JP2014210260A - Self-induced vibration gel containing iron complex site - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive self-induced vibration gel which is self-driven by converting a Belousov-Zhabotinsky reaction (BZ reaction) directly into mechanical energy, without use of an external power source or an external controller, and does not use a rare-metal ruthenium-based complex.SOLUTION: The type of the catalyst is changed advantageously from a rare metal to a base metal by introducing an Fe(bpy)complex to the principal chain of a gel through a chemical bond by using a monomer including an iron-bipyridium (Fe(bpy)) complex, leading to substantial cost reduction and stabilization of the available amount and costs, an important problem for mass production.

Description

  The present invention relates to a self-oscillating gel containing an iron complex moiety.

  Living organisms are autonomous molecular systems that are driven by converting chemical reactions directly into dynamic energy inside the living body without relying on external control devices and external power sources. If a molecular system that autonomously drives like a living organism can be constructed in a tailor-made manner, a system that drives without depending on an external power supply / external control device can be artificially constructed (Non-patent Document 1, 2). In order to construct such a molecular system, a self-excited vibration gel using a Belousov-Zhabotinsky reaction (BZ reaction) (Non-Patent Documents 3 and 4) as a chemical reaction source has been developed. Yes. A self-oscillating gel is a soft material that self-excites like a cardiomyocyte. During the BZ reaction, the redox state of the metal catalyst vibrates with a periodic rhythm. Since the self-excited vibration gel contains the metal catalyst for the BZ reaction in the main chain, it synchronizes with the periodic change of the oxidation-reduction state of the metal catalyst and its swelling ratio (water content) changes.

Research on polymer systems using the BZ reaction as a driving source was made in 1982 by Ishiwatari (Shinshu Univ.) And others by covalently bonding a metal catalyst to a linear polymer (Non-patent Document 5), and in 1996 Yoshida (Tokyo Univ.) Have succeeded in gelation by introducing a chemical bond into a polymer chain (Non-patent Document 6). These self-excited polymer systems are achieved by covalently bonding a ruthenium-bipyridine complex (hereinafter referred to as “Ru (bpy) ₃ ”) as a BZ reaction catalyst to a polymer chain. The hydration structure of the Ru (bpy) ₃ site introduced into the polymer chain by a covalent bond is different between the oxidized state (Ru (III)) and the reduced state (Ru (II)). Therefore, the self-excited vibrating gel having Ru (bpy) ₃ site swells because it has a higher affinity with water in the oxidized state, and contracts because it has a lower affinity with water in the reduced state. Such a self-excited swelling / shrinking motion can be used as an actuator, and the merit of not requiring an external control device or an external power source can be utilized (Non-patent Documents 7 and 8).

  Array using self-excited vibration gel and manufacturing method thereof, autonomous responder and manufacturing method thereof (Patent Document 1), array using self-excited vibration gel, autonomous responder, autonomous response device, autonomous response method And a method for producing an array of autonomously responsive gels (Patent Document 2).

Shingo Maeda, Yusuke Hara, Ryo Yoshida, Shuji Hashimoto (2008) Creation of self-oscillating gel actuators for the realization of chemical robots, Polymer Proceedings, 10 (65), pp.634-640. Yusuke Hara (2009) Creation of a new self-excited vibration polymer driven in a biological environment and analysis of self-excited viscous vibration, 66 (8), pp.289-297. Zaikin, A.N .; Zhabotinsky, A.M. (1970). Concentration Wave propagation in two-dimensional liquid-phase self-oscillating system, Nature, 225, pp.535-537. Field, R.J .; Burger, M. (1985). Oscillations and Traveling Waves in Chemical Systems; John Wiley & Sons: New York, NY, USA. Ishiwatari, T .; Kawaguchi, M .; Mitsuishi, M. (1984). Oscillatry reactions in polymer systems, Journal of Polymer Science Part A: Polymer Chemistry, 22, pp. 2699-2704 Yoshida, R .; Takahashi, T .; Yamaguchi, T .; Ichijo, H. (1996). Self-oscillating gel, Journal of the American Chemical Society, 118, pp. 5134-5135. R. Yoshida, T. Sakai, Y. Hara, S. Maeda, S. Hashimoto, D. Suzuki, Y. Murase: “Self-oscillating gel as novel biomimetic materials” Journal of Controlled Release, 140 (3), pp. 186-193 (2009). S. Maeda, Y. Hara, S. Nakamaru, S. Hashimoto: “Design of autonomous gel actuators” Polymers, 3 (1), pp.299-313 (2011).

JP 2010-222465 A JP 2010-58185 A

In a new self-excited vibration gel that directly drives the Belousov-Zhabotinsky reaction (BZ reaction) directly into mechanical energy without using an external power supply / external control device, the BZ reaction site is Until now, this has been achieved only with Ru-based complexes.
For example, although Patent Documents 1 and 2 exemplify a ruthenium complex, a cerium complex, a manganese complex, or an iron-phenanthroline complex, what is described as a specific gel has the following structure: There is no specific description of gels other than ruthenium complexes.

Thus, conventionally, since it was an essential requirement to use a Ru-based complex which is a rare metal as a BZ reaction site, the cost was high and it was a great obstacle to practical use.
In addition, since it is a rare metal, the price of the Ru-based complex is greatly affected by the international situation, and it has a problem that securing of the availability will not be stable in the future. Therefore, in order to put the self-excited vibration gel into practical use, it has been desired to develop a new self-excited vibration gel capable of stabilizing cost and availability.

  The present invention has been made in view of the current situation, and directly converts the Belousov-Zhabotinsky reaction (BZ reaction) into mechanical energy without using an external power source or an external control device. An object of the present invention is to provide an inexpensive self-excited vibration gel that does not use a ruthenium complex, which is a rare metal, as a BZ reaction site.

As a result of intensive studies to achieve the above object, the present inventors copolymerize a monomer containing an iron-bipyridine complex (Fe (bpy) ₃ ) and a monomer that forms the main chain of the polymer chain. Thus, the inventors have obtained the knowledge that an inexpensive new self-excited vibration gel that can be driven by directly converting the BZ reaction into dynamic energy without using an external power source / external control device can be achieved.

［２］ゲルを構成する高分子主鎖が、下記の式で表される構成単位を有していることを特徴とする［１］に記載の自励振動ゲル。

［３］前記高分子ゲルの構造が、インターペネトレーションネットワーク(IPN)もしくはセミインターペネトレーションネットワーク(Semi-IPN)構造を有することを特徴とする［１］又は［２］に記載の自励振動ゲル。 The present invention has been completed based on these findings, and according to the present invention, the following inventions are provided.
[1] A self-excited vibrating gel that can directly drive the Belousov-Zhabotinsky reaction by directly converting it into mechanical energy,
A self-excited vibration gel characterized in that a polymer main chain constituting the gel has a site containing an iron-bipyridinium complex represented by the following formula as a catalyst for the reaction and a crosslinking site.

[2] The self-excited vibrating gel according to [1], wherein the polymer main chain constituting the gel has a structural unit represented by the following formula.

[3] The self-excited vibrating gel according to [1] or [2], wherein the polymer gel has an interpenetration network (IPN) or semi-interpenetration network (Semi-IPN) structure.

The novel self-excited vibrating gel using Fe (bpy) ₃ as a catalyst of the present invention can be driven without the need for an external power supply and an external control device using the Belousov-Zhabotinsky reaction (BZ reaction) as a driving source. It is. The present invention makes it possible to synthesize a self-excited vibration gel that is less expensive than a self-excited vibration gel using a Ru-based catalyst that is a conventional rare metal. Ru-based catalysts are widely known to have effects such as the BZ reaction being stopped by the influence of light. However, if Fe (bpy) ₃ catalyst is used, it is stable without being affected by light. This is an epoch-making technology that can cause self-excited vibration.

The figure which shows the space-time plot of the gel obtained in Example 3

Hereinafter, the novel self-oscillating gel of the present invention will be described in detail.
In the present invention, a self-oscillating gel that is driven by directly converting a chemical reaction into mechanical energy contains an iron-bipyridinium complex that functions as a catalyst for the Belousov-Zhabotinsky reaction (BZ reaction). It has the site | part in the polymer chain which comprises a gel with a chemical bond, It is characterized by the above-mentioned.

Specifically, the novel self-oscillating gel of the present invention is synthesized using a monomer containing an iron-bipyridinium complex. The monomer containing the iron-bipyridinium complex in the present invention is a novel compound having, for example, the following structure:
Fe (4-vinyl-4'-methyl-2,2-bipyridine) bis (2,2'-bipyridine) bis ((tetrafluoroborate)
(Hereinafter referred to as “Fe (bpy) ₃ monomer”).

In the exemplified monomer, Fe (bpy) ₃ and a vinyl group are directly bonded. However, in the present invention, the site containing Fe (bpy) ₃ may be chemically bonded to the polymer chain. It goes without saying that a site other than (bpy) ₃ , for example, an ethylene oxide group may be bonded between Fe (bpy) ₃ and a vinyl group, or may be hanging in a branched structure. Absent.

The main chain of the self-oscillating gel of the present invention is composed of a monomer containing the Fe (bpy) ₃ , a temperature-responsive monomer, and a hydrophilic monomer. In order to control the elastic modulus, a hydrophobic monomer or a macromonomer is used. You may contain.

  In addition to the so-called normal gel having a single network, the gel synthesized in the present invention has an IPN structure (double network structure) in which the gel network exists inside the gel (JPGong, Y. Katsuyama, T. Kurokawa, Y Osada “Double Network Hydrogels with Extremely High Mechanical Strength” Advanced Materials, 15 (14), 1155-1158 (2003).), Or a semi-IPN structure in which a linear polymer is present inside the gel. In this case, the gel with the Semi-IPN structure or IPN structure is higher in the elastic modulus of the gel if it is an acrylamide gel or an acrylamide polymer or a copolymer having such a main chain, and the gel tends to be tough. The use scenes such as artificial muscles are greatly expanded.

In the present invention, the content of the iron-bipyridine (Fe (bpy) ₃ ) complex, which is a metal catalyst for the BZ reaction introduced by chemical bonding into the main chain of the gel, is 0.5 to 10 mol%, preferably 0.5 to 5 mol. %, More preferably 1 to 3 mol%.

  In the present invention, as a main chain capable of constituting a polymer chain of a self-excited vibration gel capable of directly converting a chemical reaction into mechanical energy, for example, N-isopropylacrylamide, N-ethoxyethylmethacrylamide, N-alkyl substitution ( Among the (meth) acrylamide derivatives, Nn-propylacrylamide, Nn-propylmethacrylamide, N-tetrahydrofurfurylmethacrylamide, N-ethoxyethylacrylamide, N-tetrahydrofurfurylacrylamide, vinylpyrrolidone, dimethylacrylamide, methylaminopropylacrylamide, Examples thereof include dimethylaminopropylacrylamide methyl chloride quaternary salt, hydroxyethylacrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and the like. Examples of the site for controlling water solubility include vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 4-vinylbenzene sulfonic acid, and methacryl sulfonic acid. These may be used individually by 1 type and may be used in combination of 2 or more type.

In the present invention, a self-excited vibration gel capable of directly converting a chemical reaction into dynamic energy can be produced by a polymer chain constituting a gel obtained by copolymerizing the above monomers, and Fe that is a catalyst for a BZ reaction. There is no particular limitation as long as (bpy) ₃ can be chemically encapsulated in the main chain of the gel. The polymerization method is not limited to heat or light, and means is not selected as long as a gel can be synthesized. Moreover, said monomer may be used independently and may be used in combination of 2 or more type.

  Solvents used for the polymerization of the gel include, for example, water, lower alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, aromatic / aliphatic or heterocyclic compounds such as toluene, cyclohexane and hexane, acetone, methyl ethyl ketone and tetrahydrofuran. Various organic solvents such as can be used.

  In the present invention, the monomer concentration during polymerization is 10 to 50% by weight, preferably 15 to 30% by weight, and more preferably 18 to 25% by weight. If the monomer concentration is too low, no gel is formed, and if it is too high, the gel becomes brittle.

Examples of the polymerization initiator include persulfates such as sodium persulfate and potassium persulfate, peroxides such as benzoyl peroxide, hydroperoxides such as cumene hydroperoxide, and azo compounds such as azobisisobutyronitrile. Can be mentioned.
The polymerization initiator concentration is usually preferably from 0.1 to 10 mol% based on the monomer used. Further, a chain transfer agent such as alkyl mercaptan, a polymerization accelerator such as a Lewis acid compound, and a pH adjuster such as phosphoric acid, tartaric acid, lactic acid and citric acid may be used to regulate the molecular weight. The polymerization temperature is appropriately determined depending on the solvent used and the polymerization initiator, but is usually room temperature to 200 ° C.

  EXAMPLES Hereinafter, although this invention is demonstrated using an Example, this invention is not limited to these Examples.

[Example 1: Production of Fe (bpy) ₃ -containing monomer]
(Synthesis of 4-methyl-4 '-(2-methoxyethyl) -2,2'-bipyridine)

  Under a nitrogen atmosphere, 43.25 g (427 mmol) of diisopropylamine and 200 ml of THF were charged into a 5 L three-necked flask, and 267 ml (427 mmol) of a 1.6Mn-butyllithium hexane solution was added dropwise at -25 ° C. Subsequently, a THF 1.5 L solution of 75.00 g (407 mmol) of 4,4′-dimethyl-2,2′-bipyridine was added dropwise at 0 ° C. or less. After stirring at the same temperature for 1 hour, 36.05 g (448 mmol) of chloromethoxymethane was added dropwise at 5 ° C. or lower, and the temperature was naturally raised to room temperature. The reaction was stopped by dropwise addition of an aqueous THF solution, and extracted with 1 L of ethyl acetate to obtain a crude product. Purification was performed using a developing solvent dichloromethane: methanol 30: 1 to 10: 1 using silica gel column chromatography to obtain 4-methyl-4 '-(2-methoxyethyl) -2,2'-bipyridine.

The analysis results of the obtained compound are shown below.
NMR (CDCl3): 8.60ppm (2H, d), 8.40ppm (2H, s), 7.02ppm (2H, d), 3.70ppm (sH, t), 3.24ppm (3H, s), 2.72ppm (2H, t), 2.37ppm (3H, s)

  (Synthesis of 4-methyl-4'-vinyl-2,2'-bipyridine (vbpy))

  Under an atmosphere, a 3 L three-necked flask was charged with a solution of 39.05 g (173 mmol) of 4-methyl-4 ′-(2-methoxyethyl) -2,2′-bipyridine in 500 ml of THF and cooled to −78 ° C. . A solution of 38.83 g (346 mmol) of potassium t-butoxide in 300 ml of THF was added dropwise over 40 minutes, and the mixture was stirred at the same temperature for 2 hours. The temperature was raised to −40 ° C., and an aqueous THF solution was added dropwise to stop the reaction. Extraction with ethyl acetate and washing with saturated brine gave a crude product. Purification is carried out using silica gel column chromatography in a developing solvent of dichloromethane: methanol: triethylamine 30: 1: 0.05 to 10: 1: 0.05 and 4-methyl-4'-vinyl-2,2'- in 39% yield. Bipyridine was obtained.

The analysis results of the obtained compound are shown below.
NMR (CDCl3): 8.70-8.40ppm (4H, 1m), 7.25-7.70ppm (2H, m), 6.70-6.50ppm (1H, m), 5.91ppm (1H, d), 5.42ppm (1H, d) 2.37ppm (3H, s)

(Synthesis of [Fe (vbpy) (MeCN) ₄ ] (BF ₄ ) ₂ )
In a nitrogen atmosphere, a 3-necked flask was charged with a solution of Fe (BF ₄ ) ₂ · 6H ₂ O (3.37 g, 10 mmol) in 50 ml of acetonitrile and 50 ml of methanol, and the above 4-methyl-4′-vinyl-2,2 ′ was added at room temperature. -A solution of 1.96 g (10 mmol) of bipyridine in 10 ml of dichloromethane was added. After stirring for 10 minutes, the solvent was distilled off to obtain a crude product. The operation of dissolving in acetonitrile and filtering insolubles, and dropping into water to cause crystallization was repeated twice. The following [Fe (vbpy) (MeCN) ₄ ] (BF ₄ ) ₂ was obtained through filtration, washing and drying.

(Synthesis of [Fe (vbpy) (bpy) ₂ ] (BF ₄ ) ₂ )
In a nitrogen atmosphere, a three-necked flask was charged with 50 ml of a solution of 4.5 g (7.6 mmol) of [Fe (vbpy) (MeCN) ₄ ] (BF ₄ ) ₂ in acetonitrile and 2.38 g (15.3 mmol) of 2,2′-bipyridine at room temperature. ) In 50 ml of dichloromethane was added over 1 hour. After stirring for 30 minutes, the solvent was distilled off to obtain a crude product. It was dissolved in acetone and dropped into water for crystallization. After filtration, washing and drying, the following [Fe (vbpy) (bpy) ₂ ] (BF ₄ ) ₂ (hereinafter referred to as “Fe (bpy) ₃ ) monomer” is obtained. )

元素分析、計算値(%)：C，53.70；H，3.82；N，11.39

Elemental analysis, calculated value (%): C, 53.70; H, 3.82; N, 11.39

[Example 2: Synthesis and qualitative analysis of (NIPAAm-co-Fe (bpy) ₃ ) gel]
N-isopropylacrylamide (NIPAAm), Fe (bpy) ₃ monomer obtained in Example 1, methylenebisacrylamide (BIS), azobisisobutyronitrile (AIBN) were dissolved in a mixed solvent of ethanol and water, (NIPAAm-co-Fe (bpy) ₃ ) gel was performed by heating at 60 ° C. for 20 hours. Thereafter, (NIPAAm-co-Fe (bpy) ₃ ) gel was purified using ethanol and water. NIPAAm gel is widely known to be colorless and transparent or white depending on the synthesis method. (NIPAAm-co-Fe (bpy) ₃ ) gel became a red colored gel derived from Fe (bpy) ₃ . UV measurement was performed on Fe (bpy) ₃ monomer and (NIPAAm-co-Fe (bpy) ₃ ) gel.

As a result of the UV measurement, a characteristic absorption wavelength derived from Fe (bpy) ₃ was observed in (NIPAAm-co-Fe (bpy) ₃ ) gel. This characteristic absorption wavelength is a peak that cannot be seen in the NIPAAmn chain alone, so it is clear that it originates from an iron complex. This revealed that Fe (bpy) ₃ was copolymerized in (NIPAAm-co-Fe (bpy) ₃ ) gel.

[Example 3: Production of gel containing Fe (bpy) ₃ ]
The Fe (bpy) ₃ monomer obtained in Example 1, acryloylmorpholine (ACMO), and N, N′-methylenebisacrylamide were dissolved in a mixed solvent of ethanol and water, and the gel was polymerized at 60 ° C. Thereafter, the gel was purified using ethanol and water.

The obtained gel was immersed in a BZ reaction solution in which malonic acid, sodium bromate, and nitric acid were dissolved in water. The appearance of the BZ reaction in the gel was photographed with a microscope. He also analyzed the video using software and wrote a spatiotemporal plot. The results are shown in FIG. The spatiotemporal plot shown in FIG. 1 proved that the BZ reaction occurred inside the new self-excited vibrating gel containing Fe (bpy) ₃ .

Claims (3)

A self-excited vibrating gel that can directly drive the Belousov-Zhabotinsky reaction directly into mechanical energy,
A self-excited vibration gel characterized in that a polymer main chain constituting the gel has a site containing an iron-bipyridinium complex represented by the following formula as a catalyst for the reaction and a crosslinking site.

The self-excited vibrating gel according to claim 1, wherein the polymer main chain constituting the gel has a structural unit represented by the following formula.

  The self-excited vibration gel according to claim 1 or 2, wherein the polymer gel has an interpenetration network (IPN) or semi-interpenetration network (Semi-IPN) structure.

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