FR2738249A1 - MESOGENIC METAL COMPLEXES, PROCESS FOR POLYMERIZING THESE COMPLEXES AND ANISOTROPIC POLYMERS THUS OBTAINED - Google Patents

Abstract

The invention concerns novel mesogenic metallic complexes which can be polymerized photochemically in their liquid crystalline state and correspond to formula (I), in which at least one of the two R groups is a group which can be polymerized photochemically and M is a metal, in particular zinc. The invention also concerns a process for photochemically polymerizing these complexes, and the resultant columnar anisotropic liquid-crystalline polymers containing one metallic centre per monomer unit.

Description

MESOGENIC METAL COMPLEXES, PROCESS FOR
POLYMERIZATION OF THESE COMPLEXES AND POLYMERS
ANISOTROPES SO OBTAINED
The present invention relates to mesogenic metal complexes, to the photopolymerization process of these complexes and to the anisotropic polymers of columnar structure thus obtained.

 Consumer electronics devices increasingly include optical or electro-optical devices, for example for storing information, for projection, for example high-definition televisions or image storage.

The optical components required in these devices, including among others linear and circular polarizers, beam splitters, shutters, switches, filters, dichroic mirrors, prisms, and others, are currently produced using techniques and materials. conventional, and are too expensive compared to the price of a consumer device. At the same time, there is a general trend toward miniaturization of electronic components, which should lead to devices of smaller size and lower cost. For these reasons, the electronics industry has an urgent need for new materials and production methods to design and produce new optical components with new functions or integrating several functions into a single device.

 It has emerged that among the new materials that can be used in these electro-optical devices, the polymers endowed with an anisotropy of their properties, in particular their optical properties, seemed to be of particular interest for such applications. The oriented polymer films are indeed of great interest because of their anisotropic properties, among which the most important is optical anisotropy. The most conventional method for orienting a polymer is to deform it, but this method can not be applied in the case where very thin oriented films have to be produced on surfaces with complex geometries, or at high speed.

This is why "in situ" photopolymerization of liquid crystalline monomers has been developed. The crosslinking of liquid crystal molecules has been known for a long time and was first carried out by thermally triggered polymerization, i.e. a liquid crystal mixture comprising a thermal initiator is heated to a temperature at which the initiator dissociates to initiate polymerization; However, this process has many drawbacks related in particular to the difficulty of having initiators covering the entire range of temperatures, and the premature polymerization occurring during heating and leading to unwanted liquid crystalline phases or unordered states. in situ photopolymerization of liquid crystalline monomers, allows on the other hand to precisely control the orientation of the optical axes within the material, and to confer to it optical functions difficult to obtain by other methods such as those mentioned above.

 In this photopolymerization technique, monomers that form a crystalline liquid phase, namely a mesophase or a phase having a mesomorphic character that is to say that they are in certain temperature zones in an intermediate form between the form crystalline specific to certain solid bodies and the disordered form characteristic of the liquid state are oriented by means of a suitable surface treatment of the support (then called "rubbed substrate") or under the action of an external electric or magnetic field, to thereby give macroscopic anisotropic domains, for example nematic twisted or other ... and are then polymerized under irradiation including ultraviolet.

The in situ photopolymerization technique of liquid crystalline monomers has been implemented in particular in the document by DJ Broer, GN Mol,
Polym. Eng. Science, 31, 625-631 (1991) which relates to a process for in situ photopolymerization of nematic liquid crystal monomers diacrylates. In this process, low molecular weight organic mesogens having polymerizable groups at each end of the molecule, consisting of acrylate functions, are deposited on a suitable support and are then oriented in their crystalline liquid state by application of an electric field. external or by a surface treatment of the support ("rubbed substrate"). The desired molecular order is then permanently fixed by polymerization initiated by ultraviolet irradiation at a wavelength of 365 nm. The possible orientations are uniaxial orientations in the plane, uniaxial homeotropic, homeoplanar, "twisted" or other.

 Although the optical properties of these purely organic materials are already attractive for some applications, it would be desirable to increase the birefringence and the refractive indices.

The process described in the previously cited publication has been modified in the
RAM Hikmet, J. Lub, P. Maassen vd Brink,
Macromolecules, 25, 4194-4199 (1992) which relates to the gel structure formation by polymerization of a mixture of two nematic liquid crystalline molecules, one having two photopolymerizable functions (acrylates) and the other not possessing . The result is a highly anisotropic system in which the polymerized molecules form a stationary matrix, while the non-reactive molecules form a mobile phase whose orientation can be changed by the application of an external field. The potential application of this Such a network could be, for example, a fast shutter in which the transition from a light diffusing state to a non-diffusing state would require less energy than current devices. The refractive indices obtained, however, need to be further increased in order to improve the contrast between the diffusing state and the non-diffusing state.

On the other hand, it is known that the molecular structure of low molecular weight liquid crystals can affect the physical properties of these. Thus, in the documents of C. Bertram,
DW Bruce, DA Dunmur, SE Hunt, PM Maitlis, M.

Mc Cann, J. Chem. Soc., Chem. Common. 69-70 (1991) and DW Bruce, DA Dunmur, PM Maitlis, MM
Manterfield, R. Orr, J. Mater. Chem. 1, 255-258 (1991) has been shown that the anisotropy of polarizability and birefringence increased during the complexation of a nematic organic ligand by metal centers such as iridium, palladium or platinum. Finally, it was shown in the document
H. Tereao, S. Eguchi, M. Ibamoto, H. Asano, Chem. Lett.

1001-1004 (1987) that the inclusion of metals, such as barium and lead, in a polymer obtained by laser irradiation leads to an increase in the refractive indices of the polymer relative to those of the organic polymer. However, the isotropic nature of the material thus prepared does not make it possible to confer on it the birefringence or the desired spontaneous orientation.

 The polymeric materials for electro-optical applications mentioned above do not exhibit both the macroscopic orientation, the high birefringence as well as the high refractive indices at room temperature required for this type of application. It is certainly known that birefringence and spontaneous orientation are characteristics of liquid crystal compounds, especially of low molecular weight, but these properties have never been obtained with polymers which also have high refractive indices.

 There is therefore an unmet need for anisotropic polymers having simultaneously excellent optical properties, namely high birefringence and high refractive index and structural, namely long-range molecular order.

 The object of the invention is therefore essentially to prepare by in situ photopolymerization of new crystalline liquid monomeric molecules, anisotropic polymers satisfying all the requirements mentioned above.

dans laquelle les deux groupes R peuvent être identiques ou différents et représentent chacun H, un halogène (F, Cl, Br, I) ou un groupe choisi parmi CN,
NO2, CF3, OH, les groupes alkyles et alkoxy linéaires et ramifiés de 1 à 30 atomes de carbone éventuellement substitués et/ou éventuellement interrompus par un ou plusieurs atome(s) choisi(s) parmi S, N, O, les groupes alkényles de 2 à 30 atomes de carbone, les groupes alkynyles de 2 à 30 atomes de carbone, les groupes alkoxycarbonyles de 2 à 30 atomes de carbone éventuellement substitués, les groupes

où
Alk représente un groupe alkyle de 1 à 30 atomes de carbone éventuellement substitué, les groupes cycloalkyles de 3 à 20C, et les fonctions polymérisables par voie photochimique, à la condition que l'un au moins des deux groupes R soit une fonction polymérisable par voie photochimique ; n est un nombre entier égal au nombre de carbones présents dans la chaîne hydrocarbonée du complexe et est compris entre 1 et 40, de préférence entre 6 et 40 et M est un métal divalent.This and other objects are achieved according to the invention and, in a first aspect, new mesomorphic compounds capable of being photochemically polymerized in their crystalline liquid state. These compounds are metal complexes of general formula (I)

wherein the two R groups may be the same or different and each represents H, halogen (F, Cl, Br, I) or a group selected from CN,
NO 2, CF 3, OH, linear and branched alkyl and alkoxy groups of 1 to 30 carbon atoms optionally substituted and / or optionally interrupted by one or more atom (s) chosen from S, N, O, the alkenyl groups from 2 to 30 carbon atoms, alkynyl groups of 2 to 30 carbon atoms, optionally substituted alkoxycarbonyl groups of 2 to 30 carbon atoms,

or
Alk represents an optionally substituted alkyl group of 1 to 30 carbon atoms, cycloalkyl groups of 3 to 20C, and photochemically polymerizable functions, with the proviso that at least one of the two R groups is a polymerizable functional group. photochemical; n is an integer equal to the number of carbons present in the hydrocarbon chain of the complex and is between 1 and 40, preferably between 6 and 40 and M is a divalent metal.

 These molecules are crystalline liquid thermotropic, columnar hexagonal at room temperature, colorless, which therefore contain both metals and polymerizable functions.

 In a second aspect, the subject of the invention is also a process for the in situ photopolymerization of the abovementioned compounds or molecules of formula (I) in which the monomer (I) in its crystalline liquid state - in its mesophase is subjected to polymerization conditions by photochemical means, that is to say is irradiated with an adequate radiation so as to cause its photopolymerization via the group or groups R. The subject of the invention is also the polymer obtained by this process.

 Finally, the subject of the invention is still a process for the preparation of the novel crystalline liquid monomer molecules mentioned above, as well as the new intermediate compounds involved in this process for the preparation of liquid crystalline monomeric molecules and whose specific structure makes it possible to obtain the novel crystalline liquid monomeric molecules of the invention as well as the anisotropic polymers of the invention.

 The polymerization in their mesophase of these new thermotropic crystalline liquid molecules, generally hexagonal columnar containing metals still called "metallomésogènes", makes it possible to obtain polymers endowed with a high thermal stability, that is to say stable up to at least 250 ° C. The in-situ photopolymerization process in the crystalline liquid state freezes the orientation of the material and stabilizes the values of the refractive indices and consequently the birefringence as a function of the temperature. from a polymerizable metal complex, a polymer containing a metal center complexed in each monomer unit, whereas with the methods of the prior art, the percentage of metal incorporated in each monomer unit is less than 50%. characteristics allow access to new optical properties, stable according to the temperature, based on these liquid crystal polymer materials containing metal centers.

 In formula I, at least one of the two Rs is a preferably photochemically polymerizable function, both Rs are such a polymerizable function, this type of function can easily be determined by those skilled in the art of photopolymerization ; an example of a preferred function is the acrylate function O-CO-CH = CH 2, but it will also be possible to use the methacrylate functions, vinyl ether, the other R being chosen from the groups already mentioned above.

 n may range from 1 to 40, but is preferably 6 to 40, n is preferably 11. It is obvious that ligands with chain lengths other than 11 may also be used in the process. method of the invention provided however that they exhibit a crystalline liquid behavior.

According to the invention, the metal M is advantageously chosen from the group of metals having a low redox power, the divalent metals with solid electronic layers: Be, Mg, Ca, Sr, Ba,
Ra, Zn, Cd, Hg do not interfere with the radical process of polymerization, zinc being the preferred metal.

 On the other hand, it is preferable not to use transition metals that could interfere with the photopolymerization process.

n est compris entre 1 et 40, de préférence entre 6 et 40, n étant encore de préférence égal à 11.By way of non-limiting example of the metal complexes of the invention, mention may be made of zinc complexes A containing acrylate functions at the end of the chain, of formula

n is between 1 and 40, preferably between 6 and 40, n being still preferably 11.

 The invention also relates to a process for the photopolymerization of the new metal complexes of the invention in which these monomers (I) in their mesophase are irradiated so as to cause a photopolymerization reaction in situ, whereby a polymer containing a complexed metal center in each monomer unit is obtained.

 The monomer may for example be melted beforehand in its isotropic phase with addition of an effective amount, for example from 1% to 5% by weight, of a radical polymerization initiator, between two plates of a suitable support, and then irradiated. for example at room temperature using particularly ultraviolet radiation.

 The conditions of in situ photopolymerization are known to those skilled in the art and can be easily determined; irradiation with ultraviolet radiation using, for example, a high-pressure mercury lamp, the irradiation time, the power density and the other process parameters can be fixed without difficulty by skilled in the field of photopolymerization possibly using some routine experiments.

 The polymer is obtained with a conversion of more than 40%, it is obvious that the conversion rate can be optimized by the skilled person by acting on the various parameters that influence the photopolymerization process. The polymer according to the invention is therefore characterized in that it consists of the monomer units of the general formula (I). It has already been mentioned below that, thanks to the method of the invention, polymers containing a metal center complexed in each monomer unit are obtained; this structural characteristic represents a decisive advantage of the polymers according to the present invention, because until now the percentage of incorporated metal was less than 50%.

 According to a preferred embodiment of the present invention, the polymers obtained are polymers of columnar structure in which the columnar units are formed by the column stacking of disk-shaped monomeric molecules. These columns are assembled in a regular two-dimensional network where the axes of the columns are at the nodes of a hexagonal, rectangular or oblique system.

 Finally, as already mentioned above, the subject of the invention is also a process for the preparation of monomeric mesogenic metal complexes of formula (I), and the invention also relates to the novel intermediate compounds involved in the process of synthesis of new mesogenic compounds (I). These intermediate compounds have an appropriate specific structure found in the compounds (I) and communicating to them most of their crystalline liquid and complexing properties, which are fundamental in the context of the present invention, in order to then obtain the desired anisotropic polymer presenting the whole. characteristic properties of the present invention.The process for preparing the compounds of formula (I) comprises firstly the synthesis of the ligand (V) from which is prepared the metal complex of formula (I).

où n et R ont les significations déjà données ci-dessus pour le composé (I).The ligand (V) has the following general formula

where n and R have the meanings already given above for the compound (I).

 This ligand may for example be prepared according to the following procedure, in the case where the R group is attached by an oxygen atom to the rest of the molecule, the ligand is then called (VI). It is obvious that the synthesis can be easily adapted by the skilled person in the case of other attachments.

I. Procedure for the synthesis of the ligand (VI)
A. Esterification of 3,4 (dihydroxy) benzoic acid

R'OH represents any alcohol, R 'can be in particular a linear or branched alkyl radical of 1 to 20 carbon atoms, a cycloalkyl group of 3 to 20 carbon atoms, a haloalkyl group of 1 to 20 carbon atoms. arbone; methanol is the preferred alcohol.

The conditions of the esterification are known to those skilled in the art and will not be detailed further. Reference may be made, where appropriate, to the specific example given below.

B) Chain grafting

R ', n have the meaning already given above, and X represents a halogen. The conditions of such a reaction are known or can easily be determined by those skilled in the art, however one will operate for example by suspending the compound (II) in a sufficient amount of solvent such as DMF, with XCnH2nOH and K2CO3 . The mixture is then heated to a sufficient temperature and for a sufficient time (for example 2 to 3 hours at 80 ° C.) Then the solution is concentrated to dryness at room temperature.

Another solvent such as acetone is added, and the potassium carbonate is separated for example by filtration. The desired product is then optionally recrystallized, for example from acetone. Extensive bibliographic research indicates that compound (III) is a novel compound not cited in the literature.

C) Deprotection of the carboxylic acid function
The carboxylic acid function of the compound (III) is then deprotected in a manner known to those skilled in the art according to the following scheme

 For example, the compound (III) is suspended in a sufficient amount of ethanol with sodium hydroxide. The mixture is refluxed for a sufficient time and the pH is lowered, for example, to around 1 by addition of an acid such as HCl, 10%. A precipitate is formed and finally, if necessary, recrystallization.

 Compound (IV), after extensive bibliographic research, proved to be a novel compound not yet described in the literature.

D) Grafting of functions R "
The grafting on the compound (IV) described above can be carried out by any suitable method and can be easily accomplished by those skilled in the art.

où n et X ont les significations déjà données plus haut et O-R" comprend les groupes R déjà définis ci-dessus pour la formule (I) qui sont rattachés par un atome d'oxygène à la chaîne hydrocarbonée reliée au reste de la molécule (par exemple si R est un groupe acrylate alors R" est un groupe acryloyl). This grafting will answer for example to the following diagram

where n and X have the meanings already given above and OR "comprises the groups R already defined above for the formula (I) which are attached by an oxygen atom to the hydrocarbon chain connected to the rest of the molecule (by for example, if R is an acrylate group then R "is an acryloyl group).

 The product (IV) may for example be suspended in a suitable solvent (THF, for example) with triethylamine. The halide R "-X is then added and the reaction is allowed to proceed for a sufficient period of time.The reaction product is recovered by dry concentration, addition of water, extraction with a suitable solvent, such as chloroform, finally purification by chromatography.

 A literature search revealed that the product (VI), or polymerizable ligand, was a new product.

II. Procedure for the synthesis of the metal complex (I) of the ligand (VI) or (V)
This procedure is schematized as follows

The brackets [] represent the remainder of the molecule that is attached to the carboxyl group of the ligand where
M 'is an alkaline metal.

M has the meaning already given above in the description, MX 'may be any metal salt capable of reacting with the compound (VII) to give the compound (I). It can be chosen from nitrates, sulphates, acetates, chlorides, etc. The coefficients are of course adapted according to the
As mentioned above, the compound (I) is a new compound, as revealed by a thorough literature search.

 The invention will now be described with the aid of the following example given by way of illustration and not limitation.

39,7 mmoles (6,12 g) d'acide 3,4-(dihydroxy)-benzoïque 1 sont mises en solution dans 75 ml de méthanol avec 11,6 mmoles (2 g) d'acide para-toluène-sulfonique. La solution est portée à 80"C pendant 12 heures. A température ambiante, la solution est concentrée à 10 ml environ, puis est rendue basique (pH=8) par- l'addition de 23,6 mmoles (946 mg ) de soude dans 25 ml d'eau distillée.EXAMPLE Process for preparing a polymer according to the invention formed of zinc complexes
I. Procedure for the synthesis of the ligand: 3,4-di (11-acryloylundecyloxy) benzoic acid
A) Esterification of 3,4- (dihydroxy) benzoic acid

39.7 mmol (6.12 g) of 3,4- (dihydroxy) -benzoic acid 1 are dissolved in 75 ml of methanol with 11.6 mmol (2 g) of para-toluenesulfonic acid. The solution is heated at 80 ° C. for 12 hours at room temperature, the solution is concentrated to about 10 ml and then made basic (pH = 8) by the addition of 23.6 mmol (946 mg) of sodium hydroxide. in 25 ml of distilled water.

 The aqueous phase is extracted several times with 25 ml of ethyl ether. The organic phase is dried over Na 2 SO 4 and then concentrated to dryness, giving the methyl ester 2 in the form of a light brown powder dried in a desiccator (mass = 4.71 g, ie 28.4 mmol or a yield of 71E).

3 mmoles (0,5 g) de 3,4-(dihydroxy)benzoate de méthyle 2 sont mises en suspension dans 50 ml de DMF avec 6 mmoles (1,5 g) de 1l-bromoundécan-1-ol et 5 g de
K2CO3. Ce mélange est porté à 800C pendant 2 heures 30 minutes. A température ambiante, la solution est concentrée à sec. Au solide obtenu, on ajoute 100 ml d'acétone puis le carbonate de potassium, K2C03 insoluble, est séparé par filtration. On laisse recristalliser le filtrat dans l'acétone à 40C, puis on recueille le produit cristallisé sur verre fritté et enfin on le sèche au dessicateur. On obtient 1,14 g (2,2 mmoles) de 3, 4-di (îl-hydroxyundécyloxy)benzoate de méthyle 3 sous la forme d'une poudre blanche (rendement=75%). Ce produit 3 est un produit nouveau non décrit dans la littérature.B) Grafting of the crames

3 mmol (0.5 g) of methyl 3,4- (dihydroxy) benzoate 2 are suspended in 50 ml of DMF with 6 mmol (1.5 g) of 11-bromoundecan-1-ol and 5 g of
K2CO3. This mixture is heated at 800C for 2 hours 30 minutes. At room temperature, the solution is concentrated to dryness. To the solid obtained, 100 ml of acetone is added, then the potassium carbonate, insoluble K 2 CO 3, is separated by filtration. The filtrate is allowed to crystallize from acetone at 40 ° C., the crystallized product is then collected on sintered glass and finally dried in a desiccator. 1.14 g (2.2 mmol) of methyl 3,4-di (l-hydroxyundecyloxy) benzoate 3 are obtained in the form of a white powder (yield = 75%). This product 3 is a new product not described in the literature.

2,2 mmoles (1,14 g) de 3,4-di(11-hydroxyundécyloxy) benzoate de méthyle 3 sont mises en suspension dans 50 ml d'éthanol avec 1 g de soude. Ce mélange est porté au reflux pendant 4 heures. A température ambiante, on ajoute une solution à 10% re .nC1 dans l'eau jusqu'à obtenir un pH de 1. Il se forme alors un précipité blanc que l'on recueille sur verre fritté. On recristallise la poudre obtenue dans 50 ml d'éthanol à chaud. On obtient 0,76 g (1,5 mmoles) d'acide 3,4di(ll-hydroxyundécyloxy) benzoïque 4 sous la forme d'une poudre blanche (rendement=69%). C) Deprotection of the carboxylic acid function

2.2 mmol (1.14 g) of methyl 3,4-di (11-hydroxyundecyloxy) benzoate 3 are suspended in 50 ml of ethanol with 1 g of sodium hydroxide. This mixture is refluxed for 4 hours. At room temperature, a 10% solution in water is added until a pH of 1 is reached. A white precipitate is then formed which is collected on sintered glass. The resulting powder is recrystallized from 50 ml of hot ethanol. 0.76 g (1.5 mmol) of 3,4di (11-hydroxyundecyloxy) benzoic acid 4 is obtained in the form of a white powder (yield = 69%).

 Product 4 is a new product, not described in the literature.

1 mmole (9,49 g) d'acide 3,4-di(llhydroxyundécyloxy) benzol que 4 est mise en suspension dans 10 ml de THF anhydre (préalablement distillé sur sodium en boite à gants sous argon sec désoxygéné) avec 3 mmoles (0,30 g) de triéthylamine. On ajoute sous atmosphère d'argon 3 mmoles (0,236 ml) de chlorure d'acryloyle. Au bout de 28 heures, on arrête la réaction en concentrant le mélange réactionnel à sec. Le produit obtenu est purifié par chromatographie sur colonne de silice. Le dichlorométhane est d'abord utilisé comme éluant, puis on augmente progressivement la polarité de l'éluant par addition d'éther éthylique. On obtient 90,34 g de produit pur 5 (0,56 mole) sous la forme d'une poudre blanche, soit un rendement de 57%.Le produit 5 est un produit nouveau, non décrit dans la littérature.D) Grafting of acrylate functions

1 mmol (9.49 g) of 3,4-di (11-hydroxyundecyloxy) benzol acid, which is suspended in 10 ml of anhydrous THF (previously distilled on sodium in a glove box under deoxygenated dry argon) with 3 mmol ( 0.30 g) of triethylamine. 3 mmol (0.236 ml) of acryloyl chloride are added under an argon atmosphere. After 28 hours, the reaction is stopped by concentrating the reaction mixture to dryness. The product obtained is purified by chromatography on a silica column. The dichloromethane is first used as eluent, then the polarity of the eluent is gradually increased by the addition of ethyl ether. 90.34 g of pure product (0.56 mol) are obtained in the form of a white powder, ie a yield of 57%. Product 5 is a new product, not described in the literature.

 The overall yield of the four steps constituting the synthesis of the ligand is 212.

 Table 1 below gives the elemental analysis of the polymeric sand ligand 5.

TABLE 1

<tb><SEP> ELEMENT <SEP> CARBON <SEP> HYDROGEN <SEP> OXYGEN
<tb><SEP>%<SEP> Theoretical <SEP> 69.74 <SEP> 9.03 <SEP> 21.23
<tb>% <SEP> experimental <SEP> 69.52 <SEP> 9.05 <SEP> 21.12
<tb> II. Procedure for the synthesis of the zinc complex
A ligand 5
The synthesis of the zinc A complex of ligand 5 corresponds to the following scheme
5 + NaOH o NaOOC- [] + H2O
ZnSO4. 6H2O + 2NaOOC- [OZn (OOC-j) 2 + Na2S 4 + 6H2O
6 A
1 mmol of acid 5 is suspended in 10 ml of distilled water. The solution is carefully neutralized with 1 mmol (0.04 g) of sodium hydroxide dissolved in 2 ml of water. To this clear solution is added slowly and with vigorous stirring an aqueous solution of zinc sulphate (0.5 mmol in 10 ml of water). After stirring for two hours, the white precipitate is filtered, washed extensively with water and then dissolved in chloroform. The suspensions are filtered off on filter paper and the mother liquors for filtration are concentrated to dryness. A paste is obtained which is dried under vacuum for 48 hours. The yield of the reaction is 76%.

 The zinc complex A is characterized by infrared, nuclear magnetic resonance (proton and carbon 13) and elemental analysis.

The elemental analysis of the zinc complex A is given in Table 2 below
TABLE 2

<tb><SEP> ELEMENT <SEP> CARBON <SEP> HYDROGEN <SEP> ZINC
<tb><SEP>%<SEP> Theoretical <SEP> 66.25 <SEP> 8.42 <SEP> 5.15
Experimental <tb>% <SEP><SEP> 65.27 <SEP> 8.17 <SEP> 4.48
<Tb>
There is therefore a good agreement between the theoretical and experimental data confirming that the indicated structure of the zinc complex A is actually obtained.

Differential scanning calorimetry (DSC) measurements have been carried out, they show that complex A has a crystalline liquid phase,
M, from room temperature to 630C, the temperature at which the compound melts in an isotropic state I.

 Table 3 gives the temperatures ("C") and phase transition enthalpies of the zinc complex A obtained by DSC.

TABLE 3

<tb> TRANSITION <SEP> T (OC) <SEP> AH (kj / mol) <SEP>
<tb><SEP> M-wI <SEP> 63 <SEP> +18
<tb><SEP> I-oM <SEP> 43 <SEP> 618
<Tb>
X-ray powder diffraction patterns were also made in the mesophase.

They show characteristic lines of a hexagonal columnar crystalline liquid phase. The values of intercolumn distance and hexagonal mesh surface at different temperatures are shown in Table 4.

TABLE 4

<SEP> v
<tb> TEMPERATURE <SEP> D (A) <SEP> S (A2) <SEP>
<tb><SEP>("c)<SEP>
<tb><SEP> 24 <SEP> 39.2 <SE> 1334.1
<tb><SEP> 40 <SEP> 39.1 <SE> 1326.2
<Tb>
On the other hand, measurements of refractive indices were made on the monomer in its discotic phase and in its isotropic phase. The results of these measurements are given in Table 5.

TABLE 5: Refractive indices measured by the
Abbe refractometer of the monomer in its phase
discotic and in its isotropic phase.

<Tb>

<SEP> Status <SEP> of <SEP> Treatment <SEP> Indices <SEP> Birefringence
<tb><SEP> subject
<tb> Monomer
<tb><SEP> Dhv <SEP> Non-Oriented <SEP> 1.524 <SEP> 1.517 <SEP> 0.007
<tb><SEP> Dh <SEP> oriented <SEP> 1,527 <SEP> 1,516 <SEP> 0,011 <SEP>
<tb><SEP> Isotro <SEP> e <SEP> 1,521 <SEP>
<tb> Polymer <SEP> 1,535 <SEP> has <SEP> not <SEP> pu <SEP> ne <SEP> can <SEP> be
<tb><SEP> Dh <SEP> be <SEP> measured <SEP> calculated <SEP> - <SEP>
<Tb>
III. Photopolymerization of zinc complex A
The monomer A, previously melted in its isotropic phase with 2.5% initiator (Irgacures 651) between two glass plates, is pressed to obtain a thin film. This is irradiated at room temperature in its crystalline liquid mesophase. columnar for 20 minutes using a 100 W high pressure mercury lamp (0.8 mW.cm-2 at 365 nm).

The polymer is obtained with a conversion of 40-50%.

 The polymer obtained is transparent, colorless and does not show a crystalline liquid transition as a function of temperature. Its structure is that of an unoriented hexagonal columnar mesophase with an intercolumnal distance of 33.7 Å that has been observed by X-ray diffraction at room temperature.

 The refractive index of the polymer could be measured and is 1.535 at 25 ° C.

 The anisotropic liquid polymers obtained by the process just described, give materials that can be used in electrooptical or optical systems such as beam polarizing dividers. They can also be used for one-dimensional conduction of electrical and / or luminous energy due to the presence of the metal, as well as in specific applications to liquid crystal polymers for which the materials must possess high thermal stability.

Claims (12)

 1. mesogenic metal complex capable of being polymerized photochemically in its crystalline liquid state, characterized in that it has the following formula (I)

 wherein the two R groups may be the same or different and each represents H, halogen (F, Cl, Br, I) or a group selected from CN, NO 2, CF 3, OH, linear and branched alkyl and alkoxy groups of 1 to 30 carbon atoms optionally substituted and / or optionally interrupted by one or more atom (s) chosen from S, N, O, the alkenyl groups from 2 to 30 carbon atoms, alkynyl groups of 2 to 30 carbon atoms, optionally substituted alkoxycarbonyl groups of 2 to 30 carbon atoms,

 or Alk represents an optionally substituted alkyl group of 1 to 30 carbon atoms, cycloalkyl groups of 3 to 20C, and photochemically polymerizable functions, with the proviso that at least one of the two R groups is a polymerizable functional group. photochemical; n is an integer from 1 to 40 and M is a metal.  2. Complex according to claim 1, characterized in that M is chosen from Be, Mg, Ca, Sr, Ba, Ra, Zn, Cd and Hg.  3. Complex according to claim 1, characterized in that the two groups R represent photochemically polymerizable functions.  4. Complex according to claim 1, characterized in that R, when it is a polymerizable function, is selected from acrylates, methacrylates, vinyl ethers.  The complex of claim 1 wherein M is zinc, n = 11 and R is an acrylate function.  6. Photochemically polymerization process, characterized in that it consists in subjecting to photochemical polymerization conditions a monomer (I) according to claim 1 being in its crystalline liquid phase.  7. Process according to claim 7, characterized in that the polymerization is carried out by ultraviolet irradiation.  8. Process according to claim 6, characterized in that the polymerization is carried out in the presence of 1 to 5% by weight of a radical initiator.  9. Crystalline liquid polymer characterized in that it is formed of recurring monomeric units of formula (I) and in that it contains a metal center per monomeric unit.  10. Compound of formula (III)

 wherein n is an integer from 1 to 40, and R 'and a group selected from linear or branched alkyl groups of 1 to 20 carbon atoms, cycloalkyl groups of 3 to 20 carbon atoms, haloalkyl groups of 1 at 20 carbon atoms.  11. Compound of formula (IV)

 where n is an integer from 1 to 40.  12. Compound of formula (V)

 where n and R have the meaning already given in claim 1.