Fullerene liquid crystal and preparation method thereof

Abstract

The application relates to a fullerene liquid crystal and a preparation method thereof, and belongs to the technical field of liquid crystal materials. The fullerene liquid crystal is a polymer or an oligomer with a terminal group of fullerene. The polymer or the oligomer is an aliphatic polyether, a polyester or the like which is incompatible with the fullerene, and includes a polyether such as polyethylene glycol and polytetrahydrofuran, and a polyester such as polycaprolactone. The fullerene liquid crystal is self-assembled to form a fullerene supramolecular liquid crystal through pi-pi interaction between the fullerenes and microphase separation between the fullerenes and polymer chains. The fullerene liquid crystal is free of liquid crystal units, has a simple preparation method, low cost, a wide liquid crystal phase temperature range, and a fullerene content of more than 60%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid crystal materials, and particularly relates to a fullerene liquid crystal and a preparation method thereof. BACKGROUND

[0002] Fullerenes have special physical and chemical properties, which can be applied to nonlinear optical materials, free radical scavengers, conductive materials and semiconductors, solar cells and organic superconductors, and thus have become a research hotspot in recent years. The fullerene liquid crystal has greater application potential by combining the liquid crystal with light, electricity, sound and the like.

[0003] At present, the main method for constructing the fullerene liquid crystal is to combine the C 60 molecule with different liquid crystal base elements to induce the formation of the fullerene liquid crystal through the ordered arrangement of the liquid crystal base elements. However, the introduction of the liquid crystal base element increases the difficulty of synthesis of the target molecule, and causes a low content of the fullerene. For example, Deschenaux et al. [Pieper, Pauline.; Russo, Virginie.; Heinrich, Benoît.; Donnio, Bertrand.; Deschenaux, Robert. The Journal of Organic Chemistry 2018, 83 (6), 3208-3219] designed and synthesized a dendritic compound containing two fullerenes. The dendritic molecule is connected with a plurality of cyanophenyl elements as the liquid crystal base element at the end, and the content of the fullerene is only 18%, which is difficult to meet the actual application needs.

[0004] Tu et al. [Zhang, X.; Hsu, C.-H.; Ren, X.; Gu, Y.; Song, B.; Sun, H.-J.; Yang, S.; Chen, E.; Tu, Y.; Li, X.; Yang, X.; Li, Y.; Zhu, X. Angew. Chem. Int. Ed. 2015, 54, 114-117] designed and synthesized a class of fullerene derivatives based on gallic acid with a long alkyl substituent by connecting the fullerene and the gallic acid liquid crystal base element. Although the fullerene liquid crystal compound has a high content of the fullerene, the molecular structure is complex, and a plurality of steps of reactions are needed to obtain the target product, which limits its wide application.

[0005] CN103980123B discloses a high fullerene content liquid crystal compound based on protocatechuic acid and a preparation method thereof, the fullerene liquid crystal compound comprises a protocatechuic acid derivative liquid crystal mer part, a fullerene part and a flexible connecting arm part.

[0006] Based on the above analysis, there is currently no method for constructing a fullerene liquid crystal based on fullerene and non-liquid crystal mer. The existing method for constructing a fullerene liquid crystal based on fullerene and liquid crystal mer has problems such as more reaction steps, lower yield, higher cost and lower fullerene content.

[0007] Therefore, it is urgent to develop a liquid crystal compound with simple molecular design, efficient synthesis steps and low phase transition temperature. SUMMARY

[0008] To solve the above technical problems, the purpose of the present application is to provide a fullerene liquid crystal and a preparation method thereof, specifically a fullerene liquid crystal without liquid crystal mer and an efficient preparation method thereof. The fullerene liquid crystal is a polymer or oligomer with fullerene as the end group, and the polymer or oligomer is incompatible with fullerene, such as aliphatic polyether and polyester. The fullerene liquid crystal self-assembles to form a fullerene supramolecular liquid crystal through the π-π interaction between fullerenes and the microphase separation between fullerenes and polymer chains. The fullerene liquid crystal disclosed in the present application does not contain liquid crystal mer, has a simple preparation method, low cost, a wide temperature range of liquid crystal phase, and a fullerene content of more than 60%.

[0009] To achieve the above-mentioned purposes, the present application realizes the following technical solutions:

[0010] The first purpose of the present application is to provide a fullerene liquid crystal, the fullerene liquid crystal is a polymer or oligomer with fullerene as the end group; it comprises a fullerene part and a polymer or oligomer part; the fullerene part and the polymer or oligomer part are connected by an ester group;

[0011] The fullerene liquid crystal is fullerene liquid crystal A or fullerene liquid crystal B; the structural formula of the fullerene liquid crystal A is:

[0012] ;

[0013] The structural formula of the fullerene liquid crystal B is:

[0014] ;

[0015] wherein P is a polymer or oligomer chain incompatible with the fullerene; the polymer or oligomer chain includes but is not limited to a polyether-type polymer or oligomer chain, a polyester-type polymer or oligomer chain.

[0016] In one embodiment of the present application, the polyether-type polymer or oligomer chain (P) of the fullerene liquid crystal A has the following structure:

[0017] ;

[0018] wherein a is selected from any integer between 1 and 3, preferably 1; m represents the number of repeating units of the polyether, the value of which is determined by the molecular weight of the polyether or its oligomer; the molecular weight of the polyether is selected from 340 g / mol to 2000 g / mol, preferably 500 g / mol, 1000 g / mol, 1500 g / mol.

[0019] In one embodiment of the present application, the polyester-type polymer or oligomer chain (P) of the fullerene liquid crystal A has the following structure:

[0020] ;

[0021] wherein a is selected from any integer between 1 and 6, preferably 4; m represents the number of repeating units of the polyester, the value of which is determined by the molecular weight of the polyester or its oligomer; the molecular weight of the polyester is selected from 500 g / mol to 2000 g / mol, preferably 1500 g / mol.

[0022] In one embodiment of the present application, the polyether-type polymer or oligomer chain (P) of the fullerene liquid crystal B has the following structure:

[0023] ;

[0024] wherein a is selected from any integer between 1 and 3, preferably 1 or 3; m represents the number of repeating units of the polyether, the value of which is determined by the molecular weight of the polyether or its oligomer; the molecular weight of the polyether is selected from 800 g / mol to 3000 g / mol, preferably 1000 g / mol.

[0025] In one embodiment of the present application, the polyester-type polymer or oligomer chain (P) of the fullerene liquid crystal B has the following structure:

[0026] ;

[0027] Wherein, a is selected from any integer from 1 to 6, preferably 4; b is selected from any integer from 2 to 6, preferably 2; m and n represent the number of repeating units of the polyester, which is determined by the molecular weight of the polyester or its oligomer; the molecular weight of the polyester is selected from 800 g / mol to 3000 g / mol, preferably 2000 g / mol.

[0028] The second object of the present application is to provide a preparation method of fullerene liquid crystal, the reaction route is as shown in the figure, and specifically comprises the following steps: Figure 1

[0029] In an organic solvent, fullerene acid and polyether polyol or polyester polyol are used as reactants, 4-dimethylaminopyridine (DMAP), p-toluenesulfonic acid (PTSA) and N,N-diisopropylamide (DIPC) are used as catalysts, esterification reaction occurs to obtain the final product, which is a fullerene liquid crystal containing C 60 ; the fullerene acid is fullerene acetic acid.

[0030] In an embodiment of the present application, the organic solvent is o-dichlorobenzene and N,N-dimethylformamide.

[0031] The present application also provides a fullerene liquid crystal blend comprising at least one fullerene liquid crystal A and / or at least one fullerene liquid crystal B.

[0032] The present application also provides a preparation method of a fullerene liquid crystal blend, which is realized by the following technical scheme:

[0033] Different types of fullerene liquid crystal A, different types of fullerene liquid crystal B or fullerene liquid crystal A and fullerene liquid crystal B are heated after blending, or are dissolved in a good solvent for blending, and then the good solvent is removed to obtain the fullerene liquid crystal blend.

[0034] In an embodiment of the present application, the polymer or oligomer part of the fullerene liquid crystal homologues is selected from one or more of polyethylene glycol, polytetrahydrofuran and polycaprolactone, preferably polyethylene glycol; and the good solvent is selected from dichloromethane, trichloromethane, tetrahydrofuran, toluene and the like, preferably dichloromethane.

[0035] The present application also claims protection of the fullerene liquid crystal prepared by the above preparation method, and the corresponding blend, wherein the fullerene liquid crystal comprises a fullerene part and a polymer or oligomer part, and the two parts are connected by an ester bond.

[0036] In the above technical scheme, the prepared fullerene liquid crystal A is represented by C 60 -Pn, and the fullerene liquid crystal B is represented by C 60 -Pn-C 60 ​wherein P represents the corresponding polymer or oligomer, and n represents the corresponding molecular weight of the polymer or oligomer. For example: polyethylene glycol mono-fullerene acetate is represented as C 60 -PEOn represents poly-caprolactone mono-fullerene acetate is represented as C 60 -PCLn represents polyethylene glycol di-fullerene acetate is represented as C 60 -PEOn-C 60 represents.

[0037] The above technical solutions of the present application have the following advantages compared with the prior art:

[0038] 1. The present application provides a kind of fullerene liquid crystal and its preparation method. Compared with the existing fullerene liquid crystal, the molecular design of the fullerene liquid crystal described in the present application is simple, does not contain liquid crystal base element, is composed of fullerene and polymer or oligomer. And the polymer or oligomer part is cheap, easy to obtain, greatly simplifies the synthesis step, only one esterification reaction can obtain the fullerene liquid crystal.

[0039] 2. The transition temperature of the fullerene liquid crystal of the present application into liquid crystal phase is near room temperature, for example, C 60 -PEO1.5k enters the transition temperature of liquid crystal phase at 28 ℃, and C 60 -PEO1k enters the transition temperature of liquid crystal phase at 15 ℃.

[0040] 3. The temperature range of the liquid crystal phase of the fullerene liquid crystal compound described in the present application is relatively wide, for example, C 60 -PEO1.5k compound liquid crystal phase temperature range is 28~95 ℃, C 60 -PEO1k compound liquid crystal phase temperature range is 15~190 ℃.

[0041] 4. When the fullerene liquid crystal is prepared by the preparation method of the present application, the content of fullerene can be more than 60%, for example, C 60 -PEO340 C 60 The content of 63% is reached.

[0042] 5. When the fullerene liquid crystal homologues described in the present application are blended, the blending method is simple, and the obtained blend can be adjusted according to the actual needs of the two components ratio to obtain fullerene liquid crystal with target characteristics. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to the specific embodiments of the present application and in combination with the drawings, wherein:

[0044] Figure 1 is the synthesis route map of the fullerene liquid crystal in the present application;

[0045] Figure 2 Quantitative nuclear magnetic resonance hydrogen spectrum (1H NMR) of polyethylene glycol mono-fullerene acetate (C60-PEO1.5k) in Example 1 of the present application; 60 1 H NMR);

[0046] Figure 3 Mass spectrum (MALDI-TOF) of polyethylene glycol mono-fullerene acetate (C60-PEO1.5k) in Example 1 of the present application; 60

[0047] Figure 4 Differential scanning calorimetry analysis (DSC) of polyethylene glycol mono-fullerene acetate (C60-PEO1.5k) in Example 1 of the present application; 60

[0048] Figure 5 X-ray diffraction analysis (XRD) of polyethylene glycol mono-fullerene acetate (C60-PEO1.5k) in Example 1 of the present application; 60

[0049] Figure 6 Polarizing microscope photograph (POM) of polyethylene glycol mono-fullerene acetate (C60-PEO1.5k) in Example 1 of the present application; 60

[0050] Figure 7 Polarizing microscope photograph (POM) of polyethylene glycol mono-fullerene acetate (C60-PEO1k) in Example 2 of the present application; 60

[0051] Figure 8 Polarizing microscope photograph (POM) of polyethylene glycol mono-fullerene acetate (C60-PEO500) in Example 3 of the present application; 60

[0052] Figure 9 Polarizing microscope photograph (POM) of polycaprolactone mono-fullerene acetate (C60-PCL1.5k) in Example 4 of the present application; 60

[0053] Figure 10 Polarizing microscope photograph (POM) of polyethylene glycol di-fullerene acetate (C60-PEO1k-C60-PEO1k) in Example 5 of the present application; 60 60

[0054] Figure 11 Polarizing microscope photograph (POM) of polytetramethylene oxide di-fullerene acetate (C60-PTMO1k-C60-PTMO1k) in Example 6 of the present application; 60 60 ​​​​​​​​​​​Polarizing microscope image (POM);

[0055] Figure 12 The polycaprolactone bis-fullerene acetate (C) in Example 7 of this invention 60 -PCL2k-C 60 Polarizing microscope image (POM);

[0056] Figure 13 C in Embodiment 8 of the present invention 60 -PEO500 and C 60 - A polarizing microscope image (POM) of PEO1.5k blended at a 1:1 (mass ratio). Detailed Implementation

[0057] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0058] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0059] The CAS numbers of the organic reagents used in this invention are listed below:

[0060] Table 1

[0061]

[0062] Note: References for the synthesis of fullerene acetic acid: (Wang Naixing; Sun Chenghua. Synthesis of methylene[6,6]-fullerene

[60] monocarboxylic acid. Organic Chemistry 2001, 21, 611-613. Ye Guangming; Ni Jin; Jiang Yunyun; Wu Qiuye; Liao Hongli. Synthesis of methylene[6,6]-Fullerene[C60] monocarboxylic acid derivatives. Fine Chemical Intermediates 2007, 37, 29-31.)

[0063] In the following embodiments of the present invention, an Agilent Direct Drive II 600 MHz nuclear magnetic resonance hydrogen spectrometer is used. 1 The test was performed using 10 H NMR, with deuterated trichloromethane as the solvent and tetramethylsilane (TMS) as the internal standard. The solution concentration was 10 mg / mL.

[0064] In the following embodiments of the present invention, a Bruker Ultrafle Xtreme matrix-assisted laser desorption / ionization time-of-flight mass spectrometer (MALDI-TOF) was used for testing. The tests were performed in reflectance mode. The matrix used was trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malonitrile (DCTB), and the cation salt was sodium trifluoroacetate (CF3COONa).

[0065] In the following embodiments of the present invention, a TA Q2000 differential scanning calorimeter (DSC) was used for testing. The test atmosphere was a nitrogen atmosphere with a nitrogen flow rate of 25 mL / min and a heating / cooling rate set to 10 °C / min.

[0066] In the following embodiments of the present invention, Xeuss 3.0 X-ray diffraction (XRD) was used for testing, with a Cu target (λ = 1.54 Å) as the light source and a Dectris 2R 1M detector.

[0067] In the following embodiments of the present invention, observations were performed using an Olympus Corporation BX51-P polarizing optical microscope (POM).

[0068] Example 1

[0069] This embodiment provides a polyethylene glycol monofullerene acetate (C 60 The preparation method of -PEO1.5k) is as follows:

[0070] In a round-bottom flask, fullerene acetic acid (0.2 g), polyethylene glycol monomethyl ether (molecular weight 1500 g / mol, 0.39 g), o-dichlorobenzene (7.26 g), and N,N-dimethylformamide (1.47 g) were added sequentially, and the mixture was magnetically stirred to ensure complete dissolution of the raw materials. Then, 4-dimethylaminopyridine catalyst (0.095 g), p-toluenesulfonic acid (0.133 g), and N,N-diisopropylamide (0.131 g) were added sequentially. The mixture was stirred at room temperature for 12 h, then filtered, washed, and evaporated to dryness. The crude product was subjected to column chromatography to obtain the final product, which precipitated in methanol. After filtration, a dark brown product was obtained and dried in a vacuum oven.

[0071] Figure 2 C 60 -PEO 1.5k NMR spectrum ( 1 (H NMR), in which the signal at chemical shift 4.85 ppm is the proton signal on the cyclopropane linked to the fullerene; the signal at chemical shift 4.66 ppm is the proton signal on the methylene group on the ester linked to the fullerene. The integral area ratio of the two signals is 1:2, proving the successful synthesis of C.60 -PEO1.5k.

[0072] Figure 3 C 60 -PEO1.5k matrix assisted laser desorption ionization time-of-flight mass spectrum (MALDI-TOF). The results show that each group of peaks is different by 44.024 (m / z), which is the mass-to-charge ratio of a polyethylene glycol repeating unit. The molecular ion peak appears at 2047.668 (m / z), which is C 60 -PEO1.5k sodium ion peak (m / z theoretical value 2047.766) when the polyethylene glycol repeating unit is 28, further proving that C 60 -PEO1.5k.

[0073] Figure 4 C 60 -PEO1.5k differential scanning calorimetry analysis (DSC), according to the two endothermic peaks on the heating curve, the liquid crystal phase temperature range is obtained: 28 ℃~95 ℃.

[0074] Figure 5 C 60 -PEO1.5k X-ray diffraction analysis (XRD), by comparing the peak positions of the diffraction peaks in the figure, the diffraction peaks can be obtained. The ratio of the diffraction peaks is 1:2, which indicates that the micro arrangement of the sample is a lamellar arrangement structure. When the temperature exceeds 100 ℃, the measured diffraction peak disappears, indicating that the sample enters an amorphous state, which is consistent with the clearing point temperature measured by DSC.

[0075] Figure 6 is the polarizing microscope photo (POM) of the sample taken at 80 ℃ for 3 h, which presents a granular liquid crystal texture.

[0076] Example 2

[0077] This example provides a preparation method of a polyethylene glycol monofullerene acetate (C 60 -PEO1k), which is similar to Example 1, and the only difference is that equimolar polyethylene glycol monomethyl ether (molecular weight 1000 g / mol) is used instead of polyethylene glycol monomethyl ether (molecular weight 1500 g / mol).

[0078] Figure 7 is the polarizing microscope photo (POM) of the sample taken at 100 ℃ for 3 h, which presents a granular liquid crystal texture, and its liquid crystal phase temperature range is: 15 ℃~190 ℃.

[0079] Example 3

[0080] This example provides a preparation method of a polyethylene glycol monofullerene acetate (C60 The preparation method of the polyethylene glycol monomethyl ether single fullerene acetate (C

[0081] Figure 8 The polarizing microscope (POM) of the sample taken at 150 ℃ for 3 h presents a granular liquid crystal texture, and its liquid crystal phase temperature range is room temperature to 240 ℃ (beginning to decompose).

[0082] Example 4

[0083] This example provides a preparation method of a polycaprolactone single fullerene acetate (C 60 The preparation method of the polyethylene glycol monomethyl ether single fullerene acetate (C

[0084] Figure 9 The polarizing microscope (POM) of the sample taken at 80 ℃ for 1 h presents a granular liquid crystal texture, and its liquid crystal phase temperature range is 22 ℃ to 107 ℃.

[0085] Example 5

[0086] This example provides a preparation method of a polyethylene glycol double fullerene acetate (C 60 The preparation method of the polyethylene glycol monomethyl ether single fullerene acetate (C 60 The preparation method of the polyethylene glycol monomethyl ether single fullerene acetate (C

[0087] Figure 10 The polarizing microscope (POM) of the sample taken at 160 ℃ for 3 h presents a granular liquid crystal texture, and its liquid crystal phase temperature range is room temperature to 240 ℃ (beginning to decompose).

[0088] Example 6

[0089] This example provides a preparation method of a polytetramethylene ether double fullerene acetate (C 60 The preparation method of the polyethylene glycol monomethyl ether single fullerene acetate (C 60 The preparation method of the polyethylene glycol monomethyl ether single fullerene acetate (C

[0090] Figure 11 is the polarized optical micrograph (POM) of the sample taken at 120 ℃ for 3 h, showing rod-like liquid crystal texture, and its liquid crystal phase temperature range is room temperature to 240 ℃ (beginning to decompose).

[0091] Example 7

[0092] This example provides a preparation method of a polycaprolactone bis-fullerene acetate (C 60 -PCL2k-C 60 ), which is similar to Example 1, except that 0.4 times the molar amount of polycaprolactone diol (molecular weight 2000 g / mol) is used to replace polyethylene glycol monomethyl ether (molecular weight 1500 g / mol), and the reaction time is extended to 24 h.

[0093] Figure 12 is the polarized optical micrograph (POM) of the sample taken at 120 ℃ for 3 h, showing rod-like liquid crystal texture, and its liquid crystal phase temperature range is room temperature to 240 ℃ (beginning to decompose).

[0094] Example 8

[0095] This example provides a preparation method of a fullerene liquid crystal blend, the specific steps are as follows:

[0096] C 60 -PEO500 and C 60 -PEO1.5k are dissolved in the minimum amount of dichloromethane at a mass ratio of 1:1, vacuum dried, and the solvent is removed to obtain a fullerene liquid crystal blend.

[0097] Figure 13 is the polarized optical micrograph (POM) of the sample taken at 120 ℃ for 3 h, showing rod-like liquid crystal texture, and its liquid crystal phase temperature range is room temperature to 240 ℃ (beginning to decompose).

[0098] Comparative Example 1

[0099] This comparative example provides a reaction of fullerene acetate and polyethylene glycol monomethyl ether, which is similar to Example 1, except that an equimolar amount of polyethylene glycol monomethyl ether (molecular weight 5000 g / mol) is used to replace polyethylene glycol monomethyl ether (molecular weight 1500 g / mol).

[0100] No liquid crystal phase is observed under POM for this sample.

[0101] Comparative Example 2

[0102] This comparative example places polyethylene glycol monomethyl ether (1500 g / mol) under POM observation, and no liquid crystal phase is observed under POM for this sample.

[0103] Obviously, the above-mentioned embodiments are only examples for clearly illustrating the present application, and are not intended to limit the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and also impossible to enumerate all the embodiments. The obvious changes or variations derived from the above description are still within the protection scope of the present application.

Claims

1. A fullerene liquid crystal, characterized in that, The fullerene liquid crystal is a polymer with fullerene end groups; it includes a fullerene portion and a polymer portion; the fullerene portion and the polymer are connected by ester bonds; The fullerene liquid crystal is either fullerene liquid crystal A or fullerene liquid crystal B; the structural formula of fullerene liquid crystal A is: ； The structural formula of the fullerene liquid crystal B is: ； Wherein, P represents a polymer chain; the polymer chain includes polyether polymer chains and polyester polymer chains; the polymer chain is incompatible with fullerenes; The structure of the polyether polymer chain of the fullerene liquid crystal A is as follows: ； Where a is any integer from 1 to 3; m represents the number of repeating units of the polyether, the value of which is determined by the molecular weight of the polyether; the molecular weight of the polyether is 340 g / mol to 2000 g / mol; The structure of the polyester polymer chain of the fullerene liquid crystal A is as follows: ； Where a is any integer from 1 to 6; m represents the number of repeating units of the polyester, the value of which is determined by the molecular weight of the polyester; the molecular weight of the polyester is 500 g / mol to 2000 g / mol. The structure of the polyether polymer chain of the fullerene liquid crystal B is as follows: ； Where a is any integer from 1 to 3; m represents the number of repeating units of the polyether, the value of which is determined by the molecular weight of the polyether; the molecular weight of the polyether is 800 g / mol to 3000 g / mol; The structure of the polyester polymer chain of the fullerene liquid crystal B is as follows: ； Where a is any integer from 1 to 6; b is any integer from 1 to 6; m and n represent the number of repeating units of the polyester, the value of which is determined by the molecular weight of the polyester; the molecular weight of the polyester is 800 g / mol to 3000 g / mol.

2. The method for preparing the fullerene liquid crystal according to claim 1, characterized in that, The process includes the following steps: in an organic solvent, fullerene acid is reacted with polyether monool, polyether diol, polyester monool or polyester diol as raw materials, and an esterification reaction is carried out under the action of a catalyst to obtain the fullerene liquid crystal.

3. The preparation method according to claim 2, characterized in that, The catalyst is one or more of 4-dimethylaminopyridine, p-toluenesulfonic acid, and N,N-diisopropylamide.

4. The preparation method according to claim 2, characterized in that, The fullerenoic acid is C. 60 Fullerene acetic acid, C 60 Fullerene propionic acid or C 60 Fullerene malonic acid.

5. A fullerene liquid crystal blend, characterized in that, It comprises at least one fullerene liquid crystal A as described in claim 1 and / or at least one fullerene liquid crystal B as described in claim 1.

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