High-strength self-supporting polypyrrole nanoarray and preparation method and application thereof

Abstract

The application belongs to the technical field of polymer preparation, and particularly relates to a high-strength self-supporting polypyrrole nano array and a preparation method and application thereof. The preparation method comprises the following steps: (1) first, dispersing a hydroxypropyl-beta-cyclodextrin and polyethylene glycol aqueous solution onto an ice surface, and then adding a pyrrole monomer to form a dispersion liquid; (2) adding an acid solution containing an oxidizing agent to the dispersion liquid, and obtaining the high-strength self-supporting polypyrrole nano array after reaction. The application directly uses a macroscopic ice block as a hard template for polypyrrole preparation, and introduces a cyclic molecule hydroxypropyl-beta-cyclodextrin with hydrophilic and hydrophobic dual functions and polyethylene glycol with a linear polymer chain as an array growth aid, so that a high-strength polypyrrole nano sheet array with a self-supporting structure is prepared through a one-step polymerization method. The high-strength polypyrrole nano sheet array can be used as a conductive filler of polyurethane in the field of 3D printing technology, and greatly improves the mechanical properties and antistatic ability of products.

Description

Technical Field

[0001] This invention belongs to the field of polymer preparation technology, specifically relating to a high-strength self-supporting polypyrrole nanoarray, its preparation method, and its application. Background Technology

[0002] 3D printing technology, as a revolutionary manufacturing method, exhibits numerous significant advantages over traditional manufacturing techniques. Traditional manufacturing techniques are often limited by mold preparation and processing methods, resulting in high manufacturing costs, long production cycles, and difficulty in achieving free design of product structures. 3D printing, with its unique layer-by-layer manufacturing method, enables controlled material arrangement during the printing process, effectively solving these bottlenecks. In practical applications, 3D printing technology can address the high costs of traditional processes through small-batch customized production, freeing users from the constraints of structural design. The most crucial aspect of 3D printing is the preparation of the printing material. Thermoplastic engineering plastics do not undergo chemical bonding during 3D printing, allowing for recycling, melting, and reuse, making them the most common materials used in 3D printing.

[0003] Polyurethane is a class of polymeric materials prepared through chemical reactions from raw materials such as isocyanates, polyols, and chain extenders. Its unique molecular structure and tunable chemical composition endow it with an extremely wide range of performance characteristics. Since the industrial production of polyurethane, its elastomer form has established an important position due to its unique performance advantages. This material combines the high elasticity of rubber with the high strength of plastics, and through flexible molecular design, it can meet the needs of different application scenarios. It is now widely used in key fields such as automobile manufacturing, medical devices, sports equipment, and aerospace. The core feature of polyurethane lies in its microphase separation structure. This interpenetrating network structure ensures both high load-bearing capacity and excellent deformation recovery properties. Precise control of this special morphology allows polyurethane to maintain stable mechanical properties over a wide temperature range, making it a polymeric system with high application value in the field of engineering materials. The hard segments of polyurethane consist of rigid urethane units formed by the stepwise polymerization of isocyanates and chain extenders, forming a physical cross-linked network through multiple hydrogen bonds; the soft segments consist of long chains of polyols with conformational freedom, imparting elastic response characteristics to the material through chain segment movement. This combination of rigidity and flexibility allows the material to effectively disperse stress while resisting permanent deformation. By adjusting the ratio of hard to soft segments, selecting different types of polyols (such as polyester, polyether, and polycarbonate types), and controlling the synthesis process, it is possible to precisely customize the crystallinity, crosslinking density, and microstructure of the material, thereby obtaining a continuous performance spectrum from ultra-soft elastomers to rigid structural components.

[0004] Currently, the development of 3D printing polyurethane materials mainly focuses on optimizing the material's mechanical properties; however, research on the antistatic properties of 3D printing polyurethane materials is still lacking. Existing technologies mostly employ the addition of various conductive polymer fillers to address the poor antistatic properties of polyurethane. However, the interfacial bonding force between conductive polymer fillers and polyurethane is low, making direct printing through blending difficult. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength self-supporting polypyrrole nanoarray, its preparation method, and its application. Macroscopic ice blocks are directly used as a hard template for polypyrrole preparation. Hydroxypropyl-β-cyclodextrin, a cyclic molecule with both hydrophilic and hydrophobic functions, and polyethylene glycol with linear polymer chains are introduced as array growth aids. A one-step polymerization method is used to prepare a high-strength polypyrrole nanosheet array with a self-supporting structure. This is a simple and efficient method for preparing high-strength self-supporting polypyrrole nanoarrays, which can be used as a conductive filler for polyurethane in the field of 3D printing technology, greatly improving the mechanical properties and antistatic capabilities of the product.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0008] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol on the ice surface, then add pyrrole monomer, and let it stand to form a dispersion; the mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is (1-3):1;

[0009] (2) Add an acid solution containing an oxidant to the dispersion, react, and after washing and drying, a high-strength self-supporting polypyrrole nanoarray is obtained.

[0010] Polypyrrole (PP) is a heterocyclic polymer formed by the polymerization of pyrrole monomers. Its basic structural unit is the pyrrole ring, and each pyrrole molecule consists of one nitrogen atom and four carbon atoms. During polymerization, pyrrole monomers are interconnected through α-carbon atoms, forming linear or branched structures. This structure endows PPI with unique physicochemical properties. In the PPI molecule chain, the pyrrole rings are connected through α-carbon atoms, forming a continuous conjugated π-electron system. This conjugated structure allows electrons to move freely within the polymer chain, thus giving PPI excellent electrical conductivity. Furthermore, the conductivity of PPI can be further modulated by doping. However, PPI contains rigid groups within its molecule, making it difficult to melt and dissolve, thus hindering its processing. Current technologies mostly use one-dimensional PPI nanoparticles or two-dimensional PPI nanosheets as conductive fillers in polyurethane. However, PPI nanoparticles or PPI nanosheets are difficult to disperse in molten resin, making it difficult to effectively construct a spatial structure and affecting the formation of the conductive network. On the other hand, adding large amounts of PPI can lead to a decrease in the mechanical properties of the composite material.

[0011] In previous work (CN121182184A, etc.), the inventors prepared curved polyaniline using ice micropowder as a template and used it as a conductive filler for polyurethane. However, this process requires the preparation of micron-sized ice powder, which is energy-intensive. Furthermore, the polymerization of aniline is carried out in an aqueous solution of ice micropowder. Due to the limitations of the size and morphology of the ice micropowder, it is impossible to prepare curved polyaniline on a large scale, making it difficult to promote its industrial use. More importantly, two-dimensional nanosheets have a large specific surface area and high surface energy, and tend to spontaneously aggregate to reduce energy. Under external forces, they are prone to slippage or debonding from the resin matrix, resulting in the destruction of conductive pathways. At the same time, the two-dimensional sheet structure is difficult to form an effective conductive network at low concentrations; at high concentrations, it will damage the film-forming properties of polyurethane, making the material brittle and rough, thus affecting the performance of 3D printed products.

[0012] To further improve the electrical and mechanical properties of polypyrrole materials, this invention directly uses macroscopically structured ice as a hard template for polypyrrole preparation. By introducing cyclic molecules with dual hydrophilic and hydrophobic functions, such as hydroxypropyl-β-cyclodextrin, and polyethylene glycol with linear polymer chains, as array growth aids, a self-supporting polypyrrole nanosheet array is prepared via a one-step polymerization method. The type of ice is not particularly limited, as long as it can provide a large, smooth planar structure to facilitate the formation of a thin liquid film from the mixed solution.

[0013] In traditional particulate-filled systems, conductive pathways rely on the physical contact between filler particles or sheets. Only when the filler content reaches the percolation threshold and the distance between particles or sheets is sufficiently close can a conductive network be formed throughout the entire material. In contrast to zero-dimensional polypyrrole nanoparticles or nanosheets, the array structure itself is a pre-constructed continuous conductive pathway, independent of random contact between fillers. Even at low addition levels, as long as the network structure remains intact in the resin, electrons can be transported along the network skeleton over long distances. During deformation, the array can adapt to deformation through bending, twisting, and sliding of the skeleton, rather than breaking. Even if local microstructural reorganization occurs, the overall conductive pathway can still be maintained. Furthermore, the network structure of the self-supporting polypyrrole nanosheet array can interpenetrate with the resin matrix, uniformly transfer stress, inhibit crack propagation, and easily form continuous conductive pathways, achieving high conductivity with low addition levels. Among these, the three-dimensional polypyrrole array, as a continuous reinforcing phase, forms an interpenetrating network structure in the resin matrix, which can efficiently conduct electrons and transfer loads through mechanical interlocking and interfacial bonding.

[0014] In this invention, ice acts as a macroscopic hard template. Compared to the ice micropowder used in patent technology CN121182184A, it has no special requirements for structure and morphology; it only requires ice to raise a large plane, making it easier to prepare on a large scale. Typically, existing technologies for preparing conductive array structures require two-dimensional materials such as graphene, graphene oxide, and boron nitride as substrates, utilizing the surface provided by inorganic two-dimensional field materials as the reaction substrate, on which conductive polymer arrays are grown. On the one hand, these technologies not only involve the preparation of complex substrates, but the conductive polymer arrays grown on these substrates are organic materials with low interaction with the inorganic substrate, making them prone to detachment and resulting in poor structural stability. On the other hand, the substrates in these technologies cannot be removed, preventing the preparation of simple conductive polymer arrays.

[0015] This invention uses ice as a hard template, where pyrrole monomers self-assemble on the ice surface under the action of hydroxypropyl-β-cyclodextrin to form an array structure. The macroscopic ice structure is not only easy to prepare but also easy to remove. After the reaction is complete, the ice substrate can be removed simply by heating, without damaging the array structure.

[0016] Hydroxypropyl-β-cyclodextrin acts as a molecular template in the early stages of polymerization. Unlike typical cyclodextrins, hydroxypropyl-β-cyclodextrin possesses a hydrophobic cavity and a hydrophilic shell (hydroxypropyl substituents). In the aqueous phase, hydrophobic pyrrole monomers tend to enter the hydrophobic cavity of hydroxypropyl-β-cyclodextrin, forming inclusion complexes; furthermore, the hydroxyl groups on hydroxypropyl-β-cyclodextrin readily form hydrogen bonds with pyrrole monomers. This inclusion and hydrogen bonding anchors the pyrrole monomers to the cyclodextrin molecules, preventing their disordered migration in solution. The pyrrole molecules are confined around the cavity, and their polymerization reaction can only proceed along the cavity opening, inducing polymer growth. The arrangement of pyrrole molecules within the cyclodextrin lays the molecular foundation for the subsequent formation of a regular three-dimensional array structure.

[0017] In previous work, the inventors simply used hydroxypropyl-β-cyclodextrin as a template agent. However, the polypyrrole nanoarray structure prepared by this method was irregular, affecting the formation of conductive pathways. Therefore, this invention adds polyethylene glycol (PEG), with linear polymer chains, as an array growth aid to the cyclic hydroxypropyl-β-cyclodextrin. Hydroxypropyl-β-cyclodextrin has hydrophobic cavities, enabling it to form host-guest inclusion complexes with pyrrole monomers, which inherently improves the dispersion stability of pyrrole in the aqueous phase. However, relying solely on hydroxypropyl-β-cyclodextrin, these inclusion complexes may still aggregate in locally high-concentration areas on ice surfaces. When PEG is added, its long-chain molecules can adsorb onto the surface of droplets or micelles, effectively inhibiting the coalescence of pyrrole droplets through steric hindrance. Specifically, hydroxypropyl-β-cyclodextrin and PEG have complementary effects; hydroxypropyl-β-cyclodextrin acts through molecular inclusion, while PEG acts through physical barriers. Together, they form a more stable dispersion system. During the settling period, polyethylene glycol (PEG) and hydroxypropyl-β-cyclodextrin (Hβ-Cyclodextrin) form a complex micelle structure near the ice surface, and pyrrole monomers undergo pre-oriented alignment on the ice surface. Simultaneously, the entire system gradually reaches thermodynamic equilibrium at low temperatures, laying the structural foundation for subsequent polymerization. Before the polymerization reaction begins, PEG primarily acts as a dispersant and stabilizer, helping pyrrole monomers form a uniform pre-assembled structure on the ice surface. Upon the addition of the oxidant, the polymerization reaction initiates, and PEG forms a dynamic molecular barrier around the pyrrole monomers through physical encapsulation and hydrogen bonding. This barrier does not prevent the diffusion of the oxidant but slows down the contact rate between the pyrrole monomers and the oxidant, thus reducing the initial polymerization rate. However, after the formation of the pyrrole prepolymer, it has little impact on the subsequent polymerization rate. The slower initial polymerization rate is conducive to homogeneous nucleation and controlled growth, avoiding random three-dimensional aggregation caused by the initial rapid polymerization of pyrrole monomers. This kinetic regulation causes polypyrrole to tend to grow in the form of two-dimensional nanosheets and align into an array structure along the direction induced by the ice surface.

[0018] In the reaction system of this invention, the reaction liquid is dispersed onto the surface of ice, effectively constructing a solid (ice)-liquid (reaction liquid) two-phase interface. The ice surface provides a rigid, flat two-dimensional substrate at extremely low temperatures. In low-temperature environments, the viscosity of water increases significantly, and its molecular diffusion ability weakens. Furthermore, the ice surface typically exhibits microscopic irregularities and grain boundary structures. These surface defects and grain boundaries act as physical barriers during the liquid film spreading process. The reaction liquid also contains solutes such as hydroxypropyl-β-cyclodextrin, polyethylene glycol, pyrrole monomers, and oxidants, the presence of which further affects the spreading behavior of water. Their adsorption further reduces the wettability of the ice surface, helping the liquid film maintain a stable state within a confined area. This allows the reaction liquid to form a liquid film of a certain thickness and limited size on the ice surface, ensuring that the polymerization reaction can proceed within a confined space, thereby inducing two-dimensional anisotropic growth and ultimately forming an ordered array structure with self-supporting capabilities.

[0019] The reaction liquid spreads into a thin liquid film on the ice surface, greatly restricting the physical space of the polymerization reaction (from a three-dimensional bulk phase to a two-dimensional plane). Within the thin liquid film, the hydroxypropyl-β-cyclodextrin-pyrrole inclusion complex, driven by the minimization of interfacial energy, tends to accumulate and oriented at the ice-liquid interface (solid substrate) or liquid-gas interface (surface), with its hydrophilic shell facing outward and its hydrophobic cavities facing in the same direction. The ether bonds and terminal hydroxyl groups on the polyethylene glycol molecular chain can form a hydrogen bond network with hydroxypropyl-β-cyclodextrin, resulting in a regular arrangement of hydroxypropyl-β-cyclodextrin. This arrangement forces the polymerization of pyrrole monomers along specific crystal planes, avoiding random, isotropic homogeneous nucleation, inhibiting disordered three-dimensional aggregation in the bulk phase, and thus promoting the lateral growth of the lamellar array.

[0020] Moreover, the surface of ice is not perfectly flat, but rather has micron / nanoscale grain boundaries and steps. When the reaction solution freezes or partially freezes on the ice surface, the hydroxypropyl-β-cyclodextrin and pyrrole complex is repelled and enriched at the grain boundaries between ice crystals. These grain boundaries form a natural array of nanochannels. When the polymerization reaction occurs within these confined channels, polypyrrole is forced to grow along the direction of the channels (i.e., the orientation of the ice crystals), forming the initial "array" prototype. During polymerization, the ice is not only a low-temperature substrate but also a dynamic sacrificial template. The channels formed by the tiny cracks on the ice surface are interconnected, forming a continuous network template. Under the action of hydroxypropyl-β-cyclodextrin, polypyrrole grows along the walls of these channels, forming a continuous three-dimensional network that replicates the gaps between ice crystals; different polypyrrole chains are interconnected through the physical entanglement or hydrogen bond network of cyclodextrin molecules, enhancing the interlayer bonding strength; polyethylene glycol, on the other hand, promotes the formation of a regular arrangement of hydroxypropyl-β-cyclodextrin. This arrangement forces the polymerization of pyrrole monomers along specific crystal planes, avoiding random, isotropic homogeneous nucleation and thus promoting the lateral growth of the sheet array. When the ice melts, the remaining polypyrrole network (which can also be directly removed from the ice surface) becomes a self-supporting three-dimensional nanosheet array structure.

[0021] Furthermore, the settling time is 5-10 minutes. By allowing it to stand for a period of time, hydroxypropyl-β-cyclodextrin can better bind to the ice template through hydrogen bonding or electrostatic interactions.

[0022] Furthermore, the mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is (1.5-2.5):1. Specifically, it can be 1.5:1, 1.7:1, 1.9:1, 2.1:1, 2.3:1, or 2.5:1. Insufficient hydroxypropyl-β-cyclodextrin will not adequately function as a template agent, resulting in an incomplete array structure; excessive hydroxypropyl-β-cyclodextrin leads to a high nucleation density, preventing the polypyrrole from fully expanding in the two-dimensional direction. Simultaneously, during polymerization, hydroxypropyl-β-cyclodextrin tightly binds to the polypyrrole network through hydrogen bonds and physical entanglement. When the amount of hydroxypropyl-β-cyclodextrin is appropriate, some of it can be removed during washing, and the remaining small amount can act as a structural reinforcing agent, strengthening the interlayer connections through hydrogen bond bridging. However, when hydroxypropyl-β-cyclodextrin is used in excess, a large number of hydroxypropyl-β-cyclodextrin molecules are physically embedded in the polypyrrole network and cannot be completely removed by conventional washing. These residual insulating molecules are distributed on the surface and between the polypyrrole sheets. On the one hand, they act as physical barriers, hindering electronic transitions between polypyrrole chains and charge transport between sheets, increasing contact resistance. On the other hand, the numerous hydroxyl groups on the hydroxypropyl-β-cyclodextrin molecules can form hydrogen bonds with the positive charge centers on the polypyrrole chains, partially shielding the effect of dopants and reducing the effective doping degree. Therefore, in the process optimization of preparing self-supporting polypyrrole arrays by ice-surface polymerization, the amount of hydroxypropyl-β-cyclodextrin needs to be controlled to avoid performance degradation caused by excessive dosage while ensuring sufficient template coverage and structure guidance.

[0023] Furthermore, in step (1), the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is (0.1-0.4):1. Specifically, it can be 0.10:1, 0.15:1, 0.20:1, 0.25:1, 0.30:1, 0.35:1, or 0.40:1. In particular, the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is (0.2-0.3):1. The presence of the solute improves the solubility of polyethylene glycol, and at the same time, an appropriate amount of polyethylene glycol can fully exert its steric hindrance and auxiliary polymerization effect, forming a good synergistic effect with hydroxypropyl-β-cyclodextrin, enabling the pyrrole monomer to achieve uniform dispersion and pre-assembly on the ice surface, laying an ordered structural foundation for subsequent polymerization. During the polymerization process, a moderate amount of polyethylene glycol can effectively regulate the reaction kinetics, inhibit disordered nucleation caused by rapid polymerization, and will not excessively hinder the contact between the monomer and the oxidant. The resulting polypyrrole nanosheet array exhibits a uniform morphology and good orientation, achieving a complete self-supporting structure. When the amount of polyethylene glycol relative to hydroxypropyl-β-cyclodextrin is too high, it not only affects the template function of hydroxypropyl-β-cyclodextrin but also impacts the dispersion and diffusion capabilities of the pyrrole monomers. More importantly, excessive polyethylene glycol forms an overly dense molecular barrier around the pyrrole monomers, severely hindering the diffusion of the oxidant to the monomers, leading to a slow polymerization rate or even incomplete polymerization. In this case, a large amount of unpolymerized pyrrole remains in the reaction system, significantly reducing the conductivity and electrochemical properties of the product. Furthermore, excessive physical embedding of polyethylene glycol within the polypyrrole backbone dilutes the proportion of the active component; although mechanical properties may be further improved, the electrical properties of the material are significantly compromised.

[0024] Furthermore, in step (1), the number-average molecular weight of the polyethylene glycol is 1000-10000. Specifically, PEG1000, PEG1200, PEG1500, PEG2000, PEG2500, PEG3000, PEG4000, PEG5000, PEG8000, PEG10000, etc., can be selected. In particular, polyethylene glycol with a number-average molecular weight of 1000-5000 that has good solubility and dispersibility can be selected. If the molecular weight of polyethylene glycol is too small, its steric hindrance effect is relatively weak; if the molecular weight is too large, not only is the cost higher, but the molecular chain movement is also difficult, which is not conducive to the uniform and regular polymerization of pyrrole monomers.

[0025] In this invention, the method of adding the reactants is not particularly limited and can employ common methods in the art, such as dripping, pouring, or coating. The reason for first dispersing the hydroxypropyl-β-cyclodextrin solution onto the ice surface is that the ice template surface contains a large number of hydroxyl groups, exhibiting strong hydrogen bond donor and acceptor capabilities. The outer shell of the hydroxypropyl-β-cyclodextrin molecule is rich in hydroxypropyl groups and unsubstituted hydroxyl groups, which can form a dense hydrogen bond network with the hydroxyl groups on the ice surface. This hydrogen bonding firmly anchors the hydroxypropyl-β-cyclodextrin molecules to the ice-liquid interface, while also connecting the hydroxypropyl-β-cyclodextrin molecules to each other, forming an ordered molecular layer. Orienting the hydrophobic cavities of the hydroxypropyl-β-cyclodextrin provides an ideal molecular platform for the subsequent pre-organization of pyrrole monomers, providing ordered inclusion sites for the pyrrole monomers and controlling the thickness and interlayer spacing of the polypyrrole nanosheets. Then, pyrrole monomers are added, which are captured by the anchored hydroxypropyl-β-cyclodextrin, achieving in-situ pre-organization. After the addition of ammonium persulfate, the polymerization reaction occurs on the surface of the template layer. At the same time, the introduction of hydroxypropyl-β-cyclodextrin also promotes the regularity of the polypyrrole structure, greatly improving the thermal stability of polypyrrole and making it more suitable for resin processing.

[0026] Furthermore, the oxidant is one or more of ammonium persulfate, potassium persulfate, sodium persulfate, ferric chloride, and hydrogen peroxide. Specifically, ammonium persulfate can be used as an initiator. Ammonium persulfate, as a single-electron oxidant, initiates the oxidative polymerization of pyrrole; simultaneously, the sulfate or bisulfate ions generated from the decomposition of ammonium persulfate also have a doping effect, which can improve the conductivity of polypyrrole. Adding an acid solution containing the oxidant dropwise to the dispersion eventually forms a mixed liquid film on the surface of the ice cube, where the pyrrole monomers complete the polymerization reaction. Specifically, the ice cube is placed horizontally to facilitate the stability of the liquid film. The method of adding the oxidant is not particularly limited; however, it can be added dropwise according to the size of the dispersion film containing the monomers to better promote the dispersion of the substances.

[0027] Furthermore, the mass ratio of the oxidant to the pyrrole monomer is (1-5):1. Specifically, it can be 1:1, 2:1, 3:1, 4:1, or 5:1. In particular, the mass ratio of the oxidant to the pyrrole monomer is (2-4):1 or (2.5-3.5):1. After the acid solution containing the oxidant is added dropwise to the dispersion to form a mixed solution, the reaction can begin. The concentration of the mixed solution is not particularly limited, but in particular, the concentration of pyrrole monomer in the mixed solution is 0.1-1.5 g / 100 ml. Specifically, in this invention, the concentration of pyrrole monomer does not need to be precisely controlled and can be adjusted to approximately 0.5-1.1 g / 100 ml using deionized water. A lower monomer concentration can prevent excessive growth of the self-supporting polypyrrole structure and improve the regularity of the array structure. Moreover, the reaction system of this invention uses water as a solvent, which facilitates the recovery and reuse of unreacted monomers and other raw materials in the mixed solution, effectively reducing the cost of industrial production. An appropriate amount of oxidant can effectively promote the polymerization of pyrrole monomers and improve the regularity of polypyrrole nanosheet arrays. However, when the amount of oxidant is too high, the excessively high core density restricts the full expansion of nanosheets in the two-dimensional direction, which is not conducive to the formation of large-sized nanosheets. This results in the loss of the continuous network characteristics unique to nanosheet arrays and a decrease in self-support.

[0028] Furthermore, the molar ratio of the acid to the pyrrole monomer is (1-5):1. Specifically, it can be 1:1, 2:1, 3:1, 4:1, or 5:1. Doping polypyrrole with acid can significantly improve its electrical conductivity and enhance the conductivity uniformity of the network structure. Simultaneously, acid doping strengthens the electrostatic interactions and hydrogen bond network between polypyrrole chains, helping to maintain the structural integrity of the self-supporting array during the drying process.

[0029] Furthermore, the acid is one or more of organic or inorganic acids.

[0030] Furthermore, the organic acid is one or more of p-toluenesulfonic acid, dodecylbenzenesulfonic acid, sodium dodecyl sulfonate, camphorsulfonic acid, sulfosalicylic acid, and oxalic acid.

[0031] Furthermore, the inorganic acid is one or more of sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid. Specifically, a 1 mol / L hydrochloric acid solution can be used.

[0032] Furthermore, the reaction temperature is below 0°C. Controlling the ice surface polymerization temperature below 0°C can effectively improve the fineness and performance of the self-supporting polypyrrole array structure. Specifically, it can be -10 to 0°C. In particular, from the perspective of ease of operation, the reaction can be carried out at 0°C.

[0033] Furthermore, the reaction time is 20-40 min. Specifically, it can be 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, 32 min, 34 min, 36 min, 38 min, or 40 min. The reaction time for preparing polypyrrole using the conventional aqueous solution method in existing technologies can typically reach several hours, or even tens of hours, severely impacting production efficiency. In the system of this invention, due to the solid-liquid interface effect and the template-regulating effect of hydroxypropyl-β-cyclodextrin in the reaction liquid film, the vertical growth of polypyrrole is facilitated, and the pyrrole monomer can complete polymerization in a short time. Further, the reaction time can be 25-35 min. Due to the presence of a smooth ice surface and the solid-liquid interface template formed by hydroxypropyl-β-cyclodextrin, within the aforementioned shorter reaction time, the pyrrole monomer preferentially grows along the bottom solid-liquid interface. If the reaction time is insufficient, polymerization will be incomplete, failing to form a continuous network structure. However, when the reaction time is too long, not only will over-polymerization destroy the array structure, but the already formed polypyrrole chains will also be exposed to excessive oxidant, resulting in a peroxidation reaction. Oxidizing agents possess strong oxidizing properties and continue to attack the conjugated double bonds on the polypyrrole backbone during the later stages of polymerization, disrupting the conjugated structure of polypyrrole. This peroxidation reaction significantly reduces the electrical conductivity of polypyrrole and damages its self-supporting structure, making the entire network structure fragile. During subsequent washing and drying processes, this damaged array structure is more prone to collapse due to capillary forces, resulting in decreased mechanical strength, reduced flexibility, and even an inability to maintain its intact morphology.

[0034] Furthermore, the washing process involves using deionized water.

[0035] Furthermore, the drying is performed in a vacuum drying oven.

[0036] It is worth mentioning that, unlike the ice micropowder method previously used by the inventors to prepare polyaniline, this method is only applicable to the preparation of polypyrrole arrays. This is because the oxidative polymerization of pyrrole has the kinetic characteristics of rapid initiation and slow growth. Under the action of oxidants such as ammonium persulfate, pyrrole monomers are oxidized to generate cationic free radicals. These active species tend to grow chains on the surface of existing nuclei rather than continuously generating new nuclei. This kinetic characteristic allows for effective separation of nucleation and growth in the ice surface polymerization of pyrrole: initially, a limited number of nuclei are formed, and then these nuclei slowly expand along the two-dimensional direction, eventually forming a large-sized, interconnected nanosheet array. In contrast, the oxidative polymerization of aniline follows an autocatalytic mechanism; once initiated, the reaction rate increases exponentially, exhibiting strong burst nucleation characteristics. These nuclei collide with each other before they can undergo anisotropic growth, and the final product is a random particulate aggregate that cannot form a regular nanosheet array. Furthermore, pyrrole molecules possess good planarity, and their five-membered ring structure allows for ordered arrangement of molecules through π-π stacking interactions. The five-membered ring structure also makes its molecular size highly compatible with hydroxypropyl-β-cyclodextrin. Under the synergistic effect of the ice template, hydroxypropyl-β-cyclodextrin, and polyethylene glycol, this self-assembly tendency facilitates the formation of a regular two-dimensional sheet structure. In contrast, aniline molecules have a six-membered ring structure, which has poor cavity compatibility with hydroxypropyl-β-cyclodextrin, and the π-π stacking interactions between benzene rings are weak, making it impossible to construct a self-supporting array structure.

[0037] On the other hand, the present invention also provides a high-strength self-supporting polypyrrole nanoarray prepared by the preparation method and its application.

[0038] The polypyrrole prepared by the method of this invention exhibits a nanosheet array structure. Compared with the nanorod or nanowire arrays commonly used in the art, the nanosheet array has significant advantages: In terms of improving conductivity, the nanosheets are more likely to form face-to-face overlaps during growth. This large contact area makes the electron transport resistance between the layers much lower than that between the points of contact between nanorods or nanowires. Therefore, with the same filler volume fraction, the conductive network formed by the nanosheet array is more continuous and dense, with a lower percolation threshold. This means that less polypyrrole can be used to achieve higher conductivity, thereby maximizing the preservation of the original flexibility and processing properties of the polyurethane matrix. In terms of improving mechanical properties, a more efficient load transfer interface is formed between the nanosheet array and the polyurethane matrix. Two-dimensional nanosheets have a large specific surface area, enabling them to establish broader hydrogen bonding interactions and physical entanglements with polyurethane molecular chains. When the composite material is subjected to external tensile force, these nanosheets do not exist as isolated rigid inclusions, but participate in deformation as an interconnected continuous layered network, uniformly dispersing concentrated stress into a large area of ​​the matrix. In contrast, while nanorod arrays can also provide reinforcement, their geometric shape limits the number of connection points between rods, making them prone to local stress concentration under external forces. Furthermore, the mechanical properties of rod-shaped structures differ significantly between oriented and non-oriented directions, which can easily lead to performance degradation of composite materials in specific directions.

[0039] Specifically, high-strength self-supporting polypyrrole nanoarrays can be used in 3D printing technologies such as photopolymerization, selective laser sintering, fused deposition modeling, or layered solid fabrication. Furthermore, this invention also discloses a 3D-printed polyurethane material comprising a polyurethane resin material, a high-strength self-supporting polypyrrole nanoarray, and inorganic reinforcing fillers. Due to the limiting effect of the ice template and the hydroxypropyl-β-cyclodextrin template, the self-supporting polypyrrole nanoarray prepared by this invention has vertically arranged polypyrrole nanosheets in the longitudinal direction and a micron-sized array substrate in the transverse direction, which can serve as a conductive and reinforcing filler for the polyurethane resin material. Further, photopolymerization or fused deposition modeling can be used. Specifically, fused deposition modeling is used to prepare the polyurethane material. The printing temperature in fused deposition modeling is not particularly limited and can be between 180-200℃, or adjusted according to the specific production process. Even further, the 3D-printed polyurethane material may also contain coupling agents, flow modifiers, lubricants, antioxidants, UV stabilizers, hydrolysis inhibitors, colorants, and other additives. In particular, there are no special limitations on the type of inorganic reinforcing filler, which may include granular, fibrous, and sheet-like structured fillers.

[0040] Furthermore, the reinforcing filler is inorganic nanoparticles. Introducing inorganic nanoparticles and a self-supporting polypyrrole array into the polyurethane matrix can construct an organic-inorganic hybrid dual-network reinforcement system. The three-dimensional self-supporting polypyrrole network provides continuous skeletal reinforcement at the micrometer scale. When external forces are applied to the composite material, this network, running throughout the entire material, can uniformly transfer and disperse the load, inhibiting crack initiation and propagation. Simultaneously, the inorganic nanoparticles dispersed in the polyurethane matrix play a role at the nanoscale. They act as stress concentration points, inducing craze formation, consuming fracture energy, and restricting chain segment movement through interfacial interactions with the polyurethane molecular chains. More importantly, these nanoparticles can be positioned in the gaps or lamellar surfaces of the polypyrrole network, acting as a bridge between the polypyrrole skeleton and the polyurethane matrix, further strengthening the interfacial bonding. This multi-level reinforcing synergistic effect of the macroscopic network and nanoparticles can significantly improve the tensile strength of the composite material while maintaining the elongation at break, overcoming the embrittlement defects caused by traditional high-filler systems. Meanwhile, due to the residual hydroxyl groups of hydroxypropyl-β-cyclodextrin during the preparation process, the polypyrrole array has a certain number of hydrogen bonding sites on its surface, which can interact with the hard segments of polyurethane. Inorganic nanoparticles can also act as rigid particle reinforcement and toughening agents. When these two fillers coexist, not only is the stress transfer efficiency between the particles and polypyrrole enhanced, but the entire hybrid network is further stabilized. By controlling the ratio and surface chemical properties of the two fillers, a synergistic reinforcement system that is both interconnected and each plays its own role can be constructed in the polyurethane matrix. In particular, to improve the compatibility of inorganic nanoparticles with the resin, they can be modified with silane coupling agents, such as KH-550, KH-560, KH-561, or KH-570. It should be noted that the types of raw materials used in this invention are not particularly limited; they can be prepared using conventional processes in the art or commercially available. For example, the thermoplastic polyurethane can be the commonly used Wanhua Q / 0600.

[0041] Beneficial effects:

[0042] (1) This invention directly uses ice cubes as a hard template for polypyrrole preparation, and introduces hydroxypropyl-β-cyclodextrin, a cyclic molecule with both hydrophilic and hydrophobic functions, and polyethylene glycol with linear polymer chains as array growth aids. A one-step polymerization method is used to prepare a self-supporting polypyrrole nanosheet array, which is a simple and efficient method for preparing high-strength self-supporting polypyrrole nanoarrays. Using ice cubes as a hard template, pyrrole monomers self-assemble on the surface of the ice cubes under the action of hydroxypropyl-β-cyclodextrin to form an array structure. The macroscopically structured ice cubes are not only easy to prepare, but also easy to remove without damaging the array structure.

[0043] (2) This invention adds polyethylene glycol with linear polymer chains as an array growth aid to the cyclic molecule hydroxypropyl-β-cyclodextrin. Hydroxypropyl-β-cyclodextrin has hydrophobic cavities, which can form host-guest inclusion complexes with pyrrole monomers, thereby improving the dispersion stability of pyrrole in the aqueous phase. The long-chain molecules of polyethylene glycol can be adsorbed on the surface of droplets or micelles, effectively inhibiting the coalescence of pyrrole droplets through steric hindrance. Before the polymerization reaction begins, polyethylene glycol mainly acts as a dispersion stabilizer, helping pyrrole monomers to form a uniform pre-assembled structure on the ice surface. When the oxidant is added, the polymerization reaction starts, and polyethylene glycol forms a dynamic molecular barrier around the pyrrole monomers through physical encapsulation and hydrogen bonding, avoiding random three-dimensional aggregation caused by the initial rapid polymerization of pyrrole monomers. This kinetic regulation makes polypyrrole tend to grow in the form of two-dimensional nanosheets and arrange into an array structure along the direction induced by the ice surface.

[0044] (3) Compared to zero-dimensional polypyrrole nanoparticles or polypyrrole nanosheets, the array structure itself is a pre-constructed continuous conductive path, without relying on random contact between fillers. Furthermore, the network structure of the self-supporting polypyrrole nanosheet array can interpenetrate with the resin matrix, uniformly transfer stress, inhibit crack propagation, and easily form a continuous conductive path, achieving high conductivity with low addition amounts. Overall, this invention provides a simple and high-yield method for preparing high-strength self-supporting polypyrrole nanoarrays. The high-strength self-supporting polypyrrole nanoarrays obtained using this method have high yield and uniform size, and can be used as conductive fillers for polyurethane in the field of 3D printing technology, improving the mechanical properties and antistatic capabilities of the products. Attached Figure Description

[0045] Figure 1 A scanning electron microscope image of the high-strength self-supporting polypyrrole nanoarray prepared in Example 10;

[0046] Figure 2 Here is a scanning electron microscope image of the polypyrrole prepared in Comparative Example 1;

[0047] Figure 3 The image shows a scanning electron microscope (SEM) image of polypyrrole prepared for Comparative Example 2. Detailed Implementation

[0048] In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the specific embodiments of the present invention will be described in further detail below with reference to specific examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0049] The performance testing method for the products prepared in the following examples and comparative examples is as follows: Under the same conditions, the effect of polypyrrole prepared in Examples 1-10 and Comparative Examples 1-2 on the performance of 3D printed polyurethane products is tested.

[0050] Specifically, the 3D printing polyurethane material comprises 100 parts thermoplastic polyurethane, 9 parts polypyrrole, 3 parts nano-silica (average particle size 100nm), 3 parts zinc stearate, and 1 part KH-550. The 3D printing polyurethane material is printed into strips, and the elongation at break of the strips is tested according to GB / T528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber," and its conductivity is tested using a conductivity meter.

[0051] Example 1

[0052] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0053] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG1500 on the surface of ice placed horizontally, and then add pyrrole monomer. Let stand for 10 min to form a dispersion. The mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 1:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.3:1.

[0054] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to adjust the concentration of pyrrole monomer to 0.8 g / 100 ml. The mixture was reacted at 0 °C for 40 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 3.8:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 4.5:1. It was used as a conductive reinforcing filler for thermoplastic polyurethane. The results showed that its elongation at break was 519% and its conductivity was 36.64 × 10⁻⁶. -4 S / cm.

[0055] Example 2

[0056] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0057] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG3000 on the surface of ice placed horizontally, and then add pyrrole monomer. Let stand for 5 minutes to form a dispersion. The mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 2.3:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.1:1.

[0058] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to adjust the concentration of pyrrole monomer to 0.8 g / 100 ml. The mixture was reacted at 0 °C for 20 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 2.2:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 2:1. It was used as a conductive reinforcing filler for thermoplastic polyurethane. The results showed that its elongation at break was 520% ​​and its conductivity was 37.81 × 10⁻⁶. -4 S / cm.

[0059] Example 3

[0060] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0061] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG1000 on the surface of ice placed horizontally, and then add pyrrole monomer and let stand for 6 min to form a dispersion; the mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 2:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.2:1.

[0062] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to obtain a mixed solution with a pyrrole monomer concentration of 0.8 g / 100 ml. The mixture was reacted at 0 °C for 30 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 3:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 3.5:1. This was used as a conductive reinforcing filler for thermoplastic polyurethane. Testing showed that its elongation at break was 521% and its electrical conductivity was 37.22 × 10⁻⁶. -4 S / cm.

[0063] Example 4

[0064] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0065] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG2500 on the surface of ice placed horizontally, and then add pyrrole monomer and let stand for 8 min to form a dispersion; the mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 1.3:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.15:1.

[0066] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to adjust the concentration of pyrrole monomer to 0.8 g / 100 ml. The mixture was reacted at 0 °C for 25 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 2.4:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 4:1. It was used as a conductive reinforcing filler for thermoplastic polyurethane. The results showed that its elongation at break was 517% and its conductivity was 36.75 × 10⁻⁶. -4 S / cm.

[0067] Example 5

[0068] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0069] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG2000 on the surface of ice placed horizontally, and then add pyrrole monomer. Let stand for 6 minutes to form a dispersion. The mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 3:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.2:1.

[0070] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to obtain a mixed solution with a pyrrole monomer concentration of 0.8 g / 100 ml. The mixture was reacted at 0 °C for 30 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 3:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 3.5:1. This was used as a conductive reinforcing filler for thermoplastic polyurethane. Testing showed that its elongation at break was 522% and its conductivity was 37.13 × 10⁻⁶. -4 S / cm.

[0071] Example 6

[0072] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0073] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG1500 on the surface of ice placed horizontally, and then add pyrrole monomer and let stand for 6 min to form a dispersion; the mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 2.5:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.35:1.

[0074] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to adjust the concentration of pyrrole monomer to 0.8 g / 100 ml. The mixture was reacted at 0 °C for 35 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 3.2:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 2.5:1. It was used as a conductive reinforcing filler for thermoplastic polyurethane. The results showed that its elongation at break was 524% and its conductivity was 37.17 × 10⁻⁶. -4 S / cm.

[0075] Example 7

[0076] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0077] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG2000 on the surface of ice placed horizontally, and then add pyrrole monomer and let stand for 6 min to form a dispersion; the mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 2:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.4:1.

[0078] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to adjust the concentration of pyrrole monomer to 0.8 g / 100 ml. The mixture was reacted at 0 °C for 30 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 3:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 3.5:1. It was used as a conductive reinforcing filler for thermoplastic polyurethane. The results showed that its elongation at break was 526% and its conductivity was 36.86 × 10⁻⁶. -4 S / cm.

[0079] Example 8

[0080] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0081] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG2500 on the surface of ice placed horizontally, and then add pyrrole monomer. Let stand for 5 minutes to form a dispersion. The mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 1.6:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.2:1.

[0082] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to obtain a mixed solution with a pyrrole monomer concentration of 0.8 g / 100 ml. The reaction was carried out at 0 °C for 28 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 2.8:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 3:1. It was used as a conductive reinforcing filler for thermoplastic polyurethane. The test showed that its elongation at break was 523% and its electrical conductivity was 38.42 × 10⁻⁶. -4 S / cm.

[0083] Example 9

[0084] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0085] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG1000 on the surface of ice placed horizontally, and then add pyrrole monomer. Let stand for 7 minutes to form a dispersion. The mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 2:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.25:1.

[0086] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to adjust the concentration of pyrrole monomer to 0.8 g / 100 ml. The mixture was reacted at 0 °C for 32 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 3.5:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 3.7:1. It was used as a conductive reinforcing filler for thermoplastic polyurethane. Testing showed that its elongation at break was 525% and its conductivity was 38.25 × 10⁻⁶. -4 S / cm.

[0087] Example 10

[0088] A method for preparing a high-strength self-supporting polypyrrole nanoarray includes the following steps:

[0089] (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG2000 on the surface of ice placed horizontally, and then add pyrrole monomer and let stand for 6 min to form a dispersion; the mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 2:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.2:1.

[0090] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to obtain a mixed solution with a pyrrole monomer concentration of 0.8 g / 100 ml. The mixture was reacted at 0 °C for 30 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain a high-strength self-supporting polypyrrole nanoarray. The mass ratio of oxidant to pyrrole monomer was 3:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 3.5:1. This was used as a conductive reinforcing filler for thermoplastic polyurethane. Testing showed that its elongation at break was 527% and its conductivity was 38.78 × 10⁻⁶. -4 S / cm.

[0091] Comparative Example 1

[0092] A method for preparing polypyrrole includes the following steps:

[0093] (1) First, disperse the aqueous solution of β-cyclodextrin and polyethylene glycol PEG2000 on the surface of ice placed horizontally, and then add pyrrole monomer and let stand for 6 min to form a dispersion; the mass ratio of β-cyclodextrin to pyrrole monomer is 2:1; the mass ratio of polyethylene glycol to β-cyclodextrin is 0.2:1.

[0094] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to adjust the concentration of pyrrole monomer to 0.8 g / 100 ml. The mixture was reacted at 0 °C for 30 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain polypyrrole. The mass ratio of oxidant to pyrrole monomer was 3:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 3.5:1. It was used as a conductive reinforcing filler for thermoplastic polyurethane. Testing showed that its elongation at break was 477% and its conductivity was 4.02 × 10⁻⁶. -4 S / cm.

[0095] Comparative Example 2

[0096] A method for preparing polypyrrole includes the following steps:

[0097] (1) First, disperse the aqueous solution of pyrrole monomer on the surface of ice placed horizontally, and then add hydroxypropyl-β-cyclodextrin and polyethylene glycol PEG2000. Let stand for 6 min to form a dispersion; the mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is 2:1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is 0.2:1.

[0098] (2) A hydrochloric acid solution containing ammonium persulfate oxidant was added dropwise to the dispersion to adjust the concentration of pyrrole monomer to 0.8 g / 100 ml. The mixture was reacted at 0 °C for 30 min. The product was washed with deionized water and dried in a vacuum drying oven to obtain polypyrrole. The mass ratio of oxidant to pyrrole monomer was 3:1; the molar ratio of hydrochloric acid (HCl) to pyrrole monomer was 3.5:1. It was used as a conductive reinforcing filler for thermoplastic polyurethane. Testing showed that its elongation at break was 483% and its conductivity was 9.51 × 10⁻⁶. -4 S / cm.

[0099] Figure 1 The image shows a scanning electron microscope (SEM) image of the high-strength self-supporting polypyrrole nanoarray prepared in Example 10. As can be seen from the image, the polypyrrole array structure is relatively regular, with well-developed lamellar morphology. The polypyrrole nanosheets are interconnected, forming more uniform pores, which can effectively construct conductive pathways in the matrix resin. This indicates that hydroxypropyl-β-cyclodextrin possesses hydrophobic cavities, improving the dispersion stability of pyrrole in the aqueous phase. Long-chain polyethylene glycol molecules can adsorb onto the surface of droplets or micelles, effectively inhibiting the coalescence of pyrrole droplets through steric hindrance, thus avoiding random three-dimensional aggregation caused by the initial rapid polymerization of pyrrole monomers. This kinetic regulation causes polypyrrole to tend to grow in the form of two-dimensional nanosheets and arrange itself into an array structure along the direction induced by the ice surface.

[0100] Figure 2 The scanning electron microscope (SEM) image of polypyrrole prepared for Comparative Example 1 showed that it did not form a nanosheet array; instead, due to the addition of polyethylene glycol, it exhibited a relatively loose aggregated structure. This is because Comparative Example 1 used hydroxypropyl-free β-cyclodextrin as an adjuvant. When the solution was dispersed on the ice surface, hydroxypropyl-β-cyclodextrin could rapidly accumulate at the ice-water interface and achieve stable anchoring by forming dynamic hydrogen bonds with ice through its peripheral hydroxyl groups. This anchoring not only fixed the cyclodextrin molecules to the ice surface but also oriented its hydrophobic cavities, providing a molecular template for the ordered inclusion of pyrrole monomers and subsequent anisotropic growth. β-cyclodextrin, on the other hand, is completely different. It has a large number of hydroxyl groups distributed inside and outside the molecule, giving it a very strong tendency for intermolecular hydrogen bonding association. In the low-temperature environment of the ice surface, β-cyclodextrin not only has poor dispersibility but also rapidly forms tight two-dimensional crystals or aggregates through hydrogen bonds, rather than anchoring itself to the ice surface as a single molecule. This self-aggregation behavior prevents it from forming a uniformly oriented monolayer template on the ice surface. Its cavity orientation is also disordered, which cannot provide ordered inclusion sites for pyrrole monomers and prevents pyrrole from polymerizing into a regular array structure.

[0101] Figure 3The scanning electron microscope (SEM) image of polypyrrole prepared for Comparative Example 2 also showed that it did not form a regularly arranged array structure, but rather exhibited a large number of irregularly stacked structures. In Comparative Example 2, an aqueous solution of pyrrole monomer was first dispersed on an ice surface, and then hydroxypropyl-β-cyclodextrin was added. This resulted in a large amount of hydroxypropyl-β-cyclodextrin and polyethylene glycol remaining in the bulk solution phase, which was not conducive to the uniform and sequential polymerization of pyrrole monomer and prevented the formation of an array structure.

[0102] Combining the mechanical and electrical conductivity data from various embodiments and comparative examples, it can be seen that the well-organized, high-strength, self-supporting polypyrrole nanoarray structure can significantly disperse the stress on polypyrrole, improving the elongation at break and electrical conductivity of polyurethane composites. This is because the polypyrrole array structure itself is a pre-constructed continuous conductive pathway, without relying on random contact between fillers. Even with very low addition amounts, electrons can be transported long distances along the network skeleton because its network structure remains intact in the resin; during deformation, the array can adapt to deformation through bending, twisting, and sliding of the skeleton, rather than breaking. Even if local microstructure reorganization occurs, the overall conductive pathway can still be maintained. Furthermore, the network structure of the self-supporting polypyrrole nanosheet array can interpenetrate with the resin matrix, uniformly transfer stress, inhibit crack propagation, and easily form a continuous conductive pathway, achieving high conductivity with low addition amounts. Among them, the three-dimensional polypyrrole array, as a continuous reinforcing phase, forms an interpenetrating network structure in the resin matrix, which can efficiently conduct electrons and transfer loads through mechanical interlocking and interfacial bonding. Meanwhile, inorganic nanoparticles dispersed in the polyurethane matrix play a role at the nanoscale. They act as stress concentration points, inducing craze formation, consuming fracture energy, and restricting chain segment movement through interfacial interactions with the polyurethane molecular chains. This synergistic effect of macroscopic network and multi-level reinforcement by nanoparticles can significantly improve the tensile strength of the composite material while maintaining the elongation at break, overcoming the embrittlement defects caused by traditional high-filler systems.

[0103] Specifically, compared to Example 10, Comparative Example 1, using hydroxypropyl-free β-cyclodextrin as an additive, could not produce a sheet-like polypyrrole array structure, but instead formed an irregularly stacked structure. Although the irregularly stacked polypyrrole structure can also provide reinforcement, due to its geometric limitations, there are fewer connection points between them, making it difficult to construct a conductive network. At the same time, local stress concentration is prone to occur under external forces, leading to a deterioration in the mechanical properties and electrical conductivity of the polyurethane composite material.

[0104] The preparation process of Comparative Example 2 differs from that of Example 10. In Comparative Example 2, an aqueous solution of pyrrole monomer was first dispersed on an ice surface, and then hydroxypropyl-β-cyclodextrin was added. The pyrrole monomer added first is in a free-diffusion state in the solution and cannot form specific adsorption on the ice surface. It will occupy the anchoring sites of the subsequent hydroxypropyl-β-cyclodextrin, resulting in a large amount of hydroxypropyl-β-cyclodextrin and polyethylene glycol remaining in the bulk solution phase. The polymerization reaction takes place in the bulk solution phase, which is not conducive to the uniform and sequential polymerization of pyrrole monomer, and it is impossible to form a porous array structure. The wettability of the melt deteriorates during processing, which is not conducive to improving product performance.

[0105] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for preparing a high-strength self-supporting polypyrrole nanoarray, characterized in that, Includes the following steps: (1) First, disperse the aqueous solution of hydroxypropyl-β-cyclodextrin and polyethylene glycol on the ice surface, then add pyrrole monomer, and let stand to form a dispersion; the mass ratio of hydroxypropyl-β-cyclodextrin to pyrrole monomer is (1-3):1; the mass ratio of polyethylene glycol to hydroxypropyl-β-cyclodextrin is (0.1-0.4):1; (2) An acid solution containing an oxidant is added dropwise to a dispersion, and after reaction, a high-strength self-supporting polypyrrole nanoarray is obtained after washing and drying; the oxidant is one or more of ammonium persulfate, potassium persulfate, and sodium persulfate.

2. The method for preparing a high-strength self-supporting polypyrrole nanoarray as described in claim 1, characterized in that, In step (1), the number-average molecular weight of polyethylene glycol is 1000-10000.

3. The method for preparing a high-strength self-supporting polypyrrole nanoarray as described in claim 1, characterized in that, In step (2), the acid is one or more of organic or inorganic acids.

4. The method for preparing a high-strength self-supporting polypyrrole nanoarray as described in claim 3, characterized in that, The organic acid is one or more of p-toluenesulfonic acid, dodecylbenzenesulfonic acid, sodium dodecyl sulfonate, camphorsulfonic acid, sulfosalicylic acid, and oxalic acid.

5. The method for preparing a high-strength self-supporting polypyrrole nanoarray as described in claim 3, characterized in that, The inorganic acid is one or more of sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid.

6. The method for preparing a high-strength self-supporting polypyrrole nanoarray as described in claim 1, characterized in that, The drying step (2) is performed by placing the product in a vacuum drying oven.

7. A high-strength self-supporting polypyrrole nanoarray, characterized in that, It is prepared by the method for preparing a high-strength self-supporting polypyrrole nanoarray according to any one of claims 1-6.

8. An application of the high-strength self-supporting polypyrrole nanoarray as described in claim 7, characterized in that, The high-strength self-supporting polypyrrole nanoarray is used in 3D printing technologies such as photopolymerization, selective laser sintering, fused deposition modeling, or layered solid manufacturing.

9. A 3D printing polyurethane material, characterized in that, It comprises polyurethane resin material, a high-strength self-supporting polypyrrole nanoarray, and inorganic reinforcing filler; the high-strength self-supporting polypyrrole nanoarray is the high-strength self-supporting polypyrrole nanoarray as described in claim 7.

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