Anti-gelling spinning method for liquid crystal elastomer fiber

Abstract

The present invention belongs to the technical field of liquid crystal elastomer fibers, and discloses a method for anti-gelling spinning of liquid crystal elastomer fibers. The present invention obtains an oligomer solution component A by Aza-Michael reaction of a liquid crystal monomer and a thiol substance, and then mixes it with component B to obtain a precursor spinning solution; then the precursor spinning solution is volatilized by a solvent to adjust the concentration for spinning, and after spinning, it is cross-linked and cured with ultraviolet light to obtain a liquid crystal elastomer fiber; wherein, component B is a mixed solution of an anticoagulant with an active functional group and ether. The elimination of the gel phenomenon in the precursor spinning solution obtained by the present invention improves the stability and preservation of the spinning solution, and solves the problem that the precursor spinning solution is easy to gel and easy to clog the tube. In addition, the spinning solution can break through the gel point and has universality in spinning, and component B acts as a cross-linking agent during UV curing, and the mechanical properties of the prepared liquid crystal elastomer fiber are enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid crystal elastomer fibers, and in particular relates to an anti-gelling spinning method for liquid crystal elastomer fibers. Background Art

[0002] Liquid crystal elastomer (LCE) is an interdisciplinary subject that has emerged in recent decades. Preparing liquid crystal elastomer into fibers can improve response speed and mechanical properties. It has great application prospects in military and intelligent materials such as aerospace drives, soft robots, artificial muscles, exoskeletons and micro-nanogenerators.

[0003] Existing methods for preparing liquid crystal elastomer fibers typically involve preparing a spinning solution and then spinning. Elastomer fibers are obtained after solvent evaporation, increasing the concentration of the spinning solution and gelling. However, to prevent gelation in the spinning apparatus, which could cause tube blockage, the initial spinning solution is typically at a low concentration and cannot be stored for extended periods. Therefore, addressing this gelation phenomenon is crucial for the industrialization of liquid crystal elastomer spinning processes. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary object of the present invention is to provide a method for anti-gelling spinning of liquid crystal elastomer fibers.

[0005] The present invention proposes a method for mixing components A and B in the preparation of a precursor spinning solution to prevent gelation of the spinning solution, thereby overcoming the problems of short spinning solution shelf life, low spinning solution concentration, easy gelation of the spinning solution, and discontinuous spinning process. Furthermore, because component B acts as a post-crosslinker and effectively promotes the overall spinning solution concentration to exceed the gel point for spinning, the mechanical properties of the prepared fiber are greatly enhanced, overcoming the poor mechanical properties and insufficient driving capacity of liquid crystal elastomer fibers.

[0006] Another object of the present invention is to provide liquid crystal elastomer fibers prepared by the above method.

[0007] The purpose of the present invention is achieved through the following solutions:

[0008] A method for anti-gelling spinning of liquid crystal elastomer fibers, comprising the following steps:

[0009] (1) mixing and reacting a benign solvent, a liquid crystal monomer, a thiol substance, and an alkaline catalyst to obtain an oligomer solution component A, adding an initiator, and then mixing and stirring with component B to obtain a precursor spinning solution;

[0010] (2) volatilizing the solvent from the precursor spinning solution to a concentration of 0-80 wt %, preferably 40-60 wt %, and spinning to obtain liquid crystal elastomer fibers;

[0011] Wherein, component B is a mixed solution of an anticoagulant with active functional groups and ether.

[0012] The benign solvent in step (1) is one or more of toluene, dichloromethane, chloroform, petroleum ether, N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0013] The liquid crystal monomer in step (1) is one or more of liquid crystal monomer RM-82, liquid crystal monomer RM-257, liquid crystal monomer BAB6, and liquid crystal monomer LC-756.

[0014] The thiol substance in step (1) is one or more of 3,6-dioxa-1,8-octanedithiol, pentaerythritol tetrakis-3-mercaptopropionate, trimethylolpropane tris(3-mercaptopropionate), 1,8-octanedithiol, 1,10-decanedithiol, and 1,6-hexanedithiol.

[0015] The alkaline catalyst in step (1) is one of di-n-propylamine, triethylamine, methyltriethylamine, triethylenediamine, N,N-dimethylcyclohexylamine, N,N'-diethylpiperazine, and N,N'-lutidine.

[0016] The initiator in step (1) is one of 1-hydroxycyclohexyl phenyl ketone, benzoin diethyl ether, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, and 1,1'-(methylenebis-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone].

[0017] The anticoagulant with active functional groups in step (1) is a small molecule monomer substance that is soluble in a benign solvent and has a similar structure or functional group (with an unsaturated π bond) to the liquid crystal monomer, including but not limited to one or more of siloxanes, olefinic acids, olefinic esters, and olefinic ethers.

[0018] The anticoagulant with active functional groups in step (1) is one or more of vinyl-terminated dimethylpolysiloxane, 1,3-dimethyl-1,3-diphenyl-1,3-divinyldisiloxane, vinyl tri(β-methoxyethoxy)silane, vinyl triethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, tetramethyltetravinylcyclotetrasiloxane, 2-acrylate-2-hydroxy-1,3-propylene glycol, tripropylene glycol diacrylate, acrylic acid, 2-ethylhexyl acrylate, butyl acrylate, diallyl phthalate, polyethylene glycol diacrylate, vinyl butyl ether, and vinyl ethyl ether.

[0019] The mass ratio of the benign solvent, liquid crystal monomer, alkaline catalyst, initiator and anticoagulant with active functional groups in step (1) is 70-85:10-25:0.1-2:0.1-2:0.5-10.

[0020] The molar ratio of the carbon-carbon double bond of the liquid crystal monomer in step (1) to the thiol functional group of the thiol substance is 1.2:1-1.6:1, and the molar ratio of the dithiol functional group substance to the polythiol functional group substance in the thiol substance is 10:1-15:1.

[0021] The amount of ether used in step (1) is 30-60wt% of component B.

[0022] The reaction in step (1) is specifically stirred at room temperature for 3-6 hours.

[0023] The spinning in step (2) includes but is not limited to one of template spinning, dry spinning, wet spinning, electrospinning, 3D printing spinning, reactive spinning and bionic spinning, or a combination of spinning methods.

[0024] After spinning in step (2), the fibers are cross-linked and cured under ultraviolet light (UV); wherein the UV irradiation intensity is 150-200 mw / cm -2 .

[0025] The spinning speed in step (2) is 0.2-10.0 mL / min / hole, and the nozzle diameter of the spinning device is 0.1-1.0 mm.

[0026] Liquid crystal elastomer fiber prepared by the above method.

[0027] The mechanism of the present invention is:

[0028] Under alkaline catalysis, the thiol groups in the thiol substance and the carbon-carbon double bonds in the liquid crystal monomer undergo an Aza-Michael reaction to form a low-molecular-weight polymer. During the spinning process, the spinning solution is irradiated with UV light, and the initiator triggers a click reaction between the remaining thiol groups and the carbon-carbon double bonds, as well as an addition reaction between the carbon-carbon double bonds, to form a high-polymer elastomeric fiber. Under the traction of the drafting device, the liquid crystal elastomeric fiber is further highly oriented, achieving a driving ability that responds to external stimuli.

[0029] Due to the elimination of the gel phenomenon, the spinning solution evaporates to an adjustable concentration, breaking through the upper limit of the spinning solution concentration limit of traditional methods. During the UV crosslinking and curing process, the anticoagulant component B with active functional groups also acts as a crosslinking agent.

[0030] In the present invention, the type and amount of the anticoagulant component B with active functional groups are regulated to enhance the tensile strength and flexibility of the liquid crystal elastomer fiber and realize the multifunctionality of the liquid crystal elastomer fiber.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] Eliminating the gelation phenomenon in the precursor spinning solution obtained by the present invention improves the stability and storage of the spinning solution, solving the problem of the precursor spinning solution being prone to gelation and tube clogging. Furthermore, the spinning solution can break through the gel point, making it universally applicable. Component B acts as a crosslinking agent during UV curing, enhancing the mechanical properties of the prepared liquid crystal elastomer fiber.

[0033] The precursor spinning solution described in this invention eliminates gelation, making it versatile and suitable for template spinning, dry spinning, wet spinning, electrospinning, 3D printing, and biomimetic spinning. Compared to the prior art CN 113802209A, the present invention overcomes the limitations of the spinning solution's gel point, offers controllable spinning solution concentration, and enhances spinning continuity. It also eliminates the need for complete evaporation of the spinning solution solvent to produce elastomeric fibers, as described in CN 113802209A. Compared with CN 116288796 A, the precursor spinning solution described in the prior art CN 116288796 A is a high-viscosity, high-concentration liquid crystal spinning slurry. Experiments have shown that it is easy to gel and difficult to preserve. In addition, the spinning of CN 116288796 A requires specific equipment and is not universal. The precursor spinning solution described in the present invention effectively alleviates gelation at high concentration and high viscosity, greatly improving the safety and reliability of the spinning process, and the spinning process has universal characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A is the gelation and tube blocking phenomenon during the spinning process of Comparative Example 1; B1 is the storage condition of the spinning solution obtained in Comparative Example 1; B2 is the storage condition of the spinning solution obtained in Example 1.

[0035] Figure 2 The gelation curves of the formulations described in Comparative Example 1 and Example 2 are shown.

[0036] Figure 3 Liquid crystal elastomer fibers obtained from the spinning solution obtained in Example 2 using different spinning methods, from left to right are wet spinning, printing spinning and dry spinning.

[0037] Figure 4 1 is a stress-strain curve diagram of the liquid crystal elastomer fibers obtained in Comparative Example 1 and Examples 1-2. DETAILED DESCRIPTION

[0038] The present invention will be described in further detail below with reference to the Examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. Where specific conditions are not specified in the Examples, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0039] Unless otherwise specified, all reagents used in the examples can be purchased from the market.

[0040] Example 1

[0041] (1) 6 g of dichloromethane, 0.9 g of liquid crystal monomer RM-257, 0.25 g of thiol substance (the mass ratio of 3,6-dioxa-1,8-octanedithiol to pentaerythritol tetra-3-mercaptopropionate is 4:1), and 0.05 g of di-n-propylamine are added to a closed reactor, and reacted for 3 h under stirring at room temperature and normal pressure. After the reaction, component A of oligomer solution is obtained, 0.02 g of 1-hydroxycyclohexyl phenyl ketone is added, and the mixture is mixed with component B (prepared by mixing 0.05 g of 1,3-dimethyl-1,3-diphenyl-1,3-divinyldisiloxane and 0.05 g of ether) and stirred to obtain a precursor spinning solution; wherein the molar ratio of the carbon-carbon double bond of the liquid crystal monomer to the thiol functional group of the thiol substance is 1.2:1, and the molar ratio of the dithiol functional group substance to the polythiol functional group substance in the thiol substance is 11:1;

[0042] (2) The solvent of the precursor spinning solution is evaporated to a mass percentage concentration of 40%, and the liquid crystal elastomer fiber is obtained by dry spinning using a dry-wet spinning device. In particular, a UV irradiation device is set at the nozzle of the spinning device, and the UV irradiation intensity is 200mw / cm -2 The spinning speed is 10.0 mL / min / hole, the nozzle diameter of the spinning device is 0.1 mm, and a collecting device with a roller is set at the end of the spinning device to collect the liquid crystal elastomer fibers.

[0043] Example 2

[0044] The difference between this embodiment and embodiment 1 is that in step (2), the solvent of the precursor spinning solution is volatilized to a mass percentage concentration of 60%.

[0045] Comparative Example 1

[0046] The difference between this comparative example and Example 1 is that component B is not added in step (1).

[0047] Test results

[0048] The gel situation of the precursor spinning solution of Comparative Example 1 during the spinning process is as follows Figure 1 As shown in A. Figure 1 B1 and B2 are comparison diagrams of the storage conditions of the spinning solutions obtained in Comparative Example 1 and Example 1 after being placed for 24 hours. B1 is gelled, and B2 is not gelled.

[0049] The formulations described in Comparative Example 1 and Example 2 were prepared into solutions according to the method of step (1), and reacted for 0-450 min to obtain gelation curves. Figure 2As shown, the spinning solution solvent of Comparative Example 1 evaporates quickly and begins to gel after a period of time (spinning solution concentration 40-50wt%), while the solvent in the spinning solution of Example 2 evaporates relatively slowly due to the presence of component B. The weight loss residual mass percentage curve of the spinning solution during the solvent evaporation process decreases relatively slowly, and the mass percentage concentration rising curve of the spinning solution is also relatively gentle relative to Comparative Example 1, and no gelation occurs during the test process.

[0050] The precursor spinning solution obtained in Example 2 was used to obtain liquid crystal elastomer fibers such as Figure 3 Liquid crystal elastomer fibers can be obtained by wet, printing, and dry spinning, demonstrating the universal applicability of the spinning solution described in the present invention. The regularity of the fibers obtained by the dry spinning method is higher than that obtained by the printing method and higher than that obtained by the wet spinning method.

[0051] The liquid crystal elastomer fibers obtained in Comparative Example 1 and Examples 1-2 were subjected to mechanical property tensile tests according to the national standard GB / T43938.1. Figure 4 As shown, the control example is less than the embodiment 1 and is less than the embodiment 2. The mechanical properties of the control example fiber are inferior to those of the embodiment. Because the B component of the embodiment has a reactive functional group and acts as a crosslinking agent, the mechanical properties of the fiber are enhanced compared to the control example. The fiber of Example 2 breaks through the gel point (spinning solution concentration of 40-50wt%) during spinning to obtain a fiber. Its structural density is improved compared to the fiber spun at a low concentration, so the mechanical properties are further enhanced, which is the best in the test.

[0052] Based on the above test results, it is clear that the precursor spinning solution described in the embodiments of the present invention has advantages such as being difficult to gel and having a long shelf life. Its versatility allows it to be adapted to various spinning methods. Furthermore, the mechanical properties of the liquid crystal elastomer fibers obtained by spinning without gel limitations are significantly improved, demonstrating its universal applicability in this field.

[0053] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for anti-gelling spinning of liquid crystal elastomer fibers, characterized in that: The following steps are involved: (1) A benign solvent, a liquid crystal monomer, a thiol substance, and an alkaline catalyst are mixed and reacted to obtain an oligomer solution component A, an initiator is added, and then mixed and stirred with component B to obtain a precursor spinning solution; (2) volatilizing the solvent of the precursor spinning solution to a concentration of 0-80 wt%, and spinning to obtain liquid crystal elastomer fibers; Wherein, component B is a mixed solution of an anticoagulant with active functional groups and ether; The liquid crystal monomer in step (1) is one or more of liquid crystal monomer RM-82, liquid crystal monomer RM-257, liquid crystal monomer BAB6, and liquid crystal monomer LC-756; The anti-coagulant with active functional groups in component B is one or more of vinyl-terminated dimethylpolysiloxane, 1,3-dimethyl-1,3-diphenyl-1,3-divinyldisiloxane, vinyl tri(β-methoxyethoxy)silane, vinyl triethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, tetramethyltetravinylcyclotetrasiloxane, 2-acrylate-2-hydroxy-1,3-propylene glycol, tripropylene glycol diacrylate, acrylic acid, 2-ethylhexyl acrylate, butyl acrylate, diallyl phthalate, polyethylene glycol diacrylate, vinyl butyl ether, and vinyl ethyl ether.

2. The anti-gelling spinning method of liquid crystal elastomer fiber according to claim 1, characterized in that: The thiol substance in step (1) is one or more of 3,6-dioxa-1,8-octanedithiol, pentaerythritol tetrakis-3-mercaptopropionate, trimethylolpropane tris(3-mercaptopropionate), 1,8-octanedithiol, 1,10-decanedithiol, and 1,6-hexanedithiol.

3. The anti-gelling spinning method of liquid crystal elastomer fiber according to claim 1, characterized in that: The benign solvent in step (1) is one or more of toluene, dichloromethane, chloroform, petroleum ether, N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide; The alkaline catalyst in step (1) is one of di-n-propylamine, triethylamine, methyltriethylamine, triethylenediamine, N,N-dimethylcyclohexylamine, N,N'-diethylpiperazine, and N,N'-lutidine; The initiator in step (1) is one of 1-hydroxycyclohexyl phenyl ketone, benzoin diethyl ether, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, and 1,1'-(methylenebis-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone].

4. The anti-gelling spinning method of liquid crystal elastomer fiber according to claim 1, characterized in that: The mass ratio of the benign solvent, liquid crystal monomer, alkaline catalyst, initiator and anticoagulant with active functional groups in step (1) is 70-85:10-25:0.1-2:0.1-2:0.5-10.

5. The anti-gelling spinning method of liquid crystal elastomer fiber according to claim 1, characterized in that: The molar ratio of the carbon-carbon double bond of the liquid crystal monomer in step (1) to the thiol functional group of the thiol substance is 1.2:1-1.6:1, and the molar ratio of the dithiol functional group substance to the polythiol functional group substance in the thiol substance is 10:1-15:

1.

6. The anti-gelling spinning method of liquid crystal elastomer fiber according to claim 1, characterized in that: The amount of ether used in step (1) is 30-60 wt% of component B; the reaction in step (1) is specifically stirred at room temperature for 3-6 hours.

7. The anti-gelling spinning method of liquid crystal elastomer fiber according to claim 1, characterized in that: Step (2) volatilizing the solvent of the precursor spinning solution to a concentration of 40-60wt%; The spinning in step (2) includes one of template spinning, dry spinning, wet spinning, electrospinning, 3D printing spinning, reactive spinning and bionic spinning, or a combination of the spinning methods.

8. The anti-gelling spinning method of liquid crystal elastomer fiber according to claim 1, characterized in that: Step (2) is followed by UV cross-linking and curing after spinning; wherein the UV irradiation intensity is 150-200 mw / cm 2 ; The spinning speed in step (2) is 0.2-10.0 mL / min / hole, and the nozzle diameter of the spinning device is 0.1-1.0 mm.

9. Liquid crystal elastomer fiber prepared by the method according to any one of claims 1 to 8.

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