CN112831008A - Styrene butadiene rubber liquid crystal elastomer with self-repairing and welding functions and preparation method thereof - Google Patents

Styrene butadiene rubber liquid crystal elastomer with self-repairing and welding functions and preparation method thereof Download PDF

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CN112831008A
CN112831008A CN202110187286.9A CN202110187286A CN112831008A CN 112831008 A CN112831008 A CN 112831008A CN 202110187286 A CN202110187286 A CN 202110187286A CN 112831008 A CN112831008 A CN 112831008A
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李杨
雷岚
韩丽
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Dalian University of Technology
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Abstract

A styrene butadiene rubber liquid crystal elastomer with self-repairing and welding functions and a preparation method thereof belong to the field of synthesis and application of styrene butadiene rubber functionalized polymers. The invention combines the method of active anion polymerization and hydrosilylation, random styrene butadiene rubber (r-SBR) is taken as a main chain, liquid crystal monomer (M) at the end of hydrosilylation is introduced to synthesize liquid crystal polymer r-SBR-g-M, hexamethylene diisocyanate (HMDI) and 2-amino-4-hydroxy-6-methylpyrimidine (UPy-NCO) are respectively taken as covalent bond cross-linking agent and hydrogen bond cross-linking agent, and styrene butadiene rubber liquid crystal elastomer r-SBR-g- [ M-5%, 5% with different molecular weights are synthesized by a series of reaction steps]The structure is as follows:
Figure DDA0002943432160000011
the preparation method is simple, and the prepared liquid crystal elastomer has the following thermal properties: t isgAt 6-14 ℃ and TiIs 42-52 ℃; the styrene butadiene rubber liquid crystal elastomer has the self-repairing and welding efficiency of 83.1% -100% at 60 ℃, has good self-repairing and welding performance, and can effectively improve the stability and service life of rubber materials and the utilization rate of residual materials.

Description

Styrene butadiene rubber liquid crystal elastomer with self-repairing and welding functions and preparation method thereof
Technical Field
The invention belongs to the field of synthesis and application of styrene-butadiene rubber functionalized polymers, and relates to a styrene-butadiene rubber elastomer with self-repairing and welding functions and a preparation method thereof, in particular to a styrene-butadiene rubber liquid crystal elastomer with self-repairing and welding functions and a preparation method thereof.
Background
The liquid crystal elastomer combines the anisotropy of liquid crystal and the elasticity of rubber, has excellent molecular synergistic effect, executes adaptive motion by changing the volume or shape of the liquid crystal elastomer under the stimulation of external environment (such as light, heat, electricity, magnetism and the like), and has potential application prospect in the fields of intelligent bionic drive, tissue engineering, soft body robots and the like. Styrene Butadiene Rubber (SBR) is a general synthetic rubber, has the advantages of wear resistance, heat resistance, aging resistance and the like, and is a key advanced basic material for developing high-performance functional materials. The molecular composition of the rigid styrene and flexible butadiene segments in the SBR can be conveniently regulated and controlled by living anionic polymerization, so that the required polymer performance is realized. In addition, the microstructure of polybutadiene is easy to regulate, which provides more possibilities for the design of new materials. In recent years, the styrene butadiene rubber industry gradually moves to greenization, intellectualization and high performance, and the improvement of the utilization rate of styrene butadiene rubber materials and the development of intelligent high performance styrene butadiene rubber have important significance. Therefore, development of liquid crystal elastomer materials based on SBR is expected to lead to further development of SBR toward high performance and intellectualization.
After suffering from macroscopic damage, the self-repairing/welding material can heal/weld damaged parts spontaneously or under the stimulation of external environment (such as light, heat, electricity, magnetism, humidity, pH and the like) through the reconstruction of the microstructure in the material, so that the stability, the utilization rate and the service life of the material are effectively improved, and the self-repairing/welding material is widely concerned in recent years. The liquid crystal elastomer with the dynamic bond crosslinking network structure can give important self-repairing/welding performance to the material by triggering the destruction and recombination of the network topological structure under the external stimulation. Under mild conditions, 2-ureido-4-pyrimidone (UPy) can form a stable dimer through stronger self-complementary quadruple hydrogen bond action, and presents better thermodynamic stability and rapid kinetic reversibility. The SBR main chain, the liquid crystal elements, the UPy hydrogen bond, the covalent bond crosslinking and other modules are reasonably combined, and the development of the high-performance styrene-butadiene rubber material with controllable structure and liquid crystallinity and self-repairing/welding has important significance.
The invention combines the method of active anion polymerization and hydrosilylation, takes random styrene-butadiene rubber (r-SBR) with different molecular weights as a main chain, introduces a liquid crystal monomer (M) at the end of the hydrosilylation to synthesize a liquid crystal polymer r-SBR-g-M, hexamethylene diisocyanate (HMDI) and 2-amino-4-hydroxy-6-methylpyrimidine (UPy-NCO) are respectively used as a covalent bond crosslinking agent and a hydrogen bond crosslinking agent, styrene butadiene rubber liquid crystal elastomer r-SBR-g- [ M-5%, 5% ] with different molecular weights and covalent bond and hydrogen bond crosslinking density of 5 mol% are synthesized through a series of reaction steps, on the basis of the liquid crystal elastomer, the self-repairing and welding functions of the material are realized at 60 ℃, and the styrene butadiene rubber material is further developed towards high performance and intellectualization.
Disclosure of Invention
The invention aims to synthesize a styrene butadiene rubber liquid crystal elastomer with a definite structure by using random styrene butadiene rubber as a main chain. And on the basis of the liquid crystal elastomer, the destruction and recombination of a network topological structure are generated by using UPy hydrogen bond crosslinking under the stimulation of temperature, so that the self-repairing and welding functions of the material are realized.
In order to achieve the purpose, the invention adopts the following technical scheme:
styrene-butadiene rubber liquid crystal elastomer with self-repairing and welding functions, wherein r-SBR-g- [ M.HMDI.UPy ] is adopted]Random styrene butadiene rubber (r-SBR) with different molecular weights is taken as a main chain, a liquid crystal monomer (M) with 50mol percent is grafted on a butadiene polymerization unit to synthesize a liquid crystal polymer r-SBR-g-M by a hydrosilylation method, and 1, 4-olefin in the r-SBR-g-M is further subjected to epoxidation and ring opening reaction under the conditions of M-chloroperoxybenzoic acid and zirconium tetrachloride to generateForming a hydroxylated liquid crystal polymer r-HSBR-g-M, and finally simultaneously introducing 5mol percent of HMDI covalent bond crosslinking agent and UPy-NCO hydrogen bond crosslinking agent into the hydroxylated 1, 4-olefin to synthesize the styrene butadiene rubber liquid crystal elastomer r-SBR-g- [ M-5 percent, 5 percent]The liquid crystal forming region is [ T ]g 6-14℃-LC-Ti 42-52℃]。
The structural formula of the r-SBR-g- [ M-5%, 5% ] is as follows:
Figure BDA0002943432140000021
the thermal properties of the liquid crystal elastomer are as follows: t isgAt 6-14 ℃ and TiIs 42-52 ℃; the elongation at break of the initial film is 278%, 499% and 438%, the elongation at break after self-repairing for 24h at 60 ℃ is 231%, 445% and 436%, the elongation at break after self-welding for 1h at 60 ℃ is 285%, 519% and 395%, the self-repairing and welding efficiency is 83.1% -100%, and the self-repairing and welding performance is better.
The random styrene-butadiene rubber main chain (r-SBR) is obtained by a living anion polymerization method, has the characteristics of controllable molecular weight and narrow distribution, and is characterized in that a polarity regulator (TMEDA, THF or NaODP) is added into a polymerization system to regulate and control the random structure and microstructure of the main chain; the main chain (r-SBR) of the random styrene-butadiene rubber is of a random structure, and the number average molecular weight (M) of the random styrene-butadiene rubber isn) 21.5 to 47.2kg mol-1The molecular weight distribution index (PDI) is 1.03-1.06, the styrene block content is 4.3-6.9 mol%, the mass fraction of butadiene polymerization units in the SBR is 70-80%, preferably 72.7-80.7 wt.%, and the molar content of 1, 2-olefin in the butadiene polymerization units is 51.5-64.0 mol%, and the structural formula is as follows:
Figure BDA0002943432140000031
the liquid crystal forming interval of the liquid crystal monomer (M) with the end being silicon hydrogen is [ T ]m 58℃-LC-Ti 77℃]It is smectic phase liquid crystal. The structural formula is as follows:
Figure BDA0002943432140000032
the grafting density of the chemical crosslinking agent HMDI is 0-20 mol%, and the structural formula is as follows:
Figure BDA0002943432140000033
the grafting density of the hydrogen bond crosslinking agent UPy-NCO is 0-20 mol%, and the structural formula is as follows:
Figure BDA0002943432140000034
a preparation method of a styrene butadiene rubber liquid crystal elastomer with self-repairing and welding functions comprises the following steps:
first, synthesizing liquid crystal monomer M with silicon hydrogen at end
1.1) Synthesis of Ethyl p-hydroxyazobenzoate Azo-OH
At room temperature, adding ethyl p-aminobenzoate into diluted HCl aqueous solution to form amino hydrochloride, placing the amino hydrochloride into water bath at 0-5 ℃, dropwise adding sodium nitrite aqueous solution into the aqueous solution to form diazonium salt, and stirring for reaction for 30-60 min. Dissolving phenol into NaOH solution, and placing the solution in a water bath at 0-5 ℃. And slowly dropwise adding the diazonium salt aqueous solution into a NaOH solution of phenol to react for 60-120 min. After the reaction was completed, the reaction was acidified to pH 3-4 with 5 wt.% hydrochloric acid to give a large amount of yellow solid, which was filtered with suction and recrystallized from ethanol to give Azo-OH as yellow powder.
1.2) Synthesis of intermediate Azo-Vinyl
Dissolving Azo-OH into pyridine and dichloromethane to obtain a mixed solution, dissolving 10-undecenoyl chloride into dichloromethane, slowly dropwise adding the mixed solution, and reacting at 25-40 ℃ for 6-12 h. After the reaction was complete, the solvent was removed under reduced pressure and the residue was acidified with (5-15) wt.% hydrochloric acid to pH 3-4 overnight. And (3) carrying out suction filtration to obtain a crude product, washing the crude product to be neutral by using a large amount of warm water, drying the crude product, and recrystallizing the dried crude product by using ethanol to obtain yellow powder Azo-Vinyl. Wherein: 10-undecylenecarbonyl chloride: Azo-OH ═ (1-2):1 (molar ratio).
1.3) Synthesis of liquid Crystal monomer M
Under the protection of argon, 1,3, 3-tetramethyldisiloxane and toluene were added into a three-neck flask. Then, Azo-Vinyl was dissolved in toluene, and a cassett catalyst was added thereto, and the resulting toluene solution was slowly added dropwise to the above solution at room temperature. After the dropwise addition, reacting at 45-80 ℃ for 12-36h, removing the solvent under reduced pressure after the reaction is finished, and recrystallizing with ethanol to obtain yellow powder M. Wherein: Azo-Vinyl: 1,1,3, 3-tetramethyldisiloxane ═ 1 (15-30) (molar ratio).
The synthetic route of the liquid crystal monomer M is as follows:
Figure BDA0002943432140000041
secondly, synthesizing a hydrogen bond cross-linking agent UPy-NCO
Under the protection of argon, 2-amino-4-hydroxy-6-methylpyrimidine is added into a round-bottom flask, hexamethylene diisocyanate (HMDI) and pyridine are added into the round-bottom flask, and the mixture is stirred and reacted for 12 to 24 hours at the temperature of between 60 and 100 ℃. And after the reaction is finished, adding n-pentane into the reaction solution, performing suction filtration, washing the obtained solid powder with acetone to remove unreacted HMDI, and then drying in a vacuum drying oven to constant weight to obtain the hydrogen bond cross-linking agent UPy-NCO. Wherein: 2-amino-4-hydroxy-6-methylpyrimidine: HMDI ═ 1 (5-8) (molar ratio).
The synthetic route of the hydrogen bond crosslinking agent UPy-NCO is as follows:
Figure BDA0002943432140000042
thirdly, synthesizing the random styrene butadiene rubber main chain r-SBR
In a glove box, cyclohexane was added to the ampoule, and after sealing, the ampoule was taken out of the glove box and kept ready. Adding butadiene and styrene into the cyclohexane solvent, adding an initiator, uniformly mixing, quickly adding a polarity regulator N, N, N, N-Tetramethylethylenediamine (TMEDA) with the equivalent weight of N-BuLi, reacting at 25-40 ℃ for 3-6h, and adding refined isopropanol to terminate the reaction. And (3) precipitating the reaction solution in a large amount of methanol, and drying the obtained viscous liquid in vacuum to constant weight to obtain the styrene butadiene rubber main chain r-SBR with different molecular weights.
The r-SBR synthetic route of the random styrene-butadiene rubber main chain is as follows:
Figure BDA0002943432140000043
fourthly, synthesizing styrene butadiene rubber liquid crystal elastomer r-SBR-g- [ M.HMDI.UPy ]
In a glove box, r-SBR, M (feed molar ratio [ SiH: C ═ C ] ═ 0.5-1), a cassett catalyst, and toluene were added to an ampoule and mixed well. Taking out after sealing, and stirring in oil bath at 45-60 ℃ for reaction for 36-72 h. And after the reaction is finished, removing the solvent under reduced pressure, dissolving the reactant by using a small amount of tetrahydrofuran, dripping ethanol into the solution to continuously separate out solids, centrifuging, and removing unreacted liquid crystal monomers from the obtained solids by repeating the operation to obtain pure r-SBR-g-M.
r-SBR-M was dissolved in methylene chloride, M-chloroperoxybenzoic acid (M-CPBA, molar ratio [ M-CPBA: C ═ C ] ═ 0.1 to 0.25) was dissolved in methylene chloride, and the resulting solution was added to the methylene chloride and reacted at 25 to 40 ℃ for 2 to 6 hours. And after the reaction is finished, removing the solvent under reduced pressure, dissolving the reactant by using a small amount of tetrahydrofuran, dripping ethanol into the solution to separate out a viscous solid, centrifuging and pouring out the supernatant, and repeating the operation on the obtained viscous solid to remove M-chloroperoxybenzoic acid and M-chlorobenzoic acid in the system to obtain pure r-ESBR-g-M.
r-ESBR-g-M was dissolved in THF, and deionized water and ZrCl were added thereto4(molar ratio of feed [ Epo: H ]2O:ZrCl4]15-40 (0.2-1)), and reacting at 25-40 ℃ for 1-3 h. After the reaction is finished, dropwise adding ethanol into the solution to precipitate viscous solid, centrifuging, and repeating the operation on the obtained solid to remove ZrCl4To obtain pureNeat r-HSBR-g-M.
Under the protection of argon, r-HSBR-g-M, a certain amount of covalent cross-linking agent (HMDI) and a certain amount of hydrogen bond cross-linking agent (UPy-NCO) are dissolved in dry chloroform (the amount of HMDI and UPy-NCO are both 5mol percent of butadiene units), and dibutyl dilaurate is added dropwise and reacted for 24-48h at the temperature of 45-60 ℃. After the reaction is finished, the reaction solution is settled in ethanol, and the obtained solid is dried in vacuum to constant weight, so that the styrene butadiene rubber liquid crystal elastomer r-SBR-g- [ M-5%, 5% ] with different molecular weights is obtained.
Liquid crystal performance analysis: the liquid crystal texture of the liquid crystal elastomer was observed by a polarizing microscope (POM) equipped with a hot stage and a digital camera. The molecular weight and molecular weight distribution index (ratio of weight average molecular weight to number average molecular weight) of the styrene-butadiene rubber main chain were measured by Gel Permeation Chromatography (GPC), and the glass transition temperature T of the liquid-crystalline elastomer was measured by differential thermal scanning (DSC)gAnd clearing spot Ti。
And (3) tensile test: instron 5567A materials testing machine, room temperature at 5mm/min speed for tensile test.
Self-repairing performance test: hot pressing at 100 deg.C under 4MPa to prepare 300 μm polymer film, cutting the film sample into two pieces, immediately contacting the sections for 1min, and repairing at 60 deg.C for 24h without external force. Welding performance: the specimens were cut into two pieces, then stacked 1-2mm from their edges, placed between two glass slides, and welded on a 60 ℃ hot stage for 1 h. And after the repair or welding is finished, performing a tensile test on the repaired or welded sample strip at room temperature, and evaluating the repair and welding efficiency by using the elongation at break, namely the percentage of the elongation at break of the repaired/welded sample strip in the elongation at break of the initial sample strip.
The invention has the beneficial effects that: the random styrene-butadiene rubber main chain r-SBR designed and synthesized based on the active anion polymerization has the characteristics of controllable molecular weight and narrow distribution (M)n21.5 to 47.2kg/mol, PDI 1.03 to 1.06), a styrene block content of 4.3 to 6.9 mol%, a mass fraction of butadiene polymerization units in SBR of 72.7 to 80.7 wt.%, a molar content of 1, 2-olefin in butadiene polymerization units of 51.5 to 64.0 mol%, based on which a main chain is synthesizedThe finished liquid crystal elastomer r-SBR-g- [ M-5%, 5%]Thermal performance of (2): t isgAt 6-14 ℃ and TiIs 42-52 ℃. The elongation at break of the initial films with different molecular weights is 278%, 499% and 438%, the breaking strength is 1.18MPa, 2.09MPa and 1.38MPa, the elongation at break after self-repairing for 24h at 60 ℃ is 231%, 445% and 436%, the elongation at break after welding for 1h is 285%, 519% and 395%, the self-repairing and welding efficiency of the material is 83.1% -100%, the material has good self-repairing and welding performance under mild conditions, and the stability, service life and utilization rate of residual materials of the rubber material are effectively improved.
Drawings
FIG. 1 shows a liquid crystal monomer M1H NMR spectrum and peak position attribution.
FIG. 2 is a view of the main chain r-SBR1H NMR spectrum.
FIG. 3 shows a liquid crystal monomer, a main chain r-SBR and a liquid crystal elastomer1And H NMR spectrum comparison.
FIG. 4 is a DSC plot of the main chain r-SBR and the liquid crystalline elastomer r-SBR-g- [ M-5%, 5% ]: (a) r-SBR; (b) r-SBR-g- [ M-5%, 5% ].
FIG. 5 is a photograph of polarization texture of r-SBR-g- [ M-5%, 5% ]: FIG. 5(a) is a texture picture of r-SBR21.5k-g- [ M-5%, 5% ]; FIG. 5(b) is a texture picture of r-SBR35.4k-g- [ M-5%, 5% ]; FIG. 5(c) is a texture picture of r-SBR47.2k-g- [ M-5%, 5% ];
FIG. 6 is a stress-strain curve for r-SBR-g- [ M-5%, 5% ] initial film, self-healing film and solder film: FIG. 6(a) is a stress-strain curve of r-SBR21.5k-g- [ M-5%, 5% ] of the initial film, self-healing film and solder film, FIG. 6(b) is a stress-strain curve of r-SBR35.4k-g- [ M-5%, 5% ] of the initial film, self-healing film and solder film, and FIG. 6(c) is a stress-strain curve of r-SBR47.2k-g- [ M-5%, 5% ] of the initial film, self-healing film and solder film.
Detailed Description
The present invention is further illustrated by the following specific examples.
Example 1
First, synthesizing liquid crystal monomer M with silicon hydrogen at end
1.1) Synthesis of Ethyl p-hydroxyazobenzoate Azo-OH
In a 500mL beaker, ethyl p-carbamate (10g,0.0605mol), deionized water 30mL, and concentrated hydrochloric acid 30mL (diluted to 120mL) were added, stirred until well mixed, and placed in an ice bath at 0 ℃. Sodium nitrite (5.15g, 0.075mol) was dissolved in 30mL of deionized water and added dropwise to the above-mentioned mixed system of concentrated hydrochloric acid and ethyl p-aminobenzoate, and the system gradually clarified to form a yellow solution. After the dropwise addition, the reaction was continued for 60min with stirring. Phenol (6.84g,0.073mol), NaOH (7.2g, 0.18mol) and 20mL of deionized water were added to a 500mL beaker, and the resulting mixture was placed in an ice bath at 0 ℃ and the yellow solution was slowly added dropwise to produce a yellow solid in the solution, and after the addition was complete, the reaction was stirred for 120 min. After the reaction was complete, the reaction was acidified with 5% hydrochloric acid to pH 5, yielding a large amount of yellow solid. Suction filtration was carried out, washing was carried out 3 times with distilled water, and the obtained solid was recrystallized from ethanol to obtain Azo-OH as a yellow powder.
1.2) Synthesis of intermediate Azo-Vinyl
Azo-OH (5g,0.018mol) was dissolved in 8mL of pyridine and 50mL of dichloromethane to give a mixed solution, and 10-undecenoyl chloride (3.8g,0.019mol) was dissolved in 50mL of dichloromethane and slowly added dropwise to the above mixed solution. After completion of the dropwise addition, the reaction was carried out at 25 ℃ for 12 hours. After the reaction was completed, the solvent was removed under reduced pressure, and the residue was acidified with 5 wt.% dilute hydrochloric acid to pH 3-4 overnight. And (3) carrying out suction filtration to obtain a crude product, washing the crude product to be neutral by using a large amount of warm water, drying the crude product, and recrystallizing the dried crude product by using ethanol to obtain yellow powder Azo-Vinyl.
1.3) Synthesis of liquid Crystal monomer M
1,1,3, 3-tetramethyldisiloxane (30.8g,0.229mol) and 30mL of toluene were added to a 250mL three-necked flask under an argon blanket. After that, Azo-Vinyl (5g,0.0114mol) was dissolved in 50mL of toluene, 6 drops of a Karster catalyst were added thereto, and the resulting toluene solution was slowly added dropwise to the above solution at room temperature. After the dropwise addition, the mixture was reacted at 45 ℃ for 36 hours, and after the reaction, the solvent was removed under reduced pressure, and the mixture was recrystallized from ethanol to give yellow powder M.
Secondly, synthesizing a hydrogen bond cross-linking agent UPy-NCO
2-amino-4-hydroxy-6-methylpyrimidine (10g,79.9mmol) was added to a round-bottom flask under argon protection, and hexamethylene diisocyanate (HMDI,100mL,624mmol) and 7mL pyridine were added thereto, and the reaction was stirred at 100 ℃ overnight for 12 h. And after the reaction is finished, adding 30mL of n-pentane into the reaction solution, performing suction filtration, washing the obtained solid powder with acetone to remove unreacted HMDI, and then drying in a vacuum drying oven to constant weight to obtain the hydrogen bond crosslinking agent UPy-NCO.
Thirdly, synthesizing the random styrene butadiene rubber main chain r-SBR
In the glove box, 60mL of cyclohexane was put in the ampoule, and after sealing, the ampoule was taken out of the glove box for use. Butadiene (Bd,2.7g,49.9mmol) previously killed was introduced into the cyclohexane solvent through a guide pin, St (0.9g,8.6mmol) was added to the cyclohexane solution of butadiene through a sealed syringe and mixed uniformly, and after adding N-BuLi (1.6mol/L, 0.11mL) as an initiator and mixing uniformly, a polarity modifier N, N, N, N-Tetramethylethylenediamine (TMEDA) equivalent to N-BuLi was rapidly added, and after reacting at 35 ℃ for 4 hours, purified isopropanol was added to terminate the reaction. And (3) precipitating the reaction solution in a large amount of methanol, and drying the obtained viscous liquid in vacuum to constant weight to obtain the styrene butadiene rubber main chain r-SBR. The number average molecular weight of the polymer was 21.5 kg. mol-1The molecular weight distribution index was 1.06. Styrene block content 4.3 mol%, mass fraction of butadiene units 77.2 wt.%, molar content of 1, 2-olefin in butadiene polymerization units 64.0 mol%, glass transition temperature of polymer: t isg＝-45℃。
Fourthly, synthesizing styrene butadiene rubber liquid crystal elastomer r-SBR21.5k-g- [ M-5%, 5% ]
In a glove box, r-sbrr 21.5k, M (molar feed ratio [ SiH: C ═ C ] ═ 0.55), 6 drops of a cassett catalyst, and toluene were added to an ampoule and mixed well. And taking out after sealing, and stirring in an oil bath at 45 ℃ for reaction for 72 hours. And after the reaction is finished, removing the solvent under reduced pressure, dissolving the reactant by using a small amount of tetrahydrofuran, dripping ethanol into the solution to continuously separate out a solid, centrifuging, and removing the unreacted liquid crystal monomer from the obtained solid by repeating the operation to obtain pure r-SBR21.5k-g-M.
r-sbr21.5k-M was dissolved in dichloromethane, M-chloroperoxybenzoic acid (M-CPBA, molar ratio [ M-CPBA: C ═ C ] ═ 0.25) was dissolved in dichloromethane, and the resulting solution was added to react at 40 ℃ for 2 hours. And after the reaction is finished, removing the solvent under reduced pressure, dissolving the reactant by using a small amount of tetrahydrofuran, dropwise adding ethanol into the solution to separate out a viscous solid, centrifuging and pouring out the supernatant, and repeating the operation on the obtained viscous solid to remove M-chloroperoxybenzoic acid and M-chlorobenzoic acid in the system to obtain pure r-ESBR21.5k-g-M.
r-ESBR21.5k-g-M was dissolved in THF, and deionized water and ZrCl were added thereto4(molar ratio of feed [ Epo: H ]2O:ZrCl4]1:15:0.5), and reacting at 25 ℃ for 2 h. After the reaction is finished, dropwise adding ethanol into the solution to precipitate viscous solid, centrifuging, and repeating the operation on the obtained solid to remove ZrCl4To obtain pure r-HSBR21.5k-g-M.
Under the protection of argon, r-HSBR21.5k-g-M, a certain amount of covalent cross-linking agent (HMDI) and a certain amount of hydrogen bond cross-linking agent (UPy-NCO) are dissolved in dry chloroform, 2 drops of dibutyl dilaurate are added dropwise, and reflux reaction is carried out for 24 hours at 60 ℃. After the reaction is finished, the reaction solution is settled in ethanol, the obtained solid is dried in vacuum to constant weight, and the styrene butadiene rubber liquid crystal elastomer r-SBR21.5k-g- [ M.5%. 5%]Thermal properties: t isgAt 6 ℃ TiIs 50 ℃. The elongation at break and the breaking strength of the initial film are 278 percent and 1.18MPa respectively, the elongation at break after self-repairing for 24 hours at 60 ℃ is 231 percent, the repairing efficiency is 83.1 percent, the elongation at break after welding for 1 hour is 285 percent, and the welding efficiency is 100 percent.
The liquid crystal texture of the liquid crystal elastomer is observed by a polarizing microscope with a hot stage and a digital camera, and the heating or cooling rate is 2 ℃/min.
Weighing 5-10mg of liquid crystal elastomer, measuring the DSC curve, measuring the sample in nitrogen atmosphere, and increasing and decreasing the temperature at 10 ℃ min-1(ii) a Selecting the secondary temperature rise curve of the liquid crystal polymer to record the glass transition temperature (T)g) And liquid crystal phase-isotropic transition temperature (T)i)。
FIG. 1 shows a liquid crystal monomer M1H NMR spectrum and peak assignment, in the figure:
M:1H NMR(400MHz,CDCl3)δ＝8.13(d,J＝8.6Hz,2H,Ar-H),7.96-7.84(m,4H,Ar-H),7.24-7.16(m,2H,Ar-H),4.62(m,1H,Si-H),4.35(d,J＝7.1Hz,2H,-COOCH2CH3),2.53(t,J＝7.5Hz,2H,-CH2COO-),1.89-1.62(m,2H,-CH2CH2COO-),1.33(dd,J＝32.5,25.4Hz,17H,-(CH2)7-and-COOCH2CH3),0.48(d,J＝7.3Hz,2H,-Si-CH2-),0.13-0(m,12H,(CH3)2-Si-O-Si-(CH3)2).
FIG. 2 is a schematic representation of r-SBR1The result of the H NMR spectrum showed that the styrene block content in r-SBR ranged from 4.3 to 6.9 mol%, confirming the random structure of the main chain. The mass fraction of butadiene polymerization units in r-SBR is 72.7-80.7 wt.%, and the molar content of 1, 2-olefin in the butadiene polymerization units is 51.5-64.0 mol.%.
FIG. 3 shows a liquid crystal monomer, a main chain r-SBR and a liquid crystal elastomer1H NMR spectrum comparison shows that the liquid crystal elastomer r-SBR-g- [ M.5%. 5%)]The grafting ratio of the liquid crystal monomer M was about 50 mol%. From the DSC curve of fig. 4, it can be seen that: t of r-SBR of different molecular weightsgIs-45 to-23 ℃. r-SBR-g- [ M-5%, 5%)]Exhibit a lower Tg(6-14 ℃ C.) and Ti(42-52 ℃) is favorable for realizing self-repairing and welding functions of the styrene butadiene rubber material under mild conditions. In FIG. 5, it can be seen that: the liquid crystal elastomer presents an obvious liquid crystal texture in a liquid crystal forming interval and has liquid crystal property; as can be seen from fig. 6: different molecular weight r-SBR-g- [ M-5%, 5%]The results of the elongation at break and the strength at break of the initial film, the self-repairing film and the welding film show that the self-repairing efficiency and the welding efficiency of the styrene-butadiene rubber material are (83.1-100)%, and the styrene-butadiene rubber material has better self-repairing and welding functions under mild conditions.
Example 2:
first, synthesizing liquid crystal monomer M with silicon hydrogen at end
1.1) Synthesis of Ethyl p-hydroxyazobenzoate Azo-OH
In a 500mL beaker, add ethyl carbamate (15g,0.0908mol), deionized water 45mL and concentrated hydrochloric acid 45mL (diluted to 150mL), stir until well mixed, place it in an ice bath at 5 ℃. Sodium nitrite (7.73g, 0.11mol) was dissolved in 45mL of deionized water and added dropwise to the above-mentioned mixed system of concentrated hydrochloric acid and ethyl p-aminobenzoate, and the system gradually clarified to form a yellow solution. After the dropwise addition, the reaction was continued for 45min with stirring. Phenol (10.3g,0.11mol), NaOH (10.8g, 0.27mol) and 30mL of deionized water were added to a 500mL beaker, placed in a water bath at 3 ℃, the yellow solution was slowly added dropwise to produce a yellow solid in the solution, and after the addition was complete, the reaction was stirred for 90 min. After the reaction was complete, the reaction was acidified with 5% hydrochloric acid to pH 5, yielding a large amount of yellow solid. Suction filtration, washing with distilled water for 2-3 times, and recrystallizing the obtained solid with ethanol to obtain yellow powder Azo-OH.
1.2) Synthesis of intermediate Azo-Vinyl
Azo-OH (5g,0.018mol) was dissolved in 10mL of pyridine and 70mL of dichloromethane to give a mixed solution, and 10-undecenoyl chloride (5.7g,0.029mol) was dissolved in 70mL of dichloromethane and slowly added dropwise to the above mixed solution. After the completion of the dropwise addition, the reaction was carried out at 40 ℃ for 6 hours. After the reaction was completed, the solvent was removed under reduced pressure, and the residue was acidified with 10 wt.% dilute hydrochloric acid to pH 3-4 overnight. And (3) carrying out suction filtration to obtain a crude product, washing the crude product to be neutral by using a large amount of warm water, drying the crude product, and recrystallizing the dried crude product by using ethanol to obtain yellow powder Azo-Vinyl.
1.3) Synthesis of liquid Crystal monomer M
1,1,3, 3-tetramethyldisiloxane (23.2g,0.171mol) and 20mL of toluene were added to a 250mL three-necked flask under an argon blanket. After that, Azo-Vinyl (5g,0.0114mol) was dissolved in 50mL of toluene, 6 drops of a Karster catalyst were added thereto, and the resulting toluene solution was slowly added dropwise to the above solution at room temperature. After the dropwise addition, the mixture was reacted at 60 ℃ for 24 hours, and after the reaction, the solvent was removed under reduced pressure, and the mixture was recrystallized from ethanol to give yellow powder M.
Secondly, synthesizing a hydrogen bond cross-linking agent UPy-NCO
Under the protection of argon, 2-amino-4-hydroxy-6-methylpyrimidine (10g,79.9mmol) was added to a round-bottom flask, and hexamethylene diisocyanate (HMDI,64mL,400mmol) and 10mL of pyridine were added thereto, and reacted at 60 ℃ for 24 h. And after the reaction is finished, adding 30mL of n-pentane into the reaction solution, performing suction filtration, washing the obtained solid powder with acetone to remove unreacted HMDI, and then drying in a vacuum drying oven to constant weight to obtain the hydrogen bond crosslinking agent UPy-NCO.
Thirdly, synthesizing the random styrene butadiene rubber main chain r-SBR
In the glove box, 60mL of cyclohexane was put in the ampoule, and after sealing, the ampoule was taken out of the glove box for use. Butadiene (Bd,2.7g,49.9mmol) previously killed was introduced into the cyclohexane solvent through a guide pin, St (0.9g,8.6mmol) was added to the cyclohexane solution of butadiene through a sealed syringe and mixed uniformly, and after adding N-BuLi (1.0mol/L, 0.10mL) as an initiator and mixing uniformly, a polarity modifier N, N, N, N-Tetramethylethylenediamine (TMEDA) equivalent to N-BuLi was rapidly added, and after reaction at 40 ℃ for 3.5 hours, purified isopropanol was added to terminate the reaction. And (3) precipitating the reaction solution in a large amount of methanol, and drying the obtained viscous liquid in vacuum to constant weight to obtain the styrene butadiene rubber main chain r-SBR. The polymer had a number average molecular weight of 35.4 kg. mol-1The molecular weight distribution indices were 1.06, respectively. Styrene block content 6.9 mol%, mass fraction of butadiene units 72.7 wt%, molar content of 1, 2-olefin in butadiene polymerization units 51.5 mol%, glass transition temperature of polymer: t isg＝-31℃。
Fourthly, synthesizing styrene butadiene rubber liquid crystal elastomer r-SBR35.4k-g- [ M.5%. 5% ]
In a glove box, r-sbrr35.4k, M (feed molar ratio [ SiH: C ═ C ] ═ 0.6), 6 drops of a cassett catalyst, and toluene were added to an ampoule and mixed well. And taking out after sealing, and stirring in an oil bath at 60 ℃ for reaction for 36 hours. And after the reaction is finished, removing the solvent under reduced pressure, dissolving the reactant by using a small amount of tetrahydrofuran, dripping ethanol into the solution to continuously separate out solids, centrifuging, and removing unreacted liquid crystal monomers from the obtained solids by repeating the operation to obtain pure r-SBR35.4k-g-M.
r-sbr35.4k-g-M was dissolved in dichloromethane, M-chloroperoxybenzoic acid (M-CPBA, molar ratio [ M-CPBA: C ═ C ] ═ 0.20) was dissolved in dichloromethane, and the resulting solution was added to react at 30 ℃ for 3 hours. And after the reaction is finished, removing the solvent under reduced pressure, dissolving the reactant by using a small amount of tetrahydrofuran, dropwise adding ethanol into the solution to separate out a viscous solid, centrifuging and pouring out supernatant, and repeating the operation on the obtained viscous solid to remove M-chloroperoxybenzoic acid and M-chloroperbenzoic acid in the system to obtain pure r-ESBR35.4k-g-M.
r-ESBR35.4k-g-M was dissolved in THF, to which was then added deionized water and ZrCl4(molar ratio of feed [ Epo: H ]2O:ZrCl4]1:30:0.4), and reacting at 30 ℃ for 2 h. After the reaction is finished, dropwise adding ethanol into the solution to precipitate viscous solid, centrifuging, and repeating the operation on the obtained solid to remove ZrCl4To obtain pure r-HSBR35.4k-g-M.
Under the protection of argon, r-HSBR35.4k-g-M, a certain amount of covalent cross-linking agent (HMDI) and a certain amount of hydrogen bond cross-linking agent (UPy-NCO) are dissolved in dry chloroform, 2 drops of dibutyl dilaurate are added dropwise, and the reaction is carried out for 24 hours at 60 ℃. After the reaction is finished, the reaction solution is settled in ethanol, the obtained solid is dried in vacuum to constant weight, and the styrene butadiene rubber liquid crystal elastomer r-SBR35.4k-g- [ M.5%. 5%]. Thermal properties: t isgAt 6 ℃ TiIt was 42 ℃. The elongation at break and the breaking strength of the initial film are 499% and 2.09MPa respectively, the elongation at break after self-repairing for 24h at 60 ℃ is 445%, and the repairing efficiency is 89.1%. The elongation at break of 1h of welding was 519%, and the welding efficiency was 100%.
Example 3:
first, synthesizing liquid crystal monomer M with silicon hydrogen at end
1.1) Synthesis of Ethyl p-hydroxyazobenzoate Azo-OH
In a 500mL beaker, add ethyl carbamate (20g,0.12mol), deionized water 50mL and concentrated hydrochloric acid 50mL (diluted to 170mL), stir until well mixed, place in an ice bath at 0 ℃. Sodium nitrite (10.28g, 0.15mol) was dissolved in 55mL of deionized water and added dropwise to the above-mentioned mixed system of concentrated hydrochloric acid and ethyl p-aminobenzoate, and the system gradually clarified to form a yellow solution. After the dropwise addition, the reaction was continued for 60min with stirring. Phenol (13.7g,0.15mol), NaOH (14.4g, 0.36mol) and 40mL of deionized water were added to a 500mL beaker, and the above yellow solution was slowly added dropwise in an ice bath at 0 ℃ to produce a yellow solid in the solution, and after the addition was complete, the reaction was stirred for a further 120 min. After the reaction was complete, the reaction was acidified with 5% hydrochloric acid to pH 5, yielding a large amount of yellow solid. And (4) carrying out suction filtration, washing with distilled water for 2-3 times, and recrystallizing the obtained solid with ethanol to obtain Azo-OH.
1.2) Synthesis of intermediate Azo-Vinyl
Azo-OH (5g,0.018mol) was dissolved in 10mL of pyridine and 70mL of dichloromethane to give a mixed solution, and 10-undecenoyl chloride (7.1g,0.036mol) was dissolved in 80mL of dichloromethane and slowly added dropwise to the above mixed solution. After the completion of the dropwise addition, the reaction was carried out at 30 ℃ for 8 hours. After the reaction was completed, the solvent was removed under reduced pressure, and the residue was acidified with 10 wt.% dilute hydrochloric acid to pH 3-4 overnight. And (3) carrying out suction filtration to obtain a crude product, washing the crude product to be neutral by using a large amount of warm water, drying the crude product, and recrystallizing the dried crude product by using ethanol to obtain yellow powder Azo-Vinyl.
1.3) Synthesis of liquid Crystal monomer M
1,1,3, 3-tetramethyldisiloxane (15.5g,0.114mol) and 20mL of toluene were added to a 250mL three-necked flask under an argon blanket. After that, Azo-Vinyl (5g,0.0114mol) was dissolved in 50mL of toluene, 6 drops of a Karster catalyst were added thereto, and the resulting toluene solution was slowly added dropwise to the above solution at room temperature. After the dropwise addition, the mixture was reacted at 80 ℃ for 12 hours, and after the reaction, the solvent was removed under reduced pressure, and the mixture was recrystallized from ethanol to give yellow powder M.
Secondly, synthesizing a hydrogen bond cross-linking agent UPy-NCO
Under the protection of argon, 2-amino-4-hydroxy-6-methylpyrimidine (10g,79.9mmol) was added to a round-bottom flask, and hexamethylene diisocyanate (HMDI,83mL,519mmol) and 12mL pyridine were added thereto, and reacted at 80 ℃ for 18 h. After the reaction is finished, adding 45mL of n-pentane into the reaction solution, carrying out suction filtration, washing the obtained solid powder with acetone to remove unreacted HMDI, and then drying in a vacuum drying oven to constant weight to obtain the hydrogen bond crosslinking agent UPy-NCO.
Thirdly, synthesizing the random styrene butadiene rubber main chain r-SBR
In a glove box, 60mL of cyclohexane is put into an ampoule bottleAnd (5) taking out the sealed glove box for later use. Butadiene (Bd,5.4g,99.8mmol) previously killed was introduced into the cyclohexane solvent through a guide pin, St (1.8g,17.2mmol) was added to the cyclohexane solution of butadiene through a sealed syringe and mixed uniformly, and after adding N-BuLi (1.0mol/L, 0.16mL) as an initiator and mixing uniformly, a polarity modifier N, N, N, N-Tetramethylethylenediamine (TMEDA) equivalent to N-BuLi was rapidly added, and after reacting at 25 ℃ for 6 hours, purified isopropanol was added to terminate the reaction. And (3) precipitating the reaction solution in a large amount of methanol, and drying the obtained viscous liquid in vacuum to constant weight to obtain the styrene butadiene rubber main chain r-SBR. The polymer number average molecular weight was 47.2 kg. mol-1The molecular weight distribution indices were 1.03, respectively. Styrene block content 6.3 mol%, mass fraction of butadiene unit 80.7 wt%, molar content of 1, 2-olefin in butadiene polymerization unit 56.8 mol%, glass transition temperature of polymer: t isg＝-23℃。
Fourthly, synthesizing styrene butadiene rubber liquid crystal elastomer r-SBR47.2k-g- [ M.5%. 5% ]
In a glove box, r-sbrr 47.2k, M (molar ratio [ SiH: C ═ C ] ═ 0.7), 6 drops of a cassett catalyst, and toluene were added to an ampoule and mixed well. And taking out after sealing, and stirring in an oil bath at 50 ℃ for reaction for 68 hours. After the reaction is finished, removing the solvent under reduced pressure, dissolving the reactant by using a small amount of tetrahydrofuran, dripping ethanol into the solution to continuously separate out solids, centrifuging, and removing unreacted liquid crystal monomers from the obtained solids by repeating the operation to obtain pure r-SBR47.2k-g-M.
r-SBR47.2k-M was dissolved in dichloromethane, M-chloroperoxybenzoic acid (M-CPBA, molar ratio [ M-CPBA: C ═ C ] ═ 0.15) was dissolved in dichloromethane, and the resulting solution was added to the dichloromethane, followed by reaction at 25 ℃ for 6 hours. And after the reaction is finished, removing the solvent under reduced pressure, dissolving the reactant by using a small amount of tetrahydrofuran, dropwise adding ethanol into the solution to separate out a viscous solid, centrifuging and pouring out the supernatant, and repeating the operation on the obtained viscous solid to remove M-chloroperoxybenzoic acid and M-chlorobenzoic acid in the system to obtain pure r-ESBR47.2k-g-M.
r-ESBR47.2k-g-M was dissolved in THF, and then deionized water and ZrCl were added thereto4(molar ratio of feed [ Epo: H ]2O:ZrCl4]1:40:0.4), and reacting at 40 ℃ for 1 h. After the reaction is finished, dropwise adding ethanol into the solution to precipitate viscous solid, centrifuging, and repeating the operation on the obtained solid to remove ZrCl4To obtain pure r-HSBR47.2k-g-M.
Under the protection of argon, r-HSBR47.2k-g-M, a certain amount of covalent cross-linking agent (HMDI) and a certain amount of hydrogen bond cross-linking agent (UPy-NCO) are dissolved in dry chloroform, 2 drops of dibutyl dilaurate are added dropwise, and reflux reaction is carried out for 48 hours at 50 ℃. After the reaction is finished, the reaction solution is precipitated in ethanol, the obtained solid is dried in vacuum to constant weight, and the styrene butadiene rubber liquid crystal elastomer r-SBR47.2k-g- [ M-5%. 5%]. Thermal properties: t isgAt 14 ℃ TiThe temperature was 52 ℃. The elongation at break and the breaking strength of the initial film are 438 percent and 1.38MPa respectively, the elongation at break after self-repairing is carried out for 24 hours at 60 ℃ is 436 percent, the repairing efficiency is 99.5 percent, the elongation at break during welding for 1 hour is 395 percent, and the welding efficiency is 90.2 percent.
The above-mentioned embodiments only express the embodiments of the present invention, but not should be understood as the limitation of the scope of the invention patent, it should be noted that, for those skilled in the art, many variations and modifications can be made without departing from the concept of the present invention, and these all fall into the protection scope of the present invention.

Claims (7)

1. A styrene butadiene rubber liquid crystal elastomer with self-repairing and welding functions is characterized in that the styrene butadiene rubber liquid crystal elastomer r-SBR-g- [ M.HMDI.UPy ] takes random styrene butadiene rubber (r-SBR) as a main chain, a liquid crystal monomer (M) at the end of silicon hydride is introduced to synthesize a liquid crystal polymer r-SBR-g-M by a silicon hydride addition method, hexamethylene diisocyanate (HMDI) and 2-amino-4-hydroxy-6-methylpyrimidine (UPy-NCO) are respectively taken as a covalent bond crosslinking agent and a hydrogen bond crosslinking agent, and the styrene butadiene rubber liquid crystal elastomer is synthesized through a series of reaction steps, wherein the structural formula is as follows:
Figure FDA0002943432130000011
2. the styrene-butadiene rubber liquid crystal elastomer with self-repairing and welding functions as claimed in claim 1, wherein the thermal properties of the liquid crystal elastomer are as follows: t isgAt 6-14 ℃ and TiIs 42-52 ℃; the self-repairing and welding efficiency of the material at 60 ℃ is 83.1% -100%.
3. The styrene-butadiene rubber liquid crystal elastomer with the self-repairing and welding functions as claimed in claim 1, wherein the random styrene-butadiene rubber main chain (r-SBR) is obtained by a living anion polymerization method, and a polarity regulator (TMEDA, THF or NaODP) is added into a polymerization system to regulate the random structure and the microstructure of the main chain; the number average molecular weight (M) of the random styrene-butadiene rubber main chain (r-SBR)n) 21.5 to 47.2kg mol-1The molecular weight distribution index (PDI) is 1.03-1.06, the styrene block content is 4.3-6.9 mol%, the mass fraction of butadiene polymerization units in SBR is 70-80 wt.%, the molar content of 1, 2-olefin in butadiene polymerization units is 51.5-64.0 mol%, and the structural formula is as follows:
Figure FDA0002943432130000012
4. the styrene-butadiene rubber liquid crystal elastomer with self-repairing and welding functions as claimed in claim 1, wherein the liquid crystal forming interval of the liquid crystal monomer M at the silicon-hydrogen terminal is [ T ]m 58℃-LC-Ti 77℃]Smectic phase liquid crystal; the structural formula is as follows:
Figure FDA0002943432130000013
5. the styrene-butadiene rubber liquid crystal elastomer with the self-repairing and welding functions as claimed in claim 1, wherein the grafting density of the hydrogen bond crosslinking agent UPy-NCO is 0-20 mol%, and the structural formula is as follows:
Figure FDA0002943432130000021
6. the styrene-butadiene rubber liquid crystal elastomer with the self-repairing and welding functions as claimed in claim 1, wherein the grafting density of the chemical crosslinking agent HMDI is 0-20 mol%, and the structural formula is as follows:
Figure FDA0002943432130000022
7. the preparation method of styrene-butadiene rubber liquid crystal elastomer with self-repairing and welding functions as claimed in any one of claims 1 to 6, characterized by the following steps,
first, synthesizing liquid crystal monomer M with silicon hydrogen at end
1.1) Synthesis of Ethyl p-hydroxyazobenzoate Azo-OH
At room temperature, adding ethyl p-aminobenzoate into an HCl aqueous solution to form amino hydrochloride, placing the amino hydrochloride into a water bath at 0-5 ℃, and dropwise adding a sodium nitrite aqueous solution into a hydrochloride aqueous solution to form diazonium salt; after the dropwise adding is finished, stirring and reacting for 30-60min, and clarifying the solution; dissolving phenol into NaOH solution, and placing the solution in a water bath at 0-5 ℃; slowly dripping the diazonium salt aqueous solution into NaOH solution of phenol, and continuing to react for 60-120min after the dripping is finished; after the reaction was complete, the reaction was acidified with hydrochloric acid to pH 5 yielding a large amount of yellow solid which was worked up to give Azo-OH as a yellow powder;
1.2) Synthesis of intermediate Azo-Vinyl
Dissolving Azo-OH into pyridine and dichloromethane to obtain a mixed solution, and then dissolving 10-undecylenoyl chloride into dichloromethane to be slowly dripped into the mixed solution; after the dropwise addition is finished, reacting for 6-12h at 25-40 ℃; after the reaction was complete, the solvent was removed under reduced pressure and the residue was acidified with dilute hydrochloric acid to pH 3-4 overnight; carrying out suction filtration to obtain a crude product, and carrying out post-treatment to obtain yellow powder Azo-Vinyl; wherein the molar ratio of 10-undecenoyl chloride to Azo-OH is (1-2) to 1;
1.3) Synthesis of liquid Crystal monomer M
Under the protection of argon, 1,3, 3-tetramethyldisiloxane and toluene are added into a three-neck flask; then dissolving the Azo-Vinyl into toluene, adding a Kanst catalyst into the toluene, and slowly dropwise adding the obtained toluene solution into the solution at room temperature; after the dropwise addition is finished, reacting for 12-36h at 45-90 ℃, and performing post-treatment after the reaction is finished to obtain yellow powder M; wherein the molar ratio of the Azo-Vinyl to the 1,1,3, 3-tetramethyl disiloxane is 1 (15-30);
secondly, synthesizing a hydrogen bond cross-linking agent UPy-NCO
Adding 2-amino-4-hydroxy-6-methylpyrimidine into a round-bottom flask under the protection of argon, adding hexamethylene diisocyanate (HMDI) and pyridine, and stirring and reacting at 60-100 ℃ for 12-24 h; after the reaction is finished, adding n-pentane into the reaction solution, carrying out suction filtration, washing the obtained solid powder with acetone to remove unreacted HMDI, and then drying in a vacuum drying oven to constant weight to obtain a hydrogen bond cross-linking agent UPy-NCO; wherein: the molar ratio of the 2-amino-4-hydroxy-6-methylpyrimidine to the HMDI is 1 (5-8);
thirdly, synthesizing the random styrene butadiene rubber main chain r-SBR
Introducing butadiene which is pre-killed with impurities into a cyclohexane solvent through a guide pin, adding styrene into the cyclohexane solution of the butadiene, uniformly mixing, adding an initiator, uniformly mixing, quickly adding a polarity regulator N, N, N, N-Tetramethylethylenediamine (TMEDA) which has the same equivalent weight as N-BuLi, reacting at 25-40 ℃ for 3-6h, and adding isopropanol to terminate the reaction; the reaction solution is deposited in a large amount of methanol and is post-treated to obtain styrene butadiene rubber main chain r-SBR with different molecular weights;
fourthly, synthesizing styrene butadiene rubber liquid crystal elastomer r-SBR-g- [ M.HMDI.UPy
In a glove box, adding r-SBR, M, a Kaster catalyst and toluene into an ampoule bottle and uniformly mixing; taking out after sealing, and stirring in an oil bath at 45-60 ℃ for reaction for 36-72 h; after the reaction is finished, carrying out post-treatment to obtain pure r-SBR-g-M;
dissolving r-SBR-M in dichloromethane, dissolving M-chloroperoxybenzoic acid (M-CPBA, controlling the molar ratio [ M-CPBA: C ═ C ] ═ 0.1-0.25) in dichloromethane, adding the solution into the dichloromethane, and reacting for 2-6h at 25-40 ℃; after the reaction is finished, carrying out post-treatment to obtain pure r-ESBR-g-M;
r-ESBR-g-M was dissolved in THF, and deionized water and ZrCl were added thereto4(molar ratio of feed [ Epo: H ]2O:ZrCl4]1, (15-40) (0.2-1)), and reacting at 25-40 ℃ for 1-3 h; after the reaction is finished, carrying out post-treatment to obtain pure r-HSBR-g-M;
under the protection of argon, r-HSBR-g-M, a certain amount of a covalent cross-linking agent (HMDI) and a certain amount of a hydrogen bond cross-linking agent (UPy-NCO) are dissolved in dry chloroform, wherein the amount of the HMDI and the UPy-NCO is calculated according to a designed covalent bond and hydrogen bond cross-linking density, dibutyl dilaurate is dropwise added, and reflux reaction is carried out at 45-60 ℃ for 24-48 h; after the reaction is finished, the styrene butadiene rubber liquid crystal elastomer r-SBR-g- [ M.HMDI.UPy ] with different molecular weights and crosslinking densities is obtained by post treatment.
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