JPH07138553A - Stimulus-responsive material - Google Patents

Abstract

PURPOSE:To obtain a stimulus-responsive material which changes its spatial quantity on receiving two or more stimuli by using a block or graft copolymer having at least two kinds of stimulus-responsive polymer chains having different soubility parameters. CONSTITUTION:The title material is a block or graft copolymer having two kinds of stimulus-responsive polymer chains A and B, noncompatible with each other and having different solubility parameters. On responding to a plurality of stimuli, the copolymer absorbs or discharges water, changing its length, area, or volume. Polymer chains A and B, each responding to temp. and/or pH, pref. respond at 0-70 deg.C and at a pH of 3-11 from the viewpoint of a living body component in the application area such as an artificial muscle. A methylcellulose chain and a polymer chain comprising alkylated acrylamide monomer units are examples of a temp.-responsive polymer chain; a polymer chain comprising dissociatable monomer units such as (meth)acrylic acid units is usable as a pH-responsive polymer chain. The material can be used as a higher-order-motion actuator which changes every time it receives multiple stimuli.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stimuli-responsive material which is accompanied by a change in spatial volume by giving a stimulus in the presence of water. More specifically, it relates to a material capable of reversibly repeating swelling and contraction due to temperature change and / or pH change.

[0002]

2. Description of the Related Art Many polymers and materials exhibiting stimulus responsiveness are known so far, and temperature, light, pH, ion concentration, potential, solvent affinity and the like are used as stimuli.

For example, as an example showing temperature responsiveness, poly-
N-isopropyl acrylamide and other acrylamide polymers, polyvinyl methyl ether,
Polyacrylic acid / PVA blends, etc. are known as examples showing responsiveness, and attempts are being made to use them for actuators including artificial muscles, energy conversion materials, control release of drugs, and cell culture. .

Such stimulus responsiveness is basically caused by repeated absorption of liquid (water) into the material matrix and elimination of liquid (water) from the matrix.
In the conventional materials, there was no response to a plurality of stimuli, and a single stimulus and a single response, and only a single function was known. For this reason, the use has been extremely limited.

[0005]

SUMMARY OF THE INVENTION In view of such a situation, the present invention is to provide a stimulus-responsive material which independently responds to a plurality of stimuli.

[0006]

In order to respond to a plurality of stimuli, it is thought that basically the purpose can be achieved by mixing respective stimuli-responsive materials, but in reality, most polymers are Since polymers are incompatible systems and are not mixed with each other, finding a compatible system requires a great amount of labor, and even if a compatible system is found, the application development is extremely limited. The present inventors have found that these problems can be solved by using a block- or graft copolymer using a polymer that responds to each stimulus. That is, the present invention is achieved by the following.

(1) Mainly constituting a block or graft copolymer represented by the general formula AmBn (m and n are integers of 1 to 5) composed of stimuli-responsive polymer chains A and B having different solubility parameters. A stimuli-responsive material that is a component material and has a spatial amount that changes with respect to at least two or more stimulus conditions. (2) The stimulus-responsive material according to (1), wherein the stimulus-responsiveness is temperature responsiveness and / or pH responsiveness. (3) The stimuli-responsive material according to (1) or (2), wherein the amount of space that changes in response to a stimulus is length, area, or volume. (4) The temperature response region of the polymer chains A and / or B is 0 ° C.
To 70 ° C., the stimuli-responsive material according to (1) to (3). (5) The pH responsive region of the polymer chains A and / or B is pH
The stimuli-responsive material according to (1) to (3), which is present in the range of 3 to pH 11.

The stimuli-responsive material of the present invention is expected to be used mainly for artificial muscles, control release of drugs, separation and purification of biological components such as proteins, cell culture, etc. Therefore, it responds to mild stimuli. Is desired.

In the block or graft copolymer represented by the general formula AmBn constituting the stimuli-responsive material of the present invention, when both polymer chains A and B have temperature responsiveness, one has temperature responsiveness and the other has When both have pH responsiveness, both may have pH responsiveness. The temperature responsiveness is desired to be expressed in the range of 0 ° C to 70 ° C. When the temperature is 0 ° C or lower, the material of the present invention is used in an aqueous system, so that problems such as freezing occur. On the other hand, when the temperature is 70 ° C or higher, biological components such as proteins cause problems such as denaturation, which is not desirable. The pH responsiveness is desirably expressed in the range of pH 3 to pH 11. A pH of 2 or less, or a pH of 12 or more is not desirable because problems such as denaturation occur with biological components such as proteins. When the respective A and B polymer chains are temperature responsive, it is desirable that the transition temperature difference be 5 ° C. or more. Below this, the phase change associated with the secondary stimulation becomes unclear, which is not desirable in terms of function expression. Also, the A and B polymer chains have pH
When it is responsive, it is desirable that the amount of change in pH which is the primary and secondary stimulus is 2 or more. Below this, changes due to secondary stimulation become unclear, which is not desirable in terms of function expression.

As the monomer for inducing the temperature-responsive polymer chain, N-alkyl-substituted acrylamides such as N-isopropylacrylamide, (meth) acryloyloxyethylpyrrolidone, vinyl ethers such as vinylmethyl ether, and the like, and as the polymer chain, Methyl cellulose, 12% acetylated polyvinyl alcohol, polyethylene oxide and the like can be mentioned, but they may be copolymerized with other vinyl monomers as long as they do not affect the temperature responsiveness. Specific examples include (meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, vinyl acetates such as vinyl acetate and vinyl propionate, styrene, vinyl chloride, Vinyl compounds such as N-vinylpyrrolidone and (meth) acrylamides can be used.

Monomers that induce a pH-responsive polymer chain include (meth) acrylic acid, styrene sulfonic acid, and 2
-Acrylamido-2-methylpropanesulfonic acid
Examples of such monomers include monomers having a dissociative group such as, but other vinyl monomers within a range that does not affect the pH responsiveness, such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate (meth).
Acrylic esters, vinyl acetate, vinyl propionate and other vinyl esters, styrene, vinyl chloride, N
-Copolymerizable with vinyl compounds such as vinylpyrrolidone and (meth) acrylamides.

The molecular weight of the polymer chain represented by A or B is 1
000 to 50,000 is preferable. When it is 1000 or less, the stimulus response ability is not sufficient and the change of the space amount becomes insufficient. On the other hand, when it is 50,000 or more, it becomes difficult in terms of composition.

The block or graft copolymer of the present invention can be synthesized by a known method. When synthesizing a block copolymer, a living polymerization method, a method of synthesizing a polymer chain in which a reactive group such as an amino group, a hydroxyl group, or a carboxyl group is introduced at both ends or one end and coupling these, an iniferter is used. Radical polymerization method. Further, the graft copolymer can be synthesized by synthesizing a macromonomer corresponding to the A chain or B chain and then performing radical or anionic polymerization. Since the polymer chain exhibiting pH responsiveness has active hydrogen, it cannot be directly used for anionic polymerization or coupling reaction. At that time, the objective is achieved by protecting the carboxyl group by esterification or the like and removing the protecting group by hydrolysis after copolymerization.

Although the block or graft copolymer represented by the general formula AmBn used in the present invention has a stimulus-responsive property, it may be soluble in water depending on the conditions, so that it is insolubilized in consideration of practical use. It is desirable to perform processing. This method can be achieved by cross-linking by γ-ray irradiation, chemical cross-linking using a polyfunctional monomer, or the like.
In addition, IPN trapped in a water-insoluble gel such as polyvinyl alcohol or poly 2-hydroxyethyl methacrylate
Can be achieved by

Although the block or graft copolymer in the present invention is a binary system of A and B, it is a multi-component copolymer having a polymer chain C or D introduced therein, and there are three types. It does not exclude that it is possible to respond to the above stimuli.

In the stimuli-responsive material having a block or graft copolymer represented by the general formula AmBn as a main constituent of the present invention, the A chain and the B chain have different solubility parameters from each other, and thus the protein, Different affinity (interaction) with biological components such as polysaccharides, lipids, cell components and drugs. Therefore, since it is possible to express selectivity for two or more kinds of substances and the adsorption and release of these substrates can be independently controlled according to each stimulus, it is suitable as a material for separation and purification or a material for control release. In addition, since the volume changes with each of the primary and secondary stimuli, higher-order motility, which has never been achieved as an actuator, can be obtained. The stimuli-responsive material can also be used as a chemical valve or the like by immobilizing it on the surface of a porous membrane or the surface of porous beads.

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited to the examples.

Example 1 N-isopropylacrylamide 0.1 mol, azobisisobutyronitrile 0.5 mmol and aminoethanethiol 0.0 were placed in a glass polymerization tube.
7 mol and 30 ml of DMF as a solvent were charged, the tube was sealed under vacuum, and polymerization was carried out at 60 ° C. When identification was performed after reprecipitation purification, it was found to be a polymer (PIPAm) having a number average molecular weight of 2500 in which one amino group was introduced per molecule.

Methacryloyloxyethylpyrrolidone (0.1 mol) and p, p'-diisocyanatodiphenyldisulfide (3 mmol) were placed in a Pyrex glass polymerization container, degassed and irradiated with UV using a mercury lamp.
Photopolymerization was carried out for an hour. After identification by reprecipitation purification,
A polymer (PMEP) having a number average molecular weight of 7,800 and an isocyanate number of 1.98 in one molecule was obtained.

The above-mentioned one-end aminated PIPAm and both-end diisocyanated MEP were dissolved in DMF so that the terminal functional group ratio (isocyanate: amino group) before the reaction was 1: 1 and the mixture was dissolved at 0 ° C. for 48 hours. The coupling reaction,
A block copolymer was obtained.

When the DSC of this block copolymer was measured in the presence of water, transition temperatures of 34 ° C. and 50 ° C. were observed. The copolymer was dissolved in DMF, butanediol and pyridine as a catalyst were added, and the mixture was cast on a glass plate.
It was heated to 80 ° C. and chemical crosslinking was introduced. Vacuum dry D
After distilling off MF and the like, it was immersed in cold water to give a hydrogel. It was found that when the temperature of the gel was 40 ° C., it contracted, and then when it was 60 ° C., it contracted further, and it independently responded to each stimulus.

(Example 2) One-terminal aminated PIPAm was prepared in the same manner as in Example 1. In addition, polytrimethylsilylmethacrylic acid ester (PTMSM) was prepared by photopolymerization in the same manner as in Example 1 as a prepolymer of diisocyanate at both ends. Both were subjected to a coupling reaction to carry out block copolymerization, and then 1N hydrochloric acid was added to the reaction system to hydrolyze the silyl ester to obtain a copolymer of isopropylamide and methacrylic acid. After purification by reprecipitation, it was dissolved in DMF, toluene diisocyanate was added thereto, and chemical crosslinking was introduced to cause gelation, and then the solvent was replaced to obtain a hydrogel.

The gel swelled below 30 ° C. to 35 ° C. and shrank at higher temperatures. Next, an aqueous solution of sodium hydroxide was added to the gel kept in warm water at 40 ° C.
When it was set to H10, it swelled. When this system was brought to 20 ° C., the gel swelled further, and it was shown to respond independently to each stimulus.

[0024]

The stimuli-responsive material of the present invention, unlike conventional ones, has a multifunctional property of independently responding to multiple stimuli, so that it can contribute to high performance of various mechanochemical materials and actuators. .

Claims (1)

[Claims] 1. At least two different solubility parameters
A stimuli-responsive material which is a material having a block or graft copolymer composed of two stimuli-responsive polymer chains as a main constituent, and having a change in spatial amount with respect to at least two stimulus conditions.