A pH-responsive actuating fiber and a preparation method thereof

Abstract

The present application relates to a kind of pH response driven fiber and its preparation method, the pH response driven fiber has the properties of contraction in basic solution with pH value ≤11, elongation in acidic solution with pH value ≥1;The pH response driven fiber is tannic acid modified composite fiber, and the composite fiber is polymer A / polyvinyl alcohol composite fiber;Polymer A is the high polymer with amine group in side chain;Preparation method is: after high polymer A / polyvinyl alcohol composite fiber is immersed in tannic acid solution and swells, the pH value of solution is regulated to 8-9, and heated to 50-60 DEG C, and oxygen is imported, in oxygen atmosphere, covalent crosslinking reaction occurs between tannic acid and polymer A, and the product after reaction is washed and dried after deionized water to obtain the product.The preparation method of the present application is simple;The product prepared can effectively control the elongation and contraction behavior by controlling the acid-base value of solution, and has faster driving rate in strong acid and strong base.

Description

Technical Field

[0001] The invention belongs to the technical field of artificial driving materials and relates to a driving fiber with pH response and a preparation method thereof. Background Art

[0002] An actuator is a system that converts energy from one form into mechanical energy, such as heat, electricity, or light. The most traditional actuator systems include the internal combustion engine, steam engine, and now the electric motor. In the human body, the isothermal conversion of chemical energy into mechanical energy is fundamental to the ability of organisms to move. For example, muscles reversibly relax and contract, powered by ATP hydrolysis. All of these biological systems have extremely high energy conversion efficiencies, with animal muscles converting over 50% of dietary energy into useful work. This high efficiency is largely due to the direct conversion of chemical energy, which avoids unnecessary intermediate heat generation. Inspired by the physical adaptability, flexibility, reconfigurability, and versatility of mollusks and human muscles, actuators have been developed for a variety of applications, including artificial muscles, wearables, haptic devices, and medical devices.

[0003] Converting chemical energy into mechanical energy can be exploited through proton transfer, charge transfer, redox, photoisomerization, and phase transitions to induce conformational changes in polymer chains, achieving macroscopic actuation of materials. Currently, actuation systems utilizing proton transfer are primarily focused on polycarboxylic acid systems. Carboxylate groups deprotonate in alkaline solutions and become negatively charged, leading to mutual repulsion between polycarboxylic acid chains, manifesting as macroscopic material elongation. In acidic solutions, protonated carboxyl groups become uncharged, resulting in interchain hydrogen bonding, which manifests as macroscopic material contraction. Currently, the most studied pH-driven systems for contraction in acid and elongation in alkali are polyacrylic acid and polymethacrylic acid molecules. However, the construction of pH-driven systems for contraction in alkali and elongation in acid remains a research gap. Unidirectional stimulus actuation can lead to untargeted motion during actuation, making it difficult to precisely control local and global motion. Therefore, it is necessary to design pH actuators with opposing stimulus behaviors. Global motion can be programmed and combined using two pH-responsive actuators through gating. This expands the diversity and selectivity of actuation mechanisms, enabling more controlled actuation effects and better accommodating applications in fields such as soft robotics and artificial muscles.

[0004] Currently, a variety of materials have been fabricated into actuators, such as polymers, carbon nanotubes, graphene, and organic-inorganic hybrids. Consequently, actuators have been fabricated in a variety of forms, such as three-dimensional blocks, two-dimensional films, and one-dimensional fibers. Fiber actuators are a particularly attractive strategy because fibers are flexible and highly anisotropic. Furthermore, animal locomotion is achieved through the contraction and extension of muscles, which have a fibrous structure. Muscle actuation is generated by the step-by-step motion of myosin motor proteins on actin filaments. When the motion of these very simple nanoscale motor proteins is translated into simple muscle contraction / extension, a variety of different motions can be generated. Inspired by examples from nature, we clearly recognize that even simple changes in fiber length can induce very complex motions, making fiber actuators highly valuable for research.

[0005] Therefore, it is of great significance to study a driving fiber that is pH-responsive and can achieve reversible and stable elongation and contraction and its preparation method to solve the problems existing in the existing technology. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems existing in the prior art and provide a pH-responsive driving fiber and a preparation method thereof.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A pH-responsive actuating fiber that contracts in alkaline solutions with a pH value of ≤11 and elongates in acidic solutions with a pH value of ≥1 (when the pH is greater than 11, the fiber does not contract but elongates; when the pH is less than 1, the fiber does not elongate but contracts). Work can be continuously performed by changing the pH value of the solution.

[0009] The pH-responsive driving fiber is a tannic acid-modified composite fiber, and the composite fiber is a polymer A / polyvinyl alcohol composite fiber;

[0010] Polymer A is a polymer with an amine group on the side chain;

[0011] In the polymer A / polyvinyl alcohol composite fiber, there is hydrogen bonding interaction between polyvinyl alcohol and polymer A to enhance the mechanical properties of the fiber;

[0012] There is a covalent cross-linking effect between tannic acid and polymer A to stabilize the shape and size of the fiber.

[0013] In alkaline solution, the side chain amine groups of polymer A are deprotonated, the hydrogen bonds between the molecular chains are restored, the molecular chains collapse, and the fibers shrink; in acidic solution, the side chain amine groups of polymer A are protonated, the electrostatic repulsion between the molecular chains occurs, the molecular chains stretch, and the fibers elongate.

[0014] As the preferred technical solution:

[0015] In the pH-responsive actuating fiber as described above, the polymer A is chitosan, polyacrylamine or branched polyethyleneimine.

[0016] As described above, a pH-responsive driving fiber has a tensile strength of 1 to 5 MPa and an elongation at break of 80 to 120% in an acidic solution of pH = 1, and a tensile strength of 30 to 40 MPa in an alkaline solution of pH = 11 (the tensile strength test is carried out after the fiber is placed in an acidic / alkaline solution for equilibrium), and an elongation at break of 40 to 70%.

[0017] The pH-responsive actuating fiber exhibited a tensile strength varying between 1-5 MPa and 30-40 MPa, an elongation at break varying between 80-120% and 40-70%, and a work density stable at 5-20 kJ / m during 10 acid-base cycles (each acid-base cycle being placed in an acidic solution and then in an alkaline solution). 3 scope.

[0018] By controlling the pH value in the environmental solution, its elongation and contraction behavior can be controlled, and a variety of movements can be imitated, such as the driver actively lifting heavy objects, the relaxation-contraction movement of muscles, and the claw-shaped grasper.

[0019] The present invention also provides a method for preparing a pH-responsive driving fiber as described in any of the above items, wherein the polymer A / polyvinyl alcohol composite fiber is immersed in a tannic acid solution to swell, the pH value of the solution is adjusted to 8-9, and the solution is heated to 50-60°C. Oxygen is introduced. In the oxygen atmosphere, a covalent cross-linking reaction occurs between the tannic acid and the polymer A. The reaction product is washed with deionized water and dried at room temperature to obtain a pH-responsive driving fiber.

[0020] As the preferred technical solution:

[0021] In the method for producing a pH-responsive driving fiber, the polymer A / polyvinyl alcohol composite fiber is obtained by wet spinning a mixed solution of polymer A and polyvinyl alcohol as a spinning solution into an alkaline coagulation bath.

[0022] A method for producing a pH-responsive actuated fiber, wherein the spinning solution is a homogeneous transparent solution obtained by blending a polymer A solution with a polyvinyl alcohol solution for 10 to 12 hours, wherein the concentration of the polymer A solution is 20 to 40 mg / mL, and the concentration of the polyvinyl alcohol solution is 100 to 200 mg / mL;

[0023] The alkaline coagulation bath refers to a NaOH solution with a concentration of 1 mol / L.

[0024] In the method for driving a pH-responsive fiber as described above, the mass ratio of polymer A to polyvinyl alcohol is 2-4:1-2.

[0025] In the method for driving a pH-responsive fiber as described above, the concentration of the tannic acid solution is 20-40 mg / mL; and the mass ratio of tannic acid to polymer A is 1-2:1-2.

[0026] In the method for driving a pH-responsive fiber as described above, the polymer A / polyvinyl alcohol composite fiber is immersed in a tannic acid solution for 30 minutes, oxygen is introduced into the tannic acid solution, and the immersion is continued for 1 to 6 hours.

[0027] The principle of the present invention is:

[0028] The polymer A of the present invention refers to a class of polymers with amine groups in their side chains. It can deprotonate in alkaline solutions, causing the molecular chain to collapse, and protonate in acidic solutions, causing the molecular chain to expand, exhibiting pH responsiveness. Polymer A and polyvinyl alcohol are processed into fibers using a wet spinning method. The polyvinyl alcohol and polymer A form hydrogen bonds, enhancing the mechanical properties of the fibers. Finally, a tannic acid crosslinking network is introduced into the fibers, ensuring that the fibers maintain dimensional stability in strong acids and bases.

[0029] In the driving fiber of the present invention, when the fiber is immersed in an acidic solution, the amine groups in the side chains of polymer A are protonated and positively charged. Due to the electrostatic repulsion, the molecular chain stretches, the tensile strength of the fiber decreases, and the fiber macroscopically manifests as elongation. When immersed in an alkaline solution, the amine groups in the side chains of polymer A are deprotonated, the molecular chain is uncharged, hydrogen bonds interact between molecules, the molecular chain collapses, the tensile strength of the fiber increases, and the fiber macroscopically manifests as contraction. If the fiber is not cross-linked with tannic acid, it will completely dissolve in the water environment after entering the acidic solution and will not be able to maintain the stability of the drive. In addition, a large number of experiments have shown that only fibers formed by the composite of polymer A, polyvinyl alcohol and tannic acid can achieve the above-mentioned effect, and if polyvinyl alcohol or tannic acid is replaced by other substances, the ideal effect cannot be achieved.

[0030] Beneficial effects:

[0031] (1) The pH-responsive actuating fiber of the present invention can effectively control the elongation and contraction behavior of the device by controlling the pH value of the solution. The maximum pH actuation range is pH 1 to 11, and it has a faster actuation rate in strong acids and bases.

[0032] (2) The pH-responsive driving fiber has a fiber tensile strength changing between 1-5 MPa and 30-40 MPa after 10 acid-base cycles, and a stable work density of 5-20 kJ / m 3 .

[0033] (3) The preparation method of the pH-responsive driving fiber constructs the driving fiber with excellent performance in a simple and green manner, and the maximum work density is 20 kJ / m 3 . BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Schematic diagram of the pH-responsive driving fiber actively pulling a heavy object;

[0035] Figure 2 Schematic diagram of the pH-responsive driving fiber simulating the relaxation-contraction movement of a muscle;

[0036] Figure 3 Schematic diagram of the pH-responsive driving fiber used as a claw-shaped grabber. DETAILED DESCRIPTION

[0037] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not used to limit the scope of the present application. Furthermore, it should be understood that after reading the content taught by the present application, those skilled in the art can make various modifications or changes to the present application, and these equivalent forms also fall within the scope of the appended claims of the present application.

[0038] The performance index test / calculating method related to the present application is as follows:

[0039] The tensile strength is tested by using a universal testing machine (model: UTM2502, Suns), and the test standard refers to GB / T1040.3-2006.

[0040] Work density: the work density is calculated by using the following formula W=(L d -L c )(m c -ρ s V c )g / V f , wherein L d is the length of the fiber elongated in the alkaline solution, L c is the length of the fiber contracted in the acidic solution, m c is the mass of the loaded weight, ρ s is the density of the aqueous solution, ρ s =1.0 g / cm 3 , and V cis the volume of the loaded object, g is the acceleration due to gravity, g = 9.8 N / kg, V f is the fiber volume.

[0041] Example 1

[0042] A method for preparing a pH-responsive actuating fiber, comprising the following steps:

[0043] (1) Preparation of raw materials:

[0044] Polymer A: chitosan (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd., brand: C105799);

[0045] Polyvinyl alcohol: Manufacturer: Thermo Fisher Scientific, brand: 041242.22;

[0046] Tannic acid;

[0047] NaOH solution;

[0048] (2) Blending the aqueous solution of polymer A with the aqueous solution of polyvinyl alcohol for 10 h to obtain a homogeneous transparent solution, which is the spinning solution;

[0049] The mass ratio of polymer A to polyvinyl alcohol is 2:1; the concentration of the polymer A aqueous solution is 20 mg / mL, and the concentration of the polyvinyl alcohol aqueous solution is 100 mg / mL;

[0050] (3) extruding the spinning solution of step (2) into a 1 mol / L NaOH solution, and wet spinning to obtain a polymer A / polyvinyl alcohol composite fiber; in the polymer A / polyvinyl alcohol composite fiber, there is a hydrogen bond interaction between the polyvinyl alcohol and the polymer A;

[0051] The wet spinning process parameters were as follows: extrusion speed 0.8 mL / min, needle specifications: inner diameter 0.34 mm, outer diameter 0.64 mm, and total needle length 30 mm;

[0052] (4) The polymer A / polyvinyl alcohol composite fiber was immersed in a 30 mg / mL tannic acid aqueous solution for 30 min to swell, and then the solution pH was adjusted to 8, heated to 50 ° C, and oxygen was introduced. The solution was immersed for another 6 h. In the oxygen atmosphere, a covalent cross-linking reaction occurred between the tannic acid and the polymer A. The reaction product was washed with deionized water and dried at room temperature to obtain a pH-responsive actuating fiber.

[0053] The mass ratio of tannic acid to polymer A is 1:1.

[0054] The resulting pH-responsive actuating fiber has the properties of shrinking in alkaline solutions with a pH value of ≤11 and elongating in acidic solutions with a pH value of ≥1. The pH-responsive actuating fiber has a tensile strength of 2 MPa and an elongation at break of 80% in a hydrochloric acid solution with a pH of 1, and a tensile strength of 40 MPa and an elongation at break of 40% in a sodium hydroxide solution with a pH of 11. During 10 acid-base cycles, the tensile strength of the pH-responsive actuating fiber varied between 2 MPa and 40 MPa, and the work density remained stable at 12 kJ / m 3 .

[0055] like Figure 1 As shown, the driving fiber prepared above can be used as a soft robot to actively lift and carry heavy objects in alkaline solutions and to directionally transport heavy objects in acidic solutions.

[0056] like Figure 2 As shown, the driving fibers prepared above can be used as artificial antagonist muscles and agonist muscles in the field of soft robotics.

[0057] like Figure 3 As shown, the actuating fiber prepared above is used as a claw-shaped extractor to actively grab objects in an alkaline solution.

[0058] Comparative Example 1

[0059] A driving fiber is basically the same as Example 1, except that: the operation of step (2) is omitted, and the aqueous solution of polymer A is directly used as the spinning solution in step (3).

[0060] The final fiber had an elongation at break of 5%, and the fiber was too brittle and easily broken, making it unsuitable for practical application.

[0061] Comparing Comparative Example 1 with Example 1, it can be found that the fiber cannot resist bending and twisting in actual operation, and the fiber is too brittle and easily broken. This is because the chitosan molecule has a rigid structure, and the fiber becomes more brittle after being directly cross-linked with tannic acid.

[0062] Comparative Example 2

[0063] A driving fiber is basically the same as Example 1, except that the tannic acid solution in step (4) is replaced by a boric acid solution.

[0064] The final actuating fiber is dissolved in a hydrochloric acid solution with a pH of 1 and has a tensile strength of 15 MPa in a sodium hydroxide solution with a pH of 11.

[0065] Comparing Comparative Example 2 with Example 1, it can be found that Comparative Example 2 dissolves in a solution with a pH lower than 2. This is because boric acid mainly cross-links two adjacent hydroxyl groups of polyvinyl alcohol and cannot cross-link the polymer A network. Therefore, polymer A will dissolve in an acidic solution.

[0066] Comparative Example 3

[0067] A driving fiber is basically the same as Example 1, except that the tannic acid solution in step (4) is replaced by glutaraldehyde solution.

[0068] The final driving fiber has an elongation at break of 3%. The fiber is too brittle and easily broken, making it unsuitable for practical application.

[0069] Comparing Comparative Example 3 with Example 1, it can be found that the fiber is too brittle and cannot be driven. This is because the degree of cross-linking between glutaraldehyde and chitosan is large, which restricts the movement of the molecular chain and limits the extension of the molecular chain.

[0070] Comparative Example 4

[0071] A pH-responsive driving fiber is basically the same as Example 1, except that the polyvinyl alcohol solution in step (2) is replaced by a gelatin solution (manufacturer: Sinopharm Chemical Reagent Co., Ltd., brand: 10010326), and the tannic acid solution in step (4) is replaced by a genipin solution.

[0072] The final pH-responsive driving fiber has a tensile strength of 1 MPa in a hydrochloric acid solution with a pH of 1 and a tensile strength of 8 MPa in a sodium hydroxide solution with a pH of 11. During ten acid-base cycles, the tensile strength of the fiber gradually decreases, and the final tensile strength will be 10 kPa, making it unable to perform work stably.

[0073] Comparing Comparative Example 4 with Example 1, it can be found that the driving fiber cannot stably perform work in multiple cyclic driving cycles. This is because the cross-linking of genipin depends on the pH value of the solution, and genipin is a degradable biomolecule, so its cross-linking effect has poor stability.

[0074] Example 2

[0075] A method for preparing a pH-responsive actuating fiber, comprising the following steps:

[0076] (1) Preparation of raw materials:

[0077] Polymer A: polyacrylamine (manufacturer: Sigma-Aldrich, brand: S#479136);

[0078] Polyvinyl alcohol: Manufacturer: Thermo Fisher Scientific, brand: 041242.22;

[0079] Tannic acid;

[0080] NaOH solution;

[0081] (2) Blending the aqueous solution of polymer A with the aqueous solution of polyvinyl alcohol for 11 hours to obtain a uniform transparent solution, which is the spinning solution;

[0082] The mass ratio of polymer A to polyvinyl alcohol is 3:1; the concentration of the polymer A aqueous solution is 20 mg / mL, and the concentration of the polyvinyl alcohol aqueous solution is 150 mg / mL;

[0083] (3) extruding the spinning solution of step (2) into a 1 mol / L NaOH solution, and wet spinning to obtain a polymer A / polyvinyl alcohol composite fiber; in the polymer A / polyvinyl alcohol composite fiber, there is a hydrogen bond interaction between the polyvinyl alcohol and the polymer A;

[0084] The wet spinning process parameters are as follows: extrusion speed 0.8 mL / min, needle specifications: inner diameter 0.34 mm, outer diameter 0.64 mm, and total needle length 30 mm.

[0085] (4) The polymer A / polyvinyl alcohol composite fiber was immersed in a 20 mg / mL tannic acid aqueous solution for 30 minutes to swell, and then the pH value of the solution was adjusted to 8.2, and the solution was heated to 52°C. Oxygen was introduced and the solution was immersed for another 5 hours. In the oxygen atmosphere, a covalent cross-linking reaction occurred between the tannic acid and the polymer A. The reaction product was washed with deionized water and dried at room temperature to obtain a pH-responsive actuating fiber.

[0086] The mass ratio of tannic acid to polymer A is 1:2.

[0087] The resulting pH-responsive actuating fiber has the properties of shrinking in alkaline solutions with a pH value of ≤11 and elongating in acidic solutions with a pH value of ≥1. The pH-responsive actuating fiber has a tensile strength of 1 MPa and an elongation at break of 120% in a hydrochloric acid solution with a pH of 1, and a tensile strength of 30 MPa and an elongation at break of 50% in a sodium hydroxide solution with a pH of 11. During 10 acid-base cycles, the tensile strength of the pH-responsive actuating fiber varied between 1 MPa and 30 MPa, and the work density remained stable at 5 kJ / m 3 .

[0088] Example 3

[0089] A method for preparing a pH-responsive actuating fiber, comprising the following steps:

[0090] (1) Preparation of raw materials:

[0091] Polymer A: branched polyethyleneimine (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd., brand: P434400);

[0092] Polyvinyl alcohol: Manufacturer: Thermo Fisher Scientific, brand: 041242.22;

[0093] Tannic acid;

[0094] NaOH solution;

[0095] (2) Blending the polymer A aqueous solution with the polyvinyl alcohol aqueous solution for 12 h to obtain a uniform transparent solution, which is the spinning solution;

[0096] The mass ratio of polymer A to polyvinyl alcohol is 1:1; the concentration of the polymer A aqueous solution is 40 mg / mL, and the concentration of the polyvinyl alcohol aqueous solution is 200 mg / mL;

[0097] (3) extruding the spinning solution of step (2) into a 1 mol / L NaOH solution, and wet spinning to obtain a polymer A / polyvinyl alcohol composite fiber; in the polymer A / polyvinyl alcohol composite fiber, there is a hydrogen bond interaction between the polyvinyl alcohol and the polymer A;

[0098] The wet spinning process parameters are as follows: extrusion speed 0.8 mL / min, needle specifications: inner diameter 0.34 mm, outer diameter 0.64 mm, and total needle length 30 mm.

[0099] (4) The polymer A / polyvinyl alcohol composite fiber was immersed in a 40 mg / mL tannic acid aqueous solution for 30 minutes to swell, and then the pH value of the solution was adjusted to 8.5, and the solution was heated to 54°C. Oxygen was introduced and the solution was immersed for another 4 hours. In the oxygen atmosphere, a covalent cross-linking reaction occurred between the tannic acid and the polymer A. The reaction product was washed with deionized water and dried at room temperature to obtain a pH-responsive actuating fiber.

[0100] The mass ratio of tannic acid to polymer A is 1:1.

[0101] The resulting pH-responsive actuating fiber shrinks in alkaline solutions with a pH value of ≤11 and stretches in acidic solutions with a pH value of ≥1. The pH-responsive actuating fiber exhibits a tensile strength of 5 MPa and an elongation at break of 120% in a hydrochloric acid solution with a pH of 1, and a tensile strength of 40 MPa and an elongation at break of 40% in a sodium hydroxide solution with a pH of 11. During 10 acid-base cycles, the tensile strength of the pH-responsive actuating fiber varied between 5 MPa and 40 MPa, and the work density remained stable at 20 kJ / m 3 .

[0102] Example 4

[0103] A method for preparing a pH-responsive actuating fiber, comprising the following steps:

[0104] (2) Preparation of raw materials:

[0105] Polymer A: chitosan (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd., brand: C105799);

[0106] Polyvinyl alcohol: Manufacturer: Thermo Fisher Scientific, brand: 041242.22;

[0107] Tannic acid;

[0108] NaOH solution;

[0109] (2) Blending the aqueous solution of polymer A with the aqueous solution of polyvinyl alcohol for 10.5 h to obtain a homogeneous transparent solution, which is the spinning solution;

[0110] The mass ratio of polymer A to polyvinyl alcohol is 3:2; the concentration of the polymer A aqueous solution is 30 mg / mL, and the concentration of the polyvinyl alcohol aqueous solution is 100 mg / mL;

[0111] (3) extruding the spinning solution of step (2) into a 1 mol / L NaOH solution, and wet spinning to obtain a polymer A / polyvinyl alcohol composite fiber; in the polymer A / polyvinyl alcohol composite fiber, there is a hydrogen bond interaction between the polyvinyl alcohol and the polymer A;

[0112] The wet spinning process parameters are as follows: extrusion speed 0.8 mL / min, needle specifications: inner diameter 0.34 mm, outer diameter 0.64 mm, and total needle length 30 mm.

[0113] (4) The polymer A / polyvinyl alcohol composite fiber was immersed in a tannic acid solution with a concentration of 20 mg / mL for 30 minutes to swell, and then the pH value of the solution was adjusted to 8.7, and the solution was heated to 56°C. Oxygen was introduced and the solution was immersed for another 3 hours. In the oxygen atmosphere, a covalent cross-linking reaction occurred between the tannic acid and the polymer A. The reaction product was washed with deionized water and dried at room temperature to obtain a pH-responsive actuating fiber.

[0114] The mass ratio of tannic acid to polymer A is 1:2.

[0115] The resulting pH-responsive actuating fiber shrinks in alkaline solutions with a pH value of ≤11 and stretches in acidic solutions with a pH value of ≥1. The pH-responsive actuating fiber exhibits a tensile strength of 5 MPa and an elongation at break of 90% in a hydrochloric acid solution with a pH of 1, and a tensile strength of 35 MPa and an elongation at break of 60% in a sodium hydroxide solution with a pH of 11. During 10 acid-base cycles, the tensile strength of the pH-responsive actuating fiber varied between 5 MPa and 35 MPa, and the work density remained stable at 15 kJ / m 3 .

[0116] Example 5

[0117] A method for preparing a pH-responsive actuating fiber, comprising the following steps:

[0118] (3) Preparation of raw materials:

[0119] Polymer A: polyacrylamine (manufacturer: Sigma-Aldrich, brand: S#479136);

[0120] Polyvinyl alcohol: Manufacturer: Thermo Fisher Scientific, brand: 041242.22;

[0121] Tannic acid;

[0122] NaOH solution;

[0123] (2) Blending the aqueous solution of polymer A with the aqueous solution of polyvinyl alcohol for 11 hours to obtain a uniform transparent solution, which is the spinning solution;

[0124] The mass ratio of polymer A to polyvinyl alcohol is 4:1; the concentration of the polymer A aqueous solution is 30 mg / mL, and the concentration of the polyvinyl alcohol aqueous solution is 150 mg / mL;

[0125] (3) extruding the spinning solution of step (2) into a 1 mol / L NaOH solution, and wet spinning to obtain a polymer A / polyvinyl alcohol composite fiber; in the polymer A / polyvinyl alcohol composite fiber, there is a hydrogen bond interaction between the polyvinyl alcohol and the polymer A;

[0126] The wet spinning process parameters are as follows: extrusion speed 0.8 mL / min, needle specifications: inner diameter 0.34 mm, outer diameter 0.64 mm, and total needle length 30 mm.

[0127] (4) The polymer A / polyvinyl alcohol composite fiber was immersed in a 30 mg / mL tannic acid aqueous solution for 30 min to swell, and then the pH value of the solution was adjusted to 8.9, and the solution was heated to 58 ° C. Oxygen was introduced and the solution was immersed for another 2 h. In the oxygen atmosphere, a covalent cross-linking reaction occurred between the tannic acid and the polymer A. The reaction product was washed with deionized water and dried at room temperature to obtain a pH-responsive actuating fiber.

[0128] The mass ratio of tannic acid to polymer A is 1:1.

[0129] The resulting pH-responsive actuating fiber has the properties of shrinking in alkaline solutions with a pH value of ≤11 and elongating in acidic solutions with a pH value of ≥1. The pH-responsive actuating fiber has a tensile strength of 1 MPa and an elongation at break of 120% in a hydrochloric acid solution with a pH of 1, and a tensile strength of 30 MPa and an elongation at break of 70% in a sodium hydroxide solution with a pH of 11. During 10 acid-base cycles, the tensile strength of the pH-responsive actuating fiber varied between 1 MPa and 30 MPa, and the work density remained stable at 10 kJ / m 3 .

[0130] Example 6

[0131] A method for preparing a pH-responsive actuating fiber, comprising the following steps:

[0132] (4) Preparation of raw materials:

[0133] Polymer A: branched polyethyleneimine (manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd., brand: P434400);

[0134] Polyvinyl alcohol: Manufacturer: Thermo Fisher Scientific, brand: 041242.22;

[0135] Tannic acid;

[0136] NaOH solution;

[0137] (2) Blending the aqueous solution of polymer A with the aqueous solution of polyvinyl alcohol for 11.5 h to obtain a homogeneous transparent solution, which is the spinning solution;

[0138] The mass ratio of polymer A to polyvinyl alcohol is 2:1; the concentration of the polymer A aqueous solution is 40 mg / mL, and the concentration of the polyvinyl alcohol aqueous solution is 200 mg / mL;

[0139] (3) extruding the spinning solution of step (2) into a 1 mol / L NaOH solution, and wet spinning to obtain a polymer A / polyvinyl alcohol composite fiber; in the polymer A / polyvinyl alcohol composite fiber, there is a hydrogen bond interaction between the polyvinyl alcohol and the polymer A;

[0140] The wet spinning process parameters are as follows: extrusion speed 0.8 mL / min, needle specifications: inner diameter 0.34 mm, outer diameter 0.64 mm, and total needle length 30 mm.

[0141] (4) The polymer A / polyvinyl alcohol composite fiber was immersed in a 40 mg / mL tannic acid aqueous solution for 30 minutes to swell, and then the pH value of the solution was adjusted to 9, and the solution was heated to 60°C. Oxygen was introduced and the solution was immersed for another hour. In the oxygen atmosphere, a covalent cross-linking reaction occurred between the tannic acid and the polymer A. The reaction product was washed with deionized water and dried at room temperature to obtain a pH-responsive actuating fiber.

[0142] The mass ratio of tannic acid to polymer A is 1:2.

[0143] The resulting pH-responsive actuating fiber has the properties of shrinking in alkaline solutions with a pH value of ≤11 and elongating in acidic solutions with a pH value of ≥1. The pH-responsive actuating fiber has a tensile strength of 3 MPa and an elongation at break of 120% in a hydrochloric acid solution with a pH of 1, and a tensile strength of 35 MPa and an elongation at break of 65% in a sodium hydroxide solution with a pH of 11. During 10 acid-base cycles, the tensile strength of the pH-responsive actuating fiber varied between 3 MPa and 35 MPa, and the work density remained stable at 18 kJ / m 3 .

Claims

1. A pH-responsive actuating fiber, characterized in that: It has the property of shrinking in alkaline solutions with a pH value of ≤11 and stretching in acidic solutions with a pH value of ≥1; The pH-responsive driving fiber is a tannic acid-modified composite fiber, and the composite fiber is a polymer A / polyvinyl alcohol composite fiber; The preparation method of the pH-responsive actuating fiber is as follows: a polymer A / polyvinyl alcohol composite fiber is immersed in a tannic acid solution to swell, the solution pH is adjusted to 8-9, and the solution is heated to 50-60°C. Oxygen is introduced into the solution. In the oxygen atmosphere, a covalent cross-linking reaction occurs between the tannic acid and the polymer A. The reaction product is then washed with deionized water and dried to obtain the pH-responsive actuating fiber. The polymer A is chitosan, polyacrylamine or branched polyethyleneimine; In the polymer A / polyvinyl alcohol composite fiber, there is a hydrogen bond interaction between polyvinyl alcohol and polymer A; There is a covalent cross-linking effect between tannic acid and polymer A.

2. The pH-responsive actuating fiber according to claim 1, wherein The pH-responsive actuating fiber has a tensile strength of 1-5 MPa and an elongation at break of 80-120% in an acidic solution of pH=1, and a tensile strength of 30-40 MPa and an elongation at break of 40-70% in an alkaline solution of pH=11.

3. The pH-responsive actuating fiber according to claim 2, wherein: During 10 acid-base cycles, the tensile strength of the pH-responsive actuating fibers varied between 1-5 MPa and 30-40 MPa, the elongation at break varied between 80-120% and 40-70%, and the work density remained stable at 5-20 kJ / m 3 scope.

4. The pH-responsive actuating fiber according to claim 1, wherein The polymer A / polyvinyl alcohol composite fiber is obtained by wet spinning a mixed solution of polymer A and polyvinyl alcohol into an alkaline coagulation bath as a spinning solution.

5. The pH-responsive actuating fiber according to claim 4, characterized in that: The spinning solution is a homogeneous transparent solution obtained by mixing a polymer A solution and a polyvinyl alcohol solution for 10 to 12 hours. The concentration of the polymer A solution is 20 to 40 mg / mL, and the concentration of the polyvinyl alcohol solution is 100 to 200 mg / mL. The alkaline coagulation bath refers to a NaOH solution with a concentration of 1 mol / L.

6. The pH-responsive actuating fiber according to claim 5, characterized in that: The mass ratio of polymer A to polyvinyl alcohol is 2~4:1~2.

7. The pH-responsive actuating fiber according to claim 1, wherein The concentration of the tannic acid solution is 20-40 mg / mL; the mass ratio of tannic acid to polymer A is 1-2:1-2.

8. The pH-responsive actuating fiber according to claim 1, wherein The polymer A / polyvinyl alcohol composite fiber was immersed in the tannic acid solution for 30 minutes, and then oxygen was introduced into the tannic acid solution, and the immersion was continued for 1 to 6 hours.

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