JP5097990B2 - N-acryloylazetidine polymer and method for producing the same - Google Patents

Description

  The present invention relates to a novel water-soluble polymer having an azetidine group and a method for producing the same. Specifically, the present invention relates to an acrylamide polymer that can be used in a wide range of applications such as a curing (crosslinking) system such as a water-based adhesive, paint, and sealing agent, and a method for producing the same.

  Among acrylamides, monoalkyl-substituted acrylamide polymers have specific properties such as LCST behavior with cloud point in aqueous solution, so they can be used as high value-added polymers such as medical materials and intelligent materials. Has been studied. As a representative example, poly (N-isopropylacrylamide) has been reported as a research example by RAFT polymerization using a dithioester (Non-patent Document 1). On the other hand, N, N-dialkylacrylamide, which is a disubstituted product, has a small industrial production, but N, N-dimethylacrylamide (Non-patent Document 2) and N, N-diethylacrylamide (Non-patent Document) exhibiting water solubility. Many basic studies on the polymer of literature 3) have been made. In addition, the anionic polymerization of N, N-dialkylacrylamide has succeeded in obtaining a polymer having a narrow molecular weight distribution and a designed molecular weight under controlled polymerization conditions. Furthermore, in recent years, research has been made with an emphasis on the control of primary structure by living polymerization. In living polymerization, no termination reaction or chain transfer reaction occurs, and the growth terminal remains active even after the monomer is completely consumed, so it is possible to synthesize polymers with the molecular weight and molecular weight distribution as designed. is there. As a reported example so far, we succeeded in obtaining poly (N-isopropylacrylamide) with controlled primary structure by conducting living anionic polymerization of N-methoxymethyl-N-isopropylacrylamide and then deprotecting under acidic conditions. (Non-Patent Document 4). N, N-dimethylacrylamide, N, N-diethylacrylamide, and N, N-ethylmethylacrylamide also polymerize weak Lewis acids such as dialkylzinc (Non-patent document 5) and trialkylboron (Non-patent document 6). By adding it to the system, living anionic polymerization is stably advanced to obtain a polymer. Thus, many studies have been conducted on N, N-dialkylacrylamides so far. However, among N, N-dialkylacrylamides, there are few reports on the polymerizability to acrylamides in which the amide nitrogen forms a heterocycle.

  Accordingly, an object of the present invention is to obtain a polymer having a controlled primary structure in the anionic polymerization of N-acryloylazetidine (AAzt), which is an acrylamide having a 4-membered ring, which has not been reported so far.

F. Gannachaud, E. Rizzardo, Macromolecules, 33, 6738 (2000). X. Xie, T.E.Hogen-Esch, Macromolrcules, 29, 1746 (1996). S. Katayama, Y. Hirokawa, T. Tanaka, Macromolecules, 17, 2641 (1984). M. Ito, T. Ishizone, J. Polym. Sci., Part A: Polym Chem, 44, 4832 (2006). M. Kobayashi, S. Okuyama, T. Ishizone, S. Nakahama, Macromolecules, 32, 6466 (1999). M. Kobayashi, T. Ishizone, S. Nakahama, Macromolecules, 32, 4411 (2000).

  An object of the present invention is to synthesize a poly (N-acryloylazetidine) derivative with a narrow molecular weight distribution, controlled molecular weight, and a clear chemical structure by polymerization of an N-acryloylazetidine derivative, particularly anionic polymerization. The purpose (problem) is to establish a novel acrylamide polymer that can be used in a wide range of applications such as curing (crosslinking) systems such as coatings, sealants, and the like, and a method for producing the same.

As a result of various studies to solve the above problems, the present inventors have conducted anionic polymerization of an acrylamide derivative having an azetidine ring in which two alkyl groups of N, N-dialkyl are bonded to each other to form a ring. The inventors have found that the resulting polymer has a narrow molecular weight distribution, a controlled molecular weight, and a clear chemical structure, and reached the present invention.
That is, the present invention provides the following (1) to (7) poly (N-acryloylazetidine) derivatives and methods for producing the derivatives.

(1) having a repeating unit represented by the following general formula (I), a number average molecular weight (M _n ) of 2,000 to 1,000,000, and a molecular weight distribution (M _w / M _n , A poly (N-acryloylazetidine) derivative having _Mw of 3.0 or less by weight average molecular weight.

(In the formula, R _{1 to} R ₆ are each independently selected from a hydrogen atom, a methyl group, and an ethyl group, and at least four of R _{1 to} R ₆ are hydrogen atoms. Of the azetidine skeleton in the polymer molecule. R _{1 to} R ₆ may be different for each repeating unit.)

(2) The poly (N-acryloylazetidine) derivative according to (1) having a molecular weight distribution ( _Mw / _Mn ) of 1.5 or less.
(3) A method for producing a poly (N-acryloylazetidine) derivative according to the above (1) or (2), wherein an N-acryloylazetidine derivative represented by the following general formula (II) is subjected to addition polymerization.

(In the formula, R _{1 to} R ₆ are each independently selected from a hydrogen atom, a methyl group, and an ethyl group, and at least four of R _{1 to} R ₆ are hydrogen atoms.)

(4) A method for producing a poly (N-acryloylazetidine) derivative according to (3), wherein the polymerization mechanism of the addition polymerization is anionic polymerization.
(5) The monomer solution concentration during the anionic polymerization of the N-acryloylazetidine derivative represented by the general formula (II) as a monomer was 0.5 mol / liter or less (4 ) Of poly (N-acryloylazetidine) derivatives.
(6) A process for producing a poly (N-acryloylazetidine) derivative according to (4) or (5), wherein anionic polymerization is performed at a reaction temperature of −100 ° C. to 20 ° C.
(7) 0.1 to 0.5 mol of dialkyl zinc is added as an anionic polymerization additive to 1 mol of N-acryloylazetidine derivative represented by the general formula (2) (3) to (6) A process for producing a poly (N-acryloylazetidine) derivative according to any of the above.

  N-acryloyl azetidine polymer with clear primary structure and high water solubility has a wide range of surface treatment agents, paints, adhesives, coating agents, sealing agents, coagulant curing (crosslinking) systems, etc. Available for use.

  The poly (N-acryloylazetidine) derivative of the present invention (hereinafter sometimes referred to as “polymer”) has a repeating unit represented by the following general formula (I).

In the formula, R _{1 to} R ₆ are each independently selected from a hydrogen atom, a methyl group, and an ethyl group, and at least four of R _{1 to} R ₆ are hydrogen atoms. R _{1 to} R ₆ of the azetidine skeleton in the polymer molecule may be different for each repeating unit.

The number average molecular weight (M _n ) of the poly (N-acryloylazetidine) derivative of the present invention is 2,000 to 1,000,000, preferably 10,000, from the viewpoints of purification and handling properties of the polymer. ~ 500,000.

The molecular weight distribution (M _w / M _n , M _w is the weight average molecular weight) of the poly (N-acryloylazetidine) derivative of the present invention must be 3.0 or less, preferably 1.5 or less. Preferably it is 1.2 or less. By setting the molecular weight distribution (M _w / M _n ) to 3.0 or less, basic properties such as polymer solubility, melting point, and glass transition point are clarified. Setting of the amount of blending becomes easy. In particular, when the molecular weight distribution (M _w / M _n ) is narrowed to 1.2 or less, the content of azetidinyl groups in the polymer becomes clearer, so that adhesives, paints, sealing agents, etc. This makes it easier to design a more precise curing (crosslinking) system.

Next, the manufacturing method of the poly (N-acryloyl azetidine) derivative of this invention is demonstrated.
The poly (N-acryloylazetidine) derivative of the present invention is produced by addition polymerization of a monomer which is an N-acryloylazetidine derivative represented by the following general formula (II).

In the formula, R _{1 to} R ₆ are each independently selected from a hydrogen atom, a methyl group, and an ethyl group, and at least four of R _{1 to} R ₆ are hydrogen atoms.

A monomer of this polymer, that is, a monomer that is an N-acryloylazetidine derivative represented by the general formula (II) can be produced by a known method.
In the method for producing N-substituted acrylamide or methacrylamides of JP-B-4-65059 and the references cited therein, the N-acryloylazetidine derivative monomer is represented by the following general formula (III). Methacrylic acid halide

(Wherein X represents a chlorine atom or a bromine atom)
An azetidine derivative (IV) represented by the following general formula:

(In the formula, R _{1 to} R ₆ are each independently selected from a hydrogen atom, a methyl group, and an ethyl group, and at least four of R _{1 to} R ₆ are hydrogen atoms.)
And trialkylamines or the like as reaction aids, which can be produced by reaction.
Specific examples of the N-acryloylazetidine derivative of the present invention include N-acryloylazetidine, N-acryloyl-2-methylazetidine, N-acryloyl-3-ethylazetidine, N-acryloyl-2,4. -Diethylazetidine, N-acryloyl-2-methyl-2-ethylazetidine, N-acryloyl-3,3-dimethylazetidine, N-acryloyl-3,3-diethylazetidine and the like.

  In the production of the poly (N-acryloylazetidine) derivative of the present invention, it is necessary to use a high-purity monomer as a raw material, and a product purified by vacuum distillation or vacuum distillation is preferably used. In this purification distillation, it is preferable to use methylene blue as a polymerization inhibitor and calcium hydride as a dehydrating agent.

  The polymerization method that can be employed in the addition polymerization step is not necessarily limited to a specific polymerization method. For example, a normal radical polymerization method, a SFRP (Stable Free Radical Polymerization) method, a RAFT (Reversible Addition-Fragmentation Transfer) weight Examples thereof include a legal method, an ATRP (Atom Transfer Radical Polymerization) method, a GTP (Group Transfer Polymerization) method, and an anionic polymerization method. Among these, the anionic polymerization method is preferable from the viewpoint that the obtained polymer has a narrow molecular weight distribution and the polymerization conversion rate of the monomer is high.

  As a polymerization method, when a radical polymerization method such as a normal radical polymerization method, SFRP method, RAFT polymerization method, ATRP method, or GTP method is employed, a known polymerization initiator or solvent may be used in each polymerization method. it can. Examples of the initiator used in the radical polymerization method include 2,2′-azobisisobutyronitrile (see J. Am. Chem. Soc., 123, 7180-7181 (2001)), solvent. Examples thereof include toluene and ethyl acetate.

  The polymerization initiator used in the anionic polymerization method is not necessarily limited to a specific one, and a known anionic polymerization initiator can be used. For example, an organic lithium compound, an organic sodium compound, an organic potassium And organic metal compounds such as organic magnesium compounds.

  Among these anionic polymerization initiators, in terms of high polymerization initiation efficiency and smooth progress of the polymerization reaction, alkyl lithium, aryl lithium, aralkyl lithium, alkyl sodium, aryl sodium, aralkyl sodium, alkyl potassium, aryl Potassium, aralkyl potassium, alkyl cesium, aryl cesium, and aralkyl cesium are preferable. Among them, s-butyl lithium, t-butyl lithium, diphenylmethyl lithium, diphenylmethyl potassium, 1,1-diphenyl-3-methylpentyl lithium (s-butyl) 1: 1 adduct of lithium and 1,1-diphenylethylene), sodium naphthalene, potassium naphthalene, diphenylmethylpotassium, diphenylmethylcesium, triphenylmethylcesium Particularly preferred.

  As an anionic polymerization initiator, one kind of the above polymerization initiators may be used alone, or two or more kinds may be used in combination. Although the usage-amount of a polymerization initiator is not necessarily limited, It is using a polymerization initiator in the ratio used in the range of 0.01-5 mol with respect to a total of 100 mol of the monomer to be used, It is preferable from the viewpoint that the intended polymer can be produced smoothly.

  In the polymerization, it is preferable to use a solvent in order to make the polymerization system uniform. Examples of such solvents include aliphatic hydrocarbons such as pentane, n-hexane, and octane; alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane; benzene, toluene, ethylbenzene, and xylene. Aromatic ethers such as diethyl ether, tetrahydrofuran, 1,4-dioxane, anisole, diphenyl ether and the like. Among these, from the viewpoint of excellent solubility of the polymerization initiator, raw material monomer, organic compound as a co-catalyst, polymer, and the like, the ether compound is preferably used. 4-dioxane is particularly preferred. These organic solvents may be used alone or in combination of two or more.

In anionic polymerization, additives usually used in the polymerization system may be added for the purpose of promptly proceeding the polymerization or narrowing the molecular weight distribution. Examples of the additive include dialkyl zinc such as dimethyl zinc and diethyl zinc, Lewis acids such as triethylaluminum, trihexylaluminum, trioctylaluminum, triethylboron and triphenylboron, dimethyl ether, dimethoxyethane, diethoxyethane, 12 -Ether compounds such as crown-4,15-crown-5,18-crown-6; trimethylamine, N, N, N ', N'-tetramethylethylenediamine, N, N, N', N ", N"- Organic nitrogen compounds such as pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine, pyridine, 2,2′-dipyridyl; triethylphosphine, triphenylphosphine, 1,2-bis (diphenyl) Phosphino) ethane, etc. Organic phosphorus compounds; inorganic salts such as lithium chloride, sodium chloride and potassium chloride; alkoxide compounds such as lithium (2-methoxyethoxy) ethoxide and potassium t-butoxide; tetraethylammonium chloride, tetraethylammonium bromide, tetraethylphosphonium chloride, tetraethylphosphonium bromide Organic quaternary salts such as sodium tetraphenylborate, organic boron compounds such as tetrakis (pentafluorophenyl) sodium borate, and the like, and dialkylzinc is particularly preferable. These additives may use only 1 type and may use 2 or more types together. The addition amount of the additive is 1.0 to 50 mol, preferably 2.5 to 40 mol, relative to 1.0 mol of the anionic polymerization initiator. Moreover, 0.1-0.5 mol is preferable with respect to 1 mol of N-acryloyl azetidine derivatives, and, as for the addition amount of dialkyl zinc, 0.2-0.4 mol is more preferable.
The monomer solution concentration at the time of anionic polymerization is preferably 0.5 mol / liter or less in order to prevent precipitation of the monomer and allow the polymerization to proceed rapidly. The lower limit of the monomer solution concentration is usually about 0.05 mol / liter.

  The polymerization reaction is preferably carried out under a high vacuum or in an inert gas atmosphere such as nitrogen, argon, helium, etc., regardless of the polymerization mode (radical polymerization, anionic polymerization, etc.). Moreover, it is preferable to perform the polymerization under sufficient stirring conditions so that the polymerization reaction system becomes uniform. The temperature of the reaction system during the polymerization is preferably 40 to 120 ° C., more preferably 50 to 100 ° C. in the case of radical polymerization, and preferably −100 to 20 ° C., more preferably −80 in the case of anionic polymerization. -10 ° C. The polymerization time is not limited, but is usually 30 minutes to 120 hours, preferably 1 to 80 hours.

In the present invention, for example, the polymerization reaction can be stopped by adding a polymerization terminator to the reaction mixture at the stage where a polymer having a target molecular weight is formed by an anionic polymerization reaction. As the polymerization terminator, for example, a protic compound such as methanol, isopropanol, acetic acid, hydrochloric acid in methanol, or the like can be used. Although the usage-amount of a polymerization terminator is not specifically limited, Generally, it is preferable to use in the ratio used in the range of 1-100 mol with respect to 1 mol of used polymerization initiators.
The method for separating and obtaining the target N-acryloylazetidine-based polymer from the reaction mixture after stopping the polymerization reaction is not particularly limited, and any method according to a known method can be employed. For example, a method of pouring the reaction mixture into a poor solvent of the polymer to obtain the polymer by precipitation, a method of obtaining the polymer by distilling off the solvent from the reaction mixture, or the like can be employed.

In the production method of the poly (N-acryloylazetidine) derivative of the present invention, complicated steps such as introduction of a protecting group into the monomer and deprotection of the polymer are unnecessary, and only the vinyl polymer is efficiently used. Can be manufactured well.
The poly (N-acryloylazetidine) derivative of the present invention has a structure in which a double bond of an acryloyl group is vinyl-polymerized without opening an azetidine ring during polymerization. Since the azetidine ring is retained, the azetidine ring can be used for a wide range of applications such as curing (crosslinking) systems such as aqueous adhesives, paints, and sealing agents by utilizing the ring-opening reaction of the azetidine ring.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, the measuring method of the physical-property value in each Example is as follows.
In (a) and (b), a nuclear magnetic resonance apparatus (NMR) having the following specifications was used.
Equipment: BRUKER GPX300 (300 MHz)
Deuterated solvent: deuterated chloroform (CDCl ₃ ) ( ¹ H: 7.26 ppm, ¹³ C: 77.1 ppm)

(A) Confirmation of chemical structure In order to confirm the chemical structure of the monomer (N-acryloylazetidine) and its polymer, ¹ H-NMR and ¹³ C-NMR of each sample were measured.
(B) Number average molecular weight (M _n )
It was calculated from the area ratio between the terminal functional group moiety and the functional moiety included in the repeating structural units of the polymer obtained from the ¹ H-NMR measurement of the polymerization initiator.
In addition to the actual value (actual molecular weight) of the number average molecular weight (M _n ) calculated by the ¹ H-NMR measurement, it is calculated from the terminal functional group portion of the polymerization initiator and the monomer / polymerization initiator molar ratio. The calculated molecular weight (design molecular weight) was obtained, and it was confirmed whether the molecular weight was obtained as designed.
(C) Molecular weight distribution (M _w / M _n )
In the following gel permeation chromatograph (GPC apparatus), N, N-dimethylformamide (DMF, 0.01 mol / L lithium bromide added product) is used as the mobile phase, the column temperature is 40 ° C., and the liquid feed rate is 1.0 mL. / Min and converted using standard polystyrene (M _n = 36900, 9610).
Equipment: TOSOH HLC-8120 (DMF solvent), column: TSK-GEL GMH _XL x 2 + G ₂₀₀₀ H _XL (both equipment and column are manufactured by Tosoh Corporation)

Example 1
(1) Synthesis of monomer (N-acryloylazetidine) In a 500 mL two-necked flask under a nitrogen atmosphere, an aqueous potassium hydroxide solution (17.9 g (319 mmol) of KOH dissolved in 10 mL of water) And azetidine hydrochloride (15.2 g / 162 mmol) was further added while cooling in an ice bath. Then, while maintaining the temperature at 100 ° C. or lower, it was heated to obtain 6.57 g (115 mmol, yield 71%) of azetidine. Subsequently, 20.8 g (113 mmol) of triethylamine was added to 5.03 g (88.1 mmol) of the obtained azetidine. This mixture was added dropwise to a solution of 10.7 g (118 mmol) of acrylic acid chloride diluted with 200 mL of diethyl ether in an ice bath. After completion of the addition, 20 mL of diethyl ether was further added and reacted at room temperature for 3 hours. After confirming completion of the reaction by gas chromatography, newly generated triethylamine hydrochloride was removed by suction filtration. The filtrate was concentrated with an evaporator to remove the solvent. Subsequently, the obtained reaction solution was washed twice each with a saturated aqueous NaHCO ₃ solution and a saturated aqueous NaCl solution, dried over anhydrous magnesium sulfate, and then distilled under reduced pressure (bp 40-42 ° C./0.35 in the presence of calcium hydride). mmHg) was repeated to obtain 3.71 g (33.4 mmol, 38% yield) of N-acryloylazetidine as a colorless and transparent liquid.

(2) Purification of monomer The obtained N-acryloylazetidine fraction was distilled from a calcium hydride in the presence of calcium hydride on a high vacuum line, and then diluted with tetrahydrofuran and sealed in an ampoule equipped with a break seal. . The last distillation fraction obtained here was subjected to ¹ H-NMR and ¹³ C-NMR measurements and elemental analysis. FIG. 1 shows the measurement result of ¹ H-NMR, and FIG. 2 shows the measurement result of ¹³ C-NMR. ^A , b, c, etc. attached to the signal of the ¹ H-NMR spectrum belong to the hydrogen atom to which the subscripts a, b, c, etc. of the structural formula described in the spectrum are attached, ^“A” , “b”, “c”, etc. attached to the signal of the ¹³ C-NMR spectrum are attributed to the carbon atoms to which the subscripts “a”, “b”, “c”, etc. of the structural formula described in the spectrum are attached. From these ¹ H-NMR and ¹³ C-NMR measurement results and elemental analysis, it was confirmed that the fraction was the target N-acryloylazetidine C ₆ H ₉ NO. Further, the fraction was confirmed to be almost a single component with a purity of 99.9% or more by gas chromatography.

(3) Polymerization of monomer The purified N-acryloylazetidine obtained in (2) above was polymerized by anionic polymerization according to the break seal method at -78 ° C. for 2 hours under a high vacuum of 10 ⁻⁶ mmHg. . Diphenylmethyllithium was used as the polymerization initiator, and tetrahydrofuran was used as the solvent. Further, diethyl zinc was added as an additive to the polymerization system. After anionic polymerization for 2 hours, the glass polymerization vessel was opened, and a small amount of isopropanol was added to terminate the polymerization. Further, the obtained polymerization solution was poured into a large amount of diethyl ether to precipitate the polymer. The precipitated polymer was filtered off and dried, and the yield was measured. The dried polymer was redissolved in tetrahydrofuran and poured into a large amount of diethyl ether for reprecipitation purification. Finally, after dissolving in benzene, freeze-drying was performed, and ¹ H-NMR and ¹³ C-NMR measurements and elemental analysis were performed. Table 1 shows the measurement conditions and polymerization results, the number average molecular weight (M _n ), and the measurement results of molecular weight distribution. 3 shows the measurement result of ¹ H-NMR of the purified polymer, and FIG. 4 shows the measurement result of ¹³ C-NMR. ^A , b, c, etc. attached to the signal of the ¹ H-NMR spectrum belong to the hydrogen atom to which the subscripts a, b, c, etc. of the structural formula described in the spectrum are attached, ^“A” , “b”, “c”, and the like attached to the signal of the ¹³ C-NMR spectrum belong to the carbon atom to which the subscripts “a”, “b”, “c”, etc. of the structural formula described in the spectrum are attached. From these ¹ H-NMR and ¹³ C-NMR measurement results and elemental analysis, it was confirmed that the obtained polymer was poly (N-acryloylazetidine) polymerized only with an acryloyl group.

Example 2
In the polymerization of the monomer (3) of Example 1, anionic polymerization was carried out under the same polymerization conditions as in Example 1, except that the polymerization temperature was 0 ° C., the polymerization time was 24 hours, and diphenylmethyl potassium was used as the polymerization initiator. went. The polymerization conditions and polymerization results are shown in Table 1.

Examples 3-5
In the polymerization of the monomer (3) of Example 1, diphenylmethyllithium was used as the polymerization initiator in the same manner as in Example 1, and the amount of initiator, the amount of additive, the polymerization temperature, and the polymerization time were set as shown in Table 2. Anionic polymerization was carried out by changing. The polymerization conditions and polymerization results are shown in Table 2.

Examples 6-7
In the polymerization of the monomer (3) in Example 1, diphenylmethyl potassium was used as a polymerization initiator, and as shown in Table 2, the amount of the initiator, the amount of the additive, the polymerization temperature and the polymerization time were changed to perform anionic polymerization. It was. The polymerization conditions and polymerization results are shown in Table 2.
Examples 8-9
In the polymerization of the monomer (3) of Example 1, without addition of an additive, the amount of initiator and the polymerization were as shown in Table 2 for the case of diphenylmethyllithium and diphenylmethylpotassium as the polymerization initiator, respectively. Anionic polymerization was carried out at different temperatures and polymerization times. The polymerization conditions and polymerization results are shown in Table 2.

As described above, a polymer having a narrow molecular weight distribution M _w / M _n of 1.06 to 1.29 can be obtained by controlling the amounts of monomers, initiators and additives, reaction temperature and reaction time. I was able to. Even when no additive is used, a polymer can be obtained, but the molecular weight distribution is wider than when an additive is added.

Is a chart showing the results of ¹ H-NMR of the obtained in Example 1 (2) N-acryloyl-azetidine monomers. It is a chart which shows the measurement result of ¹³ C-NMR of the N-acryloyl azetidine monomer obtained in Example 1 (2). It is a chart which shows the measurement result of < ¹ > H-NMR of the poly (N-acryloyl azetidine) obtained in Example 1 (3). It is a chart which shows the measurement result of < ¹³ > C-NMR of the poly (N-acryloyl azetidine) obtained in Example 1 (3).

  The novel N-acryloylazetidine-based polymer of the present invention can be used in a wide range of applications such as aqueous adhesives, paints, and curing (crosslinking) systems such as sealing agents.

Claims (6)

It has a repeating unit represented by the following general formula (I), has a number average molecular weight ( _Mn ) of 2,000 to 1,000,000, and a molecular weight distribution ( _Mw / _Mn , _Mw) N-acryloyl azetidine homopolymer having a weight average molecular weight of 1.5 or less.

(In the formula, R _{1 to} R ₆ are each independently selected from a hydrogen atom, a methyl group, and an ethyl group, and at least four of R _{1 to} R ₆ are hydrogen atoms. Of the azetidine skeleton in the polymer molecule. R _{1 to} R ₆ may be different for each repeating unit.) The method for producing an N-acryloylazetidine homopolymer according to claim 1, wherein an N-acryloylazetidine derivative represented by the following general formula (II) is subjected to addition polymerization.

(In the formula, R _{1 to} R ₆ are each independently selected from a hydrogen atom, a methyl group, and an ethyl group, and at least four of R _{1 to} R ₆ are hydrogen atoms.) The method for producing an N-acryloylazetidine homopolymer according to claim 2, wherein the polymerization mechanism of the addition polymerization is anionic polymerization. Claim 3 monomer solution concentration when performing anionic polymerization of N- acryloyl azetidine derivative represented by the general formula (II) is a monomer was set to be less than 0.5 mol / l Of producing an N-acryloylazetidine homopolymer . The method for producing an N-acryloylazetidine homopolymer according to claim 3 or 4 , wherein anionic polymerization is performed at a reaction temperature of -100 ° C to 20 ° C. According to any one of claims 3-5 for adding 0.1 to 0.5 moles of dialkyl zinc respect N- acryloyl azetidine derivative 1 mol of the general formula (II) as an additive for anionic polymerization Of producing an N-acryloylazetidine homopolymer .

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