JP3131713B2 - Liquid crystalline polyester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel liquid crystalline polyester.

[0002]

2. Description of the Related Art In recent years, polymer liquid crystals have been actively studied in the field of high-performance materials utilizing high heat resistance and moldability, and in the field of functional materials utilizing changes in the liquid crystal phase structure due to external fields such as heat or electric field. It has been developed and already commercialized in the field of high-performance materials. On the other hand, in the field of functional materials, active research is being conducted for the application to optical recording, nonlinear optical materials, liquid crystal alignment films, optical fibers, optical elements for liquid crystal display elements, etc., but none has been commercialized yet. Polymer liquid crystals being studied in the field of functional materials are:
Most are side-chain type liquid crystals having a so-called mesogen group having a liquid crystal forming ability in the side chain, and there are few applications of the main-chain type liquid crystal. However, the side chain type polymer liquid crystal requires complicated steps for both monomer synthesis and polymer synthesis, and the production cost is high, so that it is not suitable for industrial use. In contrast, the main chain type polymer liquid crystal generally has a short production process and is excellent in polymer stability. Among them, polyester is the most suitable material in all aspects such as ease of production, cost and physical properties.

On the other hand, from an application point of view, a polymer liquid crystal having an optically active unit in a molecule has a liquid crystal phase such as a cholesteric phase and a chiral smectic C phase, and therefore has an optical recording or thermal recording material, a non-linear optical material. It is suitable for such functional materials and is being actively studied. Accordingly, optically active liquid crystalline polyesters are promising new functional materials, but the drawback of these polyesters is their low solubility in solvents. When used as a functional material, they are often used as films or thin films, and these films or thin films are prepared from a polymer solution. Therefore, low solubility was a serious problem in practical use.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel liquid crystalline polyester which is optically active, is easy to synthesize, has low production cost, and is excellent in stability and solubility in solvents. It is in.

[0005]

That is, the present invention relates to a liquid crystalline polyester comprising the structural units represented by the formulas (a), (b) and (c).

[0006]

Embedded image

(Wherein the c unit is a unit containing an optically active carbon, X represents an alkyl group having 1 to 4 carbon atoms or a halogen atom, and the composition ratio (molar ratio) of the constituent units a, b and c is , A / b is 95/5 to 50/50, (a + b) /
c is approximately 1.)

Hereinafter, the present invention will be described in detail. a
The unit is a unit derived from 4,4'-biphenyldicarboxylic acid or a dialkyl derivative such as dimethyl or diethyl ester, a dihalogen derivative or the like. The b unit is a unit derived from terephthalic acid or a dialkyl derivative such as dimethyl or diethyl ester or a dihalogen derivative. The derived unit.

The c unit is a unit derived from an optically active 1,4-butanediol having a substituent at the 2-position or a derivative thereof. It is essential that the 2-substituted-1,4-butanediol used as a raw material is optically active, and e. e (e
The optical purity, expressed in terms of nanotropicexcess, is at least 30%, preferably at least 50%. The substituent X is an alkyl group having 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a t-butyl group, or F, C
It is a group selected from halogen atoms such as l and Br. Among these, a methyl group, an ethyl group, and Cl are particularly preferable. Of course, the arrangement of each structural unit may be either block or random.

Regarding the composition ratio (molar ratio) of the structural units a, b and c, the ratio of a / b is 95/5 to 50/50,
Preferably, the range is 90/10 to 60/40.
When the ratio of a / b is larger than 95/5, that is, when the number of biphenyldicarboxylic acid units is too large, the solubility in a solvent is lowered, which is not preferable. When the ratio is smaller than 50/50, the liquid crystal phase is hardly developed. Not preferred.
The ratio of (a + b) / c is approximately 1, usually 45 / 55-55.
55/45, preferably 48/52 to 52/48, and more preferably 50/50.

The molecular weight of these polymers is determined by the phenol / tetrachloroethane mixed solvent (60/40 weight ratio).
The value of ηinh measured at 30 ° C. and 0.05 to 3.0.
0 is preferred, and a value of 0.07 to 2.0 is particularly preferred. If the value of ηinh is less than 0.05, the strength may be weak, and if it is more than 3.0, the melt viscosity may be too high and it may take time to develop the liquid crystal.

The method for synthesizing the polymer of the present invention is not particularly limited, and is synthesized by a polymerization method known in the art, for example, a melt polymerization method or a solution polymerization method using a corresponding acid chloride of dicarboxylic acid.

In the case of synthesis by the melt polycondensation method, for example,
4-biphenyldicarboxylic acid dimethyl ester (a component ¹ ), terephthalic acid dimethyl ester (b component ¹ ) and a general formula

[0014]

Embedded image

[0015] 2-substituted-1,4-butanediol represented by (X is similar to the above, ^{c 1} component) and a high temperature, can be prepared by polymerizing under reduced pressure. The 2-substitution-1,4
-Butanediol includes 2-methyl-1,4-butanediol, 2-ethyl-1,4-butanediol,
-Propyl-1,4-butanediol, 2-butyl-
1,4-butanediol, 2-chloro-1,4-butanediol, 2-bromo-1,4-butanediol, 2-
And iodo-1,4-butanediol. The molecular weight can be easily controlled by controlling the polymerization time or the charge composition. The polymerization conditions in that case are not particularly limited, but usually the temperature is 150 to 350 ° C., preferably 200 to 300 ° C., and the reaction time is 30 minutes or more, preferably about 1 to 20 hours. The charged composition (molar ratio) of the raw material components a ^{1 to} c ¹ is as follows:
The value of (a ¹ + b ¹ ) / c ¹ is usually 40/60 to 60
/ 40, preferably 45/55 to 55/45, more preferably 48/52 to 52/48, particularly preferably 50/55.
/ 50 is desirable.

A ¹ / b ¹ is from 95/5 to 40/60, preferably from 95/5 to 50/50, more preferably 9
0/10 to 60/40 is desirable.

In order to accelerate the polymerization reaction, conventionally known metal salts such as sodium acetate and zinc acetate can be used.

When the solution polymerization method is used, for example, 4,4-biphenyldicarboxylic acid dihalide (a ² ) ,
Terephthalic acid dihalide (b ² ) and disubstituted-1,4-butanediol (c ¹ The desired polyester can be easily obtained by dissolving the component) in a solvent and heating in the presence of an acid acceptor.
As 4,4-biphenyldicarboxylic dihalide,
4,4-biphenyldicarboxylic acid dichloride, biphenyldicarboxylic acid dibromide and the like can be mentioned. Examples of the terephthalic acid dihalide include terephthalic acid dichloride and terephthalic acid dibromide.

The solvent used is not particularly limited. For example, halogen solvents such as o- dichlorobenzene, dichloroethane and tetrachloroethane, DMSO, DMF and MM
Examples include polar solvents such as P, and ether solvents such as THF and dioxone. The acid acceptor is not particularly limited, but specific examples include pyridine, triethylamine, tripropylamine and the like.

The polymerization conditions for the solution polymerization are not particularly limited, but are usually 50 to 200 ° C., preferably 60 to 1 ° C.
The reaction time at 50 ° C. and the reaction time is preferably 1 hour to 10 hours and 2 hours to 7 hours.

Each raw material component a ² , b ² and c ¹ The composition (molar ratio) of ( a ² + b ²⁾ ) / C ¹ is usually
40 / 60-60 / 40, preferably 45 / 55-55
/ 45, more preferably 48/52 to 52/48, particularly preferably 50/50.

[0022] a ² / b ² Is from 95/5 to 40/60, preferably from 95/5 to 50/50, more preferably 9
0/10 to 60/40 is desirable.

[0023]

Since the polymer of the present invention contains optically active units, it mainly exhibits a cholesteric phase in a liquid crystal state. In addition, since it can be synthesized by a simple synthesis method using an inexpensive monomer, the production cost is low and the stability is excellent.
Furthermore, it has excellent solubility in solvents, and can be dissolved in various halogen solvents, phenol solvents or various polar solvents at a high concentration. Therefore, by using a polymer solution using these solvents, a film or a thin film can be easily formed, and application to various functional materials is possible.

[0024]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. In addition, each analysis method used in the Example is as follows.

(1) Determination of Polymer Composition The polymer was dissolved in deuterated chloroform or deuterated trifluoroacetic acid, and determined by ¹ H-NMR at 400 MHZ (JNM-GX400 manufactured by JEOL Ltd.). (2) Measurement of logarithmic viscosity The viscosity was measured at 30 ° C. in a phenol / tetrachloroethane (60/40 weight ratio) mixed solvent using an Ubbelohde viscometer. (3) Measurement of DSC DuPont 990 Thermal Analiz
er. (4) Optical Microscope Observation Observation was performed using a BH2 polarizing microscope manufactured by Olympus Optical Co., Ltd.

Example 1 A glass reactor was charged with 90 mmol of 4,4-biphenyldicarboxylic acid dimethyl ester, 10 mmol of terephthalic acid dimethyl ester, and 105 mmol of (S) -2-methyl-1,4-butanediol, and placed in a nitrogen atmosphere. The reaction was performed at 220 ° C. for 4 hours to synthesize a polymer. This polymer was dissolved in tetrachloroethane and poured into a large amount of methanol for purification. The ηinh of the obtained polymer was 0.24 and D
According to SC measurement and observation with a polarizing microscope, this polymer was found to be 9%.
It had a cholesteric liquid crystal phase in a temperature range between 2 ° C and 168 ° C. Further, it was uniformly dissolved in a phenol / tetrachloroethane mixed solvent (60/40 weight ratio) and dimethylformamide at a concentration of 10% by weight.

Examples 2 to 4 In the same manner as in Example 1, the polymers of Examples 2 to 4 shown in Table 1 were synthesized. Each polymer has a cholesteric liquid crystal phase at a temperature between a transition point from a crystal phase to a liquid crystal phase and a transition point from a liquid crystal phase to an isotropic phase, and a phenol / tetrachloroethane mixed solvent (60/40 weight ratio). And the solubility in dimethylformamide was good.

Example 5 55 mmol of 4,4-biphenyldicarboxylic acid dichloride, 45 mmol of terephthalic acid dichloride, 100 mmol of (S) -2-ethyl-1,4-butanediol and 20 ml of pyridine were prepared by adding
It was dissolved in 300 ml of orthodichlorobenzene and reacted at 70 ° C. for 3 hours under a nitrogen atmosphere. After completion of the reaction, the reaction solution was poured into methanol to recover a polymer. The polymer was further purified by dissolving the polymer in tetrachloroethane and pouring into a large amount of methanol.

Ηinh of the obtained polymer is 0.14
According to DSC measurement and observation with a polarizing microscope, this polymer has a cholesteric liquid crystal phase between a crystalline phase and an isotropic phase, and a phenol / tetrachloroethane mixed solvent (6).
(0/40 weight ratio) and dimethylformamide at a concentration of 10% by weight.

Examples 6 and 7 The polymers of Examples 6 and 7 were synthesized in the same manner as in Example 5. The properties are shown in Table 1, and all polymers show a cholesteric liquid crystal phase,
A phenol / tetrachloroethane mixed solvent (60 /
40% by weight) and good solubility in dimethylformamide.

Comparative Example 1 In the same manner as in Example 1,
4-biphenyldicarboxylic acid dimethyl ester, terephthalic acid dimethyl ester, and (S) -2-methyl-
Using 1,4-butanediol, a polymer having a molar ratio of a / b / c of 48/2/50 was synthesized. This polymer showed a cholesteric liquid crystal phase at ηinh of 0.33, but was found to contain a phenol / tetrachloroethane mixed solvent and D
It had poor solubility in MF and became cloudy at a concentration of 10 wt%.

Comparative Example 2 In the same manner as in Example 5,
Using 4-biphenyldicarboxylic acid dichloride, terephthalic acid dichloride, and (S) -2-ethyl-1,4-butanediol, the ratio of a / b / c is 12/39/49.
Was synthesized. The ηinh of this polymer is 0.
25. Although this polymer was well dissolved in the solvent, the appearance of a liquid crystal phase was not clearly observed.

[0033]

[Table 1]

[Brief description of the drawings]

FIG. 1 shows a ¹ H-NMR spectrum of a polymer of Example 1 of the present invention.

FIG. 2 shows a ¹ H-NMR spectrum of the polymer of Example 3 of the present invention.

FIG. 3 shows a DSC thermogram of the polymer of Example 5 of the present invention.

FIG. 4 shows a DSC thermogram of the polymer of Example 6 of the present invention.

Claims (1)

(57) [Claims] 1. A formula (a), (b) and (c) liquid crystalline polyester embedded image, characterized in that it is essentially constituted by a structural unit represented by (Wherein the c unit is a unit containing an optically active carbon, X represents an alkyl group having 1 to 4 carbon atoms or a halogen atom, and the composition ratio (molar ratio) of the structural units a, b and c is a
/ B is 95/5 to 50/50, (a + b) / c is approximately 1
Is).