JPH05287032A - Gradient material and its production - Google Patents

Abstract

PURPOSE:To obtain a gradient material controllable in the gradient of a desired property or characteristic by diffusing a penetrant component into the inside of a stereocomplex gel comprising a mixture of polymethyl methacrylates of different molecular structures in the presence of a polymerizable monomer and polymerizing the monomer. CONSTITUTION:A penetrant component is diffused into the inside of a stereoregular gel comprising an isotactic polymethyl methacrylate and a syndiotactic polymethyl methacrylate in the presence of a polymerizable monomer, and the monomer is polymerized. The mixing ratio of the isotactic component to the syndiotactic component is usually about 1:20-10:1, desirably about 1:5-1:1. As the polymerizable monomer, a vinyl monomer can be desirably used. As the penetrant component, a vinyl monomer miscible with the polymerizable monomer constituting the gel matrix is particularly desirable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graded material and a method for manufacturing the graded material, and more particularly to a graded material in which the physical properties or characteristics of the material can be changed (for example, continuously) within the material by a predesigned gradient. It relates to a manufacturing method.

The graded material of the present invention is a lens, an optical material such as an optical fiber, various sensor materials sensitive to light, temperature, etc., soft contact lenses, biomedical materials such as drug sustained release systems, and structural materials. Widely applicable.

[0003]

2. Description of the Related Art In recent years, in order to meet the increasingly diverse needs for polymer materials, the development of composite materials having new functions has been actively conducted. Among such composite materials, recently, a gradient material has been attracting much attention.
For example, when a material is placed in a harsh thermal environment, that is, in a sharp temperature gradient, the material may be deformed or damaged by a large thermal stress. In such a case, regarding the thermal characteristics such as thermal conductivity, thermal expansion coefficient, heat resistance, etc., it is possible to solve the problem of the deformation or damage by providing the material with a gradient suitable for the thermal environment. ..

If a material having good transparency can be provided with a gradient of refractive index, it becomes possible to give a planar material a lens effect. Furthermore, it is considered that a gradient material having a gradient in mechanical flexibility is excellent in compatibility with a living body as a material contacting a soft tissue or organ like a living body. Further, it is considered that a gradient material having a gradient in adhesiveness, for example, hydrophilicity is effective for the material requiring adhesiveness.

As described above, if a graded material having a characteristic or a gradient of physical properties suitable for the environment in which the material is used can be designed, the function of the graded material will be dramatically improved as compared with the conventional uniform material. Expected to improve.

However, until now, it has been difficult to produce a material having a predesigned gradient of physical properties or characteristics, and a definitive method for producing such a material has not yet been reported.

For example, as a conventional method for producing a gradient material, particularly as a method used in the manufacturing process of an optical fiber,

1) a fibrous matrix material,
Immerse in a polymerizable monomer solution whose refractive index changes,
A method of imparting a gradient by diffusing the monomer inside the matrix material to form a concentration gradient and further graft-polymerizing the monomer onto the matrix material;

2) Copolymerization composition in which two kinds of monomers having different monomer reactivities are copolymerized in the presence of a centrifugal force field, a produced polymer is precipitated from a mixed monomer solution and moved by centrifugal force, and changes with polymerization time. A method of imparting a gradient using a ratio;

3) Two kinds of materials having different refractive indexes are blended and molded into a fiber shape, then immersed in a solvent in which one of the materials is dissolved and the material is extracted to impart a gradient. Method;

4) A method has been developed in which a mixture of a material and a polymerizable monomer is molded into a fiber shape, the monomer is volatilized from the fiber surface, and the monomer is further polymerized to impart a gradient. ..

[0012]

However, in the above method (1), it is necessary that the matrix polymer and the monomer have an appropriate affinity for diffusing the monomer in the polymer matrix. However, the practically usable system is limited; in addition, there is a drawback that the diffusion process requires a long time and is disadvantageous to the continuous process. Furthermore, in this method, it is necessary to previously introduce into the matrix material a functional group necessary for graft-polymerizing a monomer on the matrix material, which results in an extremely complicated and complicated system.

In the above method (2), there are many problems such that the kinds of the monomers are remarkably limited, the manufacturing apparatus is complicated due to the application of centrifugal force, and the inclination is extremely difficult to control. is there.

In the above method (3), it is difficult to control the step of extracting the polymer component with the solvent, and there is a problem that it requires a considerable amount of time.

Further, the step of volatilizing the monomer in the method (4) is not only difficult to control as in the case of the above (3), but also requires a considerable amount of time.

As described above, the conventional method for producing a graded material has a number of serious drawbacks in practical use, and no definitive method for producing such a graded material has been reported yet.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a gradient material capable of controlling the gradient of desired physical properties or characteristics by a simple means and a method for producing the same.

[0018]

As a result of earnest research, the inventor has found that isotactic polymethyl methacrylate (hereinafter referred to as “Iso-PMMA”) and syndiotactic polymethyl methacrylate (hereinafter referred to as “iso-PMMA”) in the presence of a polymerizable monomer. , "Syn-PMMA") is a special gel consisting of a stereocomplex gel and the other third component (permeation component or diffusion component) is diffused as a simple method for producing the gradient material. However, it has been found that extremely suitable inclination control is possible.

The graded material of the present invention is based on such knowledge, and more specifically, at least isotactic polymethyl methacrylate (Iso-PMMA) and syndiotactic polymethyl methacrylate (Syn-P).
MMA), and has a physical property gradient based on the diffusion of permeation components therein.

Further, according to the present invention, as a method for suitably producing the above-mentioned graded material, isotactic polymethyl methacrylate (Iso-PMMA) and syndiotactic polymethyl methacrylate in the presence of a polymerizable monomer are used. Provided is a method for producing a gradient material, which comprises a step of diffusing a permeation component into a stereo complex gel composed of (Syn-PMMA) and a step of polymerizing the polymerizable monomer.

In the present invention, as described above, Is
A stereo complex gel formed by o-PMMA and Syn-PMMA in a polymerizable monomer was used, and a component (permeation component) that imparts a gradient of physical properties or characteristics to the gel was permeated into the gel by a diffusion phenomenon. After that, the above-mentioned polymerizable monomer is polymerized to fix its inclination. Therefore, in the present invention, based on the combination of the special behavior of the polymerizable monomer and the penetrating component in the stereocomplex gel, it is possible to easily obtain a gradient material in a microscopic order, which is not obtained by the conventional method. Can be obtained by the method.

In a typical embodiment of the present invention, a permeation component (third component) is diffused or permeated from the surface of the gel into the inside of the gel in a stereo complex gel formed in a polymerizable monomer solution. It is preferable that after forming a concentration gradient of the permeation component inside the material, the polymerizable monomer is polymerized to fix the concentration gradient to produce a gradient material.

Since the gradient material of the present invention as described above contains the above-mentioned stereocomplex giving a special gel structure, the gradient material is soluble in chloroform (CHCl ₃ ) at room temperature (25 ° C.), When THF (tetrahydrofuran) is used, it has the property that the portion corresponding to the stereocomplex in the gradient material is almost insoluble.

On the other hand, a simple mixture of PMMA (including an Iso-PMMA structure and a Syn-PMMA structure) generally has the above-mentioned chloroform and THF at 25 ° C.
A mere (chemically) cross-linked polymer that is soluble in both of the above and also contains a PMMA moiety is generally insoluble in both of the above-mentioned chloroform and THF at 25 ° C., so that it can be easily distinguished.

Hereinafter, the present invention will be described in detail with reference to the drawings as necessary.

(Stereo Complex) The stereo complex used in the present invention is Iso-PMMA and Sy.
It consists of n-PMMA. Iso-PM in the present invention
The structure of MA, Syn-PMMA is, for example, the structure of three consecutive monomer units (triad) of PMMA chain,
Analysis can be easily performed by measuring with a means such as high resolution nuclear magnetic resonance spectrum (NMR). The three consecutive monomer units include an isotactic structure (I), a syndiotactic structure (S), and a heterotactic structure (H). With Iso-PMMA, these monomer units are I> S and I> H / 2 are referred to, and Syn-PMMA is S> I and S> H / 2.

Certain solvents of Iso-PMMA and Syn-PMMA (eg dimethylformamide (DM
Mixing the solutions of F)) forms a gel called a stereocomplex. This gel has a gelling temperature, and at a temperature higher than the gelling temperature, the gel dissolves, and at a temperature lower than the gelling temperature, the gelling occurs again, but such a gelling phenomenon is thermally reversible (WH Watanabe et al., J. Phy
S. Chem., 65 , 896, 1961).

The above gelling temperature depends on the stereoregularity (tacticity) of Iso-PMMA and Syn-PMMA, the molecular weight, the solution concentration, the mixing ratio, the solvent species and the like. Is
The stereocomplex formed by o-PMMA and Syn-PMMA is also formed in an organic solvent other than DMF and a polymerizable monomer solution (for example, "polymer alloy:
Basics and Applications "Polymer Society, ed., P348, Tokyo Kagaku Dojin,
1981). A laminated safety glass utilizing a stereocomplex forming phenomenon in a polymerizable vinyl monomer solution has already been applied for a patent (Japanese Patent Application No. 45-8965).
4).

Iso-PMMA and Syn used in the present invention
The PMMA may be a PMMA homopolymer,
Also, as long as a mixture of at least both monomer solutions can form a stereocomplex, MM
It may be a copolymer of A (methyl methacrylate) and another monomer.

The mixing ratio of Iso-PMMA and Syn-PMMA varies depending on stereoregularity, solution concentration, molecular weight, kind of monomer, etc., but is usually about 1:20 to 10: 1, preferably 1: 5 to 1: 1. It is about 1.

(Polymerizable Monomer) As the polymerizable monomer used in the present invention, various vinyl monomers are preferably used, but it is not particularly limited as long as it has a stereocomplex forming ability.

The polymerizable monomer preferably used in the present invention is, for example, alkyl ester of acrylic acid, alkyl ester of methacrylic acid, styrene, alkyl-substituted styrene, vinyl acetate, acrylonitrile, methacrylonitrile, N-vinylpyrrolidone, hydroxyethyl. Examples thereof include vinyl monomers such as methacrylate and ethylene glycol dimethacrylate, but are not limited thereto.

(Inclined Material) A preferred embodiment of the procedure for producing the inclined material of the present invention will be described below. Iso-PM was added to the above polymerizable monomer liquid at a temperature higher than the gelation temperature.
The stereocomplex is formed by dissolving both MA and Syn-PMMA together, or mixing the solutions of the respective polymers and lowering the temperature below the gelation temperature. At the time of forming the stereo complex, it is preferable to add a polymerization initiator at the same time. The type and concentration of the polymerization initiator can be appropriately determined depending on the polymerization conditions such as heat, light, radiation and electron beam polymerization.

On the other hand, the shape of the gel is appropriately determined according to the purpose of use, such as a sheet, a film, a fiber, a rod or a particle. For example, in the case of molding into a sheet or a film, the mixture can be easily molded by flowing the mixed solution on a flat surface at a temperature higher than gelation and then lowering the temperature below the gelling temperature.

In the case of molding into a fiber or rod, the solution can be extruded by using a suitable die and the temperature can be lowered below the gel point to achieve molding. Further, in the case of molding into particles, it is possible to carry out molding by dropping the above mixed solution into a medium having a gel point or lower using a microdispenser or the like.
However, in the present invention, the method of imparting a shape to the gel is not limited to the above method.

(Permeation component) Next, the permeation component (third component or diffusion component) to be permeated into the gel in order to impart a gradient to the physical properties or characteristics of the material of the present invention will be described. The type and amount of the permeating component can be appropriately selected depending on the purpose of use.

As the permeation component, it is particularly preferable to use a vinyl monomer which can be mixed with the polymerizable monomer forming the gel matrix. It is also possible to use a mixed system of two or more kinds of vinyl-based monomers or a mixed system of vinyl-based monomers and a substance soluble in the vinyl-based monomers as the permeation component.

The physical properties and characteristics as selection criteria of the component are not particularly limited, but for example, refractive index, light transmittance, thermal conductivity, thermal expansion coefficient, specific heat, heat resistance, flexibility, hydrophilicity (water content). , Specific gravity, charge, electric conductivity, dielectric constant, piezoelectricity, pyroelectricity, dyeability, color tone, solvent resistance and the like. These physical properties or characteristics are determined by the purpose of use of the graded material.

For example, a material having a gradient refractive index is required to have good transparency and a large difference in refractive index.
Methyl methacrylate (MMA) is particularly preferably used as the polymerizable monomer constituting the stereo complex gel, and styrene monomer, chlorostyrene monomer and the like are particularly preferably used as the permeation component.

Further, when obtaining a material having a gradient in mechanical flexibility, the glass transition points of the polymer obtained from the polymerizable monomer constituting the stereo complex gel and the polymer obtained from the monomer as the permeation component are largely different from each other. preferable.

Similarly, to obtain a hydrophilic gradient material,
When obtaining a combination of monomers having different hydrophilicities and a material having a gradient charge, it is preferable to use a combination of monomers having different charges.

(Diffusion of Permeation Component) The injection or diffusion of the permeation component into the above-mentioned stereocomplex gel is carried out by treating the gel with a medium containing the permeation component (for example, the permeation component itself) at a temperature below the gel point. , Or a solution of the permeation component). The permeation component permeates from the gel surface to the inside due to the diffusion phenomenon, and a concentration gradient of the permeation component is formed inside the gel. Here, the concentration gradient is controlled by the compatibility between the polymerizable monomer of the gel matrix and the permeation component, the concentration, etc., but usually it can be controlled by the immersion time of the gel in the medium containing the permeation component. It is possible.

After injecting or diffusing the permeation component into the stereo complex gel, the permeation component permeated stereo complex gel is pulled up from the permeation component-containing medium, and heat, light, radiation or A desired gradient material can be easily obtained by polymerizing the polymerizable monomer with an electron beam.

The present invention will be described in more detail with reference to the following examples. Example 1 Iso-PMMA ([η] = 0.62, I = 90%) 1
Part and Syn-PMMA ([η] = 0.51, S = 49
%) 2 parts and 0.1% of azobisisobutyronitrile (AIBN) were dissolved in the methyl methacrylate (MMA) monomer at a temperature higher than the gelation temperature, respectively, and PM
A mixed solution having a MA concentration of 20% was prepared.

The gelation temperature of the above solution was measured by placing the solution in a glass test tube and preparing a stereo complex at a sufficiently low temperature, then gradually raising the temperature and rotating the test tube up and down. It was performed by visually observing the point at which the gel was dissolved and showed fluidity. The gelling temperature of the above mixed solution was about 62 ° C.

The above mixed solution was poured into a thin polypropylene film tube having a diameter of about 1 cm at 80 ° C., and then the temperature was lowered to room temperature to form a stereo complex gel in the tube. Then, the polypropylene tube was cut with scissors, and the gel inside was taken out. This gel retained the rod-like shape and showed sufficient strength to be handled at room temperature.

Next, the rod-shaped gel was subjected to 0.
It was immersed in a styrene monomer in which 1% AIBN was dissolved. The immersion time was changed to 1 minute, 10 minutes, 30 minutes, 1 hour, and 3 hours, and after each immersion time, the gel was pulled out from the styrene monomer, sealed in a Pyrex glass tube in which argon was substituted, and sealed. .. Next, the gel is heated at 15 ° C. using an 800 W high pressure mercury lamp.
When a photopolymerization reaction was carried out for 3 hours, a transparent polymer was obtained.

The rod-shaped polymer was cut into a disk having a thickness of about 3 mm, and the change in the refractive index from the outer circumference to the center was measured. The measurement results are shown in FIG. As can be seen from FIG. 1, a gradient material having a refractive index increasing from the center of the disk toward the outer periphery was obtained.

Example 2 The rod-shaped stereocomplex gel prepared in Example 1 was immersed in an ethyl acrylate (EA) monomer in which 0.1% AIBN was dissolved for 30 minutes at room temperature.
When photopolymerization was carried out in the same manner as in Example 1, a rod-shaped polymer was obtained. The polymer was completely transparent.

The rod-shaped polymer was cut into a disk having a thickness of about 3 mm, and the refractive index was measured in the same manner as in Example 1. As a result, the inclination that the flexibility changes from the center of the disk toward the outer circumference is obtained. Turned out to be a material.

Example 3 The rod-shaped stereocomplex gel prepared in Example 1 was immersed in a hydroxyethyl methacrylate monomer in which 0.1% AIBN was dissolved for 30 minutes at room temperature, and then the same method as in Example 1 was performed. When photopolymerized in, a rod-shaped polymer was obtained. The polymer was completely transparent.

The rod-shaped polymer was cut into a disk having a thickness of about 3 mm to prepare each section from the outer circumference toward the center, and the water content of each section was measured. The measurement result is shown in FIG.

The water content was determined as follows.

As can be seen from FIG. 2, in this example, a graded material in which the water content gradually decreased from the outer periphery to the center was obtained.

[0055]

According to the present invention, in comparison with the above-mentioned conventional method, the degree of freedom in selecting the type of the polymerizable monomer species of the gel matrix and the type of the penetrating component (for example, the polymerizable monomer) is remarkably large. Being able to impart a wide range of physical properties and gradients; rapid diffusion of permeation component into gel, easy control of concentration gradient of the permeation component, and suitable for continuous production process ; Iso-
Since the stereocomplex composed of PMMA and Syn-PMMA can form a network structure in the order of molecules, not only the permeation component is reliably fixed in the gel, but also the heavy polymer obtained by polymerizing the monomer is obtained. It is characterized in that the phase separation of the coalescence is suppressed and that the molecules can be mixed uniformly on the order of molecules.

In a general polymerization method, a mixed system of different polymers usually becomes cloudy due to phase separation, whereas in the present invention based on a stereocomplex, the above-mentioned gradient material has a molecular level. It is possible to obtain a uniform composition at a level close to (or molecularly). Based on such characteristics, the graded material of the present invention is
Since it is transparent even in a mixed system of different kinds of polymers, its application range or application is very wide.

[Brief description of drawings]

FIG. 1 is a graph showing changes in the refractive index of a gradient material obtained in Example 1.

FIG. 2 is a graph showing changes in water content of the graded material obtained in Example 3.

Claims (2)

[Claims] 1. At least isotactic polymethylmethacrylate (Iso-PMMA) and syndiotactic polymethylmethacrylate (Syn-PMMA) are included, and a gradient of physical properties based on diffusion of permeation components is provided inside. The graded material is characterized in that 2. Isotactic polymethyl methacrylate (Iso-PMMA) and syndiotactic polymethyl methacrylate (Syn) in the presence of a polymerizable monomer.
-PMMA), and a step of diffusing the permeation component inside the stereocomplex gel, and a step of polymerizing the above-mentioned polymerizable monomer.