Janus fiber and preparation method thereof

Abstract

The invention provides a Janus fiber and a preparation method thereof, and belongs to the field of materials. The method comprises the following steps: respectively preparing a liquid crystal elastomer spinning solution and a photosensitive resin spinning solution, then extruding the liquid crystal elastomer spinning solution and the photosensitive resin spinning solution by adopting a spinning device with a 3D printing Janus spinning head to form a single-strand fiber, and carrying out ultraviolet curing on the fiber to form the Janus fiber. One side of the cross section of the Janus fiber is a liquid crystal elastomer, and the other side of the cross section of the Janus fiber is photosensitive resin containing dynamic covalent bonds; different materials on the two sides of the fiber endow the fiber with reversible deformation and self-repairing performance, so that the Janus fiber has application prospects in the fields of intelligent fabrics, intelligent wearable equipment, soft robots and the like.

Description

Technical Field

[0001] The invention belongs to the field of novel material preparation, and in particular relates to a Janus fiber and a preparation method thereof. Background Art

[0002] Fibers, as an important class of materials, are widely used in textiles, construction, automobiles, aviation and medical treatment, and play a vital role in human life. Janus fibers are a unique class of fibers consisting of two or more independent parts parallel to each other at the micrometer or nanometer scale. By combining different materials and functions in one fiber, synergistic physical and chemical effects and multifunctionality that would otherwise be impossible can be achieved, showing huge and highly diverse potential in various applications such as catalysis, sensing and drug delivery.

[0003] Most of the current reports have achieved the anisotropy and multifunctionality of Janus fibers by incorporating various materials (such as functional nanoparticles and catalysts) into different sides of Janus fibers, and applied them in biological fields such as photocatalyst carriers, antibacterial applications, tissue engineering, and drug delivery. However, a simple Janus fiber network has a single function or only serves as a carrier.

[0004] In recent years, stimulus-responsive deformable fibers have received increasing attention, and Janus fibers can occupy a place among deformable fibers with their unique structural advantages. Among various stimulus-responsive deformable materials (such as gels, shape memory polymers, and dielectric elastomers), liquid crystal elastomers (LCEs) that can achieve large, reversible shape deformation are recognized as the most promising candidate materials and have versatility in creating shape deformation patterns. Dynamic covalent bonds can break and reconstruct bonds under certain conditions (such as light, heat, pH changes, etc.). Introducing dynamic covalent bonds into fibers can make the fibers functional and intelligent. To this end, the present invention intends to integrate two materials, liquid crystal elastomers and resins containing dynamic covalent bonds, into the same fiber, and proposes a Janus fiber that has both reversible deformation and self-healing properties. Summary of the invention

[0005] In order to solve the problems in the prior art, the present invention proposes a Janus fiber and a preparation method thereof, which successfully combines two materials, a liquid crystal elastomer and a resin containing dynamic covalent bonds, into the same fiber.

[0006] The present invention first provides a method for preparing Janus fiber, which comprises the following steps:

[0007] 1) mixing a liquid crystal monomer, a dithiol crosslinking agent, a first catalyst and a first solvent, washing the mixture, and volatilizing the solvent to obtain a liquid crystal oligomer; adding a photoinitiator and a second solvent to the liquid crystal oligomer, and volatilizing the solvent in vacuum to obtain a liquid crystal elastomer spinning solution;

[0008] 2) mixing poly(tetrahydrofuran) glycol, toluene-2,4-diisocyanate and a second catalyst for reaction, then adding dimethylolbutyric acid to continue the reaction; finally, introducing 2-(tert-butylamino)ethyl methacrylate for further reaction to obtain a product, and mixing the product with a third solvent and a photoinitiator to obtain a photosensitive resin spinning solution;

[0009] 3) Liquid crystal elastomer spinning solution and photosensitive resin spinning solution are poured into two barrels respectively, and the two spinning solutions are extruded simultaneously. The two spinning solutions are extruded into one fiber through a spinning head; the extruded fiber is cured by ultraviolet light to obtain Janus fiber.

[0010] The present invention also provides a Janus fiber prepared by the method. The cross section of the Janus fiber obtained by the present invention has a liquid crystal elastomer on one side and a photosensitive resin containing dynamic covalent bonds on the other side; the different materials on both sides of the fiber give the fiber programmable deformation and self-healing properties, so that the Janus fiber of the present invention has application prospects in the fields of smart fabrics, smart wearable devices, soft robots, etc.

[0011] The present invention further provides a spinning device for implementing the method, which comprises: a fiber extrusion device and a fiber collection device;

[0012] The fiber extrusion device comprises a first barrel, a second barrel, an air supply nozzle and a spinning head, wherein the first barrel is used to store the liquid crystal elastomer spinning solution, and the second barrel is used to store the photosensitive resin spinning solution; the air supply nozzle is used to independently control the air pressure in the first barrel and the second barrel, so that the materials stored in the barrels are squeezed into the spinning head under the action of the air pressure; the spinning head comprises two needles arranged at an angle of 60°, the feed ports of the two needles are respectively connected to the first barrel and the second barrel, and the spinning head has only one discharge port, which is used to combine two fibers into a single fiber;

[0013] The fiber collecting device comprises a roller and a light curing module. The light curing module performs ultraviolet light curing on the fibers extruded by the fiber extruding device, and the roller collects the light-cured fibers.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The preparation method provided by the present invention is simple in process, does not require complicated equipment, and can allow continuous, high-speed, and gentle production of Janus fibers.

[0016] 2. One side of the cross section of the Janus fiber prepared by the present invention is a liquid crystal elastomer, and the other side is a photosensitive resin containing dynamic covalent bonds; the different materials on both sides of the Janus fiber make the prepared Janus fiber have the functions of reversible deformation and self-repair. When the Janus fiber of the present invention is stretched, the fiber undergoes a winding deformation when returning to the initial length, and the fiber can return to its original shape after heating the wound fiber. The invented Janus fiber is cut into two pieces, and the fiber can self-heal in situ after heating, and the heat-repaired fiber can withstand a certain intensity of stress. Therefore, the Janus fiber of the present invention has a wide application field and high application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is a schematic diagram of the spinning device of the present invention.

[0018] Figure 2 Shown is an optical microscope image of a Janus fiber.

[0019] Figure 3 Shown is a circular cross-section of the Janus fiber obtained in Example 1.

[0020] Figure 4 Shown are the reversible deformation test results of Janus fibers.

[0021] Figure 5 Shown are the test results of the self-healing performance of Janus fibers.

[0022] Figure 6 This is the circular cross section of the Janus fiber obtained in Example 3. DETAILED DESCRIPTION

[0023] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[0024] The present invention provides an optional method for preparing Janus fibers. The prepared Janus fibers have a liquid crystal elastomer on one side and a photosensitive resin containing dynamic covalent bonds on the other side, and have the functions of reversible deformation and self-repair. The method comprises the following steps:

[0025] 1) mixing a liquid crystal monomer, a dithiol crosslinking agent, a first catalyst and a first solvent, washing the mixture, and volatilizing the solvent to obtain a liquid crystal oligomer; adding a photoinitiator and a second solvent to the liquid crystal oligomer, and volatilizing the solvent in vacuum to obtain a liquid crystal elastomer spinning solution;

[0026] 2) mixing poly(tetrahydrofuran) glycol, toluene-2,4-diisocyanate and a second catalyst for reaction, then adding dimethylolbutyric acid to continue the reaction; finally, introducing 2-(tert-butylamino)ethyl methacrylate for further reaction to obtain a product, and mixing the product with a third solvent and a photoinitiator to obtain a photosensitive resin spinning solution;

[0027] 3) Liquid crystal elastomer spinning solution and photosensitive resin spinning solution are poured into two barrels respectively, and the two spinning solutions are extruded at the same time, and the two spinning solutions are extruded into one fiber through a spinning head; during spinning, the distance between the spinning head and the collector is adjusted to 10 to 30 cm, and the materials in the two barrels are extruded by air pressure, and the air pressure of the two barrels is controlled to be 1.0 to 5.0 MPa respectively; the extruded fiber is UV-cured to obtain Janus fiber.

[0028] In some embodiments of the present invention, the liquid crystal monomer is 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene (RM257) or 1,4-bis-[4-(6-acryloxyhexyloxy)benzoyloxy]-2-methylbenzene (RM82); the dithiol crosslinker is one or more of 1,3-propanedithiol, 1,5-pentanedithiol, and 2,2′-(1,2-ethylenedioxy)bis(ethylenethiol) (DODT); the first catalyst is an alkaline catalyst, and the mass ratio of the liquid crystal monomer to the dithiol crosslinker is: (5~20):(1~5); the amount of the first catalyst used is 2~10wt% of the liquid crystal monomer.

[0029] In some embodiments of the present invention, the second catalyst is butyl dilaurate (DBTDL), and the amount of the second catalyst added is 0.1-0.5wt% of the mixture. The molar ratio of poly(tetrahydrofuran) glycol to toluene-2,4-diisocyanate is 1:2-1:5; the molar ratio of dimethylolbutyric acid to toluene-2,4-diisocyanate is 1:2-1:10; the molar ratio of 2-(tert-butylamino)ethyl methacrylate to dimethylolbutyric acid is 1:1.

[0030] The first solvent, the second solvent and the third solvent may be the same or different. In some embodiments of the present invention, the first solvent, the second solvent and the third solvent are selected from one or more of dichloromethane, chloroform, toluene, p-xylene and ethylene glycol diacetate, and the amounts of the first solvent, the second solvent and the third solvent are 30-60wt%, 0.1-0.5wt% and 30-60wt% of their respective mixtures, respectively.

[0031] In some embodiments of the present invention, the photoinitiator in step 1) and step 2) is the same, which is selected from one or more of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure 819), 2,2-dimethoxy-2-acetophenone (Irgacure 651), and 2-hydroxy-2-methylphenylacetone (Darocur 1173).

[0032] In some embodiments of the present invention, in the photosensitive resin spinning solution, the third solvent accounts for 30% to 60wt%, the photoinitiator accounts for 1wt% to 5wt%, and the remainder is the product obtained by the reaction in step 2).

[0033] The spinning device used in the preparation of Janus fibers in the embodiment is as follows: Figure 1 , which is composed of a fiber extrusion device and a fiber collection device; wherein the fiber extrusion device includes a first barrel, a second barrel, an air supply nozzle and a spinning head, the first barrel is used to store the liquid crystal elastomer spinning solution, and the second barrel is used to store the photosensitive resin spinning solution; the air supply nozzle is used to independently control the air pressure in the first barrel and the second barrel, so that the materials stored in the barrels are squeezed into the spinning head under the action of the air pressure; the spinning head is a needle head arranged at an acute angle (such as Figure 1 As shown, in some embodiments of the present invention, the two needles are at an angle of 60°), the feed ports of the two needles are connected to the first barrel and the second barrel respectively, and the spinning head has only one discharge port (the two needles share one discharge port), which is used to combine the two fibers into a single fiber; in some embodiments of the present invention, the fiber extrusion device uses a nozzle of a 3D printer to spray air, and the air pressure is controlled between 1.0 and 5.0 MPa. The liquid crystal elastomer spinning solution and the photosensitive resin spinning solution are extruded into a single strand at the same time, and the fiber extrusion rate is ensured to match the fiber collection rate. The fiber collection device includes a roller and a light curing module, the light curing module performs ultraviolet light curing on the fibers extruded by the fiber extrusion device, and the roller collects the light-cured fibers.

[0034] Example 1

[0035] A method for preparing Janus fiber comprises the following steps:

[0036] (1) Preparation of Liquid Crystal Elastomer Spinning Solution:

[0037] Weigh 10g of liquid crystal monomer, 2g of DODT, add 2wt% triethylamine and 10g of toluene, heat and stir until a uniformly mixed viscous liquid is formed, wash and dry to obtain a liquid crystal oligomer. Weigh 0.2g of liquid crystal oligomer, add 100μL I819 and 100μL toluene, and vacuum dry to obtain a liquid crystal elastomer spinning solution for use.

[0038] (2) Preparation of photosensitive resin spinning solution:

[0039] Weigh 0.05 mol of poly(tetrahydrofuran) glycol and 0.1 mol of toluene-2,4-diisocyanate, add butyl dilaurate (DBTDL, 0.1 wt% of the mixture), and heat and stir to react. Subsequently, add 0.01 mol of dihydroxymethylbutyric acid and continue the reaction. Finally, pass 0.01 mol of 2-(tert-butylamino)ethyl methacrylate and react to obtain the product. The product is further mixed with ethylene glycol diacetate (30% of the product) and I819 (1% of the product) to obtain a photosensitive resin spinning solution for use.

[0040] (3) Preparation of liquid crystal fibers:

[0041] The liquid crystal elastomer spinning solution and the photosensitive resin spinning solution prepared in steps (1) and (2) were respectively poured into the syringe in the fiber extrusion device, the distance between the needle and the collector was adjusted to 10 cm, the air pressure of the two nozzles was controlled to be 1.0 MPa and 1.0 MPa respectively, the roller winding rate was 1 r / s, and the ultraviolet lamp was turned on for photocuring to prepare Janus fiber, which was then dried at 90°C.

[0042] The obtained Janus fibers were characterized by morphology. Figure 3 It can be seen that one side is a smooth resin and the other side is a liquid crystal elastomer, and the thickness of both sides is basically the same.

[0043] The obtained Janus fiber was subjected to a reversible deformation test. The linear fiber (3 cm) was stretched 160% (4.8 cm), and the fiber was coiled when returning to its initial length. After heating at 70°C, the fiber returned to its original shape (linearity). The reversible deformation test results are shown in Figure 2. Figure 4 shown.

[0044] The obtained Janus fiber was subjected to a self-repair test. The fiber obtained in Example 1 with a length of 3 cm was cut into two parts from the middle, and the broken ends were brought close together and heated at 90°C. The fiber healed itself in situ, and the heat-repaired fiber could withstand a stress of 40 MPa (the original fiber could withstand a stress of 60 MPa). The test results are shown in Figure 5 shown.

[0045] Example 2

[0046] A method for preparing a plant tendril bionic programmable Janus fiber comprises the following steps:

[0047] (1) Preparation of Liquid Crystal Elastomer Spinning Solution:

[0048] Weigh 40g of liquid crystal monomer, 10g of DODT, add 10wt% triethylamine and 60g of toluene, heat and stir until a uniformly mixed viscous liquid is formed, wash and dry to obtain a liquid crystal oligomer. Weigh 2g of liquid crystal oligomer, add 1000μL I819 and 1000μL toluene, and vacuum dry to obtain a liquid crystal elastomer spinning solution for use.

[0049] (2) Preparation of photosensitive resin spinning solution:

[0050] Weigh 0.04 mol of poly(tetrahydrofuran) glycol and 0.2 mol of toluene-2,4-diisocyanate, add butyl dilaurate (DBTDL, 0.5 wt% of the mixture), and heat and stir to react. Subsequently, add 0.1 mol of dihydroxymethylbutyric acid and continue the reaction. Finally, pass 0.1 mol of 2-(tert-butylamino)ethyl methacrylate and react to obtain the product. The product is further mixed with ethylene glycol diacetate (60% of the product) and I819 (5% of the product) to obtain a photosensitive resin spinning solution for use.

[0051] (3) Preparation of liquid crystal fibers:

[0052] The liquid crystal elastomer spinning solution and the photosensitive resin spinning solution prepared in steps (1) and (2) were respectively poured into the syringe in the fiber extrusion device, the distance between the needle and the collector was adjusted to 30 cm, the air pressure of the two nozzles was controlled to be 5.0 MPa and 5.0 MPa respectively, the roller winding rate was 30 r / s, and the ultraviolet lamp was turned on for photocuring to prepare Janus fiber, which was then dried at 90°C.

[0053] The Janus fiber obtained in Example 2 was subjected to the same reversible deformation and self-repairing tests as in Example 1. The Janus fiber obtained in Example 2 also has the reversible deformation and self-repairing functions.

[0054] Example 3

[0055] A method for preparing a plant tendril bionic programmable Janus fiber comprises the following steps:

[0056] (1) Preparation of Liquid Crystal Elastomer Spinning Solution:

[0057] Weigh 20g of liquid crystal monomer, 10g of DODT, add 3wt% triethylamine and 30g of toluene, heat and stir until a uniformly mixed viscous liquid is formed, wash and dry to obtain a liquid crystal oligomer. Weigh 1g of liquid crystal oligomer, add 400μL I819 and 400μL toluene, and vacuum dry to obtain a liquid crystal elastomer spinning solution for use.

[0058] (2) Preparation of photosensitive resin spinning solution:

[0059] Weigh 0.05 mol of poly(tetrahydrofuran) glycol and 0.25 mol of toluene-2,4-diisocyanate, add butyl dilaurate (DBTDL, 0.3 wt% of the mixture), and heat and stir to react. Subsequently, add 0.05 mol of dimethylolbutyric acid and continue the reaction. Finally, pass 0.05 mol of 2-(tert-butylamino)ethyl methacrylate and react to obtain the product. The product is further mixed with ethylene glycol diacetate (40% of the product) and I819 (3% of the product) to obtain a photosensitive resin spinning solution for use.

[0060] (3) Preparation of liquid crystal fibers:

[0061] The liquid crystal elastomer spinning solution and the photosensitive resin spinning solution prepared in steps (1) and (2) are respectively poured into the syringe in the fiber extrusion device, the distance between the needle and the collector is adjusted to 20 cm, the air pressure of the two nozzles is controlled to be 4.0 MPa and 3.0 MPa respectively, the roller winding rate is 20 r / s, and the ultraviolet lamp is turned on for photocuring, thereby preparing Janus fibers with thicker liquid crystal elastomer side than photosensitive resin side, and drying at 90°C.

[0062] The obtained Janus fibers were characterized by morphology. Figure 6 As shown. Figure 6 It can be seen that one side is a smooth resin and the other side is a liquid crystal elastomer, and the liquid crystal elastomer side is thicker than the photosensitive resin side. The Janus fiber obtained in Example 3 was subjected to the same reversible deformation and self-repairing test as in Example 1. The Janus fiber obtained in Example 3 also has reversible deformation and self-repairing functions.

[0063] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing Janus fiber, characterized in that: The steps include: 1) mixing a liquid crystal monomer, a dithiol crosslinking agent, a first catalyst and a first solvent, washing the mixture, and volatilizing the solvent to obtain a liquid crystal oligomer; adding a photoinitiator and a second solvent to the liquid crystal oligomer, and volatilizing the solvent in vacuum to obtain a liquid crystal elastomer spinning solution; 2) mixing poly(tetrahydrofuran) glycol, toluene-2,4-diisocyanate and a second catalyst for reaction, then adding dimethylolbutyric acid to continue the reaction; finally, introducing 2-(tert-butylamino)ethyl methacrylate for further reaction to obtain a product, and mixing the product with a third solvent and a photoinitiator to obtain a photosensitive resin spinning solution; 3) Liquid crystal elastomer spinning solution and photosensitive resin spinning solution are poured into two barrels respectively, and the two spinning solutions are extruded simultaneously. The two spinning solutions are extruded into one fiber through a spinning head; the extruded fiber is cured by ultraviolet light to obtain Janus fiber.

2. The preparation method according to claim 1, characterized in that: In step 1), the liquid crystal monomer is 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene (RM257) or 1,4-bis-[4-(6-acryloxyhexyloxy)benzoyloxy]-2-methylbenzene (RM82); the dithiol cross-linking agent is one or more of 1,3-propanedithiol, 1,5-pentanedithiol, and 2,2′-(1,2-ethylenedioxy)bis(ethylenethiol) (DODT); the first catalyst is an alkaline catalyst, and the mass ratio of the liquid crystal monomer to the dithiol cross-linking agent is: (5-20): (1-5); the amount of the first catalyst used is 2-10wt% of the liquid crystal monomer.

3. The preparation method according to claim 1, characterized in that: The first solvent, the second solvent and the third solvent may be the same or different. The first solvent, the second solvent and the third solvent are selected from one or more of dichloromethane, chloroform, toluene, p-xylene and ethylene glycol diacetate. The amounts of the first solvent, the second solvent and the third solvent are 30-60wt%, 0.1-0.5wt% and 30-60wt% of their respective mixtures, respectively.

4. The preparation method according to claim 1, characterized in that: The photoinitiator in step 1) and step 2) is the same, which is selected from one or more of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure 819), 2,2-dimethoxy-2-acetophenone (Irgacure 651), and 2-hydroxy-2-methylphenylacetone (Darocur 1173).

5. The preparation method according to claim 1, characterized in that: In step 2), the second catalyst is butyl dilaurate (DBTDL), and the amount of the second catalyst added is 0.1-0.5wt% of the mixture.

6. The preparation method according to claim 1, characterized in that: The molar ratio of poly(tetrahydrofuran) glycol to toluene-2,4-diisocyanate is 1:2-1:5; the molar ratio of dimethylolbutyric acid to toluene-2,4-diisocyanate is 1:2-1:10; and the molar ratio of 2-(tert-butylamino)ethyl methacrylate to dimethylolbutyric acid is 1:

1.

7. The preparation method according to claim 1, characterized in that: In terms of mass percentage, in the photosensitive resin spinning solution, the third solvent accounts for 30% to 60% by weight, the photoinitiator accounts for 1% to 5% by weight, and the remainder is the product obtained by the reaction in step 2).

8. The preparation method according to claim 1, characterized in that: During spinning in step 3), the distance between the spinning head and the collector is adjusted to 10-30 cm, and the materials in the two barrels are extruded by air pressure, and the air pressure of the two barrels is controlled to be 1.0-5.0 MPa respectively.

9. Janus fiber prepared by the method according to any one of claims 1 to 8.

10. A spinning device for implementing the method according to any one of claims 1 to 8, characterized in that include: Fiber extrusion device and fiber collection device; The fiber extrusion device comprises a first barrel, a second barrel, an air supply nozzle and a spinning head, wherein the first barrel is used to store the liquid crystal elastomer spinning solution, and the second barrel is used to store the photosensitive resin spinning solution; the air supply nozzle is used to independently control the air pressure in the first barrel and the second barrel, so that the materials stored in the barrels are squeezed into the spinning head under the action of the air pressure; the spinning head has two feed ports and one discharge port, and its structure comprises two needles arranged at an acute angle, the feed ports of the two needles are respectively connected to the first barrel and the second barrel, and the two needles share one discharge port, which is used to combine two fibers into a single fiber; The fiber collecting device comprises a roller and a light curing module. The light curing module performs ultraviolet light curing on the fibers extruded by the fiber extruding device, and the roller collects the light-cured fibers.

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