, 2-methoxyethyl acrylate or methacrylate, and optionally 2-aminoethyl acrylates or methacrylates. quaternarized, the

polyethylene glycol (PEG) (meth) acrylates, water-soluble vinyl monomers such as N-vinyl pyrrolidone or any other hydrophilic monomer. In the rest of this specification, polylactide is understood to mean poly-L-lactides and poly-DL-lactides.

These polymers can be prepared beforehand or can be purchased from appropriate suppliers.

It is specified that hydrophilic polymer means a polymer which has a chemical affinity with water, this affinity can take place in acidic or basic medium depending on the structure of the polymer. A hydrophilic polymer may also be defined as a water-soluble or water-dispersible polymer.

A polymer is water-soluble, if soluble in water, by at least 5% by weight at 25 ° C.

A polymer is hydrodispersible, if it forms at a concentration of 5%, at 25 ° C, a stable suspension of fine particles, generally spherical. The average particle size constituting said dispersion is less than 1 μm and, more generally, varies between 5 and 400 nm, preferably from 10 to 250 nm. These particle sizes are measured by light scattering.

It is further specified that hydrolysable polymer means a polymer capable of being cleaved into these repeating units by hydrolysis in an aqueous medium, this hydrolysis can be carried out in an acidic or basic medium depending on the nature of the polymer.

The method according to the invention may comprise a step prior to step a), said functionalization step, intended to introduce at one end of a hydrophilic starting polymer, or at both ends of a hydrophilic starting polymer, a ethylenic terminal group, when the latter is not inherently part of this polymer. For example, starting from a semi-crystalline starting polymer having an ^Λ OH end, such as a (-hydroxylated polyethylene oxide or a ca-hydroxylated polycaprolactone, or two OH ends such as a poly (Ethylene oxide α, ω hydroxylated), it is necessary to react the latter, or the latter, with a compound capable of introducing an ethylenic group by reaction with the -OH end. This compound may be chosen from acids, activated esters, acryloyl halides, such as acryloyl chloride, in which case the ethylenic group introduced is an acrylate group.

The reaction scheme, with acryloyl chloride as compound, can be as follows: Polymer-OH Cl

Figure 2A

According to the invention, the hydrophilic polymer comprising an ethylenic group, intended to constitute the hydrophilic block (B), is brought into contact with an alkoxyamine as defined above and reacts with it according to a 1,2 addition mechanism. according to the following reaction scheme:

Figure 2B

the nitroxide end being hereinafter referred to as "SGl".

The alkoxyamine is generally introduced in a content ranging from 0.5% to 80% by weight relative to the weight of the hydrophilic polymer, whose number-average molar mass Mn can be in the range of 1000 g. mol ^"1 to 100 000g. ^{mol" 1} and, preferably, 5000 g. mol ^"1 to 50,000 g mol ^-1 .

A particular alkoxyamine which can be used in accordance with the invention is an alkoxyamine corresponding to the following formula (II):

which may be called, in the rest of this presentation, "MAMA-SGl".

The hydrophilic polymer (B) activated by one end SG1 or with two ends SG1 constitutes a living polymer, which will be able to serve as a basis for the controlled synthesis of the second block (A) by polymerization of one or more monomers precursors of the hydrophobic block ( A), and optionally for the controlled synthesis of the third block (A ') by polymerization of one or more precursor monomers of the second hydrophobic block (A').

With this or these activated ends, the hydrophilic polymer (B) will be able to serve as a basis for the controlled synthesis of the second or second block

(A) by polymerization of one or more precursor monomers of the hydrophobic block (A), and optionally of the third block (A ') by polymerization of one or more precursor monomers of the second hydrophobic block (A').

The monomers introduced in step b) precursors of the hydrophobic block (A) may be chosen from alkyl acrylates and methacrylates, such as methyl methacrylate, styrene, acrylic acid, methacrylamides and acrylamides. vinyl acetate, and dienes. The number-average molecular weight (Mn) of the hydrophobic block (A) and the hydrophobic block (A ') is generally in the range of 1000 g. mol ^"1 to 100 000g. ^{mol" 1,} preferably 10 000 g. mol ^"1 to 50,000 g mol ^-1 . It may be advantageous to generate the resumption of polymerization from the living hydrophilic polymer obtained at the end of step a), to add, during step b) in addition to the monomers intended to constitute the hydrophobic block (A), a solution comprising a control agent having the following formula:

and a solvent for this control agent, which solvent may be tert-butylbenzene (t-BuBz) or chlorobenzene, which solvent does not participate in the transfer reactions.

Thus, at the end of step b), a diblock copolymer (hydrophilic block (B)) - hydrophobic block (A) activated at the end of the hydrophobic block by a group of formula:

the hook indicating the location by which this group is attached to the end of the hydrophobic block (A).

The monomers introduced in step b) precursors of the second hydrophobic block (A '), in the case where the hydrophilic polymer (B) comprises at the end of step a) two activated ends, can be chosen from the same alkyl methacrylates such as methyl methacrylate, styrene, acrylic acid, alkyl methacrylamides, vinyl acetate. It is the same monomers that will form the blocks (A) and (A ') which are therefore of the same nature but may be of different lengths.

The hydrophobic block (A) which may also be named first hydrophobic block (A) and the second hydrophobic block (A ') are preferably chosen from rigid blocks whose glass transition temperature Tg is greater than 0 ^° C. The precursor monomers of these block sequences will therefore preferably be chosen so as to satisfy this condition relating to Tg.

The hydrophobic block (A) and the second hydrophobic block (A ') may be identical or different. As already mentioned, by different means that the blocks are of the same nature, and are formed from the same monomers but may differ in their length. Preferably, the hydrophilic block (B) and the hydrophobic block (A) or the hydrophobic blocks (A) and

(A ') are incompatible (i.e. they have a Flory-Huggms interaction parameter χAB> 0 at room temperature). This results in phase microseparation with the formation of a diphasic structure on a macroscopic scale, and the diblock or tπbloc copolymer prepared by the process is then nanostructured with domains whose size is less than 100 nm, preferably between 15 and 50 nm.

Steps a) and b) are generally carried out in an inert gas atmosphere, for example, nitrogen, for example by sparging nitrogen into the reaction system. Steps a) and b) are also carried out at a temperature ranging from 20 ° C. to 180 ° C., preferably from 40 ^° C. to 130 ^° C.

The process of the invention may comprise, after steps a) and b), a step of isolating the living polymer, at the end of step a), a step of isolating the diblock copolymer of the triblock copolymer of step b), for example by precipitation followed by filtration.

The method of preparing copolymers described above is particularly applicable to the preparation of a diblock copolymer, wherein: the hydrophilic block (B) is a poly (ethylene oxide) block; the hydrophobic block (A) is a polystyrene block. The process for the preparation of copolymers described above also applies particularly to the preparation of a triblock copolymer, in which: the hydrophilic block (B) is a poly (ethylene oxide) block, the hydrophilic blocks (A) ) and (A ') are polystyrene blocks, identical or different (by their length).

From a structural point of view, the process described above makes it possible to obtain diblock copolymers hydrophilic block (B) -b-hydrophobic block (A) and / or triblock copolymers (hydrophobic block A) -b- (block hydrophilic B) -b- (hydrophobic block A ').

The number average molecular weight of the diblock copolymers thus prepared is generally from 2000 to 200,000 g. mol ^"1 , preferably from 20,000 to 100,000 g, mol ^{" 1} .

The number average molecular weight of the triblock copolymers thus prepared is generally from 3000 to 300,000 g. mol ^"1 , preferably from 25,000 to 150,000 g, mol ^{" 1} . These diblock or triblock copolymers prepared by the method described above, because of their specific sequence comprising a hydrophobic block

(A), a hydrophilic block (B), and optionally a second hydrophobic block (A '), and also due to the high achievable molecular masses intrinsically due to their preparation process, allow unexpectedly to obtain mesoporous materials with a pore size greater than 15 nm, for example 15 to 100 nm.

The invention therefore also relates to the diblock copolymers (A-B) and triblocks A-B-A 'capable of being prepared by the process described in the foregoing. The block copolymer according to the invention is composed of a hydrophilic block B and at least one hydrophobic and preferably rigid lateral block A. As defined by IUPAC in 1996 in its recommendations on the nomenclature of polymers, a block copolymer is a copolymer consisting of adjacent blocks which are constitutionally different, ie blocks comprising derived units. different monomers or the same monomer, but according to a different composition or sequential pattern distribution. A block copolymer may for example be a diblock, triblock or star copolymer.

The block copolymer is, for example, a triblock copolymer ABA 'comprising a central block B connected by covalent bonds to two, for example rigid, side blocks A and A' (that is to say arranged with each coast of the central block B). A and A 'may be the same or different (this type of copolymer is sometimes also noted AbBbA').

The invention relates, according to a second object, to a process for preparing a mesoporous inorganic material from an inorganic precursor and a structuring agent, wherein said structuring agent comprises at least one diblock copolymer comprising a block hydrophilic material (B) and a hydrophobic block (A) or a tπbloc copolymer comprising a hydrophilic block (B), a hydrophobic block (A) and a second hydrophobic block (A '), said copolymer being capable of being prepared by the process of preparation described above. The process of the invention for the preparation of a mesoporous material is fundamentally characterized by the use of a specific, specific structuring agent which comprises at least one particular diblock copolymer or triblock copolymer. These diblock or triblock copolymers are specific, particularly in that they are prepared by a process which fundamentally differentiates them from analogous diblock or triblock copolymers prepared by other methods. It has been found, surprisingly, that the copolymers prepared by the preparation process according to the first subject of the invention, when they are used as structuring agents in the preparation of a mesoporous material, make it possible to achieve for the first time pore sizes greater than 15 nm, preferably 15 to 100 nm, thanks in particular to accessible molecular weights by this method of synthesis based on a specific alkoxyamine.

Such high pore sizes have never been obtained in the prior art either with structuring agents comprising surfactants or with structuring agents comprising block copolymers obtained by other synthetic methods.

This pore size is surprisingly achieved without the need to add swelling agent such as TMB to the medium from which the mesoporous materials are prepared.

In addition to the diblock copolymer or the triblock copolymer prepared by the process as described above, the structuring agent may also comprise a homopolymer (C) chosen from homopolymers miscible with the hydrophilic block (B) and the homopolymers miscible with the block. (A) or (A ') hydrophobic. In particular, this homopolymer (C) may be chosen from the hydrophilic homopolymers constituting the block (A) and the homopolymers of the precursor monomers of the block (A) or of the possible block

(AT'). The homopolymer (C) may represent up to 90% by weight of the structuring agent, preferably from 10 to 50% by weight of the structuring agent.

This homopolymer (C) may be a residual homopolymer originating from the synthesis of the diblock and triblock copolymers, and constituting a by-product thereof (which, preferably, is not separated from these copolymers at the end of the synthesis) or although it may be a homopolymer added voluntarily.

This homopolymer increases the size of either block A (A ') or B, provides an additional swelling effect on the pores and thus increases the size thereof.

The mesoporous inorganic material prepared by the process of the invention is generally a metal or metalloid oxide and the inorganic precursor thereof is generally a metal or metalloid salt or an organometallic compound.

The metal oxide or metalloid may be selected from silica, and aluminum oxides.

The inorganic precursor is preferably selected from alkoxides (alkoxides) of metals or metalloids.

The alcoholates are preferably derived from linear aliphatic alcohols saturated with 1 to 5C such as methanol, ethanol, propanol, n-propanol, butanol, isobutanol, etc.

In the case where the mesoporous material is silica, the alkoxide is preferably chosen from tetraalkoxy (1 to 5C) silane such as tetramethoxysilane (TMOS). The process for preparing mesoporous materials according to the invention, apart from the use of specific structuring agents, is known to those skilled in the art and described in the literature, in particular in the documents by Goltner: CG. Goltner, S. Henke, MC Weissenberger and M. Antometti, Angew. Chem. Int. _Ed.1 37, 613, 1998; CG. Goltner, B. Smarsly, B. Berton and M. Antonietti, Chem. Mater, 13, 1617, 2001; CG. Goltner, B. BERTON, E. KRAMER, M. ANTONIETTI, Advanced Materials 1999, 11, No. 5, 395-398 and in US-B2-7,052,665. This process may first comprise a preparation step. a solution of the structuring agent, constituted by a diblock or tπbloc copolymer as described above, optionally mixed with a homopolymer (C) as described above, in a suitable solvent, such as THF, which is generally carried out at ambient temperature and with stirring in order to obtain a perfectly homogeneous solution of the structuring agent.

To this homogeneous solution at room temperature is then added a precursor of the mesoporous material, for example a metal alkoxide such as TMOS, as well as an acidic or basic catalyst, so as to obtain a polymeric inorganic gel.

This catalyst may for example be added hydrochloric acid in an amount such that the pH is established at a value close to 2 or a basic catalyst.

This polymeric inorganic gel is then dried generally in air for several days. At the end of this drying step, the inorganic material still contains the structuring agent.

The last step of the preparation, synthesis, of the mesoporous material is a step of removal of the structuring agent by an appropriate heat treatment, such as calcination at a temperature generally of 300 to 800 ^° C. Example 12h under nitrogen or 16h under oxygen, for example at 500 ^° C.

The invention also relates to the use of a structuring agent as defined above comprising a diblock copolymer A-B or triblock A-B-A 'and optionally a homopolymer C, for the preparation of a mesoporous inorganic material, such as mesoporous silica.

The invention also relates to the use of a block copolymer comprising a hydrophilic block (B) and a hydrophobic block (A) or a triblock copolymer comprising a hydrophilic block (B), a hydrophobic block (A) and a second hydrophobic block (A '), optionally mixed with a homopolymer (C) as defined above as structuring agent of a mesoporous material.

The invention further relates to a mesoporous inorganic material obtainable by the method described above.

This material generally has a pore size greater than 15 nm, preferably 15 to 100 nm.

This material is preferably mesoporous silica.

This mesoporous material finds its use notably as a catalytic support, as a chemical and / or biological sensor, as a material for optics or electronics, for the encapsulation of proteins, as a coating or a coating. nanoporous, as filtration membrane. The invention further relates to a reinforced glass comprising said mesoporous material. The invention will now be described with reference to the following examples, given by way of illustration and not limitation:

EXAMPLES

In Examples 1 and 2 which follow, the synthesis of block copolymers according to the invention is carried out by the process according to the invention.

These copolymers are respectively a diblock copolymer PS-b-POE (Example 1) and a tπblock copolymer PS-b-POE-b-PS (Example 2).

Example 1

Synthesis of Block Copolymers PS-b-POE The synthesis of PS-i-POE block copolymers according to the invention is carried out by priming the polymerization of styrene with the macroalkoxy-SGAMAMA-POE at 110 ^° C.

MAMA-SG1 is 2-methyl-2- [N-tert-butyl-N- (1-diethoxyphosphoryl-2,2-dimethylpropyl) aminoxy] propanoic acid, i.e. alkoxyamine falling within the scope of formula (II) given above.

In order to synthesize the SG-MAMA-POE macroalkoxy program, it is first necessary to evaluate the OH function of the poly (ethylene oxide) (POE) with an acid chloride, for example acryloyl chloride, for form a poly (ethylene oxide) acrylate, and then perform a multimolecular addition of MAMA-SGi on the acrylate poly (ethylene oxide) (step a) of the process according to the invention).

Esteπfication of poly (ethylene oxide) by an acryloyl chloride

From a commercial precursor of poly (ethylene oxide) monohydroxylated molar mass in number equal to 5000g. mol ^{- 1} and an acryloyl chloride, a coupling between the POE and an acrylate unit by esterification of the alcohol function on an acid chloride (acryloxide chloride) in the presence of a base such as triethylamine ( TEA) was performed (Figure 3).

Figure 3: Esteπfication of poly (ethylene oxide) by an acid chloride

Poly (ethylene oxide) (1 equivalent) is dissolved in dichloromethane (CH ₂ Cl ₂ ). After desoxygenation under nitrogen for 15 minutes, triethylamine (TEA (5 equivalents)) is added. The acryloyl chloride (5 equivalents) is added dropwise after bubbling the solution for 15 minutes under nitrogen. The reaction is carried out overnight at room temperature under an inert atmosphere. At the end of the reaction, the solution obtained is filtered to remove the salt formed, and then washed and dried. The The solution is then concentrated by evaporation of the solvent and then precipitated in diethyl ether cold. The precipitate thus obtained is filtered on a frit then dried under a vacuum ramp.

Intermolecular addition (step a) of the process according to the invention

The 1,2-intermolecular addition (diagram 4) of the MAMA-SGi (10 equivalents) to the poly (ethylene oxide) acrylate (1 equivalent) obtained above was carried out at 100 ° ^C. C for 1 hour in tetrahydrofuran (THF) under nitrogen pressure Schlenk tube.

Figure 4: Intermolecular addition of MAMA-SGi on poly (ethylene oxide) acrylate

Once the reaction is complete, a yellow and viscous solution is obtained, it is brought to ambient temperature then precipitated in diethyl ether cold and finally filtered on a frit to recover the precipitate obtained. Once dried, the product is characterized by ¹ H proton NMR to determine the functionalization performance of MAMA-SGi on poly (ethylene oxide) acrylate, and by phosphorus NMR ( ³¹ P) to verify the presence of SGi. Polymerization of styrene (step b) of the process of the invention

Styrene is polymerized using SGi-MAMA-POE macroalcoxyamine synthesized previously. The macroalkoxyamine will make it possible to initiate the polymerization of styrene (Scheme 5). A kinetic monitoring by ¹ H NMR is carried out in order to check the good control of the polymerization.

Scheme 5: Polymerization of styrene

The polymerization of styrene is mass under an inert atmosphere at 110 ⁰ C in the presence of only SGi-MAMA-POE macroalcoxyamine and styrene, there is no addition of solvent in the reaction medium. Three copolymers called SEl, SE2, SE3 were synthesized (see Table 1).

Example 2

Synthesis of triblock copolymers PS-b-POE-b-PS The synthesis of triblock copolymers PS-> -

POE-23-PS (scheme 6) is identical to that carried out previously, except for the use of a commercial precursor of poly (ethylene oxide) bihydroxy having a molar mass in number equal to 10000 g. mol ^'1 .

Figure 6: Synthesis of triblock copolymer PS-b-POE-b-PS

Three triblock copolymers called SES1, S2S2 and SES3 were synthesized (see Table 2).

Characterization of the copolymers prepared in Examples 1 and 2

The copolymer samples synthesized in Examples 1 and 2 were characterized by NMR (Nuclear Magnetic Resonance) spectroscopy. All spectroscopic analyzes were carried out in solution in deuterated chloroform (CDCl ₃ ). This solvent is invisible in proton NMR ( ¹ H). The ¹ H and ³¹ P NMR analyzes were carried out on a BRUKER Avance DPX-300 spectrometer at a frequency 300MHz recording. This analysis allows us to calculate the composition of the copolymers (SE1, SE2, SE3, SES1, SES2 and SES3 in Example 1) obtained. The results obtained are grouped in the following tables (1 and 2):

Table 1: PS-b-POE Diblock Copolymers Synthesized in Example 1

Table 2: PS-b-POE-b-PS Triblock Copolymers Synthesized in Example 2

Exemple 3

Example 3

Synthesis of Mesoporous Silica Using the Copolymers According to the Invention as Structuring Agents For all syntheses, the silica source used is tetramethoxysilane (TMOS Si (OCH ₃ ) ₄ -). It is known to those skilled in the art that acid catalysis promotes the formation of low density branched species (polymeric gels). In addition, the structuring agents used being not loaded, the syntheses were carried out at pH = 2, that is to say at a pH close to the isoelectric point of the silica. The gels thus obtained are dried in air for several days. At the end of this step, the silica matrix always contains the structuring agent used. The last step of the synthesis therefore consists in eliminating the structuring agent by suitable heat treatment. The synthesis protocol of the silica matrices, using PS-2-type copolymers - POE and PS-ώ-POE-ώ-PS, was made from the work of Goltner and his collaborators (CG Goltner, S Henke, MC Weissenberger and M. Antonietti, Angew Chem Int, Ed ₁ 37, 613, 1998 and CG Goltner, B. Smarsly, B. Berton and M. Antonietti, Chem Mater, 13, 1617, 2001). (diagram 7):

_Copo l _ymere ^SoLvant > Solution ™ ^ _Oel Calcma ^h on ^ _{Matrix of Slo}

Tamb ("RT") homogeneous _p H = 2 / Tam ("RT") 550 ⁰ C

Figure 7: Synthesis of silica matrix using PS-b-POE and PS-b-POE-b-PS copolymers 3A - Preparation of mesoporous silicas from POE-b-PS diblock copolymers

0.5 g or 0.25 g of diblock copolymer POE-b-PS is dissolved with stirring in 4 mL or 2 mL of THF in a closed flask for 30 min at room temperature. With vigorous stirring, 0.5 g or 0.25 g of HCl (37%) and then 0.75 g or 0.375 g of tetramethoxysilane are added dropwise to the copolymer solution. The mixture is stirred at room temperature until the formation of the gel. The gel formed is air-dried at room temperature for 2-3 days and then calcined at 500 ^° C. to remove the structuring agent in order to obtain the porous silica matrix.

3B - Preparation of mesoporous silicas from PS-b-POE-b-PS triblock copolymers

In a 50 ml flask, 0.5 g or 0.2 g of PS-b-POE-b-PS triblock copolymer and 4 ml of THF are introduced at room temperature and stirred for 1 hour. With vigorous stirring, 0.79 g or 0.32 g of HCl (37%) and then 1.146 g or 0.458 g of tetramethoxysilane are added dropwise to the copolymer solution. The mixture is stirred at room temperature until the formation of the gel. The gel formed is air-dried at room temperature for 2-3 days and then calcined at 500 ^° C. to remove the structuring agent in order to obtain the porous silica matrix. (*) when the Mn of the PS block is> at the Mn of the POE block, the copolymer is dissolved in THF at a concentration of 5% (w / v) instead of 12.5% (w / v).

The synthesis parameters of the silica matrices using PS-ώ-POE diblock copolymers (Example 1) are summarized in Table 3 below.

Table 3: Parameters of synthesis of mesoporous silica using PS-b-POE (SE1, SE2 and SE3)

The synthesis parameters of the silica matrices using the PS-23-POE-23-PS triblock copolymers of Example 2 (SES1, SES2, SES3) are summarized in Table 4 below.

Table 4: Parameters of synthesis of mesoporous silica using PS-b-POE-b-PS

Characterization of silica: measurement of adsorption and desorption of nitrogen at 77 K

Nitrogen adsorption manometry is a method of characterizing divided materials to calculate the specific surface as well as the pore volume. It is essentially based on the adsorption phenomenon. Adsorption is a phenomenon that occurs whenever a gas or liquid is in contact with a solid; it is retained by the superficial atoms of the solid and concentrates on its surface. The amount adsorbed (M) on a solid surface will depend on the absolute temperature T, the pressure P and the interaction potential (E) between the vapor (adsorbate) and the surface (adsorbent). The measurements are generally carried out at constant temperature, this is simplified by:

M = Function (P, E).

An apparatus of the "ASAP 2010" type from the company Micromeπtπcs is used. It allows to do measurements of nitrogen adsorption and desorption isotherms at 77 K. It is equipped with a software allowing to trace the isotherms and to calculate the pore size and the specific surface. The mass of an empty tube containing a plunger is determined, then about 100 mg of sample is added and the total mass is determined. The sample is then degassed at 120 ^° C. for 12 h, this degassing makes it possible to release all the adsorption sites by eliminating any trace of moisture or impurity. After degassing, the sample is weighed again before the measurement.

The values obtained during the data processing for the two samples are summarized in Table 5 below. The results show that as the length of the hydrophobic block increases the mesopore diameter increases and the surface area decreases.

Table 5: Parameter Values Resulting from 77 K Nitrogen Adsorption Measurements

As for the samples synthesized using diblock copolymers, the SES1, SES2 and SES3 samples were characterized by nitrogen adsorption manometry at 77K. The data collected are summarized in Table 6 below. Table 6: Data from 77 K nitrogen adsorption measurements on SES1, SES2 and SES3 samples

The products of the invention prepared from the structuring agents SE3 and SES3 make it possible to obtain a mesoporous silica having pore sizes greater than 15 nm.

Claims

A process for preparing a diblock copolymer comprising a hydrophilic block (B) and a hydrophobic block (A), or a triblock copolymer comprising a hydrophilic block (B), a hydrophobic block (A) and a second hydrophobic block (A '), said process comprising the following steps: a) a 1,2-addition step on an ethylenic end group, or two ethylenic end groups, of a hydrophilic polymer, an alkoxyamine corresponding to the formula (I) ) next : R C (CH 3) 3 R ₃ -CON CH-C (CH ₃ ) ₃ C (O) OR ₂ P (O) (OEt) ₂ (D in which: R 1 and R 3, which may be identical or different, represent a linear or branched alkyl group having a number of carbon atoms ranging from 1 to 3; R ₂ represents a hydrogen atom, an alkali metal, such as Li, Na, K, an ammonium ion such as NH ₄ ⁺ , NBu ₄ ⁺ , NHBu 3 ⁺ , a linear or branched alkyl group having a number of carbon atoms ranging from 1 to 8, a phenyl group; b) a step of bringing into contact with the medium resulting from step a) of one or more precursor monomers of a hydrophobic block for a sufficient time to obtain the hydrophilic block copolymer (B) -jb-hydrophobic block ( A) in the case where the addition step a) has occurred on a single group ethylenic terminal of the hydrophilic polymer; or to obtain the hydrophilic block triblock copolymer (A) -b-hydrophilic block (B) -b-second hydrophobic block (A ') in the case where the addition step a) has occurred on two ethylenic terminal groups hydrophilic polymer. 2. The method of claim 1, wherein the hydrophilic polymer is selected from semicrystalline polymers and / or hydrolyzable. 3. The method of claim 1, wherein the hydrophilic polymer is selected from polymers comprising functions selected from carboxylic acid functions, anhydrides, and acrylamides. 4. The method of claim 1, wherein the hydrophilic polymer is selected from copolymers of methyl methacrylate and at least one hydrophilic monomer. 5. Process according to any one of the preceding claims, in which the hydrophilic polymer comprising an ethylenic end group or two ethylenic end groups is chosen from polycaprolactones, polylactides, polyethylene, polypropylene and polyethylene oxide. and polyamides. The method of any of the preceding claims, further comprising, prior to step a), a functionalization step of the hydrophilic polymer, said hydrophilic starting polymer, for introducing an ethylenic end group at one end of the starting polymer or at both ends of the starting polymer. The method of claim 6, wherein the hydrophilic starting polymer is ω-hydroxyl polycaprolactone, poly-hydroxyl ethylene oxide or α, ω-hydroxyl ethylene oxide. 8. Process according to any one of the preceding claims, wherein the number-average molecular weight (Mn) of the hydrophilic polymer is in the range of 1000 g. mol ^"1 to 100,000 g mol ^{" 1} and preferably 5,000 g. mol ^"1 to 50,000 grams mol ^"1; and the number-average molecular weight of the hydrophobic block (A) and the hydrophobic block (A ') is generally in the range of 1000 g. mol ^"1 to 100,000 g. mol ^{" 1} , preferably 10,000 g. mol ^"1 to 50,000 g mol ^-1 . 9. Process according to any one of the preceding claims, in which the alkoxyam used in step (a) corresponds to the following formula (II):

Process according to any one of the preceding claims, wherein the alkoxyamine is introduced, in step a), at a content ranging from 0.5% to 80% by weight relative to the weight of the hydrophilic polymer. 11. Process according to any one of the preceding claims, in which the monomers introduced in stage b) precursors of the hydrophobic block (A) and the hydrophobic block (A ') are chosen from alkyl acrylates and methacrylates such as methyl methacrylate, styrene, acrylic acid, methacrylamides and acrylamides, vinyl acetate, and dienes. The process according to any of the preceding claims, wherein the number average molecular weight of the diblock copolymers is in the range of 2000 to 200,000 g. mol ^"1 , preferably 20,000 to 100,000 g, mol ^{" 1} and the number average molecular weight of the block copolymers is in the range of 3000 to 300,000 g. mol ^"1 , preferably from 25,000 to 150,000 g. mol ^-1 . Process according to any one of the preceding claims, comprising adding, during step b) in addition to the monomers intended to constitute the hydrophobic block (A), and the hydrophobic block (A '), if any, of a solution comprising a control agent corresponding to the following formula:

and a solvent for this control agent. 14. Process according to any one of the preceding claims, in which the hydrophobic block (A) and the second hydrophobic block (A ') are chosen from rigid blocks of glass transition temperature Tg greater than 0 ^° C. 15. Process according to any one of the preceding claims, in which the hydrophobic block (A) and the second hydrophobic block (A ') are identical. 16. The method according to any one of claims 1 to 14, wherein the hydrophobic block (A) and the second hydrophobic block (A ') are different. 17. A method according to any one of the preceding claims, wherein the hydrophilic block (B) and the hydrophobic block (A) or the hydrophobic blocks (A) and (A ') are incompatible. 18. The method of claim 17, wherein the block copolymer or tπbloc is nanostructured with domains of size less than 100 nm, preferably between 15 and 100 nm. 19. A process according to any one of the preceding claims, wherein the hydrophilic block (B) is a poly (ethylene oxide) block, the hydrophobic block (A) and the second hydrophobic block (A ') are blocks. poly (styrene) same or different. 20. A diblock copolymer comprising a hydrophilic block (B) and a hydrophobic block (A), or triblock copolymer comprising a hydrophilic block (B), a hydrophobic block (A) and a second hydrophobic block (A '), capable of being prepared by the process according to any one of claims 1 to 19. A process for preparing a mesoporous inorganic material from an inorganic precursor and a structuring agent, wherein said structuring agent comprises at least one amphiphilic copolymer selected from diblock copolymers comprising a hydrophilic block (B) and a hydrophobic block (A), and the triblock copolymers comprising a block hydrophilic material (B), a hydrophobic block (A) and a second hydrophobic block (A ') according to claim 20. 22. The method of claim 21, wherein the structuring agent further comprises a homopolymer (C) selected from homopolymers miscible with the block (B) hydrophilic, and homopolymers miscible with the block (A) or the block (A). ') hydrophobic. 23. The method of claim 22, wherein the homopolymer C represents up to 90% by weight of the structuring agent, preferably from 10 to 50% by weight of the structuring agent. 24. A process according to any one of claims 21 to 23, wherein the mesoporous inorganic material is a metal or metalloid oxide and the inorganic precursor is a metal or metalloid salt or an organometallic compound. 25. The method of claim 24, wherein said metal oxide or metalloid is selected from silica, and aluminum oxides. 26. The method of claim 25, wherein said organic precursor is selected from alkoxides (alkoxides) of metals or metalloids. 27. The process according to claim 26, wherein the metal oxide is silica and the alkoxide of metal is selected from tetraalkoxy (1 to 5C) silane such as tetramethoxysilane (TMOS). 28. Use of a structuring agent as defined in any one of claims 21 to 23 for the preparation of a mesoporous inorganic material such as mesoporous silica. 29. Use of an AB or AB-A 'copolymer according to claim 20, optionally in admixture with a homopolymer (C), as defined in claim 22 or 23, as structuring agent for a mesoporous material such as mesoporous silica. . Mesoporous inorganic material obtainable by the method according to any one of claims 21 to 27. 31. The material of claim 30 wherein the pore size is greater than 15 nm, preferably 15 to 100 nm. 32. The material of any one of claims 30 to 31 which is mesoporous silica. 33. Use of the material according to any one of claims 30 to 32 as catalytic support. 34. Use of the material according to any of claims 30 to 32 as a chemical and / or biological sensor. 35. Use of the material according to any one of claims 30 to 32 as a material for optics and electronics. 36. Use of the material according to any one of claims 30 to 32 for Encapsulation of proteins. 37. Use of the material according to any one of claims 30 to 32 as a varnish or coating ("coating") nanoporous. 38. Use of the material according to any of claims 30 to 32 as filtration membrane. 39. Reinforced glass comprising the mesoporous material according to any one of claims 30 to 32.