WO2022209020A1

WO2022209020A1 - Polyrotaxane and crosslinked polyrotaxane

Info

Publication number: WO2022209020A1
Application number: PCT/JP2021/045093
Authority: WO
Inventors: 明繁瀬尾; 秀樹玉井; 友樹生越; 研一加藤; 克知大西; 佳祐足立
Original assignee: 豊田合成株式会社; 国立大学法人京都大学
Priority date: 2021-03-31
Filing date: 2021-12-08
Publication date: 2022-10-06
Also published as: JP2022155764A

Abstract

[Problem] To provide a polyrotaxane having good solubility in various solvents while having at least a certain degree or heat resistance. [Solution] A polyrotaxane, having a straight-chain molecule, a ring molecule encircling the straight-chain molecule as if skewered, and a blocking group disposed at both terminal ends of the straight-chain molecule, wherein the ring molecule includes an aromatic ring having a phenolic hydroxyl group in a side chain, and at least a portion of the phenolic hydroxyl group is substituted by a specific substituent. The specific substituent is a non-ionic group other than a hydroxypropyl group. This polyrotaxane can be a cross-linked polyrotaxane in which the ring molecules of a plurality of polyrotaxanes are cross-linked.

Description

Polyrotaxane and crosslinked polyrotaxane

The present invention relates to polyrotaxanes.

A polyrotaxane is composed of a linear molecule, a cyclic molecule that clathrates the linear molecule in a skewed manner (takes it into the pores), and blocking groups arranged at both ends of the linear molecule. It is called a slide ring material (SRM) because it is a molecular assembly having a structure in which cyclic molecules can slide relative to linear molecules. Various types of cyclic molecules and linear molecules are known, and cyclodextrin is often used as the cyclic molecule and polyethylene glycol as the linear molecule (Patent Documents 1 and 2).

Cyclodextrin has a structure in which D-glucose is linked in a ring. FIG. 4 shows the structural formula of α-cyclodextrin in which D-glucose has 6 ring members. Cyclodextrin has many hydroxyl groups at the ends of its vacancies, and the vacancies contain ether-bonded oxygen and hydrogen atoms.

WO2005/080469 WO2018/038124

However, according to the studies of the present inventors, polyrotaxanes whose cyclic molecules are cyclodextrins (hereinafter sometimes referred to as "cyclodextrin-type polyrotaxanes") have room for improvement in heat resistance and solubility in various solvents. (See Comparative Example 3 in Table 1 to be described later).

Therefore, the present applicant has previously developed a polyrotaxane using pillararene as a cyclic molecule (hereinafter sometimes referred to as "pillararene-type polyrotaxane"), and has demonstrated that the heat resistance is improved as compared with the conventional cyclodextrin type. (Japanese Patent Application No. 2020-036286 (unpublished at the time of filing of the present application). However, the pillararene-type polyrotaxane has very poor solubility in various solvents (see Comparative Example 2 in Table 1), and an alkaline aqueous solution Although it is soluble, it is only slightly soluble in dimethyl sulfoxide (DMSO) as another solvent, and therefore, there are restrictions when, for example, the polyrotaxane is subjected to a cross-linking reaction.

Therefore, an object of the present invention is to provide a polyrotaxane that has a certain level of heat resistance and is highly soluble in various solvents.

As a result of investigation by the present inventors, the reason why the solubility of the pillararene-type polyrotaxane is very poor is that the pillararene has a phenolic hydroxyl group, so that the rotaxanes aggregate due to the formation of hydrogen bonds. There were also difficulties in workability, such as the need for high temperatures to untie the aggregates. Therefore, after further investigation, the present inventors have found that aggregation can be suppressed by substituting at least a portion of the phenolic hydroxyl groups of the cyclic molecule containing an aromatic ring with a specific substituent, leading to the present invention.

[1] Polyrotaxane A polyrotaxane having a linear molecule, a cyclic molecule that encloses the linear molecule in a skewered manner, and blocking groups arranged at both ends of the linear molecule,
The cyclic molecule contains an aromatic ring having a phenolic hydroxyl group in a side chain, and at least a portion of the phenolic hydroxyl group is substituted with a specific substituent,
The specific substituent has a chemical structure represented by —O—R—X, and the R is a linear or branched alkyl group having 1 to 12 carbon atoms with one hydrogen removed. a group obtained by removing one hydrogen from a linear or branched alkyl group having 2 to 12 carbon atoms containing at least one ether group, and a cyclic alkyl group having 3 to 12 carbon atoms and having one hydrogen removed a group obtained by removing one hydrogen from a cyclic alkyl ether group having 2 to 12 carbon atoms, or a group obtained by removing one hydrogen from a cyclic alkylthioether group having 2 to 12 carbon atoms, wherein X is OH, NH ₂ or SH.
All of the specific substituents are nonionic groups.
Among the specific substituents, R is a group obtained by removing one hydrogen from a branched alkyl group having 3 carbon atoms, and the nonionic group X is OH is a hydroxypropyl group, It is also suitable among ionic groups. Substitution of at least part of the phenolic hydroxyl groups with hydroxypropyl groups is hereinafter sometimes referred to as "hydroxypropyl modification".

(action)
By substituting at least part of the phenolic hydroxyl groups of the cyclic molecule containing an aromatic ring with a specific substituent, those that were soluble only in highly polar solvents such as alkaline aqueous solutions and DMSO can be converted to tetrahydrofuran (THF), chloroform, It becomes soluble in low-polarity solvents such as toluene (see Examples in Table 1). This is probably because the phenolic hydroxyl group of the cyclic molecule was substituted with a nonionic substituent, thereby suppressing aggregation due to formation of hydrogen bonds between rotaxanes.

In this way, the improved solubility in various solvents not only improves processability (handling), but also improves mixing with various compounds and polymers from the viewpoint of compatibility. There are more options for the chemical structure of the cross-linking agent when cross-linking the polyrotaxane. For example, from the polarity index by the SP value, it is well mixed with polymer polypropylene (SP value: 18.8) that is well compatible with toluene (SP value: 18.2) to THF (SP value: 19.4). can be expected.

However, the polyrotaxane in which the cyclic molecule containing the aromatic ring is hydroxypropyl-modified has lower heat resistance than the polyrotaxane in which the cyclic molecule containing the aromatic ring is not hydroxypropyl-modified (see Examples and Comparative Example 2 in Table 1).
Similarly, polyrotaxanes in which cyclodextrin is modified with hydroxypropyl to improve solubility in various solvents have lower heat resistance than polyrotaxanes in which cyclodextrin is not modified with hydroxypropyl (Comparative Example 1 and Comparative Example 1 in Table 1). 3).
Comparing these, the polyrotaxane in which the cyclic molecule containing the aromatic ring is hydroxypropyl-modified has a higher thermal decomposition temperature than the polyrotaxane in which the cyclodextrin is modified with hydroxypropyl (see Examples and Comparative Example 1 in Table 1), and is constant. It has the above heat resistance.

[2] Crosslinked polyrotaxane A crosslinked polyrotaxane in which the cyclic molecules of the polyrotaxane of [1] are crosslinked by a crosslinking agent.

[4] Elastomer An elastomer containing the crosslinked polyrotaxane of [2] above.

The use of the elastomer is not particularly limited. For example, the elastomer can be attached with electrodes and used as a polymer actuator or a polymer sensor.

According to the present invention, it is possible to provide a polyrotaxane having a certain level of heat resistance and good solubility in various solvents.

FIG. 1 is a schematic diagram illustrating the first half of the manufacturing process of the polyrotaxane of the example. FIG. 2 is a schematic diagram of the pillar arene-type polyrotaxane (before hydroxypropyl modification) obtained in the first half of the same. FIG. 3 is a schematic diagram illustrating the latter half of the production process of the polyrotaxane of the example (hydroxypropyl modification) and the cross-linking of the obtained polyrotaxane. 4 is a schematic diagram of the polyrotaxane of Comparative Example 3. FIG.

1. Polyrotaxane (a) Cyclic Molecule Examples of aromatic rings include benzene ring, naphthalene ring, and anthracene ring.
Examples of the cyclic molecule include pillararene and calixarene having a phenolic hydroxyl group in the side chain.
In the cyclic molecule, as described above, at least part of the phenolic hydroxyl groups in the side chain is substituted with a specific substituent, and another part of the phenolic hydroxyl groups is replaced with another group such as -SH , --NH ₂ , --COOH, --SO ₃ H, --PO ₄ H, etc., or grafted chains (for example, grafted chains formed by ring-opening polymerization of lactone monomers) so as to be soluble in various organic solvents. may be substituted with a substituent having

A pillar arene is an oligomer having a structure in which arenes (aromatic rings) are linked in a cyclic and prismatic form, and is generally described as pillar [n]arene, where [n] is the ring member number of the arene. [n] is not particularly limited, but preferably 5 to 6.
Calixarene is an oligomer having a structure in which phenols are cyclically linked via methylene groups, and is generally referred to as calix[n]arene, where [n] is the number of ring members of phenol. [n] is not particularly limited, but preferably 3-10.

(b) Linear Molecules Linear molecules include, but are not limited to, polyethylene glycol, polylactic acid, polyisoprene, polyisobutylene, polybutadiene, polypropylene glycol, polytetrahydrofuran, polydimethylsiloxane, polyethylene, polypropylene, polyvinyl alcohol and Polyvinyl methyl ether etc. can be illustrated. The linear molecule is preferably polyethylene glycol, and other linear molecules may be contained together with polyethylene glycol.

(c) Blocking group The blocking group is not particularly limited, but dinitrophenyl groups, cyclodextrins, adamantane groups, trityl groups, fluoresceins, pyrenes, substituted benzenes (as substituents, alkyl, alkyloxy , hydroxy, halogen, cyano, sulfonyl, carboxyl, amino, phenyl, etc. One or more substituents may be present.), optionally substituted polynuclear aromatics (as the substituents, the above (one or more substituents may be present), steroids, and the like. It is preferably selected from the group consisting of dinitrophenyl groups, cyclodextrins, adamantane groups, trityl groups, fluoresceins and pyrenes, more preferably adamantane groups or trityl groups.

2. Cross-Linking Agent The cross-linking agent for polyrotaxane is not particularly limited, but examples include isocyanate, polyether, polyester, polysiloxane, polycarbonate, poly(meth)acrylate, polyene, copolymers thereof, and mixtures thereof.
The functional group located at each end of the cross-linking agent is not particularly limited, but is preferably an isocyanate group capable of reacting with the phenolic hydroxyl group of the cyclic molecule, and more preferably a blocked isocyanate.

3. Elastomer The elastomer may consist of only crosslinked polyrotaxane, or may be a mixture of crosslinked polyrotaxane and other elastomers.
Examples of other elastomers include, but are not limited to, silicone elastomers, styrene thermoplastic elastomers, natural rubbers, nitrile rubbers, acrylic rubbers, urethane rubbers, urea rubbers, and fluororubbers.

A polyrotaxane of the example was produced by a method including the following steps (1) to (5).

(1) Activation of both ends of polyethylene glycol (abbreviated as PEG) As shown in FIG. 2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO), NaBr and NaClO were allowed to react with the aqueous solution for 15 minutes at pH 10-11. Diluted hydrochloric acid was added to the reaction mixture to treat it, and the resulting mixture was extracted twice with dichloromethane. The resulting dichloromethane solution was collected, concentrated under reduced pressure, and recrystallized with ethanol to obtain polyethylene glycol (abbreviated as PEG-COOH) having carboxyl groups at both ends of the molecule with a weight yield of 91%.

(2) Synthesis of pillar[5]arene As shown in FIG. 1(2), dimethoxypillar[5]arene (2. 00 g, 2.67 mmol) in anhydrous chloroform (150 mL) was added with boron tribromide (13.6 g, 54.3 mmol) and stirred at 25° C. for 72 hours. The precipitate formed by adding water to the reaction solution was collected, washed with 0.5 M HCl aqueous solution and chloroform, and pillar [5]arene containing an aromatic ring having a phenolic hydroxyl group in the side chain (abbreviated as P5AOH) (1 .61 g, 2.64 mmol) was obtained quantitatively.

(3) Synthesis of pseudo-polyrotaxane As shown in FIG. 1(3), 10 mL of a P5AOH solution (0.0121 mol/L) prepared using 10 mL of a methanol aqueous solution mixed at a weight ratio of methanol:water=1:1 as a solvent. was mixed with 0.6 mL (1.894 mol/L) of PEG-COOH solution and allowed to stand at room temperature for 1 day. The resulting precipitate was washed with 10 mL of water, and the resulting residue was dried under vacuum at 50° C. for 1 day to obtain a pseudo-polyrotaxane in which P5AOH clathrates PEG-COOH (abbreviated as PseudoP5AOH-PEG).

(4) Synthesis of pillar arene-type polyrotaxane As shown in FIG. 0.12 mmol) dissolved in dimethylformamide (dryDMF) (10 mL) was sufficiently ice-cooled, PseudoP5AOH-PEG (150 mg) was added, and the mixture was stirred at 4° C. overnight. The resulting solution is concentrated under reduced pressure on a rotary evaporator and stirred with excess water. Filter the precipitate, add acetone to the resulting residue, ultrasonically wash, remove the supernatant, vacuum dry, and pillar arene-type polyrotaxane in which adamantane groups are arranged at both ends of PEG (abbreviated as P5AOH-PEG ) (104 mg). A schematic diagram of this P5AOH-PEG (also the structural formula for P5AOH) is shown in FIG.

(5) Synthesis of hydroxypropyl-modified pillar arene-type polyrotaxane As shown in FIG. 131.4 g (3000 eq.) of propylene oxide was added to the dissolved solution and stirred at room temperature for 24 hours. The reaction was concentrated under reduced pressure to remove residual propylene oxide. After the residue was acid-treated with 3M HCl aqueous solution to pH=3-4, the acid-treated solution was concentrated under reduced pressure to remove water. THF was added to the residue, the mixture was filtered, and the soluble portion was concentrated under reduced pressure. Ethanol was added to 1.5 g of the resulting liquid compound and filtered, and the insoluble portion was vacuum-dried at 40° C. for 1 day to replace at least a portion of the phenolic hydroxyl groups of the pillar arenes with hydroxypropyl groups (hydroxy 154 mg of propyl-modified) pillararene-type polyrotaxane (abbreviated as P5AOHP-PEG) was obtained.

[Comparative Example 2]
Comparative Example 2 was P5AOH-PEG (before hydroxypropyl modification) obtained in (4) above (FIG. 2).

[Comparative Example 3]
Using the PEG-COOH obtained in (1) above and a commercially available α-cyclodextrin (abbreviated as CD), a polyrotaxane of Comparative Example 3 was produced by the following method.
According to the method of literature (Macromolecules, 2005, 38, 7524-7527.), PEG-COOH 3.0 g (8.6 × 10 ^-5 mol) and α-cyclodextrin (12 g, 1.2 × 10 ^-2 mol) Dissolved in water (100 mL) and left in refrigerator overnight. The resulting paste-like mixture was freeze-dried, and the dried solids were combined with adamantaneamine (0.16 g, 1.1×10 ⁻³ mol) and BOP reagent (0.48 g, 1.1×10 ⁻³ mol). , and ethyldiisopropylamine (0.19 mL, 1.2×10 ⁻³ mol) were dissolved in 100 mL of DMF and reacted at 4° C. overnight. The resulting mixture was centrifuged twice each with a mixed solvent of DMF/MeOH (1:1) and MeOH. 80 mL of DMSO was added to the collected precipitate and washed, H ₂ O (800 mL) was added to the obtained precipitate and centrifuged, the resulting solid content was freeze-dried, and the cyclodextrin-type polyrotaxane of Comparative Example 3 ( 9.55 g to 10.3 g of CD-PEG) was obtained. A schematic diagram of this CD-PEG (also the structural formula for CD) is shown in FIG.

[Comparative Example 1]
The CD of CD-PEG of Comparative Example 3 above is hydroxypropyl-modified by the method described in paragraph 0092 of WO 2005/080469, and the hydroxypropyl-modified cyclodextrin-type polyrotaxane of Comparative Example 1 (abbreviated as CDP-PEG to do).

[measurement]
The following measurements were carried out for Examples and Comparative Examples 1 to 3.

(a) TG-DTA measurement (confirmation of heat resistance)
TG-DTA measurement was performed for each of the polyrotaxanes of Examples and Comparative Examples 1-3.
Specifically, using a differential thermal/thermogravimetric (TG-DTA) simultaneous measurement device (Hitachi High-Technologies STA7200), using platinum as a sample pan, in a _N gas stream (10 mL / min), thermal decomposition temperature rise Speed: 100 to 300°C...1°C/min, 300 to 900°C...10°C/min. Based on the weight before heating (100%), the temperature at which the weight is reduced by 50% with respect to the weight before heating is shown in Table 1 as the thermal decomposition temperature (50% weight reduction).

(B) Solubility test To 10 mg of each sample of the polyrotaxanes of Examples and Comparative Examples 1 to 3, 1 mL of a solvent was added and allowed to stand at room temperature for 24 hours. was used to determine solubility. Five kinds of solvents, namely NaOH aqueous solution, DMSO, THF, chloroform, and toluene, were used. Table 1 shows the results.

As shown in FIG. 3(6), the P5AOHP-PEG of the example can be a crosslinked polyrotaxane in which a plurality of adjacent cyclic molecules of P5AOHP-PEG are crosslinked by a crosslinking agent.
This crosslinked polyrotaxane can be used alone or mixed with other elastomers as a highly heat-resistant elastomer.
In addition, by mixing the P5AOHP-PEG of the example with another elastomer, the cyclic molecule of the P5AOHP-PEG and the functional group of the other elastomer are crosslinked directly or with a crosslinker to obtain a highly heat-resistant elastomer. can be used as
These highly heat-resistant elastomers can be used as highly heat-resistant polymer actuators or polymer sensors by attaching electrodes (for example, by attaching elastic electrode layers to both sides of a film-like elastomer). .

Specifically, a crosslinked polyrotaxane was prepared by the following method.
20 mL of THF was added to 22 mg of P5AOHP-PEG of Example, 4 mL of a cross-linking agent (hexamethylene diisocyanate) and 2 mL of dibutyltin dilaurate were added, and the mixture was stirred at room temperature (about 1 day).
THF was volatilized from the above solution (at room temperature for about half a day) to obtain a gel-like substance. This gel-like substance was applied to a glass substrate, and left to stand overnight in a draft at room temperature and dried to obtain a crosslinked polyrotaxane film.

It should be noted that the present invention is not limited to the above embodiments, and can be embodied with appropriate modifications within the scope of the invention.

Claims

In a polyrotaxane having a linear molecule, a cyclic molecule that encloses the linear molecule in a skewed manner, and blocking groups arranged at both ends of the linear molecule,
The cyclic molecule contains an aromatic ring having a phenolic hydroxyl group in a side chain, and at least a portion of the phenolic hydroxyl group is substituted with a specific substituent,
The specific substituent has a chemical structure represented by —O—R—X, and the R is a linear or branched alkyl group having 1 to 12 carbon atoms with one hydrogen removed. a group obtained by removing one hydrogen from a linear or branched alkyl group having 2 to 12 carbon atoms containing at least one ether group, and a cyclic alkyl group having 3 to 12 carbon atoms and having one hydrogen removed a group obtained by removing one hydrogen from a cyclic alkyl ether group having 2 to 12 carbon atoms, or a group obtained by removing one hydrogen from a cyclic alkylthioether group having 2 to 12 carbon atoms, wherein X is OH, NH 2 or SH.
The polyrotaxane according to claim 1, wherein the specific substituent is a hydroxypropyl group.
A crosslinked polyrotaxane in which cyclic molecules of a plurality of polyrotaxanes according to claim 1 or 2 are crosslinked.
An elastomer containing the crosslinked polyrotaxane according to claim 3.