JP2002138113A - Polymer having amino acid residue in side chain and gelled product thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new polymer having amino acid residue in the side chain usable as a pH-responsive polymer or the like which shows sharp response to acid and base, and to provide its gelled product. SOLUTION: This polymer comprises at least a repeating unit expressed by formula (1) (R represents hydrogen atom or methyl group, n is an integer of 1 to 4, and m is degree of polymerization). The gelled product and the heat- and pH-responsive polymer comprise this polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer having an amino acid residue in a side chain, a gelled product thereof, and a heat-responsive and heat-responsive polymer material using them.

[0002]

2. Description of the Related Art Conventionally, as an electrolyte polymer, anionic polymer electrolytes such as polyacrylic acid and polymethacrylic acid, poly (N, N-dimethylaminopropylacrylamide), poly (N, N-dimethylaminoethyl acrylate), etc. Are well known.

[0003] In these polymers, the electrolyte site undergoes a dissociation-undissociation change due to a change in pH or ionic strength.
Various properties such as viscosity and electrical properties change. Also,
Monomers such as acrylic acid, methacrylic acid, N, N-dimethylaminopropyl acrylamide, N, N-dimethylaminoethyl acrylate, and N-substituted acrylamide and N-substituted methacrylamide such as N-isopropylacrylamide and N-isopropylmethacrylamide Copolymers with monomers such as those exhibiting thermo-responsive properties, change their solubility in water at a certain temperature, dissolve below this temperature, become insoluble above that temperature, and dissolve at pH or ion It is also reported that the strength can be controlled.

[0004] Further, it is also known that the crosslinked gelled product of these polymer electrolytes and polymers reversibly changes the gel volume due to changes in pH and temperature. However, these polymers and their gelled products dissociate at a certain pH in the acidic or alkaline region,
There was a disadvantage that dissociation was not observed in both acidic and alkaline regions.

In order to solve such problems, the present inventors have proposed an acrylamide in which the amino group at the α-position and the carboxyl group of an amino acid such as L-lysine are protected and the amino group in the side chain is acrylamidated. A copolymer of a derivative and N-isopropylacrylamide was proposed (Patent 30).
44299).

The copolymer undergoes a deprotection reaction, whereby the amino group at the α-position and the carboxyl group of an amino acid group such as an L-lysine group become free and exhibit the properties of an amphoteric electrolyte. , Its solubility in water changes, it dissolves and becomes transparent below that temperature (phase transition temperature), becomes insoluble and becomes cloudy above its phase transition temperature, and exhibits this phase transition phenomenon over both acidic and alkaline regions. Therefore, it can be used as a thermoresponsive polymer material and a pH-responsive polymer material.

However, according to subsequent studies by the present inventors, this copolymer has a relatively high phase transition temperature, has some problems in low-temperature response, and has a problem in both acidic and alkaline regions. PH at which phase transition occurs, but attains its transparent state
The region was relatively narrow, and the boundary between the transparent pH range and the opaque pH range was not always clear, and the sensitivity of thermal responsiveness and pH responsiveness was not always satisfactory.

[0008]

SUMMARY OF THE INVENTION The present invention has been made under such circumstances, and has a low phase transition temperature, a relatively wide pH range in a transparent state, and a pH in a transparent state. To provide a novel polymer having an amino acid residue in a side chain, which has a sharp boundary between the pH region and a pH region that becomes cloudy, and exhibits a thermo-responsive property and a pH-responsive property, and a gelled product thereof. With the goal.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, the amino group in the side chain of the amino acid was protected, and the amino group at the α-position was converted to acrylamidation or methacrylamidation. It has been found that a polymer containing the obtained monomer as a repeating unit exhibits a sharp thermal response and a pH response, thereby completing the present invention. That is, according to the present invention, first, there is provided a polymer comprising a repeating unit represented by the following general formula (I).

Embedded image (R in the formula is a hydrogen atom or a methyl group, n is an integer of 1 to 4, and m indicates the degree of polymerization.) Second, a single polymer containing a repeating unit represented by the above general formula (I) Coalescence is provided. Third, the following general formula (II)
And a copolymer containing a repeating unit represented by the formula:

Embedded image (Wherein, R and n have the same meaning as described above.
Represents a hydrogen atom or a lower alkyl group, and Q2 represents a lower alkyl group. x and y indicate the mole fraction of each component in the copolymer. Fourth, a gelled product obtained by crosslinking the polymer according to any one of the first to third aspects is provided. Fifth, there is provided a thermoresponsive polymer material comprising the polymer or gelled product according to any one of the first to fourth aspects. Sixthly, there is provided a pH-responsive polymer material comprising the polymer or gelled product according to any one of the first to fourth aspects.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer containing a repeating unit represented by the following general formula (I) of the present invention can be obtained, for example, by homopolymerizing a monomer represented by the following general formula (III) or other monomer And then deprotecting the protecting group Z to synthesize the compound.

Embedded image In the general formula (I), R represents a hydrogen atom or a methyl group, n
Is an integer from 1 to 4. m indicates the degree of polymerization and is generally 5
It is 0-10000, preferably 100-5000.

Embedded image In the general formula (III), R is hydrogen or a methyl group;
n is an integer of 1 to 4, and Z represents an amino-protecting group. Examples of the amino-protecting group Z include all conventionally known protecting groups, for example, benzyloxycarbonyl,
m-chlorobenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, t-butoxycarbonyl and the like. Of these, protecting groups such as benzyloxycarbonyl and m-chlorobenzyloxycarbonyl are preferably used.

As a method for obtaining the polymer of the present invention, various methods can be employed, and examples thereof include polymerization methods such as radical polymerization in a solvent and suspension polymerization in a water / organic solvent system. The polymerization is, for example, dissolved in an organic solvent such as dimethyl sulfoxide, dioxane, methanol, and ethanol, and α, α′-azobisisobutyronitrile is used as a polymerization initiator. What is necessary is just to employ the conditions which carry out heat polymerization.

The homopolymer having a repeating unit represented by the general formula (I) of the present invention is typically produced by the reaction formula shown in the following Scheme 1.

[0013]

Embedded image

The monomer represented by the general formula (III) is a novel substance, for example, by reacting an amino acid having a protected side-chain amino group with an alkali salt such as sodium hydroxide. It is produced by first synthesizing an amino acid salt, then reacting this with an acrylic acid derivative such as acrylic acid chloride in a solvent, and forming an amide bond with the α-amino group.

Further, the copolymer of the present invention comprises a monomer represented by the above general formula (III) and another monomer such as N-
It can be obtained by copolymerizing with a monomer having an unsaturated double bond such as a substituted acrylamide derivative or an N-substituted methacrylamide derivative. Particularly, an N-substituted acrylamide derivative containing a lower alkyl group, an N-substituted methacrylamide derivative Is preferred.

A typical copolymer of the present invention contains a repeating unit represented by the following general formula (II).

Embedded image In the general formula (II), n and R have the same meaning as described above. Q1 and Q2 represent a hydrogen atom or an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group,
Shows a lower alkyl group such as a t-butyl group. Among them, Q1 is a hydrogen atom, Q2 is a combination of a lower alkyl group,
And those wherein Q1 is an ethyl group and Q2 is an ethyl group. x and y indicate the mole fraction of each component in the copolymer, and generally x is 0.5 to 0.95, preferably 0.8 to 0.95, and y is 0.05 to 0. 5, preferably 0.05 to 0.2. The molecular weight of the copolymer is generally between 10,000 and 2,000,000, preferably between 20,000 and 1,000,000.

Further, such a copolymer has the general formula (III)
And the N-substituted acrylamide or N-substituted methacrylamide monomer represented by the general formula (IV) are polymerized, and then the protective group Z is deprotected. This synthesis reaction is represented by Scheme 2.

[0018]

Embedded image

The polymer of the present invention can be made into a gelled product by a crosslinking method such as γ-ray crosslinking, chemical crosslinking, and copolymerization with a crosslinking monomer. Hereinafter, the crosslinking method will be described in detail.

(1) γ-ray crosslinking The polymer of the present invention, particularly when R in the structural formula is a hydrogen atom,
When these polymers are dissolved in water and irradiated with gamma rays, a gelled product is obtained. In this case, the concentration of the aqueous solution is 10 to 20 w
t. %, And the γ-ray irradiation amount is preferably about 70 to 150 kGy.

(2) Copolymerization with Crosslinkable Monomer As described above, the polymer of the present invention gives a gelled product by radiation crosslinking or chemical crosslinking. In the copolymerization, a production method is preferred in which a small amount of a divinyl compound is added, a gelled product is synthesized, and the protecting group is removed. For example, a monomer represented by the general formula (III) and N, N′-methylenebisacrylamide,
When a divinyl compound such as N ′-(1,2-dihydroxyethylene) -bisacrylamide is dissolved in an organic solvent such as dimethyl sulfoxide and polymerized, a gelled product having a protecting group Z is obtained. In this case, the concentration of the monomer represented by the general formula (III) is 10 to 20 wt. %, And the concentration of the crosslinking agent is preferably 0.5 to 3 mol% based on the monomer.
Then, after swelling the obtained gel having a protecting group Z in a solvent such as acetic acid, a deprotecting base such as a 25% hydrogen bromide / acetic acid solution is added to remove the protecting group (Z). A gelled product obtained by crosslinking a homopolymer having a repeating unit represented by the general formula (I) is obtained.

Further, a monomer represented by the general formula (III) and an acrylic acid monomer represented by the general formula (IV) such as N-substituted acrylamide or N-substituted methacrylamide, , N'-methylenebisacrylamide,
When a divinyl compound such as N, N '-(1,2-dihydroxyethylene) -bisacrylamide is dissolved in an organic solvent such as dimethyl sulfoxide and copolymerized, a gelled product having a protective group Z is obtained. In this case, the above general formula (II
The total concentration of the monomer represented by I) and the acrylic monomer such as N-substituted acrylamide or N-substituted methacrylamide represented by the general formula (IV) is 10 to 20 wt.
%, And the concentration of the crosslinking agent is 0.5 to 3 mol based on the total amount of the monomers.
1% is preferred. After swelling the obtained gelled product having a protecting group Z in a solvent such as acetic acid, a deprotecting base such as 2
When a 5% hydrogen bromide / acetic acid solution is added to remove the protecting group (Z), a gelled product obtained by crosslinking a copolymer having a repeating unit represented by the general formula (II) is obtained.

The aqueous solution of the homopolymer having a repeating unit represented by the general formula (I) of the present invention reversibly changes its viscosity and electrical properties due to a change in pH. Can be used.

The gelled product swells greatly in an aqueous solution, swells at a temperature lower than the transition temperature, and contracts at a temperature higher than the transition temperature, and exhibits a phase transition phenomenon, so that it can be used as a thermoresponsive polymer.

Further, the copolymer of the present invention, in particular, of the general formula (I
An aqueous solution of a copolymer having a repeating unit represented by I) dissolves in water and becomes transparent below the transition temperature, but above the transition temperature, causes phase separation and insolubilization in water, and the solution becomes cloudy. Can be used as a thermoresponsive polymer. Furthermore, since this copolymer contains a specific amino acid group, the phase separation behavior changes depending on the pH, and the aqueous solution does not undergo phase separation in the range of pH 4 to 10 over both acidic and alkaline regions. Maintains transparency and exhibits a unique behavior of causing phase separation and turbidity in the vicinity of acidity of pH 4 or less and alkalinity of pH 10 or more. Also, this copolymer is
The phase transition temperature is relatively low, the phase transition is performed over both acidic and alkaline regions, the transparent pH region is relatively wide, and the boundary between the transparent pH region and the opaque pH region is clear. As such, it exhibits a sharp thermal response and pH response.

Furthermore, the gelled product of the copolymer of the present invention, particularly the copolymer having a repeating unit represented by the general formula (II), contains a unique amino acid group, and therefore has a phase transition behavior depending on pH. Changes, and the gel is in a contracted state around pH 4 to 10, but at a pH higher than that, the gel rapidly and largely swells.

Accordingly, such a polymer of the present invention and a gelled product thereof can be used as a sensor or actuator for recognizing temperature, pH, etc., or as a separation material such as a column filler.

[0028]

Next, the present invention will be described in more detail with reference to Reference Examples and Examples. Reference Example [Synthesis of acrylamide monomer containing lysine residue (compound (4)] Compound (4) according to scheme 3 below
Was synthesized.

[0029]

Embedded image

Compound (1) (3.0 g, 10.7 mmol)
1) with a 0.1 N aqueous sodium hydroxide solution (108 m
1, 10.8 mmol) to give an aqueous solution of compound (2). Dioxane (53.5 ml), a 1N aqueous solution of sodium hydroxide (10.7 ml, 10.7 mmol) were added, and the mixture was vigorously stirred. This solution was used as solution A. Acryloyl chloride (compound (3)) (1.21 g, 13.4 mm)
ol) was dissolved in 12 ml of dioxane to prepare solution B.
1N-sodium hydroxide aqueous solution (12.3 ml, 12.
3 mmol), which was designated as solution C. B in an ice bath
The solution and the solution C were divided into four times, added to the solution A every 10 minutes, and stirred for 7 hours. After completion of the reaction, the reaction solution was adjusted to pH 5 using a 1N-hydrochloric acid aqueous solution. Dioxane was distilled off under reduced pressure, and the product was dissolved in methylene chloride. The organic phase was washed with 100 ml of water. Dehydration was performed by adding anhydrous magnesium sulfate, and the mixture was concentrated under reduced pressure, and crystals were precipitated in a hexane-chloroform mixture (180 ml: 20 ml (= 9: 1)). After standing at a low temperature, the mixture was decanted and dried under reduced pressure to obtain a white compound (4). Yield: 1.8 g, Yield: 50.3% 1H-NMR (DMSO, room temperature, δ): 1.2-1.8.
_{(M, (CH 2) 4} , 8H), 4.2-4.3 (m, C
H, 1H), 5.0 (s ,) 5.0 (s, CH 2, 1
H), 5.6 (d, CH 2 = CH, 1H), 6.0-
_{6.4 (m, CH 2 = CH} , 2H), 7.3-7.4
(M, benzene, 5H), elemental analysis: calculated (%): C, 61.1; H, 6.63; N, 8.38,
Found (%): C, 60.2; H, 6.74; N, 8.
14

Example 1 (Scheme 4) [Synthesis of Polymer (6)] The polymer (6) of the present invention (m = 1,500) was synthesized according to the following Scheme 4.

[0032]

Embedded image

1) Polymerization of acrylamide monomer containing lysine residue (compound (4)) Compound (4) (4.7 g, 14 mmol) was dissolved in 20 ml of dimethyl sulfoxide. Α, as a polymerization initiator
α'-azobisisobutyronitrile (23.3 mg,
0.14 mmol) and reacted at 60 ° C. for 24 hours under a nitrogen atmosphere. After returning to room temperature, the mixture was precipitated with water and freeze-dried to obtain a white polymer (5). Yield: 4.11 g, Yield: 87.4%

2) Synthesis of polymer (6) (m = 1,500) of the present invention by removal of protecting group Polymer (5) (2.5 g) was dissolved in 25 ml of acetic acid,
A 25% hydrogen bromide / acetic acid solution (25 ml) was added. After stirring at room temperature for 3 hours, the mixture was concentrated under reduced pressure. The product was dissolved in water and dialyzed. By freeze-drying, a white flocculent polymer (6) (m = 1,500) was obtained. Yield: 1.20 g, yield: 80.7%

Example 2 (Scheme 5) [Synthesis of Copolymer (9) (Compound (7) and Compound (4)
(X = 0.9, y = 0.1) The copolymer (9) of the present invention was synthesized according to the following scheme 5.

[0036]

Embedded image

1) Copolymerization of acrylamide monomer containing lysine residue (compound (4)) and N-isopropylacrylamide (compound (7)) Compound (7) (1.45 g, 12.8 mmol) and compound (4) ) (0.47 g, 1.42 mmol) (molar ratio;
Compound (7): compound (4) = 9: 1) was dissolved in 20 ml of dimethyl sulfoxide. Α, α 'as polymerization initiator
-Azobisisobutyronitrile (23.3 mg, 0.1
4 mmol) and reacted under a nitrogen atmosphere at 60 ° C. for 24 hours. After returning to room temperature, the mixture was precipitated with water and freeze-dried to obtain a white polymer (8). Yield: 1.71 g, Yield: 89.2%

2) Synthesis of the copolymer (9) of the present invention by removing the protecting group The polymer (8) (0.8 g) was dissolved in a 25% hydrogen bromide / acetic acid solution (25.6 ml), and the solution was stirred at room temperature. , And concentrated under reduced pressure. The product was dissolved in water and dialyzed.
By freeze-drying, a white flocculent copolymer (9) (x = 0.
9, y = 0.1; molecular weight 350,000). Yield: 0.64 g, Yield: 85.2%

Example 3 The copolymer (9) obtained in Example 2 was subjected to phase separation of 500 nm light using hydrochloric acid and an aqueous sodium hydroxide solution whose ionic strength was adjusted to 0.01 with sodium chloride as a solvent. The transmittance was examined. FIG. 1 shows the measurement results. pH 4 ~
In No. 10, phase separation occurred at around 48 to 50 ° C., and the solution became cloudy, so that the transmittance decreased. At pH 3.5 and 10.6, the phase separation temperature increases and pH 2 and pH 12
No phase separation was observed and the solution remained clear. The point at which the transmittance of light at 500 nm became 50% was defined as the phase separation temperature, and the results of examining the pH responsiveness of the copolymer (9) are shown in FIG. For comparison, Patent 30442
The relationship between the phase transition temperature and the pH of the copolymer (A) having a repeating unit represented by the following general formula (V), which was synthesized in Example 1 of No. 99, and was similarly measured is shown.

[0040]

Embedded image

As can be seen from FIG. 2, the aqueous solution of the copolymer (9) of the present invention has a transition temperature of 4 at pH 4-10.
It shows a substantially constant value of 8 to 50 ° C., below which the amino group or carboxyl group is dissociated,
The transition temperature is rapidly increasing due to the increased hydrophilicity. On the other hand, the aqueous solution of the polymer (A) has a pH of 4 to 8, the transition temperature shows an almost constant value of 54 to 57 ° C., and at a lower pH or higher, an amino group or a carboxyl group dissociates. However, the transition temperature sharply increased due to an increase in hydrophilicity, but no rapid rise in the transition temperature as in the copolymer (9) was observed. Therefore, it was found that the copolymer (9) of the present invention exhibited a sharper pH response than that of the copolymer (A) described in Japanese Patent No. 3044299.

Example 4 Synthesis of Gelled Copolymer (11) (Gelatinized Copolymer (9)) 1) Acrylamide-based monomer containing lysine residue (compound (4)) and N-isopropylacrylamide Synthesis of Gelled Copolymer (10) of (Compound 7) NIPAAm (Compound (7)) (0.73 g, 6.42)
mmol) and compound (4) (0.24 g, 0.71 mm)
ol) (NIPAAm: compound (4) = 9: 1) was dissolved in 6.2 ml of dimethyl sulfoxide. Α, α'-azobisisobutyronitrile (11.
8 mg, 0.07 mmol) N, N'-methylenebisacrylamide (11.0 mg, 0.07 m
mol) and purged with nitrogen.
The reaction was performed at 24 ° C. for 24 hours. After returning to room temperature, the gel was repeatedly washed with water to obtain a gelled copolymer (10).

2) Synthesis of the gelled copolymer (11) of the present invention by removing the protecting group The washed gelled copolymer (10) was immersed in 100 ml of acetic acid, and 30 ml of a 25% hydrogen bromide / acetic acid solution was added. In addition, it was left at room temperature for 5 hours. After the completion of the reaction, the gel was repeatedly washed with water to obtain a gelled copolymer (11).

Example 5 Swelling degree change at room temperature of the gelled copolymer (11) obtained in Example 4 using hydrochloric acid and an aqueous solution of sodium hydroxide adjusted to an ionic strength of 0.01 with sodium chloride as a solvent. It was investigated. FIG. 3 shows the measurement results. Swelling degree d / do
Was determined at each pH from the diameter d of the gel at 25 ° C. and the inner diameter do of the glass tube from which the gel was synthesized. In addition,
For comparison, a similar measurement was performed on a gelled product of the copolymer (A) having a repeating unit represented by the above general formula, which was synthesized in Example 1 of Japanese Patent No. 30444299, and the results are shown in FIG. Also described. From FIG. 3, it can be seen that the gelled copolymer (11) of the present invention exhibits a substantially constant degree of swelling at pH 4 to 9, and at lower and higher pHs, amino groups or carboxyl groups are dissociated, and The degree of swelling of the gel has increased sharply due to the increase in On the other hand, the gelled product of the polymer (A) was in a contracted state in the pH range of 4 to 8, but had a minimum value near pH 6, and the swelling degree was slightly increased at pH below and above. did. pH 4 or less, p
In the case of H9 or more, the amino group or carboxyl group was dissociated and the hydrophilicity increased, so that the swelling rate of the gel increased, but the rate of increase was lower than that of the copolymer gel compound (11). Therefore, the gelled product of the copolymer (11) of the present invention can be obtained by using the copolymer (A) described in Japanese Patent No. 3044299.
It was found to show a sharper pH response than that of

Next, the volume change of the gelled copolymer (11) with the temperature change in each pH solution was examined. The results are shown in FIG. It was found that in a solution having a pH of 2, 6, or 12, the gel continuously contracted with an increase in temperature. Therefore, it was found that the volume of the copolymer gel (11) changes not only by a change in pH but also by a change in temperature.

[0046]

(1) Since the aqueous solution of the homopolymer having a repeating unit represented by the general formula (I) of the present invention reversibly changes in viscosity and electric properties due to pH change, It can be used as a responsive polymer material. (2) The gelled product swells greatly in an aqueous solution, swells at a temperature lower than the transition temperature, and exhibits a phase transition phenomenon of contraction at a temperature higher than the transition temperature, so that it can be used as a thermoresponsive polymer. (3) An aqueous solution of the copolymer of the present invention, particularly a copolymer having a repeating unit represented by the general formula (II), is dissolved in water at a temperature lower than the transition temperature and becomes transparent. ,
Since phase separation occurs and becomes insoluble in water and the solution becomes cloudy, it can be used as a thermoresponsive polymer. Furthermore, since this copolymer contains a specific amino acid group,
Changes the phase separation behavior, and the aqueous solution maintains transparency without causing phase separation in the range of pH 4 to 10 over both acidic and alkaline regions, and has an acidity of pH 4 or less and a pH of 1 or less.
It shows a unique behavior in which phase separation occurs in the vicinity of alkalinity of 0 or more and cloudiness occurs. In addition, this copolymer has a relatively low phase transition temperature, has a phase transition over both acidic and alkaline regions, has a relatively wide transparent pH region, and further has a transparent pH state and a cloudy state. Since the boundary of the pH range is clear, it shows a sharp thermal response and pH response. (4) A gel of the copolymer of the present invention, in particular, of the general formula (II)
In the gelled product of the copolymer having a repeating unit represented by the following, since a unique amino acid group is included, the phase transition behavior changes depending on the pH, and it is in a contracted state around pH 4 to 10, but more. At a pH below that, the gel swells sharply and greatly. (5) Accordingly, such a polymer of the present invention and a gelled product thereof are effective as a thermoresponsive polymer material and a pH responsive polymer material that recognize temperature, pH, and the like. Alternatively, it can be used as a separation material such as a column packing material.

[Brief description of the drawings]

FIG. 1 is a graph showing the pH dependence of the transmittance of the aqueous copolymer solution of the present invention.

FIG. 2 is a graph showing the relationship between the phase transition temperature and the pH of the aqueous copolymer solution of the present invention.

FIG. 3 is a graph showing the relationship between the degree of swelling and the pH of the gelled copolymer of the present invention.

FIG. 4 is a graph showing a change in the degree of swelling of a gelled copolymer of the present invention with a change in temperature at each pH.

Claims (6)

[Claims] 1. A polymer comprising a repeating unit represented by the following general formula (I). Embedded image (R in the formula is a hydrogen atom or a methyl group, n is an integer of 1 to 4, and m indicates the degree of polymerization.) 2. A homopolymer containing a repeating unit represented by the above general formula (I). 3. A copolymer containing a repeating unit represented by the following general formula (II). Embedded image (Wherein, R and n have the same meaning as described above.
Represents a hydrogen atom or a lower alkyl group, and Q2 represents a lower alkyl group. x and y indicate the mole fraction of each component in the copolymer. ) 4. A gelled product obtained by crosslinking the polymer according to claim 1. 5. A thermoresponsive polymer material comprising the polymer or gelled product according to claim 1. 6. A pH-responsive polymer material comprising the polymer or gel of any one of claims 1 to 4.