CN113698518B - Liquid crystal elastomer material based on liquid metal nano droplets - Google Patents
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- 239000004997 Liquid crystal elastomers (LCEs) Substances 0.000 title claims abstract description 104
- 229910001338 liquidmetal Inorganic materials 0.000 title claims abstract description 69
- 239000000463 material Substances 0.000 title claims abstract description 48
- 239000007788 liquid Substances 0.000 claims abstract description 23
- 238000002360 preparation method Methods 0.000 claims abstract description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 3
- 230000008846 dynamic interplay Effects 0.000 claims abstract description 3
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 3
- 239000011593 sulfur Substances 0.000 claims abstract description 3
- 239000004973 liquid crystal related substance Substances 0.000 claims description 32
- 239000000178 monomer Substances 0.000 claims description 32
- 239000004970 Chain extender Substances 0.000 claims description 23
- 239000003431 cross linking reagent Substances 0.000 claims description 21
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 13
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 12
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 12
- JOBBTVPTPXRUBP-UHFFFAOYSA-N [3-(3-sulfanylpropanoyloxy)-2,2-bis(3-sulfanylpropanoyloxymethyl)propyl] 3-sulfanylpropanoate Chemical compound SCCC(=O)OCC(COC(=O)CCS)(COC(=O)CCS)COC(=O)CCS JOBBTVPTPXRUBP-UHFFFAOYSA-N 0.000 claims description 10
- 239000003054 catalyst Substances 0.000 claims description 10
- UVWIKVQDCQFPDM-UHFFFAOYSA-N [4-(6-prop-2-enoyloxyhexoxy)phenyl] 4-(6-prop-2-enoyloxyhexoxy)benzoate Chemical group C1=CC(OCCCCCCOC(=O)C=C)=CC=C1OC(=O)C1=CC=C(OCCCCCCOC(=O)C=C)C=C1 UVWIKVQDCQFPDM-UHFFFAOYSA-N 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 8
- -1 polytetrafluoroethylene Polymers 0.000 claims description 8
- WEHWNAOGRSTTBQ-UHFFFAOYSA-N dipropylamine Chemical compound CCCNCCC WEHWNAOGRSTTBQ-UHFFFAOYSA-N 0.000 claims description 6
- DNJIEGIFACGWOD-UHFFFAOYSA-N ethanethiol Chemical compound CCS DNJIEGIFACGWOD-UHFFFAOYSA-N 0.000 claims description 6
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims description 5
- 238000005520 cutting process Methods 0.000 claims description 5
- 229910052733 gallium Inorganic materials 0.000 claims description 5
- 238000009210 therapy by ultrasound Methods 0.000 claims description 5
- 238000011282 treatment Methods 0.000 claims description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- 239000011159 matrix material Substances 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 4
- 229910001128 Sn alloy Inorganic materials 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- RHZWSUVWRRXEJF-UHFFFAOYSA-N indium tin Chemical compound [In].[Sn] RHZWSUVWRRXEJF-UHFFFAOYSA-N 0.000 claims description 3
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 2
- 229910052738 indium Inorganic materials 0.000 claims description 2
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 238000006116 polymerization reaction Methods 0.000 claims description 2
- 238000012719 thermal polymerization Methods 0.000 claims description 2
- 229910052718 tin Inorganic materials 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 2
- 238000003756 stirring Methods 0.000 claims 1
- 239000002131 composite material Substances 0.000 abstract description 15
- 230000007774 longterm Effects 0.000 abstract description 3
- 238000004132 cross linking Methods 0.000 abstract 1
- 238000012360 testing method Methods 0.000 description 26
- 230000000930 thermomechanical effect Effects 0.000 description 9
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- 229920001971 elastomer Polymers 0.000 description 4
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- ISSYGWIDLYOJEN-UHFFFAOYSA-N [3-methyl-4-[4-(3-prop-2-enoyloxypropoxy)benzoyl]oxyphenyl] 4-(3-prop-2-enoyloxypropoxy)benzoate Chemical compound C=1C=C(OC(=O)C=2C=CC(OCCCOC(=O)C=C)=CC=2)C(C)=CC=1OC(=O)C1=CC=C(OCCCOC(=O)C=C)C=C1 ISSYGWIDLYOJEN-UHFFFAOYSA-N 0.000 description 2
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- YCRYSVKEWAWTGI-UHFFFAOYSA-N p,p'-Methoxychlor olefin Chemical compound C1=CC(OC)=CC=C1C(=C(Cl)Cl)C1=CC=C(OC)C=C1 YCRYSVKEWAWTGI-UHFFFAOYSA-N 0.000 description 2
- 239000012779 reinforcing material Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000007665 sagging Methods 0.000 description 2
- CNDCQWGRLNGNNO-UHFFFAOYSA-N 2-(2-sulfanylethoxy)ethanethiol Chemical compound SCCOCCS CNDCQWGRLNGNNO-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
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- C08F122/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides or nitriles thereof
- C08F122/10—Esters
- C08F122/12—Esters of phenols or saturated alcohols
- C08F122/20—Esters containing oxygen in addition to the carboxy oxygen
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Abstract
The invention discloses a liquid crystal elastomer material based on liquid metal nano liquid drops and a preparation method and application thereof. Liquid metal nano droplets are introduced into a liquid crystal elastomer base material, a dynamic interaction exists between sulfur elements in molecular chains and liquid metal, the liquid metal nano droplets can be uniformly distributed in the liquid crystal elastomer, and the liquid crystal elastomer material (LM-LCE) based on the liquid metal nano droplets is finally prepared through thermally-initiated secondary crosslinking. The mechanical property, especially the fatigue resistance, of the composite liquid crystal elastomer material is greatly improved, and the soft actuator material based on the liquid crystal elastomer and long-term industrial application beyond the soft actuator material can be effectively promoted.
Description
Technical Field
The invention relates to the field of liquid crystal elastomers, in particular to a liquid crystal elastomer material with ultrahigh fatigue resistance, which is formed by compounding liquid metal nano microdroplets and a liquid crystal elastomer base material.
Background
Liquid Crystal Elastomers (LCEs), which are unconventional types of polymeric materials that combine the anisotropy of mesogens with the entropic elasticity of elastomers, can reversibly deform in response to external stimuli (e.g., heat, light, humidity, electricity, and magnetic fields). The excellent two-way shape memory function makes LCE material possess latent application foreground in soft executor, sensor, micro mechanical system, soft robot technology, etc. However, the mechanical properties of conventional LCE materials are not fully satisfactory, especially moderate driving stress and poor fatigue resistance, which have been fundamental obstacles that hinder the practical industrial application of LCE materials. It is highly desirable to develop new LCE materials that have both large drive stroke, high drive stress and excellent fatigue resistance, but this remains a formidable challenge.
In order to improve the mechanical properties of LCE materials, most previous research work has focused on introducing new molecular structures, crystallization treatments, interpenetrating networks and adding nanofillers to enhance driving stress, elastic modulus and working capacity; however, the fatigue resistance of LCE materials is selectively neglected. Fatigue resistance of LCE materials is a critical factor for their industrial applications, and the long-term durability of LCEs has been hardly studied in the last 40 years. In fact, this drawback derives from the inherent drawbacks of LCE structural networks: to achieve high driving strain, LCE materials are always lightly crosslinked. This low crosslink density means that some polymer chains may not be chemically crosslinked, and therefore during actuation, the uncrosslinked polymer chains will suffer irreversible slippage, the physical association of the relevant polymer chains will be compromised, some parts of the molecular network will be compromised, the polymer internal structure will be permanently damaged, resulting in poor fatigue resistance.
In order to improve the fatigue resistance of LCE materials, the traditional approach of research has been to incorporate a number of reinforcing materials such as gold nanoparticles, carbon nanotubes and carbon fibers into the LCE matrix to introduce additional physical associations to reinforce the chain-like network of LCEs, but without achieving the desired effect, which may be due to phase separation that occurs without interaction between the reinforcing materials and the LCE matrix.
The document proc.natl.acad.sci.u.s.a.2019,116,21438 reports a method of introducing a liquid metal into a liquid crystalline elastomer, producing a liquid crystalline elastomer material that can be electrically driven. It uses a liquid crystal monomer of 1, 4-bis- [4- (3-acryloxypropoxy) benzoyloxy ] -2-methylbenzene. The liquid metal is introduced too much, the size of the liquid metal droplet is too large, about hundreds of micrometers, the clearing point of the liquid crystal elastomer is high, which exceeds 60 ℃, the mechanical property of the liquid crystal elastomer is not very large, and the document does not study and report the fatigue resistance of the liquid crystal elastomer.
The document Soft Matter,2020,16,5878 also reports a method of incorporating a liquid metal into a liquid crystal elastomer to produce a conductive composite liquid crystal elastomer material. It uses a liquid crystal monomer of 1, 4-bis- [4- (3-acryloxypropoxy) benzoyloxy ] -2-methylbenzene. The liquid metal is dispersed in the liquid crystal elastomer in a micron size, so that the conductivity of the composite liquid crystal elastomer is realized, but the mechanical property of the novel composite liquid crystal elastomer is not well improved, and the fatigue resistance is not researched and reported. At present, composite materials of liquid crystal elastomers and liquid metals exist, but in order to realize the conductivity of the composite materials, the liquid metals are all over micron size, and the mechanical properties of the composite materials of the liquid crystal elastomers are not greatly improved.
Disclosure of Invention
The technical problem is as follows: the invention aims to provide a liquid crystal elastomer material based on liquid metal nano liquid drops, which has ultrahigh fatigue resistance, solves the problem of short service life of the traditional liquid crystal elastomer material in the practical application process, and provides a preparation method of the material.
The technical scheme is as follows: the liquid crystal elastomer material based on the liquid metal nano liquid drops is formed by polymerizing liquid crystal monomers, after polymerization, the liquid crystal monomers are orderly arranged in a molecular chain in a liquid crystal element mode along a stretching direction to form a molecular main chain, and liquid metal is crushed into nano-scale micro-droplets and then has dynamic interaction with sulfur elements in the molecular main chain to be uniformly and stably dispersed in a liquid crystal elastomer matrix.
The liquid crystal monomer is 4- ((6- (acryloyloxy) hexyl) oxy) phenyl 4- ((6- (acryloyloxy) hexyl) oxy) benzoate.
The liquid metal is gallium indium tin alloy, and the mass ratio of gallium, indium and tin is 0.62-0.8.
The mass ratio of the liquid metal to the liquid crystal monomer is 5-8%.
The preparation method of the liquid crystal elastomer material based on the liquid metal nano liquid drops comprises the following steps:
step 1, carrying out water removal treatment on a liquid crystal monomer 4- ((6- (acryloyloxy) hexyl) oxy) phenyl 4- ((6- (acryloyloxy) hexyl) oxy) benzoate, a chain extender 2, 2-oxybis (ethane-1-thiol), a cross-linking agent pentaerythritol tetra (3-mercaptopropionate) and liquid metal;
step 2, putting all the materials in the step 1 into anhydrous dichloromethane, and then putting the materials into a brown strain bottle to be fully stirred under the condition of introducing nitrogen to form a uniform solution;
step 3, dissolving a catalyst dipropylamine in dichloromethane, and then adding the solution into the brown strain bottle;
step 4, carrying out ultrasonic treatment for 1-1.5 hours by using an ultrasonic crusher to crush the liquid metal into nano-scale, and realizing uniform mixing of the mixture;
step 5, pouring the mixture into a polytetrafluoroethylene groove, and then putting the polytetrafluoroethylene groove into a 36-45 ℃ oven for heat preservation for 1-1.5h;
step 6, cooling the polytetrafluoroethylene groove in the step 5 to room temperature to prepare an unoriented liquid crystal elastomer material LM-LCE film based on liquid metal nano liquid drops;
step 7, cutting the unoriented LM-LCE film into a long strip, stretching at room temperature and keeping the long strip fixed to obtain a stretched and oriented LM-LCE film made of liquid crystal elastomer materials based on liquid metal nano liquid drops;
and 8, putting the stretched and oriented long-strip LM-LCE film prepared in the step 7 into an oven, keeping the temperature of the oven at 36-45 ℃ for 8-11h, and naturally cooling the oven to room temperature to prepare the liquid crystal elastomer material LM-LCE film based on the liquid metal nano liquid drops and having an oriented structure.
Wherein,
the structural formula of the liquid crystal monomer 4- ((6- (acryloyloxy) hexyl) oxy) phenyl 4- ((6- (acryloyloxy) hexyl) oxy) benzoate is as follows:
the cross-linking agent pentaerythritol tetra (3-mercaptopropionate) has the following structural formula:
the chain extender 2, 2-oxybis (ethane-1-mercaptan) has the following structural formula:
the catalyst dipropylamine has the following structural formula:
the mass ratio of the liquid crystal monomer, the chain extender and the cross-linking agent in the step 1 is as follows: liquid crystal monomer Y2003: chain extender DMDE: crosslinking agent PETMP = 1;
the mass ratio of the liquid metal to the liquid crystal monomer chain extender to the cross-linking agent is as follows: liquid metal: (liquid crystal monomer + chain extender + crosslinking agent) = 1.
The chain extender 2, 2-oxybis (ethane-1-thiol) in step 1 was replaced by 3, 6-dithio-1, 8-octanediol.
The power of the ultrasonication apparatus in step 4 was set to 360W.
And in the step 7, the unoriented LM-LCE film is cut into long strips, stretched at room temperature to 2-2.7 times of the original length and kept fixed.
The liquid crystal elastomer based on the liquid metal nano droplets has super fatigue resistance, solves the problems of low durability and short service life in the practical application process of the conventional liquid crystal elastomer, and has great potential application in the fields of artificial muscles and the like.
Has the advantages that: compared with the prior art, the liquid crystal elastomer based on the liquid metal nano microdroplets has the following beneficial effects:
(1) the liquid crystal monomer used in the liquid metal nano-droplet-based liquid crystal elastomer prepared by the invention is 4- ((6- (acryloyloxy) hexyl) oxy) phenyl 4- ((6- (acryloyloxy) hexyl) oxy) benzoate. The liquid crystal elastomer has excellent strain performance, shows excellent reversible deformation under the stimulation of heat or ultraviolet light, and the size ratio of the original size to the isotropic phase reaches 2.22;
(2) the liquid crystal elastomer based on the liquid metal nano liquid drops prepared by the invention has excellent toughness. Dynamic thermodynamic tests show that the liquid crystal elastomer based on the liquid metal nano liquid drops is at room temperatureThe elongation at break reaches 1010.87 percent, and the toughness reaches 18.31MJ/m 3 The relative performance of the liquid crystal elastomer is 1 order of magnitude higher than that of the traditional liquid crystal elastomer;
(3) the liquid crystal elastomer based on the liquid metal nano liquid drops prepared by the invention has 72% of linear viscoelastic region in a dynamic thermomechanical analyzer test; under the condition of repeatedly stretching to 70 percent of the original length and releasing, the composite material can bear more than 10000 stretching cycles without obvious reduction of mechanical properties. Compared with the traditional liquid crystal elastomer, the liquid crystal elastomer is 2 orders of magnitude higher and is hundreds of times higher than the traditional liquid crystal elastomer.
(4) The liquid crystal elastomer based on the liquid metal nano liquid drops prepared by the invention has super-strong fatigue resistance far higher than that of the common liquid crystal elastomer. The method can be beneficial to realizing the industrial application of the liquid crystal elastomer, such as the application in the field of bionic materials such as artificial muscles and the like.
In the composite material, the liquid metal is dispersed in the liquid crystal elastomer in a nano level, the composite material is not conductive, but the clearing point of the composite material is obviously reduced, the mechanical property is obviously improved, and particularly the fatigue resistance is realized.
Drawings
FIG. 1 is a graph of shrinkage stress versus strain for cyclic testing of a prepared liquid metal nanodrop-based liquid crystal elastomer in a dynamic thermomechanical analyzer;
fig. 2 is a graph of storage modulus and elasticity versus strain for the prepared liquid metal nano-droplet based liquid crystal elastomer tested in a dynamic thermo-mechanical analyzer.
The specific implementation mode is as follows:
firstly, liquid crystal monomers, a chain extender, a cross-linking agent, a catalyst and liquid metal are subjected to ultrasonic crushing treatment and then are uniformly mixed. Under the condition of thermal polymerization, liquid crystal elastomer (LM-LCE) based on liquid metal nano liquid drops is prepared. The liquid crystal monomer is 4- ((6- (acryloyloxy) hexyl) oxy) phenyl 4- ((6- (acryloyloxy) hexyl) oxy) benzoate (Y2003), the chain extender is 2, 2-oxybis (ethane-1-thiol) (dme), the crosslinking agent is pentaerythritol tetrakis (3-mercaptopropionate) (PETMP), and the liquid metal is gallium indium tin alloy (mass ratio is 0.62.
The liquid crystal elastomer based on the liquid metal nano liquid drops prepared by the method has ultrahigh fatigue resistance, and the liquid crystal elastomer composite material can bear an unprecedented linear viscoelastic region of 72 percent, 10,000 times of stretching cycle (under the deformation with the maximum value of 70 percent), 2,000 times of continuous actuation deformation and the stretching deformation with the maximum value of more than 1000 percent. In addition, the LCE composite material doped with LM has large reversible deformation (maximum: 55%), high actuating stress (maximum: 1.13 MPa), completely reversible thermal/optical driving function and excellent self-healing capability under mild conditions. The mechanical property, especially the fatigue resistance, of the composite liquid crystal elastomer material is greatly improved, and the soft actuator material based on the liquid crystal elastomer and long-term industrial application beyond the soft actuator material can be effectively promoted.
The present invention is further illustrated by the following specific examples.
I preparation of liquid-crystalline elastomers based on liquid-metal nanodroplets
According to the following proportion: the mass ratio of the liquid crystal monomer Y2003 to the chain extender DMDE to the cross-linking agent PETMP is 1; the mass ratio of the liquid metal to the liquid crystal monomer, the chain extender and the cross-linking agent is 1. Weighing related monomers, a chain extender, a cross-linking agent, a catalyst and liquid metal, and adding the monomers, the chain extender, the cross-linking agent, the catalyst and the liquid metal into a 10mL brown strain bottle; adding dichloromethane; carrying out ultrasonic treatment for 1h by using an ultrasonic crusher to uniformly mix the mixture; pouring the obtained solution into a Polytetrafluoroethylene (PTFE) mould, and then putting the mould into a drying oven at 40 ℃ for heat preservation for 1.5h; the resulting pre-crosslinked LM-LCE-5 sample was then carefully winged removed from the PTFE mold; stretching the cut piece to about 270% of the original strength of the cut piece and keeping the cut piece fixed; the obtained sample was placed in an oven and kept at 40 ℃ for 10 hours to obtain an LM-LCE sample.
The structural formula of the liquid crystal monomer 4- ((6- (acryloyloxy) hexyl) oxy) phenyl 4- ((6- (acryloyloxy) hexyl) oxy) benzoate is as follows:
the cross-linking agent pentaerythritol tetra (3-mercaptopropionate) has the following structural formula:
the chain extender 2, 2-oxy-bis (ethane-1-thiol) has the following structural formula:
the catalyst dipropylamine has the following structural formula:
II, stress-strain, toughness, reversible deformation, maximum actuating stress, a linear viscoelastic region, ultraviolet light driving and shrinkage force and self-repairing test of the liquid crystal elastomer based on the liquid metal nano liquid drop prepared by the method;
(1) stress-strain test: stress-strain testing was performed at room temperature using a universal tensile tester (SANS E42.503).
(2) And (3) toughness determination: and (3) integrating the stress-strain curve measured in the step (1), and calculating the area enclosed by the curve and the X axis of the abscissa, namely the toughness.
(3) And (3) reversible deformation testing: using a dynamic thermomechanical analyzer (DMAQ 850, TA) in an iso-stress mode, the length (L) of the film at a certain time and the shortest length (L) of the film in the isotropic state were recorded in the direction of the stretching orientation by cyclic temperature increase and decrease iso ) Ratio of (d) and cycle number.
(4) Maximum actuation stress test: the shrinkage force test during temperature rise was performed in an iso-strain mode using a dynamic thermomechanical analyzer (DMAQ 850, TA).
(5) Testing of linear viscoelastic region: the maximum linear viscoelastic region of the liquid crystal elastomer based on the liquid metal nano-droplet is prepared by testing in a shaking mode by using a dynamic thermomechanical analyzer (DMAQ 850, TA).
(6) Ultraviolet light drive test: the LM-LCE film in a naturally sagging state was irradiated with a 365nm UV light source, and the length of the sample was recorded as a function of the UV irradiation time.
(7) Self-repairing test: and cutting off an LM-LCE film sample, splicing, standing at 40 ℃ for 10 hours, observing the self-repairing effect by using a metallographic microscope and a scanning electron microscope, and performing a stress-strain test after repairing by using a universal tensile tester (SANS E42.503).
Example 1: the liquid crystal elastomer based on the liquid metal nano liquid drops comprises the following specific preparation steps:
weighing liquid crystal monomer Y2003 (592.5mg, 1.1mmol), chain extender 2,2' -oxybis (ethane-1-thiol) (138.2mg, 1.0mmol), cross-linking agent pentaerythritol tetrakis (3-mercaptopropionate) (24.4mg, 0.05mmol) and liquid metal (39.7 mg) into a 10mL brown strain bottle; weighing 6.00 mu L of catalyst dipropylamine, dissolving in dichloromethane (1.8 mL), and adding into the brown strain bottle; carrying out ultrasonic treatment for 1h by using an ultrasonic crusher to uniformly mix the mixture; pouring the obtained solution into a Polytetrafluoroethylene (PTFE) mold (3 cm long × 2cm wide × 1cm deep), and then putting the mold into a drying oven at 40 ℃ for heat preservation for 1.5h; the resulting pre-crosslinked LM-LCE-5 sample was then carefully winged removed from the PTFE mold; stretching it to about 270% of its original strength after cutting and keeping it fixed; the obtained sample was placed in an oven and kept at 40 ℃ for 10 hours to obtain an LM-LCE-5 sample.
Example 2: stress-strain, toughness, reversible deformation, maximum actuating stress, linear viscoelastic region, ultraviolet light drive and contractive force and self-repairing test in the temperature rise process of the prepared liquid crystal elastomer based on the liquid metal nano liquid drops;
(1) stress-strain test: the maximum elongation at break was 1010.87% as measured by stress-strain testing at different temperatures in an iso-strain mode using a universal tensile tester (SANS E42.503).
(2) And (3) toughness determination: integrating the stress-strain curve measured in the step (1), and calculating the area enclosed by the curve and the X axis of the abscissa, wherein the result is as follows: 18.31MJ/m 3 。
(3) And (3) reversible deformation testing: using a dynamic thermomechanical analyzer (DMAQ 850, TA), the length of the film at a certain point in time (L) and the shortest length of the film in the isotropic state (L) were recorded in the direction of the stretching orientation in an iso-stress mode with cyclic temperature increase and decrease iso ) The maximum ratio of (2) to (2.22) is measured, and the cycle number of the complete reversible deformation reaches 2000.
(4) And (3) testing the shrinkage stress in the heating process: the shrinkage force test of the temperature rise process was performed in an iso-strain mode using a dynamic thermomechanical analyzer (DMA Q850, TA corporation). The maximum shrinkage stress generated by the temperature rise from 30 ℃ to 80 ℃ and then the temperature drop from 80 ℃ to 30 ℃ is measured to be 1.13MPa.
(5) Testing of linear viscoelastic region: the maximum linear viscoelastic region of the liquid crystal elastomer based on the liquid metal nano-droplets was prepared by testing in an oscillation mode using a dynamic thermomechanical analyzer (DMAQ 850, TA corporation), and the maximum linear viscoelastic region was 72% as measured at a set frequency of 1 HZ.
(6) Ultraviolet light drive test: irradiating LM-LCE film in a naturally sagging state by using a 365nm ultraviolet light source at 0.4W/cm 2 Under the irradiation of ultraviolet light, the length (L) of the recording film at a certain time in the direction of the stretch orientation and the shortest length (L) of the film in the isotropic state are recorded iso ) The maximum ratio of (a) was measured to be 2.22.
(7) Self-repairing test: and cutting off an LM-LCE film sample, splicing, placing at 40 ℃ for 10 hours, observing the self-repairing effect by using a metallographic microscope and a scanning electron microscope, and performing stress-strain test after repairing by using a universal tensile tester (SANS E42.503). The test result shows that the self-repairing efficiency of the liquid crystal elastomer composite material is 80%.
The above-mentioned embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention, and it should be noted that: it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended to cover in the appended claims all such changes and modifications that fall within the true spirit and scope of the invention.
Claims (5)
1. A liquid crystal elastomer material based on liquid metal nanometer liquid drops is characterized in that the liquid crystal elastomer material is polymerized by liquid crystal monomers, after polymerization, the liquid crystal monomers are orderly arranged in a molecular chain in a liquid crystal element mode along a stretching direction to form a molecular main chain, and liquid metal is crushed into nanometer-level microdroplets and then has dynamic interaction with sulfur elements in the molecular main chain to be uniformly and stably dispersed in a liquid crystal elastomer matrix; liquid crystal monomers, chain extenders, cross-linking agents, catalysts and liquid metal are subjected to ultrasonic crushing treatment and then are uniformly mixed; under the condition of thermal polymerization, preparing a liquid crystal elastomer based on liquid metal nano liquid drops;
the liquid crystal monomer is 4- ((6- (acryloyloxy) hexyl) oxy) phenyl 4- ((6- (acryloyloxy) hexyl) oxy) benzoate;
the liquid metal is gallium indium tin alloy, and the mass ratio of gallium to indium to tin is (0.62-0.8);
the mass ratio of the liquid metal to the liquid crystal monomer is 5-8%;
the liquid crystal monomer 4- ((6- (acryloyloxy) hexyl) oxy) phenyl 4- ((6- (acryloyloxy) hexyl) oxy) benzoate has the following structural formula:
the cross-linking agent pentaerythritol tetra (3-mercaptopropionate) has the following structural formula:
the chain extender 2, 2-oxybis (ethane-1-mercaptan) has the following structural formula:
the catalyst dipropylamine has the following structural formula:
the mass ratio of the liquid crystal monomer to the chain extender and the cross-linking agent is as follows: liquid crystal monomer: chain extender: crosslinking agent = 1;
the mass ratio of the liquid metal to the liquid crystal monomer, the chain extender and the cross-linking agent is as follows: liquid metal: (liquid crystal monomer + chain extender + crosslinking agent) = 1.
2. A method for preparing a liquid metal nano droplet-based liquid crystal elastomer material according to claim 1, characterized in that the preparation process is as follows:
step 1, carrying out water removal treatment on a liquid crystal monomer 4- ((6- (acryloyloxy) hexyl) oxy) phenyl 4- ((6- (acryloyloxy) hexyl) oxy) benzoate, a chain extender 2, 2-oxybis (ethane-1-thiol), a cross-linking agent pentaerythritol tetra (3-mercaptopropionate) and liquid metal;
step 2, placing all the materials in the step 1 into anhydrous dichloromethane, then placing the materials into a brown strain bottle, and fully stirring the materials under the condition of introducing nitrogen to form a uniform solution;
step 3, dissolving a catalyst dipropylamine in dichloromethane, and then adding the solution into the brown strain bottle;
step 4, carrying out ultrasonic treatment for 1-1.5 hours by using an ultrasonic crusher to crush the liquid metal into nano-scale, and realizing uniform mixing of the mixture;
step 5, pouring the mixture into a polytetrafluoroethylene groove, and then putting the polytetrafluoroethylene groove into a drying oven with the temperature of 36-45 ℃ for heat preservation for 1-1.5h;
step 6, cooling the polytetrafluoroethylene groove in the step 5 to room temperature to prepare an unoriented liquid crystal elastomer material LM-LCE film based on liquid metal nano liquid drops;
step 7, cutting the unoriented LM-LCE film into a long strip, stretching the long strip at room temperature, and keeping the long strip fixed to obtain a stretched and oriented LM-LCE film based on the liquid metal nano liquid drop liquid crystal elastomer material;
and 8, putting the stretched and oriented long-strip LM-LCE film prepared in the step 7 into an oven, keeping the temperature of the oven at 36-45 ℃ for 8-11h, and naturally cooling the film to room temperature to prepare the liquid crystal elastomer material LM-LCE film based on the liquid metal nano liquid drops and having an oriented structure.
3. The method for preparing a liquid crystal elastomer material based on liquid metal nano droplets as claimed in claim 2, wherein the chain extender 2, 2-oxybis (ethane-1-thiol) in step 1 is replaced by 3, 6-dithio-1, 8-octanediol.
4. The method for preparing a liquid crystal elastomer material based on liquid metal nano droplets as claimed in claim 2, wherein the power of the ultrasonic treatment of the ultrasonic crusher in the step 4 is set to 360W.
5. The method for preparing a liquid crystal elastomer material based on liquid metal nano-droplets as claimed in claim 2, wherein the unoriented LM-LCE film cut in step 7 is stretched in a long shape at room temperature, stretched to 2-2.7 times of the original length and kept fixed.
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