JPS6161147A - Photoresponsive material - Google Patents

Abstract

PURPOSE:To change color tone, volume, electric conductivity, etc. by using a crosslink type water absorptive resin having the specific constituting unit at the main chain and irradiating light thereto in the presence of water or hydrophilic medium. CONSTITUTION:The crosslink type water absorptive resin having the constituting unit expressed by the formula is used. Such resin is obtd. by adding the vinyl polymer corresponding to the above-described formula to a hydrophilicity imparting monomer, for example, acrylamide, etc. and crosslinkable monomer, for example, N,N'-methylene bis-acryl amide, etc. and copolymerizing the same. The crosslink type water absorptive resin obtd. in such a manner exhibits a strong absorption spectrum in a UV - visible region and causes a constitutional change and consequent color tone change, etc. by way of a photochemical reaction process when irradiated with light. The resin changes to a swollen gel body while entailing a change in the pH and electric conductivity of the gel when light is irradiated thereto particularly in the presence of the aq. medium. The gel shrinks when the light is shut therefrom. The resin is made usable for an optical switch, optical recording material, shape memory material, etc. by utilizing such change of the photochemical characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photoresponsive material whose multicolor tone, volume, electrical conductivity, etc. change upon irradiation with light in the presence of water or a hydrophilic medium.

[Conventional technology]

It is known that the morphology of synthetic polymers can change by using light energy.

For example, Gendai Kagaku July 1981 issue, pages 18 et seq., spirobenzopyran undergoes a reversible photoisomerization reaction between spiropyran type and merocyanine type, or a similar isomerization reaction occurs between cis type and trans type. It is introduced that a polymer containing azobenzene (stilbene) is synthesized and the viscosity changes when the solution is irradiated with light.

[Problem that the invention seeks to solve]

However, in the conventionally proposed examples, the viscosity change in the solution is small, at most twice the intrinsic viscosity, and in order to utilize this in various fields, it is required to increase the amount of change. There is also a strong desire to utilize this light-responsive change for properties other than viscosity change.

It is therefore an object of the present invention to provide novel photoresponsive materials that can change reversibly in response to light.

[Means for solving problems]

According to the research of the present inventors, by introducing a structural unit represented by the following general formula (I) into the main chain when producing a water-absorbing cross-linked resin, it is possible to The present invention was achieved by recognizing that when irradiated with light, a material can be obtained in which the volume, color tone, ridge conductivity, p, etc. of the gel change significantly, and the changes are photoreversible.

-(-CH2-C-)- That is, in the present invention, when producing a water-absorbing crosslinked resin by known vinyl polymerization from a hydrophilicity-imparting monomer and a crosslinkable monomer, the general formula (I) It is a photoresponsive material consisting of a random copolymer obtained by adding a vinyl monomer corresponding to the above and copolymerizing it.

The hydrophilicity-imparting monomer to be used is one that coelectrifies with a vinyl monomer (hereinafter sometimes simply referred to as a functional monomer) corresponding to the general formula (I) to give a hydrophilic mt copolymer. If you have one, you can ask us about it.5 For example, those which themselves give highly hydrophilic copolymers, such as (meth)acrylamide, (meth)acrylic acid, hydroxyethyl (meth)acrylate, maleic acid, vinylpyrrolidone, vinylpyridine, etc. In addition, vinyl monomers such as vinyl acetate, which are obtained by treating the obtained copolymer and being modified to, for example, vinyl alcohol units, yield a highly hydrophilic copolymer.

In the present invention, introduction of a crosslinking monomer is important. In the present invention, in order to maximize the functional properties of the functional monomer represented by the general formula ○), it is essentially necessary to introduce a crosslinking group, and the amount of the crosslinkable monomer used is Generally 0
．． It is within the range of 0.01 to 10 mol, preferably 0.3 to 5 mol. If no crosslinking group is introduced, reversibility of volume change, which is the most useful effect of the present invention, cannot be expected. On the other hand, if the introduction of the crosslinkable single body becomes higher than necessary, the volume change of the gel will be suppressed. The crosslinking monomer can be introduced using the usual method for producing water-absorbing gels, and polyfunctional monomers with different reactivity or N-hydroxymethylacrylamide, N-alcoquinemethylacrylamide, etc. It is also possible to use a method in which a soluble copolymer is synthesized once using a crosslinked precursor monomer and then made into a crosslinked polymer by heat, light, or radiation, but preferably N,N'-methylenebis(meth)acrylamide is used. It is preferable to introduce the monomer by copolymerizing a monomer having two or more vinyl groups in one molecule, such as 1-bishydroxyethyl (meth)acrylate, divinylbenzene, or a polyfunctional olefin derived from a polyhydric alcohol.

The functional monomer used in the present invention is a monomer that provides the structural unit of the general formula (I) in the copolymer, that is, a monomer of the following formula (formerly CH2=CY) (where X%Y and 2 are ), for example, Polymeriza
tionsf'l! Lhige Malachitgr
iinderivate Jahrg.

93, P1899 (I960).

Examples of the case where Y is hydrogen, X is a hydroxyl group, and Z is a phenylene group include the following monomers.

In addition, 2 is a phenylene residue bonded to a vinyl residue via a carbon atom, an oxygen atom, or a nitrogen atom, and X is a hydroxyl group R
1. Examples of cases where R2 is a dimethylamino group include the following monomers.

=7-CH2-Cf(CHI =CH Formula (formerly, a monomer in which R1 and R2 are an acylamino group is preferably used. In addition, the example shows a case where X is a hydroxyl group. As is clear from the example, it is preferable that X is a cyano group because a high magnification of photoresponsiveness can be obtained at the water swelling ratio.Although Y may be methyl, it is preferable that it be a hydrogen atom as in Example 4. preferable.

In the present invention, the content of the structural unit represented by the above-mentioned general formula (I) in the copolymer resin is not particularly limited, but for example, if volume expansion or color change as a photoresponsive gel is expected, .1 to 10 molts, preferably 0.3 to 5 molts, is sufficient.If a high change in electrical conductivity is expected, the content can be increased, but it is not recommended to use a high content. If this occurs, the hydrophilicity of the resulting resin may be reduced or the mechanical strength of the resin may be reduced, so the amount should generally be kept at 40 mol φ or less, preferably 20 mol φ or less.

The water-absorbing cross-linked resin constituting the photoresponsive material of the present invention is basically composed of a copolymer of the above-mentioned three components, but like the known water-absorbing cross-linked resin, the present invention A small proportion of other constituents, such as methyl methacrylate, styrene, vinyl ether, or similar monomers thereof, may be copolymerized to the extent that the effect of the composition is impaired.

The method for producing the four-layer fat constituting the photoresponsive material of the present invention is not particularly limited. It is obtained by In general, it is best to produce the copolymer by cross-linking if necessary after radical polymerization or ionic polymerization using a solvent with high affinity for the resulting copolymer.
Polymers with high compatibility C~) Examples include dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone,
Tetrahydrofuran, sulfolane, etc. are preferred. When polymerized in these polar solvent systems, the polymerization reaction proceeds uniformly, and the structural unit represented by the general formula (I) forms a copolymer G.
Perhaps because not only is it introduced into P on average, but also its introduction rate is high, it becomes a bundle that is significantly superior in various photoresponsive behaviors.

The water-absorbing cross-linked resin provided by the present invention exhibits a unique strong absorption spectrum in the ultraviolet to visible region, and undergoes a reversible photochemical reaction when irradiated with light from a mercury lamp, a xenon lamp, etc., resulting in a structural change and accompanying It is a photoresponsive material that causes a light absorption spectrum change, that is, a color v4 change. The cross-linked water-absorbing resin of the present invention can be produced by irradiating it with light in the presence of an aqueous medium that is substantially free of free salts, so that the resin can be produced from = 10 to 10, with changes in the pH and electrical conductivity of the gel.
It can be converted into a swollen gel 600 times (dry weight ratio), and under normal conditions, the gel shrinks when light is blocked, and the gel can be changed repeatedly between the two states, resulting in large reversible changes in shape and various physical properties. It shows a peculiar behavior that it can be done. These physical properties, especially the degree of swelling, can be freely selected by controlling the type of hydrophilic medium, copolymerization composition ratio, and crosslinking density.

The mechanism by which the crosslinked water-absorbing resin of the present invention exhibits a particularly remarkable effect is not entirely clear, but upon light irradiation, the structural unit (I) undergoes a structural change due to a photochemical reaction, resulting in a state of charge distribution. It is thought that this induces a change in the polymer chain morphology due to changes in the structure of the polymer chain.

The above-mentioned crosslinked water-absorbing resin, which is the photoresponsive material of the present invention, can be used alone, but it can be mixed with other resins or rubbers, and various sensitizers, fillers, pigments, stabilizers, and reinforcing agents can be used as necessary. It is also possible to use the composite t7 by adding the like.

As mentioned above, the features of the photoresponsive material of the present invention are maximized in the gel state in the presence of an aqueous medium substantially free of free salts, but if the resin swells, It may also be used in a hydrophilic medium other than water, such as alcohol. If a large amount of free salt exists in the system, the swelling properties of the gel as a photoresponsive behavior will decrease, so in this case, the amount of free salt dissolved in the system is preferably 10 mol/e or less, preferably 10 mol/e. It is better to keep it below this level.

The photoresponsive material of the present invention can be used as a highly absorbent gel that can respond to light and change its volume by utilizing the above-mentioned properties of the material as they are, or by converting them into, for example, photomechanical properties. optical switches, optical recording materials,
It can be used in applications such as shape memory materials, or in fields that utilize high-magnification shape changes such as valves and sealing materials.

〔Example〕

Examples of the present invention will be specifically explained below using Examples.

Example 1 Acrylamide 500mg, bisacrylamide 22m
g, p-vinyl-α, α-bis[p-(dimethylamine)phenyl]-phenylacetonitrile in butyronitrile 20m, iil was dissolved in 3 ml of dimethyl sulfoxide, and after purging with nitrogen, it was heated at 60”C for 1 By polymerizing for a period of time, a block of a crosslinked polymer that swells in water was obtained.The crosslinked polymer was cut to a thickness of about 111 m and swelled in water for 3 days to remove the solvent and unreacted polymer. The composition ratio in the copolymer was determined by elemental analysis of C, H, and N, and it was confirmed that it was a copolymer crosslinked with bisacrylamide into which VCN was introduced, which approximately corresponded to the charged composition ratio. Ta.

A section of the copolymer with a thickness of approximately 1 mm was thoroughly dried and used as a sample.
The change in swelling ratio in water over time was measured and the results are shown in FIG. When irradiated with light (I'Ig's Mizusen lamp, λ>270 nm) for 2 hours, the gel immediately became colored (λmax=62
0 nm), it started to swell and swelled to 400 times its own weight, whereas when no light was irradiated, almost no coloring was observed and the swelling ratio of the gel was at most 20
It was double that.

Example 2 Water swelling when a copolymer was obtained in the same manner as in Example 1 except that the amount of bisacrylamide (abbreviated as BAAm) was changed, and was irradiated with light for 2 hours after treatment in the same manner as in Example 1. The ratio was measured and the results are shown in Table 1. In addition, in the case where AAm was not added, the obtained copolymer was water-soluble and did not exhibit a certain shape. Furthermore, when the BAAm content was low, the shape after swelling tended to become unstable.

Table 1 Example 3 Water swelling ratio when a crosslinked polymer was obtained in the same manner as in Example 1 except that the amount of VCN was varied and irradiated with rIj1 light 2 hours after treatment in the same manner as in Example 1. measure,
The results are shown in Table 1.

Table 1 Example 4 p-vinyl-α, α-bis [
A water-swellable crosslinked polymer was obtained in the same manner as p-(dimethylamino)phenyl]-ben. When the cross-linked polymer was sufficiently swollen in water and irradiated with light under the same conditions as in Example 1, it immediately turned green as in Example 1. When the light-swollen gel was left for a day and night, the weight of the gel was the same as that before irradiation with light. amount had decreased. These behaviors could be repeated several times. The gel also showed similar behavior in methanol.

[Brief explanation of drawings]

FIG. 1 is a graph showing the photoswelling behavior of a photoresponsive material according to an embodiment of the present invention.

Claims (1)

[Claims] A photoresponsive material comprising a crosslinked water-absorbing resin having a structural unit represented by the following general formula (I) in its main chain. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (Here, X is OH or CN; Y is hydrogen or methyl group;
R^1 and R^2 are hydrogen, lower alkyl group, amino group,
The same or different substituents selected from a lower alkylamino group and a lower alkoxy group, Z is either direct or ▲ has a numerical formula, chemical formula, table, etc. ▼, -O-, -NH- and -CH_2- or A phenylene residue bonded to a vinyl or vinylidene residue via a further group. )