JPH06207188A - Electroviscous fluid - Google Patents

Abstract

PURPOSE:To provide an electroviscous fluid of quick response, a homogeneous system free from sedimentation and separation, reduced in basal vicosity without impairing its excellent electroviscous effect, consisting mainly of a side chain- type compound of liquid crystal nature having siloxane linkage-contg. spacer. CONSTITUTION:The electroviscous fluid consisting mainly of side chain-type compound of liquid crystal nature having siloxane linkage-contg. spacer. The above-mentioned compound of liquid crystal nature is e.g. a side chain-type liquid crystal compound of formula I (m/n is 1 or 4), which can be obtained, for example, by the following process: a compound of formula II, a reaction product from p-hydroxybenzoic acid and allyl bromide, is made to react with thionyl chloride to produce an acid chloride, which is then made to react with p-cyanophenol to obtain a compound of liquid crystal nature of formula III, which is then made to react with dimethylethoxysilane followed by treatment with potassium carbonate, and the resultant reaction product is made to react with allyl dimethylchlorosilane to obtain a compound of liquid crystal nature of formula IV, which is then made to react with a copolymer silicone of formula.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniform electrorheological fluid and is used as an actuator for vibration absorption, torque transmission, servo control and the like.

[0002]

2. Description of the Related Art An electrorheological fluid is a fluid whose viscosity changes momentarily and reversibly when a voltage is applied. As such a fluid, there has been a so-called Winslow fluid (USP. 2417850) in which water-containing fine particles are dispersed in insulating oil since the 1940s, and recently, a fluid in which organic semiconductor particles are dispersed (GB.217051).
0) or a fluid in which conductive particles having an insulating thin film formed on the surface are dispersed (Japanese Patent Laid-Open No. 64-6093). All of these conventional electrorheological fluids have fine particles dispersed in insulating oil and show excellent performance in the short term, but sedimentation separation of particles and coagulation of sedimented particles are unavoidable for practical application. It is one of the major obstacles.

On the other hand, even if it is uniform without using particles, for example, polar liquids such as nitromethane and nitrobenzene (Japan. J. Appl. Phys. 161).
775 (1977)), cholesteric liquid crystal mixture (C
communications 3865 (1965)) and methoxybenzylidene butylaniline (MBBA) and other low molecular weight liquid crystals (Japan. J. Appl. Phys.
17,1525 (1978) and British Published Patent No. 2
208515A), a method using a ferroelectric polymer solution (Proceedings of the 39th Symposium on Polymers, 18U07, 1990) and the like have been studied, but almost no electrorheological effect was obtained.

The present inventors have found a large electrorheological effect in a fluid containing a liquid crystalline compound having a plurality of liquid crystalline groups bonded to a molecular chain of an appropriate length as a main component, and have developed a uniform electrorheological fluid. Already proposed (European patent publication EP-047
8034A1).

[0005]

An electrorheological fluid containing a liquid crystalline compound having a plurality of liquid crystalline groups bonded to its molecular chain as a main component exhibits a large electrorheological effect and is therefore preferable. The viscosity when no voltage is applied (basic viscosity) is generally high, and there is a limit to the applications that can be used.

The present invention greatly changes the viscosity of an electrorheological fluid containing a side chain type liquid crystalline compound, which is one of the liquid crystalline compounds in which a plurality of liquid crystalline groups are bonded to a molecular chain of an appropriate length, as a main component. It is intended to realize an electrorheological fluid having a low base viscosity without impairing excellent characteristics. As described above, the electrorheological fluid having a low base viscosity has an advantage that the liquid crystal group is easily moved by the electric field and the response speed is increased. Further, by reducing the base viscosity, energy loss when no voltage is applied can be suppressed, which is a great practical advantage.

[0007]

Means for Solving the Problems The inventors of the present invention have mainly constructed a side chain type liquid crystalline compound as a method for lowering the base viscosity without impairing the excellent characteristics of the side chain type liquid crystalline compound which undergo large viscosity changes. Focusing on the spacer that connects the chain skeleton and the liquid crystal group, as a result of diligent study on the bonding group that expresses the softness of the spacer so as to enhance the mobility of the liquid crystalline group, as a result, if one or more siloxane bonds are bonded, It was found that the softness significantly reduces the viscosity of the side-chain liquid crystal compound, and the present invention was completed. That is, the present invention is an electrorheological fluid characterized by an electrorheological fluid containing a side chain type liquid crystalline compound having a spacer containing a siloxane bond as a main component.

The siloxane bond referred to in the present invention means (Si
R¹R²-O)_n-Si-R³R^Four(Where R¹,
R², R³, R^FourIs hydrogen or an alkyl group or
Represents a phenyl group. n is an integer of 1 to 10)
Dimethyl siloxane (R¹= R ²= R³= R^Four= Met
In the case of the
Are difficult to approach and the intermolecular cohesive force is small, which is preferable.

The side chain type liquid crystalline compound referred to in the present invention is a side chain type oligomer or polymer in which a liquid crystalline group is bound to a molecular chain in a hanging form like a branch via a spacer. The molecular chain referred to in the present invention is a homopolymer or a copolymer containing a molecule of a chain compound such as alkylene or siloxane containing carbon or silicon as a main component or a cyclic compound such as a benzene ring or a glucose ring as a unit. They are coalesced and the degree of polymerization thereof is 2 to 100, more preferably 2 to 30.
If necessary, the molecular chain may have a bonding group such as an ester group, an amide group, an ether group, or the like in the molecular chain. The molecular chain may be rigid, but one having high flexibility is preferable because it exhibits fluidity even at a relatively low temperature and does not hinder the alignment of the liquid crystalline substance when a voltage is applied. In particular, when an oligomer or polymer is synthesized with units constituting its molecular chain, its glass transition temperature (Tg) is room temperature or lower, preferably 0 ° C or lower, and more preferably -20.
A flexible molecular chain having a temperature of ℃ or less is preferable for obtaining an electrorheological fluid that can be used at low temperatures. Specific examples of such a flexible molecular chain include, for example, 1) methylene, ethylene, propylene, etc. —C _m H _{2 m} — (where m is 1
18 integer) alkylene group 2) oxyethylene represented by the, oxypropylene, oxybutylene, Nadeau OC _m H _2m chromatography (oxyalkylene group 3 represented here m is integers from 1 to 5)) dimethyl Siloxane, phenylmethylsiloxane, etc .-- SiR ¹ R ² O-- (wherein R ¹ and R ² represent an alkyl group or a phenyl group)
It is a homopolymer or copolymer containing siloxane, etc. In the case of these polymers, the degree of polymerization thereof is 2 to 100, more preferably 2 to 10 for alkylene, 2 to 10 for oxyalkylene, and 2 to 30 for siloxane. These flexible chains are
In the units shown in 1) and 2) above, methylene (having 1 carbon atom) for introducing a liquid crystal group instead of part of H is introduced.
To 18), amides, urethanes, esters, ethers,
In the units shown in 3), a bonding group having a divalent hand such as carbonate, an alkyl group (having 1 to 8 carbon atoms), a side chain group such as a phenyl group, and 3) instead of a part or all of R ¹ , Can have a linking group of Such a molecular chain needs to have at least two or more bonding groups capable of chemically bonding with a bonding group containing a liquid crystal group at one end or both ends or a side chain.

Among the units constituting the molecular chain, a flexible siloxane or alkylene skeleton structure is preferable in terms of exhibiting electrical characteristics and liquid crystallinity. In particular, the siloxane skeleton structure is
It has Tg of −120 ° C. or lower, is more flexible than alkylene or oxyalkylene skeleton structure at low temperature, and exhibits liquid crystallinity from a relatively low temperature when a plurality of liquid crystalline substances are bonded to a flexible molecular chain. It is preferable because it is easy and a liquid crystalline compound having a low base viscosity is easily formed. The molecular chains may have a certain length or a somewhat broad molecular weight distribution, for example, a molecular weight distribution index Mw / Mn of 2 or more.

The liquid crystalline group bonded to the molecular chain in the present invention means a Schiff base type, azo type, azoxy type, biphenyl type, terphenyl type, benzoic acid ester type, cyclohexylcarboxylic acid ester type, phenylcyclohexane type. A basic skeleton, that is, a mesogen, which expresses liquid crystals of conventionally known low-molecular liquid crystals such as biphenylcyclohexane type and cholesteryl type can be used. For more information on mesogens, see Alexandre Blumste
ibn LIQUID CRYSTALLINE O
DDER IN POLYMERS (ACADEMIC
PRESS) or M. Gordon Edition Liq
uid Crystal Polymers (Spri
Liquid C in nger-Verlag)
Rystal Polymers with Flex
Ible Spacers in Main Chain
Representative examples are listed in "Liquid Crystal Electronics" by Shoichi Matsumoto (Ohmsha) or "Introduction to Liquid Crystals" by Nakata, Hori and Mukai (Koushobo).

A method for synthesizing a side chain type liquid crystalline compound is as follows:
That is, a spacer having a siloxane bond with a liquid crystalline group may be bound to the main chain skeleton by a polymer reaction in a hanging form like a branch, or the liquid crystalline group may be bonded with a siloxane bond at the stage of the unit of the molecular chain. It is also possible to polymerize a substance that is bound in a hanging form like a branch through a spacer that it has.

As the bonding group for bonding the liquid crystal group to the molecular chain or the spacer, methylene, amide, urethane,
It may be any bond such as ester, ether and carbonate, and is not limited to the bonding method.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. The basic characteristics of the electrorheological fluid were measured according to the following method. (Measurement of base viscosity and electrorheological effect) A pair of parallel disks modified so that the entire plate-opposing surface forms an electrode (the lower disk is connected to the motor for rotation, the upper disk is a torque meter). To measure the shear stress)
A plate type rotational viscometer was used. The sample was sandwiched between the electrodes, a predetermined temperature and a shear rate were applied, and the shear stress was measured. The electrorheological effect referred to in the present invention is the increment of shear stress due to the application of voltage. In this example, the electrode diameter of the facing portion was 32 mm, and the electrode gap was 0.50 mm.

[0015]

Example 1 1) Synthesis of Side-Chain Type Liquid Crystalline Compound A p-Hydroxybenzoic acid 99 was added to a mixed solution of potassium hydroxide 100 and ethanol 500 ml dissolved in water 120.
g and potassium iodide 0.7 g were dissolved, allyl bromide 86 g was added dropwise, and the mixture was refluxed at 80 ° C. for 12 hours.
After cooling, 150 ml of water was added, the pH was adjusted to 2 with hydrochloric acid, and the deposited precipitate was separated by filtration and recrystallized from ethanol to obtain 90 g of product C.

[0016]

[Chemical 1]

To 17 g of the product C, 17 g of thionyl chloride and a few drops of dimethylformamide were added, and the mixture was stirred at room temperature for 1 hour to give an acid chloride form, and excess thionyl chloride was removed under vacuum. The acid chloride form dissolved in 100 ml of tetrahydrofuran (THF) was dissolved in 12 g of p-cyanophenol and 13 g of triethylamine (TEA) at 0 ° C.
It was dropped into 250 ml of HF and stirred at 0 ° C. for another hour. THF was removed under vacuum and the residue was dissolved in dichloromethane and washed with water. Silica gel column (Wako gel C20
0) to obtain 26 g of liquid crystal compound D.

[0018]

[Chemical 2]

After dissolving 14.9 g of the liquid crystal compound D and 7.2 g of dimethylethoxysilane in 75 ml of THF,
3 mg of chloroplatinic acid hexahydrate was added, and the mixture was refluxed at 60 ° C. for 12 hours. After removing THF, the residue was purified by a silica gel column (Wakogel C200) to obtain 13 g of a product E.

[0020]

[Chemical 3]

9.1 g of the product E dissolved in 40 ml of acetone and 20 ml of THF was added dropwise to a mixed solution prepared by dissolving 8.4 g of potassium carbonate in 35 ml of water and then adding 35 ml of acetone. Furthermore, potassium carbonate dissolved in 40 ml of water 8.
After adding 4 g and stirring vigorously at room temperature for 8 hours, 500 ml of water
Was added to 18 g of potassium dihydrogen phosphate dissolved in. After extraction with methylene chloride, the mixture was concentrated and the residue was purified by a silica gel column (Wakogel C200) to obtain 5 g of product F.

[0022]

[Chemical 4]

Product F4.0 dissolved in 10 ml of THF
TEA (1.9 ml) and allyldimethylchlorosilane (1.9 g) were added to the mixture, and the mixture was stirred for 18 hours at room temperature. After concentration, water was added to the residue and the mixture was extracted with methylene chloride and concentrated. The residue was purified by a silica gel column (Wako Gel C200) to obtain 3.8 g of liquid crystal compound G.

[0024]

[Chemical 5]

A copolymer silicone (m / n = 1.4, composed of 10.0 g of the liquid crystalline compound G, dimethylsiloxane (m) and monomethylhydrogensiloxane (n).
Polymerization degree of about 30) 3.6 g of tetrahydrofuran (TH
F) After dissolving in 70 ml, 3 mg of chloroplatinic acid hexahydrate was added and refluxed at 60 ° C. for 23 hours. After removing THF, the residue was purified by a silica gel column (Wakogel C200) to obtain 11.3 g of a side chain type liquid crystalline compound A. The result of infrared absorption spectrum analysis of the side chain type liquid crystalline compound A is S
The absorption at 2128 cm ^-1 based on i-H disappeared, and instead, the absorption at 2222 cm ^-1 based on the CN group and 1733 cm ^-1 based on the COO group occurred.

[0026]

[Chemical 6]

2) Measurement results of base viscosity and electrorheological effect are shown in Table 1. Base viscosity at 60 ° C is 4.34.
Pa · S is significantly lower than that of the comparative example. A clear liquid crystallinity and electrorheological effect were observed even at -20 ° C. At 70 ° C., it showed isotropic properties and no electrorheological effect was exhibited.

[0028]

[Comparative example]

1) Synthesis of Side-Chain Liquid Crystalline Compound B m / n =
Copolymer silicone having a polymerization degree of about 30 and 1.4.
26.7 g of a side chain type liquid crystal compound B was synthesized from 3 g and the liquid crystal compound D19.9 g. 2) Table 1 shows the measurement results of the base viscosity and the electrorheological effect. Compared with the examples, the base viscosity is 41.
Remarkably high at 92 Pa · S.

[0029]

[Table 1]

[0030]

INDUSTRIAL APPLICABILITY The present invention is an electrorheological fluid of a homogeneous system having no problem of sedimentation and separation and having a low base viscosity without impairing a large electrorheological effect. There is an advantage that the liquid crystal group is easily moved by the electric field and the response speed is fast. Also,
By reducing the base viscosity, energy loss when no voltage is applied can be suppressed. The new compact, electronically operated actuators such as valves, clutches, brakes, and torque converters can be used stably for a long period of time without the above problems.

Claims (1)

[Claims] 1. An electrorheological fluid containing a side chain type liquid crystalline compound having a spacer containing a siloxane bond as a main component.