Polyether block amide parallel hetero-hydro-responsive spiral driving fiber and preparation method and application thereof

Abstract

The application belongs to the technical field of intelligent polymer materials, and particularly relates to a kind of polyether block amide parallel hetero-humid response spiral driving fiber and its preparation method and application.The fiber has a parallel two-phase structure, including a hydrophilic polyether block amide phase and a relatively hydrophobic polyether block amide phase or a composite phase thereof, the two phases continuously extend along the fiber axis and contact each other in the fiber cross section;The fiber is prepared by parallel wet spinning, stretching orientation, hydration reprogramming and drying setting.The fiber prepared by the application realizes bidirectional / non-monotonic humid response under short-time humid stimulation, such as increase of end-to-end distance, decrease of end-to-end distance under continuous humid stimulation or reversal of curvature, has high mechanical stability in wet state, firm interface bonding, long cycle fatigue life, can be continuously prepared, and can be used for intelligent fabrics, humidity response valves, micro-fluidic switches, soft body grippers, artificial muscles, environment adaptive structures and humidity sensing / driving integrated devices.

Description

Technical Field

[0001] This invention belongs to the field of intelligent polymer materials technology, specifically relating to a polyether block amide parallel heterogeneous wet-responsive helical driven fiber and its preparation method and application. Background Technology

[0002] Moisture-responsive actuators can convert ambient humidity or moisture gradients into mechanical deformation, showing potential applications in soft robotics, smart textiles, microfluidic switches, and artificial muscles. Existing research has shown that volume changes caused by moisture absorption or loss in materials can be used to achieve bending, curling, contraction, and movement in thin films, bilayer structures, or fiber structures. For example, water gradient-driven polymer composite membranes can convert the chemical potential of moisture into mechanical work; biomimetic hygromorphic bilayer structures can bend due to the difference in moisture absorption and expansion between the two layers; and twisted or wound polymer fiber artificial muscles can achieve large-stroke stretching or torsional actuation.

[0003] However, existing wet-response actuators still have several shortcomings. First, many bilayer or Janus actuators mainly exhibit monotonous bending or unidirectional curling, making it difficult to achieve temporal multimodal responses such as the end-to-end distance first increasing and then decreasing, or the helical curvature decreasing and then increasing in the opposite direction, during the same wet stimulation process. Second, although hydrogel-based wet-response materials have high water absorption rates, they are prone to problems such as modulus reduction, insufficient load-bearing capacity, and reduced cycle stability under high hydration conditions. Third, bilayer actuators formed by coating, bonding, or composite of dissimilar materials are prone to interfacial stress concentration and interlayer delamination under repeated moisture absorption / drying cycles and large deformation conditions.

[0004] Existing technologies also have limitations in fibrous wet-response actuators. Chinese patent CN120505734B discloses a bicomponent parallel composite fiber, which prepares hydrophilic / hydrophobic bicomponent fibers through parallel wet spinning and utilizes the difference in moisture absorption and expansion between the two components to achieve wet-response bending deformation. However, the wet-response layer of this fiber adopts a dissimilar material system such as cellulose / polyurethane, and the interface between the two phases is a dissimilar material composite interface, which is prone to interfacial stress concentration and interlayer delamination under large deformation and repeated wet-dry cycles; at the same time, its response mode mainly exhibits unidirectional bending, making it difficult to achieve more complex multimodal driving behavior.

[0005] Regarding thin-film wet-response actuators, Chinese patent CN109721025B discloses a double-layer thin-film actuator that utilizes strain accumulation to drive complex motions, controlling bending orientation by setting stripe patterns on an inert layer. However, this actuator is a thin-film structure, making it difficult to integrate into flexible wearable systems such as smart fabrics; its response mode is still unidirectional bending, and it cannot achieve temporal multimodal responses such as end-to-end distance first increasing and then decreasing or curvature reversal during a single wet stimulus.

[0006] Polyether block amides (PEBAs) consist of flexible polyether soft segments and polyamide hard segments. The polyether soft segments impart moisture absorption and chain segment mobility to the material, while the crystalline regions of the polyamide hard segments serve as physical crosslinking points to maintain the stability of the material's skeleton. Different grades of PEBA exhibit varying water absorption, water vapor transport, and wet mechanical behaviors due to differences in the type and content of polyether soft segments. Therefore, by constructing homologous Janus fibers from hydrophilic and relatively hydrophobic PEBA and forming a continuous interface through wet spinning, it is possible to introduce a controllable mismatch of moisture absorption and expansion while maintaining wet mechanical stability, thereby achieving a complex wet-response helical drive. Summary of the Invention

[0007] The purpose of this invention is to provide a wet-responsive helical driven fiber based on a polyether block amide parallel heterostructure and its preparation method. By introducing dynamic arc length mismatch through the differences in moisture absorption, diffusion rate, wet expansion, and wet mechanical properties between the hydrophilic PEBA phase and the relatively hydrophobic PEBA phase, a bidirectional / non-monotonic wet response is achieved, which increases the end-to-end distance under short-term wet stimulation and decreases the end-to-end distance or reverses the curvature under continuous wet stimulation. At the same time, the interpenetration and physical crystallization of homologous polyamide hard segments at the wet molding interface are utilized to improve the stability of the two-phase interface and the stability of the wet mechanical skeleton.

[0008] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, the wet-responsive helical driven fiber having a parallel two-phase structure, including a first phase and a second phase; the first phase and the second phase are both polyether block amides; the first phase and the second phase extend continuously along the fiber axis and are in parallel contact with each other on the fiber cross section to form a continuous bonding interface.

[0009] By using polyether block amide as the main matrix material for fibers, the stability, load-bearing capacity, and cycle life of the material's mechanical skeleton in a wet state are simultaneously improved, solving the problems of significant decrease in wet modulus, insufficient load-bearing capacity, and insufficient cycle stability in some highly absorbent and responsive materials. This is because polyether block amide is composed of flexible polyether soft segments and polyamide hard segments. The polyether soft segments impart moisture absorption and chain segment movement capabilities to the material, while the crystalline regions of the polyamide hard segments serve as physical crosslinking points, helping to maintain the stability of the wet mechanical skeleton. The plasticizing effect of water molecules is limited to the polyether soft segment phase region and does not fundamentally damage the physical crosslinking network of the polyamide hard segments. Therefore, the material can still maintain good dimensional stability and mechanical strength in a wet state.

[0010] Preferably, the first phase is a hydrophilic polyether block amide, wherein the polyether soft segment is selected from one or more of polyethylene glycol and polyethylene oxide; and the polyamide hard segment is selected from one or more of polyamide 6 and polyamide 12.

[0011] Preferably, the polyether soft segment of the hydrophilic polyether block amide is polyethylene oxide, and the mass content of the polyether soft segment is 50%~55%; the hard segment is selected from polyamide 12; the hydrophilic polyether block amide has a Shore hardness of 35~40D, a tensile modulus (23 ℃, 1 mm / min) of 75~85 MPa, and an equilibrium water absorption rate of 47%~49% when immersed at 23 ℃.

[0012] In some alternatives, the first phase is Arkema PEBA 1074, whose polyether soft segment is selected from polyethylene oxide and the polyether soft segment content is 55 wt%; the hard segment is selected from polyamide 12 and the content is 45 wt%; the Shore hardness is 38 D; the tensile modulus (23 ℃, 1 mm / min) is 80 MPa; and the equilibrium water absorption rate at 23 ℃ is 48%.

[0013] Preferably, the second phase is a relatively hydrophobic polyether block amide phase or a composite phase thereof.

[0014] Preferably, in the relatively hydrophobic polyether block amide phase, the polyether soft segment can be selected from one or more of polytetrahydrofuran ether and polypropylene glycol; the polyamide hard segment can be selected from one or more of polyamide 6 and polyamide 12.

[0015] Preferably, in the relatively hydrophobic polyether block amide phase, the polyether soft segment is polytetrahydrofuran, and the polyether soft segment content is 75%~80% by mass; the hard segment is selected from polyamide 12; the relatively hydrophobic polyether block amide phase has a Shore hardness of 20~25D, a tensile modulus (23 ℃, 1 mm / min) of 8~12 MPa, and an equilibrium water absorption rate of 1.0%~1.3% when immersed at 23 ℃.

[0016] In some alternative embodiments, the relatively hydrophobic polyether block amide phase is Arkema PEBA 2533, whose polyether soft segment is polytetrahydrofuran, and the polyether soft segment mass content is 80%; the hard segment is selected from polyamide 12; the relatively hydrophobic polyether block amide phase has a Shore hardness of 22D, a tensile modulus (23 °C, 1 mm / min) of 10 MPa, and an equilibrium water absorption rate of 1.2% when immersed at 23 °C.

[0017] In some alternative solutions, the second phase may be selectively introduced with functional fillers to form a composite phase structure.

[0018] Preferably, the functional filler includes, but is not limited to, carbon nanotubes, carboxylated carbon nanotubes, hydroxylated carbon nanotubes, graphene, graphene oxide, MXene, carbon black, conductive polymers, metal nanoparticles, metal oxide nanoparticles, or other nanofillers with conductive, photothermal conversion, electromagnetic shielding, or mechanical reinforcement functions; more preferably, it is carboxylated carbon nanotubes.

[0019] Preferably, the carboxylated carbon nanotubes are carboxylated multi-walled carbon nanotubes with an outer diameter of 10~20 nm, a length of 0.5~2 μm, a purity of ≥95%, a carboxyl content of 2.0 wt%, and an oxygen content (XPS) of 5.77%.

[0020] In some alternative solutions, the carboxylated carbon nanotubes are derived from XFM18 of Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0021] In some alternative schemes, when the second phase is a composite phase structure, it is a complex of PEBA 2533 and carboxylated multi-walled carbon nanotubes.

[0022] In some alternative embodiments, the wet-responsive helical driven fiber exhibits a helical structure after initial water stimulation and drying.

[0023] In some alternative embodiments, the wet-responsive helical driven fiber exhibits a non-monotonic change in end-to-end distance and / or helical curvature with stimulation time when subjected to wet stimulation.

[0024] The non-monotonic changes include, but are not limited to: under short-term wet stimulation conditions, the end-to-end distance of the fiber increases or the helical curvature decreases; under continuous wet stimulation conditions, the end-to-end distance of the fiber decreases or the direction of helical curvature reverses.

[0025] By constructing a parallel heterogeneous fiber structure consisting of a hydrophilic polyether block amide phase and a relatively hydrophobic polyether block amide phase continuously extending along the axial direction, a wet-response helical drive can be achieved at the slender fiber scale. Moreover, a non-monotonic temporal response is generated under a single wet stimulus, which breaks through the limitation of conventional bilayer / Janus actuators that can only bend monotonically or curl in one direction. It can achieve an increase in end-to-end distance and a decrease in helical curvature under short-term wet stimulation, and a decrease in end-to-end distance or reversal of curvature direction under continuous wet stimulation. This is because there are differences in moisture absorption, diffusion rate, moisture expansion, and wet mechanics between the hydrophilic phase and the relatively hydrophobic phase, forming a dynamic arc length mismatch effect: In the initial stage of moisture stimulation, moisture preferentially enters the surface layer of the hydrophilic phase, causing local moisture absorption and expansion and segment plasticization, which reduces the curvature of the original helical structure, manifested as uncoiling and an increase in end-to-end distance; under continuous moisture stimulation, moisture further diffuses into the interior of the hydrophilic phase, further increasing the effective arc length of the hydrophilic phase. Under the constraint of the two-phase interface, the fiber releases strain mismatch energy through changes in bending direction or curvature reversal, manifested as a further decrease in end-to-end distance or reverse curling.

[0026] Meanwhile, both phases are polyether-block amide copolymers with homologous polyamide hard segments. During wet solidification, interpenetration of chains, hydrogen bonding, and physical crystallization can occur at the interface between the two phases, forming a continuous, integrated interface, rather than the weak physical interface formed by coating or bonding processes. This improves the interfacial bonding strength, making it less prone to interfacial stress concentration and interlayer delamination under large deformation and repeated wet-dry cycles, thus improving interfacial bonding stability and solving the problem of poor interface reliability in bilayer actuators prepared by coating, bonding, or dissimilar material composites. Furthermore, by introducing functional fillers into the relatively hydrophobic polyether-block amide phase to construct the composite phase, not only can the wet-driven recovery speed be accelerated, but also the multi-field response capability and application scenarios can be expanded.

[0027] A second aspect of the present invention provides a method for preparing the polyether block amide parallel heterogeneous wet-responsive helical driven fiber, comprising the following steps: S1. Preparation of spinning solution: Prepare the first phase spinning solution and the second phase spinning solution using a solvent system that can dissolve both phases of PEBA simultaneously. S2, Parallel wet spinning: The first phase spinning solution and the second phase spinning solution are respectively fed to the parallel spinneret assembly, forming parallel liquid flows at the spinneret and being squeezed into the coagulation bath to undergo solvent-non-solvent exchange and phase separation, forming parallel biphase nascent fibers. S3, Hydration Reprogramming and Drying: After the fiber obtained in step S2 is naturally dried at room temperature for 20-30 hours, a moisture stimulus is applied to it for drying and shaping, thus obtaining the moisture-responsive helical driven fiber; the moisture-responsive helical driven fiber has a steady-state helical structure.

[0028] A schematic diagram of the preparation process of the polyether block amide parallel heterogeneous wet-responsive helical driven fiber is shown below.Figure 1 Two PEBA spinning solutions are injected into parallel spinnerets via injection pumps, where they undergo synchronous phase separation in a coagulation bath to form parallel biphase nascent fibers. After drawing, collecting, and drying, straight fibers are obtained.

[0029] Preferably, in step S1, the solvent system is selected from at least one of formic acid, formic acid / cosolvent mixture, and other polar solvent systems capable of simultaneously dissolving two phases of PEBA.

[0030] Preferably, the co-solvent includes, but is not limited to, acetic acid, propionic acid, trifluoroacetic acid, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, or combinations thereof.

[0031] Preferably, the mass fraction of hydrophilic polyether block amide in the first phase spinning solution is 15% to 35%; more preferably, it is 15% to 25%.

[0032] Preferably, the preparation method of the first phase spinning solution is as follows: the first phase is added to the solvent system and magnetically stirred at 600 rpm for 10-14 h in a closed constant temperature water bath at 35-45℃ until it is completely dissolved and defoamed, thus obtaining the solution.

[0033] Preferably, the mass fraction of the relative hydrophobic polyether block amide composite phase in the second phase spinning solution is 15% to 35%; more preferably, it is 15% to 25%.

[0034] Preferably, the amount of the functional filler added is 0 to 5% of the mass of the hydrophobic polyether block amide composite phase in the second phase; more preferably, it is 0.1% to 2%.

[0035] Preferably, the second phase spinning solution is prepared by adding the second phase to a solvent system, stirring and ultrasonically dispersing it at 600 rpm in a closed water bath at 55~65℃ for 1.5~2.5h.

[0036] Preferably, the specific conditions for ultrasonic dispersion are as follows: probe-type ultrasonic dispersion is used, the power is 480W, ice water bath is used, intermittent ultrasound is used, the on-time is 3 seconds and the off-time is 3 seconds, and the ultrasound time is 20 minutes.

[0037] Preferably, in step S2, the coagulation bath is an aqueous non-solvent system, which can be selected from deionized water, water / ethanol mixed solution, salt solution or other aqueous coagulation system; the temperature of the coagulation bath is controlled at 20℃~40℃.

[0038] Preferably, in step S2, at least one phase of the spinning solution or the conveying pipeline is kept warm during the spinning process to inhibit premature gelation or phase separation of the spinning solution; the warming temperature of the spinning solution is 30~60℃; more preferably, it is 30~40℃.

[0039] Preferably, the volumetric flow rate ratio of the first phase spinning solution to the second phase spinning solution is (9~1):(1~9); more preferably, it is (1~3):1.

[0040] Preferably, in step S2, during or after coagulation in the coagulation bath, the nascent fibers are stretched or cold-stretched; the stretching or cold-stretching ratio is 1 to 10 times, corresponding to a fiber collection rate of 0.04 to 0.4 m / min; more preferably, the stretching or cold-stretching ratio is 1.5 to 5 times, corresponding to a fiber collection rate of 0.06 to 0.2 m / min.

[0041] In step S2, a partial enlarged view and cross-sectional schematic diagram of the parallel spinnerets are shown below. Figure 2 Phase 1 corresponds to the first phase, and phase 2 corresponds to the second phase. The two fluids form parallel liquid flows at the spinneret.

[0042] Preferably, in step S3, the wet stimulation method is selected from at least one of water mist, water vapor, immersion in water, and humid air.

[0043] Preferably, the wet stimulation time is 0.5~120s; more preferably, it is 1~10s.

[0044] Preferably, the drying and characterization method includes at least one of room temperature natural drying, temperature-controlled drying, and humidity-controlled drying.

[0045] Preferably, the drying and shaping time is 12-36 h; more preferably, it is 24 h.

[0046] In some alternative approaches, applying a wet stimulus to the fiber can induce selective water absorption, stress release, and segment rearrangement in the hydrophilic phase, thereby further increasing the effective arc length of the hydrophilic phase.

[0047] In step S3, a schematic diagram of hydration reprogramming and spiral shaping is shown below. Figure 3 When linear fibers are subjected to initial wet stimulation, the hydrophilic phase selectively absorbs water, releases internal stress, and rearranges chain segments, and then dries to form a stable helical configuration.

[0048] Driven fibers with a stable helical structure can be easily prepared by applying a wet stimulus to stretched, oriented, parallel biphase nascent fibers for hydration reprogramming, followed by drying and setting. This is because stretching induces macromolecular chains to align axially and regulates internal stress. Under the initial wet stimulus, the hydrophilic phase selectively absorbs water, releases internal stress, and rearranges chain segments. Combined with the deformation driving force generated by the difference in wet expansion between the two phases, the fiber spontaneously curls. Subsequently, during the drying process, the polyamide hard segments recrystallize and set, thus fixing the helical configuration into a stable structure.

[0049] This invention features a simple, continuous manufacturing process that eliminates the need for complex chemical crosslinking, demonstrating potential for industrial scale-up. It addresses the challenges of complex fabrication processes and the difficulty in continuously producing elongated fibrous actuators in some existing wet-response driven structures. The process uses wet spinning as the core forming step, offering a simple flow and controllable parameters. It eliminates the need for complex chemical reactions and multi-step composite processes, and can be adapted to conventional chemical fiber spinning equipment for continuous production.

[0050] The working mechanism of this invention is as follows: The wet response behavior of this invention mainly originates from the dynamic arc length mismatch between the hydrophilic phase (first phase) and the relatively hydrophobic phase (second phase). In the initial stage of wet stimulation, moisture preferentially enters the surface layer of the hydrophilic phase, causing local hygroscopic expansion and segment plasticization, which reduces the curvature of the original helical structure, manifested as uncoiling and an increase in end-to-end distance. Under continuous wet stimulation, moisture further diffuses into the interior of the hydrophilic phase, further increasing the effective arc length of the hydrophilic phase; under the constraint of the two-phase interface, the fiber releases strain mismatch energy through changes in bending direction or curvature reversal, manifested as a further decrease in end-to-end distance or reverse curling.

[0051] The schematic diagram of the non-monotonic humidity response is shown below. Figure 4 Steady-state helical fibers exhibit an increase in end-to-end distance or a decrease in curvature under short-term wet stimulation, and a decrease in end-to-end distance or a reversal of curvature under continuous wet stimulation.

[0052] The third aspect of the present invention provides the application of the aforementioned moisture-responsive spiral drive fiber in smart fabrics, humidity-responsive valves, microfluidic switches, soft grippers, artificial muscles, and humidity sensing and actuation integrated devices.

[0053] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber. By introducing dynamic arc length mismatch through the differences in moisture absorption, diffusion rate, wet expansion, and wet mechanical properties between the hydrophilic PEBA phase and the relatively hydrophobic PEBA phase, a bidirectional / non-monotonic wet response is achieved, which increases the end-to-end distance under short-term wet stimulation and decreases the end-to-end distance or reverses the curvature under continuous wet stimulation. At the same time, the interpenetration and physical crystallization of homologous polyamide hard segments at the wet molding interface are utilized to improve the stability of the two-phase interface and the stability of the wet mechanical skeleton. The prepared fiber has high wet mechanical stability, strong interfacial bonding, long cyclic fatigue life, and can be continuously prepared. It can be used in smart fabrics, humidity-responsive valves, microfluidic switches, soft grippers, artificial muscles, environmentally adaptive structures, and humidity sensing / driving integrated devices.

[0054] 2. This invention enables fibers to produce a non-monotonic response under a single wet stimulus by using the hydrophilic and hydrophobic parallel heterogeneous structure of PEBA and the dynamic arc length mismatch mechanism. This response includes a short-term increase in end-to-end distance and a decrease in end-to-end distance or curvature reversal under continuous wet stimulus, thereby breaking through the limitation of monotonic bending of conventional double-layer actuators.

[0055] 3. This invention uses PEBA block copolymer as the main material. The polyether soft segment provides moisture absorption and chain rearrangement capabilities, while the polyamide hard segment crystalline region serves as a physical crosslinking point, which helps maintain the wet mechanical skeleton and improves wet load-bearing capacity and cycle stability.

[0056] 4. This invention uses parallel wet spinning of homologous PEBA two-phase fibers. The two phases separate synchronously in the coagulation bath and form a continuous interface, which can reduce the risk of peeling of coated and bonded double-layer structures in large deformation wet-dry cycles.

[0057] 5. The preparation process of this invention does not require complex chemical cross-linking and can achieve continuous preparation through solution preparation, parallel wet spinning, drawing and hydration reprogramming, and has the potential for scale-up preparation.

[0058] 6. The second phase of this invention can incorporate functional fillers such as carbon nanotubes, which can accelerate the drying recovery rate of wet fibers through photothermal response. It can also be further expanded to include photothermal response, conductive sensing, mechanical reinforcement, and smart textile applications. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the wet-response spiral-driven fiber preparation process of the present invention.

[0060] Figure 2 This is a partial enlarged and cross-sectional schematic diagram of the parallel spinnerets in step S2 of the present invention, wherein 1-first phase channel; 2-second phase channel.

[0061] Figure 3 This is a schematic diagram of hydration reprogramming and spiral shaping in step S3 of the present invention.

[0062] Figure 4 This is a schematic diagram of the non-monotonic moisture response of the fiber prepared according to the present invention.

[0063] Figure 5 The results show the water contact angle test results for two PEBA polymers, PEBA 1074 and PEBA 2533.

[0064] Figure 6 Infrared spectra of two PEBA polymers, PEBA 1074 and PEBA 2533.

[0065] Figure 7 The denoted values ​​represent the axial-radial volume change rates of the two PEBA fibers after saturation water absorption.

[0066] Figure 8 X-ray diffraction patterns of PEBA 1074 fiber in dry and wet conditions.

[0067] Figure 9 Differential scanning calorimetry (DSC) curves of PEBA 1074 fiber.

[0068] Figure 10 The diagram shows the structural morphology of the parallel heterogeneous fibers prepared in Example 1 of this invention; where a is a cross-sectional view of the fiber; b is a surface view of the fiber; c is a magnified view of a portion of the fiber surface; and d is a cross-sectional view of the fiber observed through an optical microscope.

[0069] Figure 11 The dry and wet stress-strain curves are those of the parallel heterogeneous fibers prepared in Example 1 of this invention.

[0070] Figure 12 The first-load cyclic stress-strain curves of the parallel heterogeneous fibers prepared in Example 1 of the present invention are shown.

[0071] Figure 13 The stress-strain cycle curves of the parallel heterogeneous fibers prepared in Example 1 of the present invention after 200 cycles at 100% strain are shown.

[0072] Figure 14 The driving strain performance of the parallel heterogeneous fibers prepared in Example 1 of the present invention under 3s moisture stimulation.

[0073] Figure 15 The driving strain performance of the parallel heterogeneous fibers prepared in Example 1 of the present invention under 15s moisture stimulation.

[0074] Figure 16 The strain performance of the parallel heterogeneous fibers prepared in Example 1 of this invention under continuous (20 s) wet stimulation driven strain under different self-weight loads.

[0075] Figure 17 The stimulus response cycle stability of the parallel heterogeneous fibers prepared in Example 1 of the present invention under no-load conditions.

[0076] Figure 18 The stimulus response cycle stability of the parallel heterogeneous fibers prepared in Example 1 of the present invention under load. Detailed Implementation

[0077] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0078] All raw materials used in this invention are commercially available.

[0079] PEBA 1074, the polyether soft segment is selected from polyethylene oxide, with a polyether soft segment content of 55 wt%; the hard segment is selected from polyamide 12, with a content of 45 wt%; Shore hardness 38 D; tensile modulus (23 ℃, 1 mm / min) 80 MPa; equilibrium water absorption rate at 23 ℃ is 48%. From Arkema, France.

[0080] PEBA 2533, the polyether soft segment is selected from polytetrahydrofuran, with a polyether soft segment content of 80 wt%; the hard segment is selected from polyamide 12, with a content of 20 wt%; Shore hardness 22 D; tensile modulus (23 ℃, 1 mm / min) 10 MPa; equilibrium water absorption rate at 23 ℃ is 1.2%. From Arkema, France.

[0081] Carboxylated multi-walled carbon nanotubes (XFM18) with an outer diameter of 10–20 nm, a length of 0.5–2 μm, a purity ≥95%, a carboxyl content of 2.0 wt%, and an oxygen content (XPS) of 5.77% are derived from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0082] Example 1 This embodiment provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, the wet-responsive helical driven fiber having a parallel two-phase structure, including a first phase and a second phase; the first phase and the second phase extend continuously along the fiber axis and are in parallel contact with each other on the fiber cross section to form a continuous bonding interface.

[0083] The first phase is a hydrophilic polyether block amide phase, which is copolymerized from polyether soft segments and polyamide hard segments.

[0084] In the hydrophilic polyether block amide phase, the polyether soft segment is selected from polyethylene oxide, and the polyether soft segment content is 55 wt%; the hard segment is selected from polyamide 12, and the content is 45 wt%; the Shore hardness is 38 D; the tensile modulus (23 ℃, 1 mm / min) is 80 MPa; and the equilibrium water absorption rate under immersion at 23 ℃ is 48%.

[0085] The first phase was purchased from Arkema, model PEBA 1074.

[0086] The second phase introduces functional fillers to form a relatively hydrophobic polyether block amide composite phase.

[0087] In the relatively hydrophobic polyether block amide, the polyether soft segment is selected from polytetrahydrofuran, and the polyether soft segment content is 80 wt%; the hard segment is selected from polyamide 12, and the content is 20 wt%; the Shore hardness is 22 D; the tensile modulus (23 ℃, 1 mm / min) is 10 MPa; and the equilibrium water absorption rate under immersion at 23 ℃ is 1.2%.

[0088] The second phase was purchased from Arkema, model PEBA 2533.

[0089] The functional filler is a carboxylated carbon nanotube with an outer diameter of 10-20 nm, a length of 0.5-2 μm, a purity of ≥95%, a carboxyl content of 2.0 wt%, and an oxygen content (XPS) of 5.77%.

[0090] The carboxylated carbon nanotubes are XFM18 from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0091] The preparation method of the polyether block amide parallel heterogeneous wet-responsive helical driven fiber includes the following steps: S1. Preparation of spinning solution: Prepare the first phase spinning solution and the second phase spinning solution using a solvent system that can dissolve both phases of PEBA simultaneously. S2, Parallel wet spinning: The first phase spinning solution and the second phase spinning solution are respectively fed to the parallel spinneret assembly, forming parallel liquid flows at the spinneret and being squeezed into the coagulation bath to undergo solvent-non-solvent exchange and phase separation, forming parallel biphase nascent fibers. S3, Hydration Reprogramming and Drying: After the fiber obtained in step S2 is naturally dried at room temperature for 24 hours, a moisture stimulus is applied to it for drying and shaping, thus obtaining the moisture-responsive helical driven fiber; the moisture-responsive helical driven fiber has a steady-state helical structure.

[0092] In step S1, the solvent system is formic acid.

[0093] In the first phase spinning solution, the mass fraction of hydrophilic polyether block amide is 20%.

[0094] The preparation method of the first phase spinning solution is as follows: the first phase is added to the solvent system and magnetically stirred at 600 rpm for 12 h in a closed constant temperature water bath at 40℃ until it is completely dissolved and defoamed, thus obtaining the solution.

[0095] The mass fraction of the hydrophobic polyether block amide composite phase in the second phase spinning solution is 19%.

[0096] The amount of the functional filler added is 0.5% of the mass of the relative hydrophobic polyether block amide composite phase in the second phase.

[0097] The preparation method of the second phase spinning solution is as follows: the second phase is added to the solvent system, stirred and ultrasonically dispersed at 600 rpm in a closed water bath at 40°C for 2 hours.

[0098] The specific conditions for ultrasonic dispersion are as follows: probe-type ultrasonic dispersion is used, with a power of 480W, ice water bath, intermittent ultrasound, 3 seconds on and 3 seconds off, and an ultrasound time of 20 minutes.

[0099] In step S2, the coagulation bath is deionized water; the temperature of the coagulation bath is controlled at 30°C.

[0100] In step S2, the syringe and infusion tubing containing the first phase spinning solution are kept warm during the spinning process to inhibit premature gelation or phase separation of the spinning solution; the warming temperature of the first phase spinning solution is 30°C.

[0101] The volumetric flow rates of the first phase spinning solution and the second phase spinning solution are 1.44 mL / h and 0.96 mL / h, respectively, with a flow rate ratio of 1.5:1.

[0102] In step S2, during the solidification process in the coagulation bath, the nascent fibers are stretched; the stretching ratio is 5 times, corresponding to a fiber collection rate of 0.2 m / min.

[0103] In step S3, the wet stimulation method is water mist; the wet stimulation time is 5 seconds.

[0104] The drying and characterization method is natural drying at room temperature. The drying and characterization time is 24 hours.

[0105] Example 2 This embodiment provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, and the specific implementation method is the same as that in Embodiment 1, except that: The volumetric flow rates of both the first-phase spinning solution and the second-phase spinning solution are 1.2 mL / h, and the flow rate ratio is 1:1.

[0106] Example 3 This embodiment provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, and the specific implementation method is the same as that in Embodiment 1, except that: The mass fraction of the hydrophobic polyether block amide composite phase in the second phase spinning solution is 20%.

[0107] The amount of the functional filler added is 0.5% of the mass of the relative hydrophobic polyether block amide composite phase in the second phase.

[0108] Example 4 This embodiment provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, and the specific implementation method is the same as that in Embodiment 3, except that: The volumetric flow rates of the first phase spinning solution and the second phase spinning solution are 1.68 mL / h and 0.72 mL / h, respectively, with a flow rate ratio of 7:3.

[0109] Example 5 This embodiment provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, and the specific implementation method is the same as that in Embodiment 1, except that: The mass fraction of the hydrophobic polyether block amide composite phase in the second phase spinning solution is 18%.

[0110] The amount of the functional filler added is 1% of the mass of the relative hydrophobic polyether block amide composite phase in the second phase.

[0111] Example 6 This embodiment provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, and the specific implementation method is the same as that in Embodiment 3, except that: In step S2, during the solidification process in the coagulation bath, the nascent fibers are stretched; the stretching ratio is 1.5 times, corresponding to a fiber collection rate of 0.06 m / min.

[0112] Comparative Example 1 This comparative example provides a wet-responsive helical driven fiber, with the same implementation method as Example 1, except that: The second phase is a polyether-type thermoplastic polyurethane from BASF, TPU 1180AU.

[0113] Comparative Example 2 This comparative example provides a wet-responsive helical driven fiber, with the same implementation method as Example 1, except that: In the hydrophilic polyether block amide phase, the polyether soft segment is selected from polyethylene glycol, and the polyether soft segment content is 60 wt%. The polyamide hard segment is PA6, and the content is 40 wt%. The Shore hardness is 40 D. The tensile modulus (23 ℃, 1 mm / min) is 80 MPa. The equilibrium water absorption rate under immersion at 23 ℃ is 120%.

[0114] The first phase was purchased from Arkema, France, model PEBA 1657.

[0115] Comparative Example 3 This comparative example provides a wet-responsive helical driven fiber, with the same implementation method as Example 1, except that: In the first phase spinning solution, the mass fraction of hydrophilic polyether block amide is 10%.

[0116] Comparative Example 4 This comparative example provides a wet-responsive helical driven fiber, with the same implementation method as Example 1, except that: In the first phase spinning solution, the mass fraction of hydrophilic polyether block amide is 50%.

[0117] Comparative Example 5 This comparative example provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, with the specific implementation method being the same as in Example 1, except that: The amount of the functional filler added is 6% of the mass of the relative hydrophobic polyether block amide composite phase in the second phase.

[0118] Comparative Example 6 This comparative example provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, with the specific implementation method being the same as in Example 1, except that: The volumetric flow rates of the first phase spinning solution and the second phase spinning solution are 2.18 mL / h and 0.22 mL / h, respectively, with a flow rate ratio of approximately 10:1.

[0119] Comparative Example 7 This comparative example provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, with the specific implementation method being the same as in Example 1, except that: The volumetric flow rates of the first phase spinning solution and the second phase spinning solution are 0.22 mL / h and 2.18 mL / h, respectively, with a flow rate ratio of approximately 1:10.

[0120] Comparative Example 8 This comparative example provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, with the specific implementation method being the same as in Example 1, except that: In step S2, during the solidification process in the coagulation bath, the nascent fibers are stretched; the stretching ratio is 15 times, and the speed is 0.6 m / min.

[0121] Comparative Example 9 This comparative example provides a polyether block amide parallel heterogeneous wet-responsive helical driven fiber, with the specific implementation method being the same as in Example 1, except that: In step S2, the coagulation bath is deionized water; the temperature of the coagulation bath is controlled at 60°C.

[0122] Performance testing I. Performance Determination of Two PEBA Polymers Water contact angles were measured using an optical contact angle meter (OCA-20, Dataphysics, Germany). Static water contact angle test results for the two polyether block amides are shown in [link to table]. Figure 5 .from Figure 5 It can be seen that PEBA 1074 has a water contact angle of 37.2°, exhibiting hydrophilicity; while PEBA 2533 has a water contact angle of 85.1°, exhibiting hydrophobicity.

[0123] Infrared spectra of two polyether block amides were measured using a Nicolet IS10 instrument from Thermo Fisher Scientific (China) Co., Ltd., in ATR total reflectance mode, with a scanning range of 500–4000 cm⁻¹. -1 4 cm resolution -1 Infrared spectra of the two polyether block amides are shown in [reference needed]. Figure 6 .from Figure 6 It can be seen that both materials are typical polyether block amides. (Observation at 1100 cm⁻¹) -1 The relative intensity difference of the ether bond absorption peaks confirms that PEBA 2533 has a higher polyether soft segment content.

[0124] The axial and radial volume change rates of two types of polyether block amide fibers after saturation water absorption were tested. PEBA 1074 single-component fiber was prepared according to the method of the first-phase solution in Example 1, and extruded into a 30 °C deionized water coagulation bath at a rate of 2.4 mL / h through a single-channel spinneret. After 5 times stretching and natural drying at room temperature for 24 h, it was obtained. PEBA 2533 / CNT single-component fiber was prepared according to the method of the second-phase solution in Example 1, and extruded into a 30 °C deionized water coagulation bath at a rate of 2.4 mL / h through a single-channel spinneret. After 5 times stretching and natural drying at room temperature for 24 h, it was obtained. The test procedure was as follows: the test temperature was 20 °C, the humidity was 55%, and both fibers were observed under an optical microscope, recording the initial axial length L0 and radial length d0. After immersing both fibers in deionized water for 30 min, they were removed, the surface free water was wiped off with lint-free paper, and they were observed under an optical microscope, recording the axial length L and radial length d of the fibers after saturation water absorption. The rate of change ΔL = (L - L0) / L0 × 100%, Δd = (d - d0) / d0 × 100%. n = 5 for each group. The axial and radial volume change rates of the two types of polyether block amide fibers after saturation water absorption are shown in... Figure 7 .from Figure 7 It can be seen that the axial change rate of PEBA 2533 is 6.54%, and the radial change rate is 17.08%; while the axial change rate of PEBA 1074 is 14.78%, and the radial change rate is 28.62%. The difference in the axial and radial water absorption volume change rates causes strain mismatch, resulting in helical deformation of the parallel fibers.

[0125] The fiber phase was tested using a Bruker D2 PHASER A26-X1-A2E0B2A0 X-ray diffraction machine (Cu target), with a 2θ range of 5°–60°, a step size of 0.02°, and a scanning speed of 2° / min. X-ray diffraction patterns of PEBA 1074 fibers in both dry (samples dried at 60°C for 4 h in a direct-fired oven, cooled in a desiccator, and tested within 30 min) and wet (samples from the same batch soaked in deionized water for 30 min, then blotted with lint-free paper to remove surface free water, and tested immediately within 1 min) conditions are shown below. Figure 8 .from Figure 8 It can be seen that after PEBA 1074 absorbs water, the position of its characteristic diffraction peak at 2θ≈20° remains unchanged, but the width of the diffraction peak increases slightly. This indicates that water molecules mainly play a role at the interface between the soft segment polyether region and the hard segment edge, resulting in a slight decrease in the size of the hard segment crystallites and a slight decrease in the degree of order. However, the overall hard segment micro-framework of the material is not destroyed, ensuring that the material still has good dimensional stability and mechanical strength in the wet state.

[0126] Differential scanning calorimetry (DSC) curves of PEBA 1074 fibers were tested using a Mettler DSC3+ instrument. The temperature range was -50 °C to 180 °C, the heating / cooling rate was 10 °C / min, and the nitrogen gas flow rate was 50 mL / min. The DSC curves for PEBA 1074 fibers are shown below. Figure 9 .from Figure 9 It can be seen that the absorption of moisture caused the glass transition temperature of the soft segment of PEBA 1074 to decrease from 4.4 ℃ to 1.2 ℃. Water molecules played a typical physical plasticizing role, which was macroscopically manifested as a decrease in material stiffness and an increase in flexibility. However, the melting peak of the hard segment at 160 ℃ remained unchanged, proving that the plasticizing effect of moisture was limited to the soft segment phase region and did not cause essential damage to the physical cross-linking network of the hard segment.

[0127] II. Fiber Properties The morphology of the parallel heterogeneous fiber structure prepared in Example 1 of this invention is shown in the figure. Figure 10 .from Figure 10 It can be seen that the fiber cross-section is generally figure-eight shaped. Figure 10 a) It has longitudinal grooves and is tightly bonded, which is a classic parallel fiber structure. Figure 10 b and Figure 10 c); The interface between the two components is clear, and the molding is good ( Figure 10 d).

[0128] Stress-strain curve testing method: The tensile breaking strength, tensile recovery hysteresis curve, and fixed strain cycle test of the fiber were tested using a Shimadzu EZ-LX tensile testing machine. The load cell range was 10 N, the gauge length L0 = 20 mm, the tensile speed was 50 mm / min, the test temperature was 20 ℃, and the relative humidity was 55%. The fiber cross-sectional area A0 was obtained by observing the fiber cross-section with a scanning electron microscope and processing it using imageJ software; the engineering stress σ = F / A0, and the engineering strain ε = (L-L0) / L0 × 100%. Each group had n = 5. The dry and wet stress-strain curves of the parallel heterogeneous fibers prepared in Example 1 of this invention are shown in [reference needed]. Figure 11 .from Figure 11 It can be seen that the stress of the dry fiber can reach 16.3 MPa, and the strain can reach 2260%. The stress of the wet fiber decreases slightly to 15.7 MPa, while the strain increases significantly to 2685%. The tensile fracture curve does not show a step change, which proves that the two components are well bonded at the interface and no separation occurs during the tensile process.

[0129] The multi-amplitude initial loading cyclic stress-strain test method is the same as above. The same batch of samples were sequentially loaded to 50%, 100%, 200%, and 400% strain, with each amplitude subjected to one loading-unloading cycle. The loading / unloading speed was 50 mm / min, and the unloading endpoint was zero displacement. The multi-amplitude initial loading cyclic stress-strain curves of the parallel heterofibers prepared in Example 1 of this invention are shown below. Figure 12 .from Figure 12 It can be seen that the fiber has the characteristics of a highly repeatable loading response, continuous hardening after yielding, and a large hysteresis loop toughness polymer fiber.

[0130] The method for 200 stress-strain cycles at 100% strain is the same as above. The specimen is cyclicated 200 times with displacement controlled between 0% and 100% engineering strain at a speed of 50 mm / min, without any cycle intervals. The curves for the 1st, 2nd, 10th, 50th, 100th, and 200th cycles are recorded. No pre-cycling is performed before the test. The stress-strain cycle curves of the parallel heterostructure fibers prepared in Example 1 of this invention at 100% strain after 200 cycles are shown in [reference needed]. Figure 13 .from Figure 13 It can be seen that the fiber exhibits a significant Mullins effect under 100% strain, with extremely high energy dissipation capacity in the first cycle. After about 50 cycles, the hysteresis loop tends to close, and the curves of the 100th and 200th cycles highly overlap, proving that the heterogeneous fiber has excellent cyclic fatigue stability and good elastic recovery ability after undergoing initial structural rearrangement.

[0131] Test method for driven strain performance of fibers under short-term moisture stimulation: A spiral fiber with an initial end-to-end distance L0 = 100 mm was used. The upper end was fixed (vertically suspended) at 20 ℃ and 55% RH. An ultrasonic atomizer was placed 5 cm from one side of the fiber, with a spray rate of 2.5 mL / min. Stimulation was performed for 3 seconds. High-speed camera recording was used at a frame rate of 5000 fps. Image data was processed using ImageJ software. Driven strain ε = (L0 - Lt) / L0 × 100%, with shrinkage defined as positive and elongation as negative. The power density of the 808 nm light source was 500 mW / cm². 2 The irradiation distance was 5 cm, and n=5 per group. The driven strain properties of the parallel heterostructure fibers prepared in Example 1 of this invention under short-term moisture stimulation are shown in [the figure]. Figure 14 .from Figure 14 As can be seen, the fiber can achieve a macroscopic driven strain of up to -75% (the negative sign represents elongation) just 3 seconds after being stimulated by moisture. This rapid actuation behavior is further quantitatively verified in Figure b, where its negative response speed rapidly reaches its peak in the first second after stimulation, at approximately -33% / second. This phenomenon can be attributed to the rapid penetration and plasticizing effect of water molecules on the soft segments of PEBA polyether. With the assistance of 808 nm infrared light, the fiber can completely recover to its initial state in only about 8 seconds after reaching its maximum deformation; while without the assistance of infrared light, the natural recovery process of the fiber is relatively slow, and even after 20 seconds, about 20% residual strain remains. The reason is that the carbon nanotubes on the hydrophobic component side are excellent photothermal materials. Infrared light irradiation can rapidly increase the internal temperature of the fiber, accelerate the desorption and volatilization of water molecules from the soft segment phase region, thereby prompting the material to quickly recover its deformation through the original physical cross-linking network of the hard segment.

[0132] according to Figure 14 The same device was used for continuous wet stimulation for 15 seconds, and image data was recorded and processed using the same method, with n=5 per group. The driving strain properties of the parallel heterostructure fibers prepared in Example 1 of this invention under prolonged wet stimulation are shown in [the figure]. Figure 15 .from Figure 15 As can be seen, after extending the moisture stimulation to 15 seconds, the fiber exhibited a clear reverse-drive behavior. Within 3 seconds of moisture stimulation, the initial elongation was approximately 72%. Under continuous moisture stimulation, the fiber began to contract, reaching its maximum peak driven strain of approximately 75% at about 15 seconds. This demonstrates that the fiber possesses multi-directional and multi-stage actuation capabilities. With infrared light assistance, the fiber recovered its original shape in just about 5 seconds.

[0133] The test method for the strain performance of fibers under continuous (20 s) wet stimulation under different self-weight loads is the same as above, except that: the fiber mass mf is weighed, and weights of 10mf, 20mf, and 30mf are suspended at its free end; after 10 s of balancing, the length at this point is taken as the load reference L0, and continuous wet stimulation is applied for 20 s. The total stroke is calculated as (Lmax-Lmin) / L0×100%; other moisture source, video, and infrared conditions are the same. Figure 14 Test conditions: n=5 per group. The continuous (20 s) wet-stimulation driven strain properties of the parallel heterostructure fibers prepared in Example 1 of this invention under different self-weight loads are shown in [reference needed]. Figure 16 .from Figure 16 It can be seen that the fibers exhibit initial strains of approximately -10.09% and -28.26% at 10 times and 30 times their own weight, respectively. Under continuous moisture stimulation, the fiber loaded with 10 times its own weight can generate 60.24% of the total stroke, while the fiber loaded with 30 times its own weight can generate 45.73% of the total stroke. Infrared light irradiation can accelerate the fiber recovery process and cause the fiber to shrink to a certain extent through the thermal expansion of the photothermal components, which is particularly evident in the fiber loaded with 10 times its own weight, with a maximum shrinkage of 10.26%.

[0134] The method for testing the cyclic stability of the fiber's stimulus response under no-load conditions is as follows: Under no external load, a recovery cycle is defined as irradiation with wet stimulation at 15 s–808 nm, repeated 20 times; the maximum strain is recorded for each cycle; n=5 per group. The cyclic stability of the parallel heterogeneous fibers prepared in Example 1 of this invention under no-load conditions is shown in [reference needed]. Figure 17 .from Figure 17 It can be seen that during 20 consecutive stimulation cycles, the maximum strain of the fiber remained stable at around 80%, with very small fluctuations, proving that the parallel heterogeneous fiber has good fatigue life and deformation recovery ability under no-load conditions.

[0135] The method for testing the cyclic stability of fiber response under load: The fiber was subjected to cyclic loading at 10, 20, and 30 times its own weight. Figure 17 The program loops 20 times; n=5 per group. The stimulus-response cycle stability of the parallel heterogeneous fibers prepared in Example 1 of this invention under load is shown in [reference needed]. Figure 18 .from Figure 18 It can be seen that the magnitude of the self-weight load significantly affects the maximum driving strain of the fiber, but remains generally stable. The maximum shrinkage strain is stable at around 70% for 10 times the self-weight, around 55% for 20 times the self-weight, and around 40% for 30 times the self-weight. This further demonstrates that the parallel heterogeneous fiber has strong load fatigue resistance and excellent dimensional recovery accuracy.

[0136] The data from the examples and comparative examples are summarized in Table 1.

[0137] Table 1 Fiber data for each group The data in the table are the mean ± standard deviation, n=5.

[0138] Table 1 shows that Examples 1-6 can all form continuous parallel heterogeneous fibers with an average dry-state fracture stress of 14.9-16.9 MPa, an average dry-state fracture strain of 2210%-2890%, a short-term driven strain of 56.4%-75.2% over 3 seconds, a long-term driven strain of 50.8%-76.3% over 15 seconds, and a total stroke under a load of 30 times its own weight of 27.5%-47.6%, indicating that the obtained fibers have both high tensile deformation capacity and significant wet response driven performance. Among them, Example 1 shows a relatively balanced mechanical properties, short-term elongation, long-term reverse shrinkage, and load driven performance. Examples 2-5 show that the fiber forming state and wet response performance can be controlled by adjusting the concentration of the two-phase spinning solution, the two-phase flow ratio, and the content of functional fillers. In Example 6, due to the decrease in the draw ratio and the decrease in fiber orientation, although the fracture strain is increased, the fracture stress and wet response driven performance are significantly reduced. Compared to the examples, Comparative Example 1 exhibited significantly reduced fracture stress, fracture strain, and load-driven performance due to poor compatibility and interfacial bonding between the two phases. Comparative Examples 2-5 and 8 failed to form structurally stable parallel heterogeneous fibers due to unsuitable material selection, spinning solution concentration, filler content, or drafting conditions. Comparative Examples 6 and 7 suffered from significantly reduced wet-response driven strain due to deviations in the two-phase ratio, resulting in cross-sectional structural imbalance or insufficient hydrophilic driving phase. Comparative Example 9 experienced excessively rapid and uneven solvent-non-solvent exchange at a higher coagulation bath temperature, leading to defects in the core-sheath structure and interfacial formation, resulting in mechanical properties and driving performance lower than those of Example 1. These results indicate that the compatibility of the two-phase materials, spinning solution concentration, two-phase flow ratio, drafting conditions, and coagulation bath temperature need to be synergistically controlled to obtain helical driven fibers with a stable parallel structure, good mechanical properties, and high wet-response driving capability.

[0139] Therefore, this invention proposes a polyether block amide parallel heterogeneous wet-responsive helical driven fiber. By introducing dynamic arc length mismatch through the differences in moisture absorption, diffusion rate, wet expansion, and wet mechanical properties between the hydrophilic PEBA phase and the relatively hydrophobic PEBA phase, a bidirectional / non-monotonic wet response is achieved, which increases the end-to-end distance under short-term wet stimulation and decreases the end-to-end distance or reverses the curvature under continuous wet stimulation. At the same time, the interpenetration and physical crystallization of homologous polyamide hard segments at the wet molding interface are utilized to improve the stability of the two-phase interface and the stability of the wet mechanical skeleton.

[0140] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polyether block amide parallel heterogeneous wet-responsive helical driven fiber, characterized in that, The wet-responsive helical driven fiber has a parallel biphase structure, including a first phase and a second phase; the first phase and the second phase extend continuously along the fiber axis and are in parallel contact with each other on the fiber cross section to form a continuous bonding interface; the first phase is a hydrophilic polyether block amide phase; the second phase is a relatively hydrophobic polyether block amide phase or a composite phase thereof.

2. The polyether block amide parallel heterogeneous wet-responsive helical driven fiber according to claim 1, characterized in that, The second phase can be selectively incorporating functional fillers to form a composite phase structure.

3. The polyether block amide parallel heterogeneous wet-responsive helical driven fiber according to claim 2, characterized in that, The functional fillers include, but are not limited to, carbon nanotubes, carboxylated carbon nanotubes, hydroxylated carbon nanotubes, graphene, graphene oxide, MXene, carbon black, conductive polymers, metal nanoparticles, metal oxide nanoparticles, or other nanofillers with conductive, photothermal conversion, electromagnetic shielding, or mechanical reinforcement functions.

4. The polyether block amide parallel heterogeneous wet-responsive helical driven fiber according to any one of claims 1 to 3, characterized in that, The wet-responsive helical driven fiber exhibits a helical structure after initial water stimulation and drying. When subjected to wet stimulation, the end-to-end distance and / or helical curvature of the wet-responsive helical driven fiber undergo non-monotonic changes with stimulation time. The non-monotonic changes include, but are not limited to: under short-term wet stimulation conditions, the end-to-end distance of the fiber increases or the helical curvature decreases; under continuous wet stimulation conditions, the end-to-end distance of the fiber decreases or the direction of helical curvature reverses.

5. A method for preparing polyether block amide parallel heterogeneous wet-responsive helical driven fibers according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Preparation of spinning solution: Prepare the first phase spinning solution and the second phase spinning solution using a solvent system that can dissolve both phases of PEBA simultaneously. S2, Parallel wet spinning: The first phase spinning solution and the second phase spinning solution are respectively fed to the parallel spinneret assembly, forming parallel liquid flows at the spinneret and being squeezed into the coagulation bath to undergo solvent-non-solvent exchange and phase separation, forming parallel biphase nascent fibers. S3, Hydration Reprogramming and Drying: After the fiber obtained in step S2 is naturally dried at room temperature for 20-30 hours, a moisture stimulus is applied to it for drying and shaping, thus obtaining the moisture-responsive helical driven fiber; the moisture-responsive helical driven fiber has a steady-state helical structure.

6. The method for preparing polyether block amide parallel heterogeneous wet-responsive helical driven fibers according to claim 5, characterized in that, In the first phase spinning solution, the mass fraction of hydrophilic polyether block amide is 15%~35%; in the second phase spinning solution, the mass fraction of the relative hydrophobic polyether block amide composite phase is 15%~35%; the amount of the functional filler added is 0~5% of the mass of the relative hydrophobic polyether block amide composite phase in the second phase.

7. The method for preparing polyether block amide parallel heterogeneous wet-responsive helical driven fibers according to claim 5, characterized in that, In step S2, the volumetric flow rate ratio of the first phase spinning solution to the second phase spinning solution is (9~1):(1~9).

8. The method for preparing polyether block amide parallel heterogeneous wet-responsive helical driven fibers according to claim 5, characterized in that, In step S2, during or after the solidification process in the coagulation bath, the nascent fibers are stretched or cold-stretched; the stretching or cold-stretching ratio is 1 to 10 times.

9. The method for preparing polyether block amide parallel heterogeneous wet-responsive helical driven fibers according to claim 5, characterized in that, In step S3, the wet stimulation method is selected from at least one of water mist, water vapor, immersion in water, and humid air; the wet stimulation time is 0.5~120s.

10. The application of a polyether block amide parallel heterogeneous moisture-responsive helical driven fiber according to any one of claims 1 to 4 in smart fabrics, humidity-responsive valves, microfluidic switches, soft grippers, artificial muscles, and humidity sensing and driving integrated devices.

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