Method for purifying polyrotaxane and method for producing polyrotaxane

Abstract

To provide a method for purifying polyrotaxane and a method for producing polyrotaxane which enable easy production of polyrotaxane in a short time with high purity in a high yield.SOLUTION: A method for purifying polyrotaxane includes the following steps (I) and (II): (I) a step of adding a meal normal salt to an aqueous liquid containing polyrotaxane in which straight chain molecules penetrate through an opening of cyclic molecules and water, so that the polyrotaxane forms a phase insoluble in the aqueous liquid, in which the cyclic molecule includes at least one selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, and (II) a step of recovering the polyrotaxane forming the phase insoluble in the aqueous liquid.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for purifying polyrotaxane and a method for producing polyrotaxane. [Background technology]

[0002] Polyrotaxanes are polymers in which linear molecules penetrate multiple cyclic molecular openings and are enclosed within one another. Polyrotaxanes have a wide range of properties, including viscoelasticity and tensile strength, and are therefore being applied in a variety of fields.

[0003] Conventionally, the main methods for purifying polyrotaxanes have been the precipitation method (e.g., Patent Document 1) and the dialysis method (e.g., Patent Document 2). The precipitation method is simple and low-cost because the only reagents required are an organic solvent and deionized water, but there are problems with the yield and purity of the product. The dialysis method is simple and can produce a highly pure product, but it takes a long time, usually two days or more, and is expensive because a dialysis membrane is used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Retable 2015 / 041322 [Patent Document 2] Retable 2009 / 145073 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for purifying and producing polyrotaxane, which allows polyrotaxane to be obtained easily and in a short time with high purity and / or high yield. [Means for solving the problem]

[0006] As a result of extensive investigations to solve the above problems, the present inventors have surprisingly found that when a metal salt is added to a solution containing a polyrotaxane, the polyrotaxane forms a phase that can be separated from the solution. They have separated this phase and completed the present invention.

[0007] The present invention encompasses the embodiments described below.

[0008] Item 1. A method for purifying a polyrotaxane, comprising the following steps (I) and (II): (I) a step of adding a metal salt to an aqueous liquid containing a polyrotaxane in which linear molecules penetrate openings of cyclic molecules and water, so that the polyrotaxane forms a phase insoluble in the aqueous liquid, the cyclic molecule comprises at least one selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. (II) A step of recovering the polyrotaxane that forms a phase insoluble in the aqueous liquid.

[0009] Item 2. After the step (I) and before the step (II), (III) further comprising a step of mixing the aqueous liquid with an organic solvent in which the linear molecule is soluble and the cyclic molecule is insoluble; Item 2. The method for purifying according to Item 1, wherein the step (II) comprises separating the polyrotaxane present between the two phases of the aqueous liquid and the organic solvent.

[0010] Item 3. The polyrotaxane forms micelles upon addition of the metal liquid in step (I), Item 2. The purification method according to Item 1, wherein the step (II) comprises recovering micelles containing the polyrotaxane in the aqueous liquid.

[0011] Item 4. The organic solvent contains chlorobenzene or dichloroethane. 2 The manufacturing method described in

[0012] Item 5. The purification method according to any one of Items 1 to 4, wherein the metal salt contains sodium carbonate.

[0013] Item 6. The method according to any one of Items 1 to 5, wherein the linear molecule comprises at least one selected from the group consisting of polyethylene glycol, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, polymethacrylic acid, polyacrylamide, pullulan, a water-soluble cellulose derivative, polyvinylpyrrolidone, and a polypeptide.

[0014] Item 7. The purification method according to any one of Items 1 to 6, wherein the inclusion rate of the cyclic molecule is 1 to 30%, when a specified inclusion rate determined by the length of the linear molecule and the thickness of the cyclic molecule is taken as 100%.

[0015] Item 8. Some of the -OH groups of the cyclic molecules of the polyrotaxane are -O-(CHR 1 ) n -CHR 2 -OH(in the formula, R 1 is H, a methyl group, or an ethyl group, and R 2 is H, a methyl group, or an ethyl group, and n is an integer from 1 to 6; Item 7. The purification method according to any one of Items 1 to 6, wherein the inclusion rate of the cyclic molecule is 1 to 22%, when a defined inclusion rate defined by the length of the linear molecule and the thickness of the cyclic molecule is taken as 100%.

[0016] Item 9. Providing an aqueous liquid containing a polyrotaxane; and A step of purifying the polyrotaxane in the aqueous liquid by the purification method according to any one of items 1 to 8 to obtain a purified polyrotaxane. A method for producing a purified polyrotaxane, comprising:

[0017] Item 10. A step of mixing linear molecules and cyclic molecules in the presence of water to obtain pseudopolyrotaxanes in an aqueous liquid; a step of binding blocking groups to both ends of the linear molecule of the pseudopolyrotaxane to prevent the cyclic molecule from being detached from the linear molecule, thereby obtaining a polyrotaxane in an aqueous liquid; and A step of purifying the polyrotaxane in the aqueous liquid by the purification method according to any one of items 1 to 8 to obtain a purified polyrotaxane. A method for producing a polyrotaxane comprising the steps of: [Effects of the Invention]

[0018] According to the present invention, polyrotaxane can be obtained easily and in a short time with high purity and high yield. [Brief explanation of the drawings]

[0019] [Figure 1] Schematic diagram of low-inclusion polyrotaxane (PR). [Figure 2] Schematic diagram of the interface between the aqueous and organic phases. Polyrotaxanes are aligned at the interface between the aqueous and organic phases. [Figure 3] A photograph of a suspension produced by adding a metal salt and an organic solvent to an aqueous solution containing polyrotaxane and stirring. [Figure 4] Photographs showing the aqueous phase, the organic solvent phase, and the phase formed between the aqueous phase and the organic solvent phase. [Figure 5] Graph comparing the degree of impurity removal among (1) extraction method, (2) dialysis method, (3) the method of this example, and (4) a method using a sample containing only PEG without cyclodextrin (CD). DETAILED DESCRIPTION OF THE INVENTION

[0020] As used herein, the term "pseudopolyrotaxane" refers to a compound having a structure in which a linear molecule passes through an opening of a cyclic molecule and no blocking groups are bonded to either end of the linear molecule to prevent the cyclic molecule from falling off.

[0021] As used herein, the term "polyrotaxane" refers to a compound having a structure in which a linear molecule passes through the opening of a cyclic molecule and blocking molecules are bound to both ends of the linear molecule to prevent the cyclic molecule from falling off.

[0022] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0023] A method for purifying a polyrotaxane according to an embodiment of the present invention includes the following steps (I) and (II): (I) a step of adding a metal salt to an aqueous liquid containing a polyrotaxane in which linear molecules penetrate openings of cyclic molecules and water, so that the polyrotaxane forms a phase insoluble in the aqueous liquid, the cyclic molecule comprises at least one selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. (II) A step of recovering the polyrotaxane that forms a phase insoluble in the aqueous liquid.

[0024] linear molecules Examples of linear molecules include molecules that can penetrate the rings of multiple cyclic molecules. The linear molecule is preferably a polymer having a repeating unit of a monomer. Examples of linear molecules include polyalkylenes, polyesters, polyethers, polyamides, polyacrylics, and linear molecules having a benzene ring. More specific examples of linear molecules include polyethylene glycol, polyethylene oxide, polypropylene glycol, polylactic acid, polycaprolactone, polyethylene, polypropylene, polyvinyl acetal, polyvinyl methyl ether, polyvinylpyrrolidone, polyacrylamide, polymethyl acrylate, polymethyl methacrylate, and polystyrene. The linear molecule may have a branched chain as long as it is configured to be able to penetrate the rings of the above-mentioned cyclic molecules.

[0025] A particularly preferred linear molecule is a water-soluble linear molecule. The water-soluble linear molecule is not particularly limited as long as it has the property of being able to dissolve 1 g in 1 L.

[0026] Examples of water-soluble linear molecules include, but are not limited to, polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, polymethacrylic acid, polyacrylamide, pullulan, water-soluble cellulose derivatives such as hydroxypropyl cellulose, polyvinylpyrrolidone, polypeptides, and copolymers containing polyethylene glycol. The water-soluble linear molecule is at least one selected from the group consisting of the above-listed polymer species, preferably at least one selected from the group consisting of polyethylene glycol, polyvinyl alcohol, polyethyleneimine, and copolymers containing at least one of these, more preferably at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and polyethylene glycol.

[0027] The linear molecule may be a polymer whose entire structure is a repeating structure of the same monomer, or may be a block copolymer having at least two blocks, or may be a block copolymer having at least three blocks.

[0028] Each block of the "block copolymer" preferably consists of only one repeating unit, but may have a first spacer group between one repeating unit and the next. Also, adjacent blocks of the "block copolymer" may have a second spacer group, which may be the same as or different from the first spacer group.

[0029] Examples of the first and / or second spacer group include, but are not limited to, linear or branched alkyl groups having 1 to 20 carbon atoms, such as methylene, ethylene, propylene, butylene, and pentylene groups (which may be partially substituted with an aromatic ring such as a phenyl group); linear or branched ethers having 1 to 20 carbon atoms; linear or branched esters having 1 to 20 carbon atoms; and aromatic groups having 6 to 24 carbon atoms, such as a phenyl group.

[0030] Examples of the backbone forming at least two or at least three blocks include, but are not limited to, polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, polymethacrylic acid, polyacrylamide, pullulan, water-soluble cellulose derivatives such as hydroxypropyl cellulose, polyvinylpyrrolidone, polypeptides, and copolymers containing polyethylene glycol.

[0031] That is, the linear molecule is at least one selected from the group consisting of the above-mentioned polymer species, preferably at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyethyleneimine, and copolymers containing polyethylene glycol, and more preferably at least one selected from the group consisting of polyethylene glycol and polypropylene glycol.

[0032] For example, when the linear molecule is a water-soluble linear molecule composed of one type of polymer, it may be a polymer composed of only polyethylene glycol, only polypropylene glycol, only polyvinyl alcohol, only polyethyleneimine, or only polyethylene glycol.When the linear molecule is a linear molecule composed of three blocks, the central block may be polypropylene glycol and both sides may be polyethylene glycol.

[0033] The molecular weight of the linear molecule is not particularly limited, but is preferably, for example, a number-average molecular weight of 3,000 to 1,000,000, more preferably 5,000 to 500,000, more preferably 7,000 to 200,000, and even more preferably 10,000 to 100,000. Alternatively, the weight-average molecular weight is, for example, preferably 3,000 to 1,000,000, more preferably 5,000 to 500,000, more preferably 7,000 to 200,000, and even more preferably 10,000 to 100,000. The number-average molecular weight and weight-average molecular weight referred to herein can be determined from polyethylene glycol equivalent values ​​measured by gel permeation chromatography (GPC).

[0034] Both ends of the linear molecule preferably have reactive groups capable of reacting with blocking groups to prevent cyclic molecules from dropping off from the linear molecule, which makes it easier for the blocking groups described below to be bonded to both ends of the linear molecule. Examples of reactive groups include amino groups, hydroxyl groups, carboxyl groups, thiol groups, disulfides, vinyl groups, acryloyl groups, methacryloyl groups, and sulfo groups. Preferred are amino groups and carboxyl groups.

[0035] The blocking group bonded to the linear molecule of polyrotaxane is not particularly limited as long as it acts to prevent detachment of the cyclic molecule from the linear molecule. For example, the blocking group may be selected from the group consisting of dinitrophenyl groups, cyclodextrins, adamantane groups, trityl groups, fluoresceins, silsesquioxanes, pyrenes, substituted benzenes (substituents include, but are not limited to, alkyl, alkyloxy, hydroxy, halogen, cyano, sulfonyl, carboxyl, amino, phenyl, etc., and one or more substituents may be present), optionally substituted polynuclear aromatics (substituents include, but are not limited to, the same as those described above, and one or more substituents may be present), and steroids. Preferably, the group is selected from the group consisting of dinitrophenyl groups, cyclodextrins, adamantane groups, trityl groups, fluoresceins, silsesquioxanes, and pyrenes, and more preferably, the group is an adamantane group or a cyclodextrin.

[0036] cyclic molecules The cyclic molecule may be any of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, with α-cyclodextrin being particularly preferred. The cyclodextrin may be an unmodified cyclodextrin, or a cyclodextrin derivative in which some of its functional groups have been derivatized. The cyclodextrin derivative may be any of α-cyclodextrin derivatives, β-cyclodextrin derivatives, and γ-cyclodextrin derivatives. Examples of cyclodextrin derivatives include those in which at least one hydroxyl group of cyclodextrin or a hydrogen atom of the hydroxyl group is -O-(CHR 1 ) n -CHR 2 -OH(in the formula, R 1 is H, a methyl group, or an ethyl group, and R 2is H, a methyl group, or an ethyl group, and n is an integer of 1 to 6), a hydrocarbon group having a hydroxy group, or a hydrocarbon group having an amino group. Specific examples of hydrocarbon groups having a hydroxy group include a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group. Specific examples of hydrocarbon groups having an amino group include an aminomethyl group, an aminoethyl group, and an aminopropyl group. In cyclodextrin derivatives, the number of -O-(CHR 1 ) n -CHR 2 The number of -OH groups, hydrocarbon groups having a hydroxy group, or hydrocarbon groups having an amino group is preferably 2 to 80%, more preferably 3 to 50%, assuming that the state in which all -OH groups are substituted is 100%.

[0037] Some of the -OH groups of the cyclic molecule are -O-(CHR 1 ) n -CHR 2 When the cyclic molecule is substituted with -OH groups, the -OH groups are preferably 2-OH and / or 6-OH, more preferably 6-OH. Although not based on a complete theory, it is possible that some of the -OH groups of the cyclic molecule are the above-mentioned -O-(CHR 1 ) n -CHR 2 When substituted with an —OH group, the —O—(CHR 1 ) n -CHR 2 To avoid the proximity of -OH groups, i.e., so-called hydrophobic groups, cyclic molecules having such groups are also arranged to avoid each other, which is thought to determine the arrangement of cyclic molecules in polyrotaxanes, and this arrangement of cyclic molecules is also thought to result in a low inclusion rate of polyrotaxanes.

[0038] The above-mentioned -O-(CHR 1 ) n -CHR 2 Among the substituents represented by -OH groups, R 1 is H and R 2 is a methyl group, or R 1is a methyl group and R 2 is preferably H.

[0039] Inclusion rate In this specification, the inclusion rate refers to the rate of cyclic molecules contained in a polyrotaxane. Furthermore, the specified inclusion rate refers to an inclusion rate arithmetically determined from the water-soluble linear molecules and cyclic molecules used in the polyrotaxane, and specifically, is determined from the length of the water-soluble linear molecules and the thickness of the cyclic molecules.

[0040] Let us explain the specified inclusion rate in more detail. We consider the case where polyethylene glycol is used as the water-soluble linear molecule and α-CD is used as the cyclic molecule. It is known from molecular model calculations that the thickness of α-CD is equal to the thickness of two repeating units of polyethylene glycol. Therefore, the specified inclusion rate is 100% when the ratio of moles of α-CD to the number of repeating units is 1:2.

[0041] The ratio of cyclic molecules contained in the obtained polyrotaxane, i.e., the inclusion rate, is 1 It can be determined by H-NMR. 1 It can be determined from the ratio of the integral value of the peak representing the methine proton of the carbon at position 1 of α-CD (at about 4.8 ppm in chemical shift) to the integral value of the peak representing the methylene proton of PEG (at about 3.5 ppm) in H-NMR. More specifically, 1 The ratio X / Y is calculated by dividing the measured integral value X of the methine proton at the first carbon atom of glucose in α-CD, which appears at approximately 4.8 ppm in the H-NMR spectrum, by the measured integral value Y of the methylene proton of the repeating unit of PE, which appears at approximately 3.5 ppm. When the measured integral value ratio X / Y is 3:4, this indicates that the molar ratio of the number of repeating units of α-CD to PEG is 1:2, as described above, and the inclusion rate is 100%. Therefore, the inclusion rate can be calculated from the formula: (inclusion rate (%)) = (ratio of measured integral values ​​X / Y) × 4 / 3 × 100. For example, when the measured integral value ratio X / Y is 1 / 4, the inclusion rate is 33.3%.

[0042] In this manner, the inclusion rate of the polyrotaxane can be determined. In the present application, the inclusion rate of the polyrotaxane is not limited, but is preferably 1 to 30%, assuming a specified inclusion rate of 100%. A low inclusion rate of 1 to 22%, as shown in FIG. 1, is advantageous in that there is a relatively large gap between adjacent cyclic molecules in the linear molecule, and there are many portions where the linear molecules are exposed without the presence of cyclic molecules, making it easier to separate the polyrotaxane from a solution containing the polyrotaxane. For polyrotaxanes with a low inclusion rate, the inclusion rate is preferably 1 to 15%, more preferably 1 to 10%, and most preferably 1 to 8%. Polyrotaxanes with a low inclusion rate are also advantageous in that they have unique properties, such as high elongation and high toughness, such as high breaking stress.

[0043] Method for producing polyrotaxane Methods for producing polyrotaxanes are well known. The linear molecules and cyclic molecules may be produced by known methods, or commercially available products may be used. When functional groups such as hydroxyl groups of the cyclic molecules are substituted, it is desirable to perform the substitution in advance before mixing with the linear molecules. Various methods for such substitution are known, including those disclosed in WO2018 / 021267.

[0044] For example, a pseudopolyrotaxane can be obtained in an aqueous solution by first mixing and stirring linear molecules and cyclic molecules in the presence of water. The cyclic molecules are soluble in water. The solvent used to mix the linear molecules and cyclic molecules may be water alone, but it may also contain substances other than water as long as they do not interfere with the separation of the pseudopolyrotaxane from the aqueous solution. For example, the solvent may contain an organic solvent or an electrolyte such as NaOH. The organic solvent is preferably one that is compatible with water, and examples thereof include, but are not limited to, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, pyridine, tetrahydrofuran, and acetone. When the solvent used to mix the linear molecules and cyclic molecules is a mixed solvent of water and a solvent other than water, the mixing ratio of water to the solvent other than water is preferably 100:5 to 100:100.

[0045] The time and temperature for the step of stirring the linear molecules and cyclic molecules in the presence of water are not particularly limited, but the stirring time is preferably 2 to 48 hours and the stirring temperature is preferably 4°C to 30°C. After stirring, the pseudopolyrotaxane can be obtained as a supernatant or precipitate in the aqueous solution. To separate the aqueous solution into the supernatant and precipitate, known methods can be used, including separation by suction, centrifugation, decantation after standing, and filtration.

[0046] Polyrotaxane can be produced by adding a blocking agent to an aqueous solution containing the resulting pseudopolyrotaxane. By attaching blocking groups to both ends of the linear molecules of the pseudopolyrotaxane to prevent detachment of the cyclic molecules, polyrotaxane can be obtained in the aqueous solution. The blocking agent is not particularly limited as long as it can react with the linear molecules of the pseudopolyrotaxane to form blocking groups, but water-soluble blocking agents are preferred. A water-soluble blocking agent is one that exhibits a solubility of 0.1 g / L or more when dissolved alone in water.

[0047] When the blocking group of the water-soluble blocking agent is an adamantane group, the blocking agent is an adamantane having an amino group, a hydroxyl group, a carboxyl group, and a thiol group, a disulfide, a vinyl group, an acryloyl group, a methacryloyl group, or a sulfo group, preferably an amino group or a carboxyl group.

[0048] In step (I) of the polyrotaxane purification method according to an embodiment of the present invention, a metal positive salt is added to an aqueous liquid containing a polyrotaxane and water so that the polyrotaxane forms an insoluble phase in the aqueous liquid. Deionized water is preferred as the water, but this is not limiting. The addition of a metal positive salt to an aqueous liquid containing a polyrotaxane and water simply means that the metal positive salt is added to the aqueous liquid containing the polyrotaxane and water. The metal positive salt may be added to the aqueous liquid containing the polyrotaxane and water, or the aqueous liquid containing the polyrotaxane and water may be added to the metal positive salt.

[0049] The aqueous liquid containing polyrotaxane and water may be the aqueous liquid obtained after the stirring step and the blocking group addition step. Alternatively, the aqueous liquid may be obtained by producing polyrotaxane according to the above-mentioned method, separating the polyrotaxane by suction, centrifuging, decanting after standing, or filtering the polyrotaxane, and then mixing or dissolving the polyrotaxane in water. This aqueous liquid may optionally contain substances other than water (e.g., organic solvents or electrolytes such as NaOH).

[0050] The metal salt may be any salt that, when added, causes the polyrotaxane to form an insoluble phase in an aqueous liquid. The metal salt refers to a salt that contains metal ions in its structure but does not contain hydrogen ions (H+) or hydroxide ions (OH-) in its structure.

[0051] Polyrotaxanes are generally water-soluble at room temperature, and the cyclic molecules used to produce them, such as α-cyclodextrin, have many hydrophilic groups and are therefore highly soluble in water and water-soluble solvents. For this reason, precipitation and dialysis methods have traditionally been used to separate polyrotaxane from the cyclic molecules remaining after polyrotaxane synthesis, but purification by dialysis, which is used depending on the molecular weight, is the mainstream, and this usually takes more than two days.

[0052] The first property of polyethylene glycol (PEG), a linear molecule, is that it generally becomes insoluble in water when heated to the boiling point (cloud point). At temperatures above the cloud point, PEG can be transferred from water to a non-aqueous solvent. A second property of PEG is that the cloud point (lower critical solution temperature: LCST) is lowered by adding a metal salt to an aqueous solution containing PEG (Mitsui Naka and Moriya Fumio, Journal of the Japan Paper and Pulp Technology Association, 1968, vol. 22, no. 7, pp. 375-381). In other words, adding a metal salt to the solvent can make PEG water-insoluble without heating the solvent to the boiling point of water.

[0053] For this reason, a linear molecule alone and a polyrotaxane in which a linear molecule is encapsulated in a cyclic molecule do not necessarily behave in the same way with respect to a solvent or a metal salt. However, the present inventors considered that by mixing a linear molecule and a cyclic molecule in an aqueous solution to obtain a polyrotaxane, and then adding a metal salt to the aqueous solution, the polyrotaxane can be efficiently separated from unreacted cyclic molecules and the like.

[0054] Examples of metal salts include, but are not limited to, sodium carbonate (Na2CO3), magnesium sulfate (MgSO4), zinc sulfate (ZnSO4), sodium chloride (NaCl), and potassium bromide (KBr). The metal salt containing a linear molecule is preferably Na2CO3 or MgSO4, more preferably Na2CO3, because even a small amount of it lowers the cloud point of an aqueous solution containing a polyrotaxane.

[0055] The amount of metal salt added to the polyrotaxane is preferably about 100:0.01-10 in terms of the mass ratio of polyrotaxane:metal salt, but is not limited to this.

[0056] The metal salt is preferably added as an aqueous solution of the metal salt.

[0057] Adding a metal salt such that the polyrotaxane forms a phase insoluble in the aqueous liquid refers to adding the metal salt in an amount or concentration sufficient for the polyrotaxane to form a phase insoluble in the aqueous liquid. The amount or concentration sufficient for the polyrotaxane to form a phase insoluble in the aqueous liquid can be appropriately adjusted by those skilled in the art depending on the type of polyrotaxane, the type of metal salt, etc. Whether the polyrotaxane has formed a phase insoluble in the aqueous liquid can be observed with the naked eye, as the aqueous liquid becomes cloudy.

[0058] After adding a metal salt to an aqueous liquid containing polyrotaxane and water, the aqueous liquid is stirred. As the metal salt is added to the aqueous liquid containing polyrotaxane and water, eventually, at least the linear molecular portion of the polyrotaxane becomes insoluble in water, and the polyrotaxane eventually forms an insoluble phase in the aqueous liquid. Although a portion of the polyrotaxane in the aqueous liquid may form an insoluble phase, or the entire polyrotaxane may form an insoluble phase, from the viewpoint of polyrotaxane purification, it is preferable that the entire polyrotaxane in the aqueous liquid forms an insoluble phase.

[0059] Therefore, in step (II) of the polyrotaxane purification method according to an embodiment of the present invention, by recovering the polyrotaxane that forms a phase insoluble in the aqueous liquid, the polyrotaxane can be efficiently separated from the cyclic molecules remaining in the aqueous liquid. Because the polyrotaxane is present at a high concentration in the phase insoluble in the aqueous liquid, the polyrotaxane can be recovered with high purity and high yield. Examples of recovery methods include suction, centrifugation, decantation after standing, and filtration. An aqueous solution of a metal salt may be added to the polyrotaxane that has been separated and recovered from the aqueous liquid and stirred, and the phase insoluble in the aqueous solution may be recovered again by centrifugation, suction, decantation after standing, filtration, or the like. This separation procedure may be repeated two or more times.

[0060] The polyrotaxane purification method according to an embodiment of the present invention is a method that can easily obtain a product with high purity and high yield in a short time (for example, one hour or less) compared to dialysis. If inexpensive solvents and metal salts are used, polyrotaxane can be purified using only an organic solvent, water, and metal salt, which can keep the purification cost low (the only reagents required for purification are the organic solvent, metal salt, and water).

[0061] In one specific embodiment, the method for purifying a polyrotaxane further includes, after step (I) and before step (II), step (III) of mixing an aqueous liquid with an organic solvent in which the linear molecule is soluble and the cyclic molecule is insoluble, and step (II) includes separating the polyrotaxane present between the two phases, the aqueous liquid and the organic solvent.

[0062] By mixing an aqueous liquid with an organic solvent in which linear molecules are soluble and cyclic molecules are insoluble, polyrotaxane forms a phase between the aqueous liquid phase and the organic solvent phase in which linear molecules are soluble and cyclic molecules are insoluble.

[0063] Although the present invention does not wish to be bound by theory, when an aqueous liquid is mixed with an organic solvent in which linear molecules are soluble and cyclic molecules are insoluble, the aqueous liquid forms an aqueous phase, and the organic solvent in which linear molecules are soluble and cyclic molecules are insoluble forms an organic solvent phase (organic phase), and the two do not dissolve in each other and form an interface, as shown in Figure 2. Figure 2 shows a polyrotaxane in which linear molecules penetrate the openings of cyclic molecules and have blocking groups on both ends of the linear molecules. It is believed that the cyclic molecular portions of the polyrotaxane diffuse into the aqueous phase and the linear molecular portions diffuse into the organic phase, causing the polyrotaxane to segregate at the interface between the aqueous phase and the organic phase.

[0064] The organic solvent in which linear molecules are soluble but cyclic molecules are insoluble refers to an organic solvent in which linear molecules are soluble but cyclic molecules are insoluble at the temperature at which step (III) of mixing an aqueous liquid with the organic solvent in which linear molecules are soluble but cyclic molecules are insoluble. In one preferred embodiment, the organic solvent in which linear molecules are soluble but cyclic molecules are insoluble is an organic solvent in which linear molecules are soluble but cyclic molecules are insoluble at any temperature within a temperature range of 20 to 50°C. In another preferred embodiment, the organic solvent in which linear molecules are soluble but cyclic molecules are insoluble is an organic solvent in which linear molecules are soluble but cyclic molecules are insoluble at a temperature of 20°C. In yet another preferred embodiment, the organic solvent in which linear molecules are soluble but cyclic molecules are insoluble is an organic solvent in which linear molecules are soluble but cyclic molecules are insoluble at a temperature of 50°C. In yet another embodiment, the organic solvent in which linear molecules are soluble and cyclic molecules are insoluble is an organic solvent in which linear molecules are soluble and cyclic molecules are insoluble at any temperature within a temperature range of 20 to 50°C.

[0065] Whether a linear molecule is soluble in an organic solvent can be easily determined, for example, by observing the state of the solution after mixing the linear molecule with an organic solvent and stirring. If the solution after stirring is transparent or slightly cloudy, it can be determined that the linear molecule is soluble in the organic solvent. If the phases of the linear molecule and the organic solvent are observed to be separated in the solution after stirring, it can be determined that the linear molecule is insoluble in the organic solvent. Similarly, whether a cyclic molecule is insoluble in an organic solvent can be easily determined, for example, by observing the state of the solution after mixing the cyclic molecule with an organic solvent and stirring it. If the cyclic molecule and the organic solvent are observed as separate phases in the solution after stirring, it can be determined that the cyclic molecule is insoluble in the organic solvent.

[0066] Examples of organic solvents include, but are not limited to, chlorobenzene, dichloroethane, and the like.

[0067] The amount of organic solvent to be added is not particularly limited, and the volume ratio of the aqueous liquid containing the polyrotaxane, water, and metal salt to the organic solvent is preferably about 100:10 to 1000, but is not limited thereto.

[0068] The polyrotaxane present between the two phases of the aqueous liquid and the organic solvent can be separated by known methods including, but not limited to, separation by suction, decantation after standing, centrifugation, and filtration.

[0069] In one specific embodiment, the polyrotaxane forms micelles by adding the metal liquid in step (I), and step (II) comprises recovering the micelles containing the polyrotaxane in the aqueous liquid, in which no organic solvent is present.

[0070] Upon addition of a metal salt, polyrotaxane dissolved in an aqueous solution forms oil-in-water micelles in which linear molecules are positioned on the outside of the droplets and cyclic molecules are positioned on the inside. Therefore, by recovering the micelles containing polyrotaxane from the aqueous solution, the polyrotaxane can be efficiently separated from the cyclic molecules remaining in the aqueous solution. Because polyrotaxane is present at a high concentration in the micelles, which are an insoluble phase in the aqueous solution, polyrotaxane can be recovered with high purity and high yield. Recovery methods include suction, centrifugation, decantation after standing, and filtration. Once polyrotaxane has been separated and recovered from the aqueous solution, an aqueous solution of a metal salt may be added again and stirred, and the insoluble phase may be recovered again by suction, centrifugation, decantation after standing, filtration, or the like. This separation procedure may be repeated two or more times.

[0071] One embodiment of the present invention includes a method for producing a purified polyrotaxane, comprising the steps of providing an aqueous liquid containing a polyrotaxane, and purifying the polyrotaxane in the aqueous liquid by any of the purification methods described above to obtain a purified polyrotaxane.

[0072] Another embodiment of the present invention includes a method for producing a polyrotaxane, including the steps of mixing linear molecules and cyclic molecules in the presence of water to obtain a pseudo-polyrotaxane in an aqueous liquid, binding blocking groups to both ends of the linear molecules of the pseudo-polyrotaxane to prevent the cyclic molecules from detaching from the linear molecules to obtain a polyrotaxane, and obtaining the polyrotaxane by any of the purification methods described above. Details of each step are as described above.

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Example]

[0074] Example 1 Selection of organic solvent The solubility of polypropylene glycol (commercial product, weight-average molecular weight 35,000, NH2-PEG-NH2), 2-hydroxypropyl-α-cyclodextrin (synthesized according to the synthesis example in WO2018 / 021267, weight-average molecular weight 1180, hpCD), and polyrotaxane (PR) formed from NH2-PEG-NH2 and hpCD in various organic solvents (chlorobenzene, dichloroethane, diethyl ether, butanol, and methyl isobutyl ketone) was investigated. Chlorobenzene and dichloroethane dissolved NH2-PEG-NH2 and PR at 50 °C, resulting in clear solutions. Even at room temperature, mixtures of organic solvents with NH2-PEG-NH2 or PR became slightly cloudy, but NH2-PEG-NH2 and PR were soluble. On the other hand, hpCD was insoluble in chlorobenzene and dichloroethane, even at room temperature and at 50 °C. Diethyl ether, butanol, and methyl isobutyl ketone were insoluble in NH2-PEG-NH2, PR, and hpCD at room temperature and 50 °C. As a result, it was found that chlorobenzene and dichloroethane are suitable for the purification of PR after its synthesis.

[0075] Example 2 Synthesis of Polyrotaxane (PR) The amounts of each reagent were as follows: 0.2 g of polypropylene glycol (commercial product, weight-average molecular weight 35,000, NH2-PEG-NH2) with amino groups bound to both ends, 1.0 g of 2-hydroxypropyl-α-cyclodextrin (weight-average molecular weight 1,180, hpCD), 3.0 ml of PBS buffer (pH 8.0, 0.1 mol / L), 0.03 g of 3-hydroxy-1-adamantanecarboxylic acid (weight-average molecular weight 196.25) as a blocking agent, and 0.03 g of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (weight-average molecular weight 276.72) as a blocking agent.

[0076] A solution of NH2-PEG-NH2 dissolved in PBS buffer was mixed with hpCD and stirred at room temperature. The mixture was then stored in a refrigerator for 48 hours to obtain a solution containing pseudopolyrotaxane. 3-Hydroxy-1-adamantanecarboxylic acid and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride were added to the mixture and stirred at room temperature for one day. 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride was then added and stirred at room temperature for one day to obtain a polyrotaxane-containing aqueous solution with a low inclusion rate (theoretical inclusion rate: 2%).

[0077] Example 3 Extraction of polyrotaxane (PR) A centrifuge bottle was charged with 4.29 g of the polyrotaxane-containing aqueous solution obtained in Example 2 and an 8 wt% Na2CO3 aqueous solution and stirred. At this time, the mixture became cloudy, as shown in Figure 3. Next, chlorobenzene (C6H5Cl) was added, followed by shaking and centrifugation for 10 minutes (6000 rpm, RCF 4069 x g). The supernatant was removed, and 8 wt% Na2CO3 aqueous solution was added up to the shoulder of the centrifuge bottle. This cycle of shaking, centrifugation, removal of the supernatant, and addition of 8 wt% Na2CO3 aqueous solution was repeated three times, followed by centrifugation for 10 minutes (6000 rpm, RCF 4069 x g). The sample after centrifugation was as shown in Figure 4. The aqueous phase, organic solvent phase, and the interface between the aqueous and organic solvent phases were clearly distinguishable with the naked eye. The interface was recovered, and the solvent was removed using a vacuum dryer to obtain purified polyrotaxane (PR). This new purification method, which utilizes the phenomenon of a decrease in the lower critical solution temperature (LCST), shortened the time required for three cycles to about 30 minutes, with the entire process taking only about an hour. Furthermore, this purification method was able to remove almost all impurities, with a yield of over 95%.

[0078] Furthermore, when Na2CO3, MgSO4, or NaCl was used as the metal salt, polyrotaxane could be extracted by liquid-liquid phase separation even without using an organic solvent (data not shown).

[0079] Example 4 Comparison of the degree of impurity removal by polyrotaxane (PR) purification method The purified polyrotaxane (PR) sample obtained in Example 3 (referred to as "extracted PR"), the polyrotaxane-containing aqueous solution obtained in Example 2 purified with a dialysis membrane (MWCO: 12,000-14,000) for 48 hours and then exposed to approximately 1 L of water with water changes twice daily (referred to as "dialyzed PR"), a sample in which hpCD was dissolved in PBS buffer (referred to as "hpCD"), and a sample in which polypropylene glycol was dissolved in PBS buffer (referred to as "PEG-NH") were subjected to gel permeation chromatogram (GPC). The graph of the monitor display intensity versus time is shown in Figure 4. In the extracted PR sample, almost no hpCD peak was observed, indicating a significant increase in the removal rate of hpCD. As shown in Table 1, when the number-average molecular weight of PR in the sample is Mn, the weight-average molecular weight is Mw, and the ratio of the two is Mw / Mn, it was suggested that the composition of PR in the extracted PR and dialyzed PR samples was almost identical.

[0080] [Table 1]

Claims

1. A method for purifying a polyrotaxane, comprising the following steps (I) and (II): (I) a step of adding a metal salt to an aqueous liquid containing a polyrotaxane in which linear molecules penetrate openings of cyclic molecules and water, so that the polyrotaxane forms a phase insoluble in the aqueous liquid, the cyclic molecule includes at least one selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. (II) A step of recovering the polyrotaxane that forms a phase insoluble in the aqueous liquid

2. After the step (I) and before the step (II), (III) further comprising a step of mixing the aqueous liquid with an organic solvent in which the linear molecules are soluble and the cyclic molecules are insoluble; The purification method according to claim 1, wherein the step (II) comprises separating the polyrotaxane present between the two phases of the aqueous liquid and the organic solvent.

3. The polyrotaxane forms micelles upon addition of the metal liquid in step (I), The purification method according to claim 1 , wherein the step (II) comprises recovering micelles containing the polyrotaxane in the aqueous liquid.

4. The method according to claim 2, wherein the organic solvent comprises chlorobenzene or dichloroethane.

5. The method according to any one of claims 1 to 4, wherein the metal salt comprises sodium carbonate.

6. 6. The method according to claim 1, wherein the linear molecule comprises at least one molecule selected from the group consisting of polyethylene glycol, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, polymethacrylic acid, polyacrylamide, pullulan, a water-soluble cellulose derivative, polyvinylpyrrolidone, and a polypeptide.

7. The purification method according to any one of claims 1 to 6, wherein the inclusion rate of the cyclic molecule is 1 to 30%, when a specified inclusion rate defined by the length of the linear molecule and the thickness of the cyclic molecule is taken as 100%.

8. A part of the —OH groups of the cyclic molecules of the polyrotaxane is —O—(CHR1) ｎ -CHR ２ -OH (wherein, R １ is H, a methyl group, or an ethyl group, and R ２ is H, a methyl group, or an ethyl group, and n is an integer from 1 to 6; The purification method according to any one of claims 1 to 6, wherein the inclusion rate of the cyclic molecule is 1 to 22%, when a specified inclusion rate defined by the length of the linear molecule and the thickness of the cyclic molecule is taken as 100%.

9. Providing an aqueous liquid containing a polyrotaxane; and A step of purifying the polyrotaxane in the aqueous liquid by the purification method according to any one of claims 1 to 8 to obtain a purified polyrotaxane. A method for producing a purified polyrotaxane, comprising:

10. a step of mixing the linear molecule and the cyclic molecule in the presence of water to obtain a pseudopolyrotaxane in an aqueous liquid; a step of binding blocking groups to both ends of the linear molecule of the pseudopolyrotaxane to prevent the cyclic molecule from being detached from the linear molecule, thereby obtaining a polyrotaxane in an aqueous liquid; and A step of purifying the polyrotaxane in the aqueous liquid by the purification method according to any one of claims 1 to 8 to obtain a purified polyrotaxane. A method for producing a polyrotaxane comprising the steps of:

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