JP2921836B2 - Polymer composite membrane - Google Patents

Description

The present invention relates to a polymer composite membrane.

(Prior art and its problems) Today, liquid crystals are used in various fields. A characteristic of liquid crystals is that the molecular arrangement is easily changed by optical anisotropy and external fields such as electric and magnetic fields. In particular, in a ferroelectric liquid crystal, a torque generated by an interaction between spontaneous polarization and an electric field serves as a driving force, and the driving force is extremely large, and is attracting attention as a high-speed display element material. Also, some dyes have excellent optical characteristics such as an electro-optical effect due to a normal electric or photoelectric field and a non-linear optical effect. These functional low-molecular liquid crystals and dyes have various molecular design possibilities and various optical characteristics, but have fluidity and have a problem in fixing the structure.

In a conventional optical display device, functional low molecules such as liquid crystal are fixed between two glass plates to fix the functional low molecules. However, using a glass plate causes problems in terms of flexibility, weight reduction, and area increase. For this reason, a method of fixing a functional polymer using a polymer that is flexible, lightweight, and easy to increase in area is generally considered. Among polymers, ferroelectric polymers have excellent electrical properties such as high dielectric constant, high-speed switching, piezoelectricity, pyroelectricity, and electrostriction. Therefore, a liquid crystal and / or a composite film of a dye and a polymer obtained by compounding a low-molecular substance and a polymer, which have both functions, have various functions in addition to the electro-optic effect and the nonlinear optical effect of the starting material. It is promising as a wide variety of industrial materials such as devices such as optical elements such as switches and memories, second harmonic generation (of semiconductor lasers), optical bistable memories, and optical processing. Conventionally known methods for obtaining a composite film of liquid crystal and a polymer include the following two methods.

(1) A method of casting a mixed solution of a liquid crystal and a polymer by a conventional method (solvent evaporation method), that is, a method of forming a polymer such as polyvinyl chloride or polycarbonate and N- (4-ethoxybenzylidene) -4 '. -Butylaniline, butyl-4
A method of dissolving a liquid crystal such as-(4-ethoxyphenoxycarbonyl) phenyl-carbonate in a common solvent, uniformly casting the mixed solution in a Petri dish, and evaporating the solvent to form a film; That is, a liquid crystal / polymer mixed solution is dropped on a water surface through a tank wall, and several tens of composite ultrathin films obtained by self-diffusion are laminated to form a film.

However, the characteristics of the composite film of a polymer and a functional low-molecular compound such as a liquid crystal and a dye prepared as described above are not always satisfactory.

(Means for Solving the Problems) The problem of the prior art as described above is that a liquid crystal, a dye, and the like are dispersed in a porous polymer as a continuous dispersed phase.
The problem is solved by the formed polymer composite film.

Such a polymer composite film is produced, for example, by the following method. A porous polymer film having continuous pores is obtained by evaporating the solvent from a polymer solution containing water and alcohol, and the pores of the porous polymer film are filled with functional low molecules such as liquid crystals and dyes. As a result, a dispersed phase is formed, and a polymer composite film is obtained.

The dispersed phase in the present invention is obtained by uniformly dispersing a liquid crystal or a dye alone or a mixture of a liquid crystal and a dye in a polymer matrix, and is different from a heterogeneous dispersion system obtained by a conventionally known casting method.

(Effect) Ethyl alcohol and water form a cyclic cluster of three molecules due to hydrogen bonds between ethyl alcohol molecules, and these three clusters are further associated with each other to incorporate one hydronium ion. An inclusion compound is formed, and this inclusion compound is hydrogen-bonded to a water molecule. For this reason, alcohol water in a solution in which a certain amount of alcohol water is dispersed in a solution in which a polymer is dissolved in a good solvent becomes uniform spherical particles due to interfacial tension as the solvent evaporates, and the solvent evaporates. Form. After that, the alcoholic water is completely evaporated by dry heat drying at 100 ° C or higher,
It has been found that a porous membrane having a structure in which pores are connected by a channel can be obtained. In addition, since ethyl alcohol has hydrophilicity, a porous membrane is also used when a certain amount of alcohol is uniformly diffused in a solution of a polymer dissolved in a good solvent and then the solvent is evaporated in a humid environment. Can be obtained.
If the polymer composite film of the present invention is formed at a temperature slightly higher than room temperature during film formation, the dispersed phase of each other is connected by thin channels due to shrinkage during film formation.

 Further, the present invention will be described in detail.

In the present invention, (1) after dissolving a polymer in a good solvent, adding a certain amount of alcohol and water, mixing well, casting the mixture on a flat petri dish, and evaporating the solvent to obtain a porous membrane (2). ), After adding a certain amount of alcohol and thoroughly mixing in the method (1), casting the mixture on a flat petri dish and evaporating the solvent in a container (desiccator, chromatograph developing tank, etc.) whose humidity has been adjusted in advance, and the porous membrane is removed. I can. After the porous film obtained as described above is filled with a liquid crystal (and / or dye) in a reduced-pressure dryer, a sample can be obtained by attaching electrodes.

As the polymer that can be used in the present invention, any polymer can be used as long as it can form a composite film with functional low molecules such as liquid crystals and dyes. Examples of the polymer include polyethylene, polyvinyl acetate, polyacrylonitrile, polyvinyl chloride, polyvinyl compounds such as polyvinyl fluoride, and addition polymers of vinyl compounds, polyvinylidene chloride, polyvinylidene fluoride, vinylidene cyanide, vinylidene fluoride / trifluoroethylene. Copolymers, vinylidene fluoride / tetrafluoroethylene copolymers, vinylidene cyanide / vinyl acetate copolymers, and other vinyl compound or fluorine compound copolymers, polytrifluoroethylene, polytetrafluoroethylene, polyhexafluoropropylene Compounds containing fluorine, polyamides such as nylon 6, nylon 66, etc.
Polyimide, polyurethane, polypeptide, polyester such as polyethylene terephthalate, polycarbonate,
Examples include polyethers such as polyoxymethylene, polyethylene oxide, and polypropylene oxide.
As the polymer, a commercially available polymer can be used alone, but it can also be used as a mixed system in which various polymers are combined. In this case, the polymers are compatible with each other, and not only have excellent film forming properties, but also use various properties of the obtained composite film, such as chemical stability, weather resistance, impact resistance (thermal and mechanical). It is desirable to use them in combination in consideration of the purpose.

A good solvent is good for dissolving the polymer, and differs depending on the polymer. For example, polyvinyl chloride is tetrahydrofuran, cyclohexanone, methyl ethyl ketone, dimethylformamide, etc., polyvinyl acetate is chloroform, methanol, acetone, butyl acetate, etc., polyethylene oxide is benzene, dimethylformamide, etc., and vinylidene fluoride, vinylidene cyanide And copolymers thereof include ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as methyl acetate and methyl acrylate, cyclic ethers such as ethylene oxide, propylene oxide, tetrahydrofuran and dioxane, amines such as n-butylamine, amides such as dimethylformamide and dimethylacetamide. Kind. The amount of the solvent to be added may be any amount relative to the polymer, but is preferably a 20-0.5% solution in view of film forming properties.

As the liquid crystal that can be used in the present invention, any liquid crystal that can form a liquid crystal / polymer composite film can be used. For example, p-azoxyanisole, cholesteryl nonanoate, 4-methoxybenzylidene-4'-n-
Butylaniline, 4-methoxy-4'-butylazoxy-benzene, 4,4'-dimethoxyazobenzene, p-azoxyanisole, 4-cyano-4'-n-pentylbiphenyl, p-2methoxybutyl-p'-cyano Nematic liquid crystal such as biphenyl, terephthal-bis-butylaniline, N- (4-cyanobenzylidene) -4'-n-octyloxyaniline, dodecyloxyazobenzene,
Ethyl p- (p'-phenylbenzalamino) benzoate, 4-heptyloxybenzylidene-4'-pentylaniline, 4-butyloxybenzal-4-ethylaniline, 4- (4'-phenylbenzylideneamino)- n
-Butylcinnamate, 4- (4'-decyloxybenzylideneamino) 2-methylbutylcinnamate, 4-
(N-hexyloxy) phenyloxy-4 ″-(2-
Methylbutyl) biphenyl-4'-carboxylate,
Smectic liquid crystal such as ZLI-3489, cholesteryl nonanoate, (−)-2-methyl-p- (p′-methoxybenzylideneamino) cinnamic acid, cholesteryl myristate,
Cholesteric liquid crystals such as halides and esters of cholesterol and discotic liquid crystals such as hexabutoxytriphenylene are exemplified. In this case, the above liquid crystal can be used alone, but a plurality of liquid crystals can be mixed and used for the purpose of improving the performance of the base liquid crystal such as a phase transition temperature, a temperature range, a chemical stability and a film forming property.

Non-linear optics such as azo-based, anthraquinone-based, tetrazine-based, and coumarin-based dichroic dyes which are conventionally mixed with liquid crystals and used for the light absorption anisotropy of the dyes as dyes (pigment-containing) usable in the present invention. 4-dimethylamino-4'-nitrostilbene, o- (mp-) nitroaniline, 2-methyl-4-nitroaniline, merocyanine, etc. having properties, and bis (1-thio-2-phenolate)
Nickel-tetrabutylammonium, bis (1-thio-2-naphtholate) nickel-tetrabutylammonium, bis (1,2,3,4-tetrachloro-5,6-dithiophenolate) nickel (II) tetra-n And near-infrared absorbing dyes such as -butylammonium.

As the alcohol used in the present invention, lower monohydric alcohols such as methanol and ethanol are preferable. The amount of the alcohol to be added may be an arbitrary amount, but is preferably 5 to 30% with respect to the common solvent within a range where the polymer does not precipitate. In this case, if necessary, auxiliary additives such as hydrocarbons such as benzene, toluene and xylene can be added to the alcohol.

The water used in the present invention is preferably pure water. In the above, the amount of water added to the alcohol may be any amount as long as the polymer does not precipitate, but is preferably 5 to 50% based on the alcohol. Alternatively, after uniformly diffusing a certain amount of alcohol in a solution of a polymer dissolved in a good solvent, and then evaporating the solvent in a humid environment to obtain a porous polymer film, the relative humidity of the environment is Although it depends on the type of the solvent, it is 60-100%, preferably 75-95%.

In the porous polymer membrane of the present invention, since the alcohol water is uniformly present as fine droplets in the polymer solution until the time of film formation, the diameter and distribution of the pores of the dispersed phase of the resulting porous membrane are uniform. It is. In addition, since the pores in which the dispersed phase is formed are formed by alcohol, the mechanical strength and dimensional stability are greatly improved without being hindered by film formation. Such features are important in using the present porous composite membrane as an industrial material.

EXAMPLES Next, the present invention will be described in more detail with reference to examples.

Example 1 Vinylidene fluoride-trifluoroethylene copolymer [vinylidene fluoride 65%, manufactured by Daikin Industries, Ltd.] 7.5
The resulting solution was dissolved in 100 parts of a tetrahydrofuran solvent, mixed with 10 parts of ethyl alcohol, and then cast on a flat petri dish to evaporate the solvent in a chromatographic developing tank adjusted to a relative humidity of 80% to form a film. Then, in a vacuum oven at 100 ° C,
Heat treatment was performed for 8 hours to obtain a cast film. The film obtained from the SEM image of this film was found to be a porous polymer having a pore size of 4-5 μm. The porous membrane was impregnated with 2.5 parts of 4- (4'n-decyloxybenzylideneamino) 2-methylbutylcinnamate (DOBAMBC) at 100 ° C. in a vacuum oven, filled with electrodes, attached with electrodes, and did. The temperature dependence of the dielectric constant of the specimen was measured, and the vinylidene fluoride-trifluoroethylene copolymer used as a starting material, a liquid crystal
Compared to DOBAMBC. Linear permittivity ε ₃ during heating process
FIG. 1 and FIG. 2 show the temperature dispersion of the third-order nonlinear dielectric constant ε ₃ and Corresponds to the composite membrane, ○ corresponds to vinylidene fluoride-trifluoroethylene copolymer, and ● corresponds to DOBAMBC). Since DOBAMBC and vinylidene fluoride-trifluoroethylene copolymer are incompatible, the dielectric properties of the composite film reflect the properties of both phases independently, and the jumps of ε ₁ and ε ₃ at each phase transition point are generated. It is also found in composite membranes.
In FIG. 1, the peak of the liquid crystal / polymer composite film is DOBA
At the transition point (76 ° C) from the MBC crystal phase to the Sm ^* phase, the peak is at the Curie point of the vinylidene fluoride-trifluoroethylene copolymer, at 95 ° C, and the increase in the dielectric near is DOBAMB
It corresponds to the phase transition from SmA phase of C to isotropic (117 ° C). Here, the dielectric constant of the composite film is higher than that of DOBAMBC and vinylidene fluoride-trifluoroethylene copolymer, and it is noted that synergistic composite is realized in this system. Also, the jump of ε at the transition point of DOBAMBC is larger in the composite film than in the DOBAMBC alone, which indicates that the polarization reversal of the liquid crystal can be more easily controlled. For comparison, a DOBAMBC-vinylidene fluoride-trifluoroethylene copolymer obtained by casting a film using a common method using tetrahydrofuran as a common solvent is DOBAMBC-rich on one side and vinylidene fluoride-trifluoroethylene copolymer on one side. A layer rich in coalescence was formed, resulting in a non-uniform film. It was found that the dielectric constant of the heterogeneous composite film was between the dielectric constants of the two phases, and that a very common compound occurred.

Example 2 Vinylidene fluoride-trifluoroethylene copolymer 7
After dissolving a mixture of 3 parts of methyl methacrylate and 3 parts of methyl methacrylate in 100 parts of methyl ethyl ketone solvent, 20 parts of methyl alcohol,
Pure water (3 parts) was added, the mixture was cast on a flat petri dish, and the solvent was slowly evaporated to obtain a cast film. From the SEM image of the film, it was found that the obtained film was a porous film having a pore size of about 5 μm, and the pores were connected by narrow channels to form a continuous phase. This film was impregnated and filled with a liquid crystal ZLI-3489 (manufactured by Merck) at 80 ° C. in a vacuum dryer to obtain a composite film. When this composite film was heated again to 120 ° C., ZLI-3489 oozed out on the film surface. This is because the liquid crystal, ZLI-3489, seeps through continuous voids formed by the vinylidene fluoride-trifluoroethylene and methyl methacrylate matrix as a continuous phase domain, and is in good agreement with the SEM image results. . This phenomenon is observed at a transition point of the liquid crystal, ZLI-3489, from the cholesteric phase to the isotropic phase of 87 ° C. or higher.

Example 3 Vinylidene fluoride-trifluoroethylene copolymer 7.
After 5 parts were dissolved in 100 parts of tetrahydrofuran solvent, 10 parts of ethyl alcohol and 3 parts of pure water were added, mixed well, cast on a flat petri dish, and formed into a film by a solvent evaporation method. A heat treatment was performed at 6 ° C. for 6 hours to obtain a cast film having a pore diameter of about 8 μm, the pores of which were connected by thin channels to form a continuous phase. This film was impregnated and filled with 2.5 parts of liquid crystal and ZLI-3489 in a vacuum dryer at 90 ° C. to obtain a composite film, which was provided with electrodes to prepare a test sample, and the temperature dependence of the dielectric constant was measured. For comparison, a similar experiment was conducted using 7.5 parts of vinylidene fluoride-trifluoroethylene copolymer and 2.5 parts of liquid crystal and ZLI-3489 in a common solvent, 100 parts of terahydrofuran, and casting by a conventional method. Was done. The temperature distribution of the linear dielectric constant epsilon ₁ shown in Figure 3. In FIG. 3, the peak in the range of −20 to 60 ° C. corresponds to the ferroelectric phase of the liquid crystal ZLI-3489, and the peak near 70 ° C. corresponds to the Curie point of the vinylidene fluoride-trifluoroethylene copolymer. As can be seen from the difference between the two charts, the composite film in which the porous film is filled with liquid crystal (curve a) has a jump in the dielectric constant in the ferroelectric phase of the liquid crystal much longer than that obtained by the ordinary method (curve b). It is clear that the polarization reversal of the liquid crystal can be more easily controlled.

Example 4 In Example 3, 0.5 g of o-nitroaniline was dissolved in 0.5 cc of ethyl alcohol in place of ZLI-3489 to obtain ZLI-34.
Except for using a mixture mixed with 2.0 g of 89, the same treatment as in Example 3 was performed to obtain a composite film in which a polymer was mixed with a liquid crystal / dye mixture as a fine spherical dispersion.

(Effects of the Invention) As described above in detail, the polymer composite film obtained by the present invention can easily control the domain inversion characteristics. In addition, by combining a low-molecular compound and a high-molecular compound, both of which have functional properties, a performance can be obtained such that a synergistic effect of the functionality of both phases appears. As described above, the composite film obtained by the present invention can be used for the electric properties such as the dielectric constant, the nonlinear optical effect, Optical properties such as refraction are significantly improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the temperature dispersion of the linear dielectric constant of the composite membrane of the present invention obtained in Example 1, the vinylidene fluoride-trifluoroethylene copolymer as a starting material, and DOBAMBC. symbol: Composite membrane, o vinylidene fluoride-trifluoroethylene,
● DOBAMBC. FIG. 2 is a graph showing the temperature dispersion of the nonlinear dielectric constant of the composite membrane of the present invention obtained in Example 1, the vinylidene fluoride-trifluoroethylene copolymer as a starting material and DOBAMBC, and FIG. 4 is a graph showing the linear dielectric constant of the composite film of the present invention obtained in Example 3 and the composite film obtained by a conventional method. Symbol: a-composite membrane of the present invention, b-composite membrane obtained by conventional method.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-271233 (JP, A) JP-A-1-230693 (JP, A) JP-A-63-124024 (JP, A) Patent 2700656 (JP, A B2) (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/1333 G02F 1/137

Claims (5)

(57) [Claims] 1. A porous polymer film comprising a polymer excluding an acrylic resin, and a continuous dispersed phase formed by filling the pores of the polymer film with a substance. Polymer composite membrane. 2. The polymer composite film according to claim 1, wherein said dispersed phase is a liquid crystal. 3. The polymer composite film according to claim 1, wherein said dispersed phase is a dye. 4. The polymer composite film according to claim 1, wherein said dispersed phase is a mixture of liquid crystal and dye. 5. The porous polymer film formed by evaporating a solvent from a polymer solution excluding an acrylic resin containing water and alcohol, and filling the pores of the porous polymer film with a substance. The polymer composite membrane according to claim 1, wherein