阅读说明：本技术 一种基于金属配位键-氢键双交联的自愈合硅弹性体的制备方法及弹性体 (Preparation method of self-healing silicon elastomer based on metal coordination bond-hydrogen bond double crosslinking and elastomer ) 是由 田明 李建萍 宁南英 张立群 于 2018-07-13 设计创作，主要内容包括：本发明公开了一种基于金属配位键-氢键双交联的自愈合硅弹性体制备方法。通过八甲基环四硅氧烷与3-氨丙基甲基二甲氧基硅烷开环聚合制备侧链含有氨基的聚硅氧烷,然后将带有吡啶环的单体与氨基接枝反应得到带有吡啶环的聚硅氧烷,进而用金属盐和吡啶环配位络合反应得到金属配位-氢键双交联的自愈合硅弹性体。本发明设计将金属配位键和氢键设计在一个交联网络结构,用更简化的合成工艺和方法,制备更稳定和高效自愈合硅弹性体。(The invention discloses a preparation method of a self-healing silicon elastomer based on metal coordination bond-hydrogen bond double crosslinking. The self-healing silicon elastomer with metal coordination-hydrogen bond double crosslinking is prepared by ring-opening polymerization of octamethylcyclotetrasiloxane and 3-aminopropylmethyldimethoxysilane to prepare polysiloxane with amino groups on side chains, grafting reaction of a monomer with a pyridine ring and the amino groups to obtain the polysiloxane with the pyridine ring, and then coordination and complexation reaction of metal salt and the pyridine ring. The invention designs the metal coordination bond and the hydrogen bond in a cross-linked network structure, and prepares the stable and efficient self-healing silicon elastomer by using a simpler synthesis process and method.)

1. A preparation method of a self-healing silicon elastomer based on metal coordination bond-hydrogen bond double crosslinking is characterized by comprising the following steps:

the preparation method comprises the steps of carrying out ring-opening polymerization on octamethylcyclotetrasiloxane and 3-aminopropylmethyldimethoxysilane to prepare polysiloxane with amino groups on side chains, then carrying out grafting reaction on a monomer with a pyridine ring and the amino groups to obtain the polysiloxane with the pyridine ring, and carrying out coordination and complexation reaction on metal salt and the pyridine ring to obtain the self-healing silicon elastomer with metal coordination-hydrogen bond double cross-linking.

2. A method for preparing a self-healing silicone elastomer according to claim 1, comprising the steps of:

(1) preparation of polysiloxanes having amino groups in the side chains

Mixing 3-aminopropylmethyldimethoxysilane and octamethylcyclotetrasiloxane according to the mass ratio of 1: 3-1: 7, adding a catalyst, uniformly mixing, pre-polymerizing for 4-6 h at 80-100 ℃, cooling to 45-55 ℃, removing water and unreacted monomers to obtain a prepolymer, heating to 110-120 ℃, reacting for 7-10 h under normal pressure, cooling to room temperature, adding an end-capping agent, heating to 160-180 ℃, removing the unreacted monomers to obtain polysiloxane with amino groups on side chains,

wherein the dosage of the catalyst is 0.1 to 0.3 percent of the mass sum of the 3-aminopropylmethyldimethoxysilane and the octamethylcyclotetrasiloxane, and the dosage of the end-capping agent is 0.1 to 0.3 percent of the mass sum of the 3-aminopropylmethyldimethoxysilane and the octamethylcyclotetrasiloxane;

(2) pendant aminopolysiloxane grafting reactions

Dissolving the product obtained in the step (1) in a solvent, dissolving a pyridine ring monomer in the solvent, heating to 110-120 ℃ in a nitrogen environment, uniformly mixing for 3-5 h, heating to 130-140 ℃, uniformly stirring for 4-6 h to obtain polysiloxane with a pyridine ring, wherein the molar ratio of the product obtained in the step (1) to the pyridine ring monomer is (2-3): 1;

(3) polysiloxane coordination complex reaction

And (3) fully dissolving the product obtained in the step (2) in a solvent, dropwise adding metal salt dissolved in the solvent, fully and uniformly stirring at room temperature, and volatilizing the solvent to obtain the self-healing silicon elastomer, wherein the molar ratio of the pyridine ring ligand to the metal ions in the product obtained in the step (3) is 1: 1-6: 1.

3. A method for preparing a self-healing silicone elastomer according to claim 1, wherein:

the polysiloxane with amino-containing side chains has 5-10% of amino-containing content and 8000-20000 of molecular weight.

4. A method for preparing a self-healing silicone elastomer according to claim 1, wherein:

the pyridine ring monomer is selected from at least one of picolinic acid or picolinic acid chloride.

5. A method for preparing a self-healing silicone elastomer according to claim 1, wherein:

the metal salt is selected from FeCl₃Bis (trifluoromethylsulfonyl) imide zinc, Fe (BF)₄)₂、ZnCl₂、Zn(ClO₄)₂、CuCl₂、LaCl₃At least one of (1).

6. A method for preparing a self-healing silicone elastomer according to claim 2, wherein:

the catalyst is at least one of potassium hydroxide, tetramethyl ammonium hydroxide, ammonium hydroxide or benzyl trimethyl ammonium hydroxide.

7. A method for preparing a self-healing silicone elastomer according to claim 2, wherein:

the end-capping reagent is at least one of glacial acetic acid, propionic acid and n-butyric acid.

8. A self-healing silicon elastomer obtained by the preparation method of the self-healing silicon elastomer based on metal coordinate bond-hydrogen bond double crosslinking according to any one of claims 1 to 7.

Technical Field

The invention relates to the technical field of elastomers, in particular to a preparation method of a self-healing silicon elastomer based on metal coordination bond-hydrogen bond double crosslinking and the elastomer.

Background

The high molecular polymer composite material is widely applied to various fields of civil engineering, transportation, aerospace and the like at present due to the advantages of high strength, light weight, good processability and the like, and has higher practical application and research values. However, the material is easily affected by chemical substances, external force, light, heat and the like during long-term use, so that the material is cracked, and the service life of the material is greatly shortened due to internal damage. Self-healing of a material refers to the ability of the material to repair itself when damaged. Self-healing materials are divided into two categories: compared with the external aid type and the intrinsic type, the intrinsic type self-healing through the valence bond action can not only repair microcracks, but also repair broken materials, so the external aid type and the intrinsic type become hot spots of current research.

Silicone rubber is a macromolecular polymer material with a main chain formed by Si-O-Si bonds, and a molecular chain of the macromolecular polymer material has both inorganic and organic properties. Compared with other traditional general rubber products, the rubber product has the characteristics of excellent high and low temperature resistance, electric insulation performance, weather resistance, chemical corrosion resistance, hydrophobicity and the like, so that the rubber product is applied to the fields of coatings, adhesives, sealing elements, biomedical devices, military aerospace and the like.

Researchers have now prepared a variety of self-healing elastomers using different methods, Wudl et al first reported a polymer material with a reversibly cross-linked network prepared using Diels-Alder (Macromolecules,2003,36(6): 1802-; herbst reported a telechelic polymer that self healed at room temperature (Polymer chemistry,2012,3(11): 3084-; li et al prepared polyacrylates grafted with a photocurable group benzophenone and a hydrogen bonding group UPy by a copolymerization method (Macromolecules,2011,44(13): 5336-5343.); although the application field of soft materials is greatly widened by adopting the methods, a plurality of problems still exist and need to be solved. The main points are as follows: (1) the polymer of covalent cross-linking has high strength, good heat resistance and small permanent deformation, but the self-healing efficiency is low; non-covalent bonds have reversible properties but tend to be weaker; (2) external stimulation (such as heat, light and the like) is often needed for self-healing, and room-temperature self-healing cannot be realized; (3) the prepared self-healing silicon elastomer has the defects of low strength, poor elasticity, high healing temperature, low healing efficiency and the like.

Disclosure of Invention

In order to solve the problems in the prior art, the invention uses non-covalent bonds with dynamic reversible characteristics to replace chemical crosslinking to prepare the silicon elastomer. Common non-covalent interactions include hydrogen bonding, ionic bonding, coordination bonding, pi-pi stacking, and the like. By comparing their bond energies, processability, mechanical properties, healing efficiency, etc., it is known that coordination bonds are the strongest non-covalent bonds and reversible hydrogen bonds allow the material to have multiple healing capabilities everywhere and the material is easy to process. Therefore, the invention designs the metal coordination bond and the hydrogen bond combination in a cross-linked network structure, and prepares the more stable and efficient self-healing elastomer by using a simpler synthesis process and method.

One of the purposes of the invention is to provide a preparation method of a self-healing silicon elastomer based on metal coordination bond-hydrogen bond double crosslinking, which comprises the following steps: the preparation method comprises the steps of carrying out ring-opening polymerization on octamethylcyclotetrasiloxane and 3-aminopropylmethyldimethoxysilane to prepare polysiloxane with amino groups on side chains, then carrying out grafting reaction on a monomer with a pyridine ring and the amino groups to obtain the polysiloxane with the pyridine ring, and carrying out coordination and complexation reaction on metal salt and the pyridine ring to obtain the self-healing silicon elastomer with metal coordination-hydrogen bond double cross-linking.

Preferably, the preparation method may comprise the steps of:

(1) preparation of polysiloxanes having amino groups in the side chains

Mixing 3-aminopropylmethyldimethoxysilane and octamethylcyclotetrasiloxane according to the mass ratio of 1: 3-1: 7, adding a catalyst, uniformly mixing, pre-polymerizing for 4-6 h at 80-100 ℃, cooling to 45-55 ℃, removing water and unreacted monomers to obtain a prepolymer, heating to 110-120 ℃, reacting for 7-10 h at normal pressure, cooling to room temperature, adding an end-capping agent, heating to 160-180 ℃, removing the unreacted monomers, and obtaining polysiloxane with amino groups on side chains.

Wherein the dosage of the catalyst is 0.1 to 0.3 percent of the mass sum of the 3-aminopropylmethyldimethoxysilane and the octamethylcyclotetrasiloxane; the dosage of the end capping agent is 0.1 to 0.3 percent of the mass sum of the 3-aminopropyl methyl dimethoxy silane and the octamethylcyclotetrasiloxane.

The catalyst is selected from the catalysts commonly used in the field, and preferably at least one of potassium hydroxide, tetramethylammonium hydroxide, ammonium hydroxide or benzyltrimethylammonium hydroxide.

The blocking agent is selected from the blocking agents commonly used in the field, and is preferably selected from one or a combination of the following substances: glacial acetic acid, propionic acid and n-butyric acid.

The side chain prepared in the step (1) contains the polysiloxane, the amino content is preferably 5% -10%, and the molecular weight is preferably 8000-20000.

(2) Pendant aminopolysiloxane grafting reactions

Dissolving the product obtained in the step (1) in a solvent, dissolving a pyridine ring monomer in the solvent, heating to 110-120 ℃ in a nitrogen environment, uniformly mixing for 3-5 h, heating to 130-140 ℃, and uniformly stirring for 4-6 h to obtain polysiloxane with a pyridine ring.

Wherein the molar ratio of the product obtained in the step (1) to the pyridine ring monomer is (2-3): 1, the pyridine ring monomer is preferably selected from one or a combination of the following substances: picolinic acid or picolinic acid chloride.

(3) Polysiloxane coordination complex reaction

And (3) fully dissolving the product obtained in the step (2) in a solvent, dropwise adding metal salt dissolved in the solvent to react with a pyridine ring ligand, fully and uniformly stirring at room temperature, then pouring into a polytetrafluoroethylene membrane, and volatilizing the solvent to obtain the self-healing silicon elastomer.

Wherein, the molar ratio of the pyridine ring ligand to the metal ions in the product of the step (3) is 1: 1-6: 1, and the metal salt is preferably selected from one or a combination of the following substances: FeCl₃Bis (trifluoromethylsulfonyl) imide zinc, Fe (BF)₄)₂、ZnCl₂Or Zn (ClO)₄)₂、CuCl₂、LaCl₃。

In the above step, the solvent is preferably anhydrous methanol or tetrahydrofuran.

The reaction process of the invention can be shown as follows:

note: the reaction substance indicated in the above reaction process is exemplified by one of the preferable ranges.

The invention also aims to provide the self-healing silicon elastomer obtained by the preparation method of the self-healing silicon elastomer based on metal coordination bond-hydrogen bond double crosslinking.

The self-healing silicon elastomer is prepared by ring-opening polymerization of octamethylcyclotetrasiloxane and 3-aminopropylmethyldimethoxysilane to prepare polysiloxane with amino groups on side chains, grafting reaction of a monomer with a pyridine ring and the amino groups to obtain the polysiloxane with the pyridine ring, and then coordination and complexation reaction of metal salt and the pyridine ring.

The self-healing silicon elastomer produced by the invention is based on chemical modification of a high polymer material-silicon rubber, and has the advantages that strong and weak coordination bonds and hydrogen bonds are designed in the same high polymer cross-linked network, the positions of the strong and weak coordination bonds are adjacent, when the self-healing silicon elastomer is subjected to stretching action, the weak coordination bonds are broken to dissipate energy, and the strong coordination bonds are still kept to prevent the material from being broken; the improvement of the hydrogen bond density is beneficial to the optimization of the mechanical property of the material and the dynamic property of the valence bond, so the material has good tensile property. On the other hand, the self-healing silicon elastomer adopts a melt method to introduce pyridine rings into macromolecules at high temperature, and has the advantages of simplicity, feasibility, high reaction activity, low price and easy obtainment of raw materials.

The self-healing silicon elastomer can perform rapid self-healing at room temperature, after a sample is cut off, the sample is spliced and contacted for more than 1 hour at room temperature (25 ℃), and the healing efficiency can reach more than 60 percent and is up to 91.7 percent. The healing process does not need heating and pressurizing, can be repeatedly healed and is convenient for practical application.

Compared with other disclosed self-healing polymer materials, the invention has the following advantages:

(1) the invention adopts the metal coordination-hydrogen bond composite chemical crosslinking structure for self-healing, does not need additional conditions, has strong adaptability and high room temperature healing efficiency.

(2) Compared with the common self-healing polymer material, the self-healing silicon elastomer of the invention not only has higher healing efficiency, but also has better mechanical tensile strength.

(3) The preparation process of the invention has simple procedures, easily obtained raw materials and easy operation.

Detailed Description

The invention will be further illustrated by reference to the following examples,

the sources of the raw materials used in the invention are all commercially available.

The self-healing efficiency of the material (mechanical properties in the performance test, measured by a common tensile machine after tabletting) was evaluated by the mechanical property test method GB/T528-. The sample strips are cut in the middle of the sample strips along the direction vertical to the stretching axis, and then certain pressure is applied to the cut surfaces (the cut surfaces are required to be tightly attached), so that the cut sample strips are closely contacted together, and self-healing can be realized after the cut sample strips are contacted for a certain time at room temperature. The drawing rate was 100 mm/min. The self-healing efficiency can be expressed by the following equation: eta_(T)＝σ_(healed)/σ_(initial)Where σ (heald) and σ (initial) are the original tensile strengths after and before healing, respectively.

The post-healing tensile strength refers to the tensile strength obtained by performing a tensile test after the sample is self-healed at a certain temperature for a certain time after being cut off.