Method of producing network polymer gel having inclusion structure

Abstract

To provide a method of producing a network polymer gel having an inclusion structure composed of a crown ether derivative and a secondary ammonium salt compound, which can reduce environmental load by eliminating or reducing a use amount of volatile organic compounds.SOLUTION: A method of producing a network polymer gel having an inclusion structure composed of a crown ether derivative and a secondary ammonium salt compound comprises forming an inclusion structure composed of a crown ether derivative and a secondary ammonium salt compound in the presence of an organic solvent containing sulfolane and / or a sulfolane derivative, and simultaneously forming a gel.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a network polymer gel having an inclusion structure of a crown ether derivative and a secondary ammonium salt compound. [Background technology]

[0002] Compounds in which a cyclic molecule incorporates a linear molecule into its cavity to form a threaded structure (also called inclusion compounds or inclusion complexes) are called rotaxanes or pseudo-rotaxanes. Because of the property that the cyclic molecule can move along the linear molecule, many types and combinations of cyclic and linear molecules have been reported.

[0003] Also, attempts have been made to polymerize rotaxanes or pseudorotaxanes by linking them together using a spacer component such as dithiol, thereby producing a crosslinked polyrotaxane that has unique physical properties as a compound without covalent bonds, as a network polymer gel. As for the network polymer gel, the present inventors have been actively conducting research on a network polymer gel using a 24-membered crown ether derivative as the cyclic molecule and a secondary ammonium salt compound as the linear molecule (see Patent Document 1).

[0004] A complex is formed spontaneously between a crown ether derivative and a secondary ammonium salt compound due to a specific interaction, generally hydrogen bond or electrostatic interaction. In order to complete the formation of such a complex, it is necessary to perform the formation of the complex in the presence of a specific organic solvent, and the characteristics required for the specific organic solvent include not inhibiting the interaction (hydrogen bond, electrostatic interaction) between the crown ether derivative and the secondary ammonium salt compound, and being able to dissolve the crown ether derivative and the secondary ammonium salt compound. In general, solvents with high polarity or dielectric constant ε tend to inhibit the interaction between the crown ether derivative and the secondary ammonium salt compound. As the organic solvent used for forming the complex, Patent Document 1 uses dichloromethane (dielectric constant 9.1, boiling point 40°C) and chloroform (dielectric constant 4.8, boiling point 61°C), Non-Patent Document 1 states that dichloromethane (mentioned above) and acetonitrile (dielectric constant 36.0, boiling point 82°C) can be used, Non-Patent Document 2 states that dichloromethane (mentioned above), acetonitrile (mentioned above), benzene (dielectric constant 2.3, boiling point 80°C), chlorobenzene (dielectric constant 5.7, boiling point 131°C), dioxane (dielectric constant 2.1, boiling point 101°C), chloroform (mentioned above), and toluene (dielectric constant 2.4, boiling point 111°C) can be used, and Non-Patent Document 3 states that chloroform (mentioned above), chlorobenzene (mentioned above), and nitromethane (dielectric constant 36.2, boiling point 101°C) can be used. In contrast, the following solvents are listed as organic solvents in which complexes are not formed or are difficult to form. The inventors confirmed that a rotaxane complex is not formed in N,N-dimethylformamide (DMF) (dielectric constant 37.1, boiling point 153°C), and also confirmed that a rotaxane complex is not formed in dimethyl sulfoxide (DMSO) (dielectric constant 46.71, boiling point 189°C) described in Non-Patent Document 1. It is noted that in a mixed solvent of chloroform and DMSO, even if the mixing ratio of chloroform is changed, rotaxane is difficult to form. Furthermore, Non-Patent Document 3 describes that a complex is not formed in dimethylacetamide (DMAc) (dielectric constant 38.3, boiling point 165°C).

[0005] As described above, all of the organic solvents used to form complexes between crown ether derivatives and secondary ammonium salt compounds have low boiling points and are solvents that correspond to volatile organic compounds (VOCs). Volatile organic compounds are a general term for organic compounds that become gaseous in the atmosphere because they are volatile, and include toluene, which is used as a solvent for paints and printing inks, tetrachloroethylene, which is used for dry cleaning, and general organic solvents used in experiments. In addition, it is known that volatile organic compounds react with ultraviolet rays from the sun to generate harmful photochemical oxidants (Ox) and turn into suspended particulate matter (SPM) and fine particulate matter (PM2.5), which puts a heavy burden on the environment and ecosystem. Therefore, there is a global demand for manufacturing (society building) that eliminates these volatile organic compounds as much as possible. According to the definition of the World Health Organization (WHO), volatile organic compounds are organic compounds with boiling points in the range of 50-100℃ to 240-260℃.

[0006] In addition, for the network polymer gel, a complex is formed between a crown ether derivative and a secondary ammonium salt compound using an organic solvent equivalent to a volatile organic compound to generate a (pseudo)rotaxane, and a stable polymer in which the complex does not dissociate is constructed. Then, the highly volatile organic solvent is temporarily removed from the network polymer gel, and the gel is re-swelled while replacing the solvent with a less volatile organic solvent. Therefore, while it is common to use an organic solvent with high volatility and low polarity that is likely to generate a (pseudo)rotaxane in order to generate a network polymer gel, it is necessary to re-swell the gel using a solvent with a lower volatility than the solvent used to generate the gel in order to maintain the shape of the polymerized gel for a long period of time. In fact, Patent Document 1 also cites the use of organic solvents, such as propionate carbonate, different from the dichloromethane and chloroform used in the formation of the complex for reswelling. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. WO2013 / 099224 [Non-patent literature]

[0008] [Non-Patent Document 1] Sheng-Hsien et al., Org. Lett.,2(23),3631-3634 (2000) [Non-Patent Document 2] Toshikazu Takata et al., Macromolecules, 34, 5449-5456 (2001) [Non-Patent Document 3] Yoshio Furusho et al., Bull. Chem. Soc. Jpn., 77, 179-185 (2004) Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method for producing a network polymer gel having an inclusion structure of a crown ether derivative and a secondary ammonium salt compound, which can reduce the environmental load by eliminating or reducing the amount of volatile organic compounds used. [Means for solving the problem]

[0010] The present inventors have found that sulfolane, which does not correspond to a volatile organic compound and has a dielectric constant of 43 and a boiling point of 285°C, has the property of not inhibiting the interaction between crown ether derivatives and secondary ammonium salt compounds and has the property of being able to dissolve crown ether derivatives and secondary ammonium salt compounds. Based on this, the present inventors have found that the formation of a complex between a crown ether derivative and a secondary ammonium salt compound proceeds in the presence of an organic solvent containing sulfolane and / or a sulfolane derivative, and have completed the present invention.

[0011] That is, the present invention is specified by the following items. (1) A method for producing a network polymer gel having an inclusion structure of a crown ether derivative and a secondary ammonium salt compound, characterized in that an inclusion structure of the crown ether derivative and the secondary ammonium salt compound is formed in the presence of an organic solvent containing sulfolane and / or a sulfolane derivative, and a gel is produced. (2) The method for producing a network polymer gel according to (1), characterized in that the organic solvent used in producing the gel is reswelled with the organic solvent without replacing the organic solvent. (3) The method for producing a network polymer gel according to (1) or (2), wherein the organic solvent is sulfolane. Effect of the Invention

[0012] In the production method of the present invention, no organic solvents corresponding to volatile organic compounds are used or can be reduced in amount, so that the burden on the environment and ecosystem can be reduced. [Brief description of the drawings]

[0013] [Figure 1] 1 shows an outline of a method for producing a network polymer gel having an inclusion structure of a crown ether derivative and a secondary ammonium salt compound according to the present invention. [Diagram 2] 1 shows the appearance of rotaxane gels prepared using sulfolane or chloroform. [Diagram 3] 1 shows the side and top views of rotaxane gels prepared using sulfolane or chloroform and then reswollen with sulfolane. [Figure 4] Side and top views of rotaxane gels prepared using sulfolane or chloroform before and after reswelling with sulfolane, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention relates to a method for producing a network polymer gel having an inclusion structure of a crown ether derivative and a secondary ammonium salt compound. Specifically, the present invention relates to a method for producing a network polymer gel having an inclusion structure by forming a complex between a crown ether derivative and a secondary ammonium salt compound in the presence of an organic solvent containing sulfolane and / or a sulfolane derivative, generating a (pseudo)rotaxane, and subjecting the generated (pseudo)rotaxane to an addition reaction (thiol-ene reaction) using a dithiol compound in an organic solvent containing sulfolane and / or a sulfolane derivative. Furthermore, the present invention relates to a production method in which the organic solvent containing sulfolane and / or a sulfolane derivative is not replaced, and the resulting mixture is reswelled again using an organic solvent containing sulfolane and / or a sulfolane derivative. FIG. 1 shows a conceptual diagram of the method for producing a network polymer gel having an inclusion structure of the present invention. In Figure 1, a 24-membered crown ether derivative (denoted as Wheel) is used as the cyclic molecule, a bis(methacryloyloxyethyl)amine derivative (denoted as Axle) is used as the secondary ammonium salt compound, 3,6-dioxa-1,8-octanedithiol (denoted as DODT) is used as the dithiol compound, and sulfolane (denoted as SL) is used as the organic solvent.

[0015] The crown ether derivative used in the present invention is not particularly limited as long as it can incorporate a secondary ammonium salt compound as a linear molecule into its cavity and form a rotaxane or (pseudo)rotaxane, which is a compound having a threading structure (inclusion compound, inclusion complex), including a 24-membered crown ether.

[0016] The secondary ammonium salt compound used in the present invention is not particularly limited as long as it can be incorporated into the pores of the crown ether derivative to form a rotaxane or (pseudo)rotaxane, which is a compound (clathrate compound, clathrate complex) having a penetrating structure, including an amine derivative. Note that, as the crown ether derivative and secondary ammonium salt compound used in the present invention, not only the crown ether derivatives and secondary ammonium salt compounds described in Patent Document 1, but also the crown ether derivatives and secondary ammonium salt compounds described in Non-Patent Documents 1 to 3 can be referred to.

[0017] In the production method of the present invention, an inclusion structure is formed in the presence of an organic solvent (SVOC solvent) containing sulfolane and / or a sulfolane derivative corresponding to a semi-volatile organic compound (SVOC), and an example of the sulfolane derivative is 3-methylsulfolane (dielectric constant 29, boiling point 279°C). The sulfolane derivative can be used alone or as a mixture with sulfolane. If only an SVOC solvent is used during the formation of the inclusion structure, the amount of organic solvent (VOC solvent) corresponding to a volatile organic compound can be reduced to zero, which is preferable in that the gel of the present invention can be produced without volatilization of VOC into the environment. Furthermore, by using an SVOC solvent, the coloring problem does not occur in the gel produced using a VOC solvent. The amount of the sulfolane derivative in the mixed solvent consisting of sulfolane and a sulfolane derivative is not particularly limited, and can be any amount, such as 0.1 to 99.9% by mass of the total mass of the mixed solvent. In the present invention, the organic solvent containing sulfolane and / or a sulfolane derivative may be an organic solvent containing sulfolane, an organic solvent containing a sulfolane derivative, or an organic solvent containing sulfolane and a sulfolane derivative, and may also be an organic solvent containing sulfolane and / or a sulfolane derivative and other organic solvents, as long as the effects of the present invention are achieved. According to the definition of the World Health Organization (WHO), semi-volatile organic compounds are organic compounds having a boiling point in the range of 240-260°C to 380-400°C. As other organic solvents, any organic solvent may be used as long as it can be included to form a complex to generate a (pseudo)rotaxane, and examples of such organic solvents include VOC solvents such as dioxane, benzene, toluene, chloroform, chlorobenzene, dichloromethane, 1,2-dichloroethane, acetone, and acetonitrile nitromethane. The relative dielectric constant of the VOC solvent is preferably 2 to 36. The boiling point of the VOC solvent is preferably 40 to 140°C, more preferably 40 to 100°C. VOC solvents with a dielectric constant greater than 36 and a boiling point higher than 140°C are less likely to form rotaxane inclusion structures, whereas solvents with a dielectric constant of 36 or less and a boiling point of 140°C or less, with both values ​​as low as possible, tend to reduce the VOC content in the resulting gel.The proportion of the VOC solvent in the solvent may be 0.1 to 50% by mass of the total mass of the solvent, but from the viewpoint of dimensional stability, it is preferable that the proportion is such that even if the VOC solvent evaporates from the generated gel, the shrinkage of the volume is indistinguishable from the appearance, and it is more preferable that the proportion is less than the proportion at which the shrinkage of the volume is indistinguishable from the appearance under the usage environment of the gel, for example, at the usage temperature. From the viewpoint of the dimensional stability of the gel and the viewpoint of reducing the environmental load, the VOC solvent is preferably 0.1 to 5% by mass, more preferably 0.1 to 1% by mass of the total mass of the solvent. Furthermore, if the content of the VOC solvent is such that the shrinkage of the volume is hardly observed, the subsequent removal process (substitution process) of the VOC solvent is simplified or becomes unnecessary.

[0018] In addition, the manufacturing method of the present invention forms an inclusion structure and generates a gel in the presence of an organic solvent containing sulfolane and / or a sulfolane derivative, which are equivalent to a semi-volatile organic compound, and reswells by adding the organic solvent without replacing the organic solvent. In the past, a (pseudo)rotaxane polymer gel was synthesized by forming an inclusion structure in the presence of an organic solvent equivalent to a volatile organic compound such as chloroform, and then the organic solvent was removed and dried, and the gel was reswelled with a different organic solvent such as a less volatile organic solvent or sulfolane. However, in the present invention, the organic solvent used to form the inclusion structure can be used in the reswelling step as it is, and solvent replacement in the conventional reswelling step can be omitted. Furthermore, when the generated (pseudo)rotaxane polymer gel is immersed in an organic solvent containing sulfolane and / or a sulfolane derivative to reswell, a gel with a high degree of swelling can be obtained. The swollen gel is less likely to generate bubbles and has high shape retention, and a gel that is more transparent than conventional gels can be obtained. In addition, a (pseudo)rotaxane polymer gel may be obtained by using an organic solvent obtained by mixing sulfolane and / or a sulfolane derivative with a VOC solvent, and the VOC solvent may be removed to a certain extent, followed by immersion in a separate organic solvent for reswelling. The organic solvent used for reswelling may be the same as that used for gel generation, but it is preferable to reduce the use of organic solvents equivalent to VOC solvents as much as possible, and it is more preferable to use only sulfolane and / or a sulfolane derivative without using VOC solvents. This is because not using a VOC solvent not only reduces the environmental load, but also contributes to either increasing the degree of swelling during reswelling, preventing the generation of bubbles, or preventing coloring of the gel. It is preferable that the VOC solvent does not remain in the gel after reswelling as much as possible, but it is acceptable if it remains to the extent that the shape of the gel is not apparently changed. When a VOC solvent is mixed and used as the solvent used for reswelling, the ratio of the mass of the VOC solvent to the total mass of the solvents should be the same as that when the gel is generated. The present invention will be described in more detail below with reference to examples, but the technical scope of the present invention is not limited to these in any way. EXAMPLES

[0019] [Preparation of rotaxane gel using sulfolane as a solvent] A homogeneous reaction solution was prepared by adding 102.4 mg (0.121 mmol) of the 24-membered crown ether derivative shown in Figure 1 and 70.6 mg (0.121 mmol) of the secondary ammonium salt compound in a molar ratio of 1:1 to a sample tube, and adding a mixture of 44.4 mg (0.244 mmol) of 3,6-dioxa-1,8-octanedithiol (2 equivalents to the secondary ammonium salt compound or crown ether derivative) and 0.6858 g of sulfolane (denoted as SL). Then, 4.4 mg of benzophenone was added as an initiator, and 0.163 g of the reaction solution was poured into a cylindrical silicon mold with a diameter x height of 8 mm x 4 mm, and UV irradiation was performed for 2 minutes to prepare a rotaxane gel containing sulfolane (polymer content is about 25 wt% in terms of the charge ratio). As a conventional technique, a rotaxane gel containing chloroform was prepared using the same procedure as above, except that the solvent was replaced with chloroform instead of sulfolane.

[0020] The physical properties of the rotaxane gel produced above were examined as follows. (1) Appearance of the prepared rotaxane gel Figure 2 shows the appearance of the rotaxane gel produced using sulfolane and chloroform after 2 minutes of UV irradiation and drying at 70°C for 48 hours in the above production process. The rotaxane gel produced using sulfolane was more transparent than the rotaxane gel produced using chloroform. This is thought to be due to the low volatility of sulfolane, which means that the colored components are not concentrated.

[0021] (2) Weight change before and after reaction The weight change of the gel before and after 2 minutes of UV irradiation was examined for the rotaxane gels prepared using sulfolane and chloroform. The results are shown in Table 1.

[0022] [Table 1]

[0023] The rotaxane gel produced using sulfolane, which has low volatility, showed high dimensional stability, as no weight change occurred before and after UV irradiation. On the other hand, the rotaxane gel produced using chloroform, which has a boiling point of 61°C, lost weight before and after UV irradiation due to the volatilization of chloroform. In the rotaxane gel produced using chloroform, which has high volatility, approximately 90% of the chloroform eventually evaporated.

[0024] (3) Change in swelling degree during reswelling Rotaxane gels prepared using sulfolane or chloroform as an organic solvent were dried at 70°C for 48 hours, and then cylindrical samples containing 4 mg of polymerized rotaxane were reswelled by immersing them in 1 g of sulfolane at 30°C, and the degree of swelling thereafter [(swollen gel weight - 4 mg) / 4 mg] was calculated. The results are shown in Table 2, and a photograph of the appearance is shown in Figure 3. Photographs of the change in size of the sample before and after reswelling in sulfolane are also shown in Figure 4.

[0025] [Table 2]

[0026] A difference in behavior was observed between the rotaxane gel produced using sulfolane and the rotaxane gel produced using chloroform when reswelled using sulfolane. From Table 2, it was observed that the rotaxane gel produced using sulfolane from the rotaxane gel production process absorbed a large amount of sulfolane added for reswelling, and a change of about 4 times in volume was observed. On the other hand, the volume change of the rotaxane gel produced using chloroform was only about 2 times, so it was found that when the rotaxane gel concentrated by the evaporation of the solvent (chloroform) is reswelled, it is difficult to absorb sulfolane. Furthermore, from Figures 3 and 4, it was found that the rotaxane gel produced using sulfolane was highly transparent, did not generate bubbles, and had no damage to its appearance. On the other hand, it was found that the rotaxane gel produced using chloroform was colored and contained bubbles, which affected the finish of the rotaxane gel after reswelling. [Industrial Applicability]

[0027] In the method for producing a network polymer gel having an inclusion structure of a crown ether derivative and a secondary ammonium salt compound, an inclusion structure of the crown ether derivative and the secondary ammonium salt compound can be formed and a gel can be produced in the presence of an organic solvent containing sulfolane and / or a sulfolane derivative. In addition, by swelling this gel, the step of solvent replacement becomes unnecessary and the burden on the environment caused by volatile organic compounds can be reduced. Furthermore, the one-step method for producing a rotaxane gel using sulfolane, which does not require a step of solvent replacement, can produce a material that is highly transparent and dimensionally stable, has no bubbles, and is free of damage to its appearance. Semi-volatile organic solvents are highly polar, so they can also dissolve metal salts, and are therefore expected to be used as electrolytes in secondary batteries.

Claims

1. A method for producing a network polymer gel having an inclusion structure of a crown ether derivative and a secondary ammonium salt compound, characterized in that an inclusion structure of the crown ether derivative and the secondary ammonium salt compound is formed and a gel is produced in the presence of an organic solvent containing sulfolane and / or a sulfolane derivative.

2. 2. The method for producing a network polymer gel according to claim 1, wherein the organic solvent used in producing the gel is not replaced, and the gel is re-swelled with the organic solvent.

3. The method for producing a network polymer gel according to claim 1 or 2, wherein the organic solvent is sulfolane.

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