Polyvinylidene fluoride piezoelectric material, method for preparing the same, and piezoelectric power generation device
By introducing pullulan and surfactants into PVDF, and promoting β-phase crystallization through hydrogen bonding and physical cross-linking networks, the problem of insufficient piezoelectric properties of PVDF piezoelectric films was solved, and efficient and low-cost preparation of PVDF piezoelectric materials was achieved.
Patent Information
- Application Number
- CN202610853060.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-12
- Publication Date
- 2026-08-25
AI Technical Summary
Existing technologies are difficult to efficiently prepare PVDF piezoelectric films rich in β-phase, resulting in insufficient piezoelectric properties. Furthermore, traditional processes are complex, costly, and the polarization direction is easily affected by the pore structure.
Pullulan and surfactants were introduced into the PVDF component to prepare PVDF piezoelectric materials via a non-solvent-induced phase separation method. The hydroxyl groups of pullulan formed hydrogen bonds and physical cross-linking networks with PVDF, which restricted the mobility of molecular chains and promoted β-phase crystallization. Combined with the pore-forming effect of the surfactant, a homogeneous through-network was formed.
The increased β-phase content in PVDF materials enhances piezoelectric properties, simplifies the preparation process, reduces production costs, and achieves a more uniform polarization effect.
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Figure CN122628463A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of piezoelectric materials technology, specifically to a polyvinylidene fluoride piezoelectric material, its preparation method, and a piezoelectric power generation device. Background Technology
[0002] Polyvinylidene fluoride (PVDF) is a semi-crystalline fluoropolymer whose molecular chains consist of alternating -CH2- and -CF2- groups. Its piezoelectric properties stem from its unique polycrystalline structure. The β phase, corresponding to the all-trans planar zigzag chain configuration (TTTT configuration), possesses the highest spontaneous polarization intensity and piezoelectric activity. Its dipole moment is perpendicular to the polymer backbone, enabling significant charge separation under external forces. The α phase, composed of the trans-lateral configuration (TGTG' configuration), is the most thermodynamically stable crystal form, but due to its non-polar crystal structure, it exhibits almost no piezoelectric activity. Therefore, preparing PVDF materials rich in the β phase is crucial for achieving high piezoelectric properties.
[0003] The basic principle of non-solvent-induced phase separation (NIPS) is to dissolve the polymer in a suitable solvent to form a homogeneous casting solution, which is then immersed in a coagulation bath. Through the dual diffusion exchange between the solvent and non-solvent, the thermodynamic state of the polymer solution becomes unstable, resulting in liquid-liquid or solid-liquid phase separation. Ultimately, the polymer-rich phase solidifies into a three-dimensional network framework structure, while the polymer-depleted phase is eluted to form a continuous or semi-continuous microporous structure. However, the crystallization of PVDF depends on the ordered arrangement of polymer molecular chains. The rapid solvent-non-solvent exchange during phase separation usually causes the polymer to precipitate rapidly, leaving insufficient time and space for ordered chain folding and crystal growth. This results in films dominated by amorphous or low-crystallinity α-phase, making it difficult to form a high-content β-phase. Furthermore, traditional NIPS research has primarily focused on separation membranes, aiming for high throughput, high selectivity, and good antifouling properties, with little attention paid to the piezoelectric properties of the films. The fabrication process of most PVDF piezoelectric films still follows a step-by-step model of "film formation-crystallization control-polarization." The phase separation process is mainly used to control the pore structure, while the induction of the β-phase depends on additional mechanical stretching, high-temperature annealing, or high-voltage polarization treatment. This not only prolongs the process and increases production costs, but also makes it difficult to achieve uniform and stable polarization in porous films because the spontaneous polarization direction obtained under the action of an external electric field is easily affected by the pore structure.
[0004] In view of this, a method for preparing PVDF piezoelectric thin films with high β-phase content and significant piezoelectric properties based on a non-solvent phase separation method is provided, which is of great significance for expanding the application of PVDF piezoelectric materials in cutting-edge fields such as sensors, energy harvesting, and flexible electronics. Summary of the Invention
[0005] To address the problems existing in the prior art, the present invention provides a polyvinylidene fluoride piezoelectric material, the raw materials of which, by mass, include 1-1.5 parts of polyvinylidene fluoride and 0-0.3 parts of pullulan, wherein the endpoint 0 is unavailable.
[0006] Furthermore, its raw materials also include 0-0.2 parts by weight of surfactant, wherein endpoint 0 is unavailable.
[0007] Furthermore, the surfactant is sodium dodecyl sulfate.
[0008] This invention also provides a method for preparing a polyvinylidene fluoride piezoelectric material, comprising, by weight, Dissolve 1-1.5 parts of polyvinylidene fluoride and 0-0.3 parts of pullulan in 8-9 parts of solvent to obtain a casting solution. The endpoint 0 of pullulan cannot be obtained. After degassing and aging the casting solution, it is cast and uniformly dispersed on the substrate surface. Then it is transferred to a phase separating agent, and the insoluble matter is collected to obtain polyvinylidene fluoride piezoelectric material.
[0009] Furthermore, the dissolution process includes stirring at a temperature of 40-80°C and a rotation speed of 200-600 rpm for 2-8 hours.
[0010] Furthermore, the aging process includes sealing and standing at a temperature of 40-80°C for 6-13 hours.
[0011] Furthermore, the solvent includes at least one selected from N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone.
[0012] Furthermore, the phase separating agent includes at least one of water, salt solution, alcohol, and alcohol solution.
[0013] Furthermore, during the mixing and dissolution process, 0-0.2 parts by mass of a surfactant are added, wherein endpoint 0 is unavailable.
[0014] The present invention also provides a piezoelectric power generation device comprising the above-mentioned polyvinylidene fluoride piezoelectric material.
[0015] Compared with the prior art, the beneficial effects of the present invention include: Pullulan, a polysaccharide, is introduced into the polyvinylidene fluoride (PVDF) composition. Each glucose unit of pullulan contains three hydroxyl groups, which can form dense OH···FC hydrogen bonds along the -CF2- backbone of PVDF. This multi-point hydrogen bonding forces the PVDF molecular chains to extend and adopt the more energy-favorable all-trans conformation, thus directly nucleating into the β phase during crystallization, rather than the α phase. Furthermore, the water solubility and highly compliant segments of pullulan result in more uniform dispersion and a higher nucleation density. In other words, the long chains of pullulan extensively entangle with PVDF and form a physical cross-linking network through hydrogen bonds, greatly restricting the mobility of the PVDF molecular chains and "locking" the formed β-phase conformation, preventing it from relaxing back to the α phase. This stabilizing effect ensures that a high content of the β phase is retained in the final material, thereby improving the piezoelectric properties of the material.
[0016] The polyvinylidene fluoride piezoelectric material of the present invention has a simple composition, and the pullulan polysaccharide used is a special microbial polysaccharide, which gives it good biodegradability and broad application prospects.
[0017] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.
[0019] Figure 1 The infrared absorption peak spectra of the materials obtained in Comparative Example 1 and Examples 2-7 are shown. Figure 2 The relative proportions of the active phase in the materials obtained in Comparative Example 1 and Examples 2-7 are shown. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.
[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0023] Pullulan is composed of glucose residues linked by α-1,4-glycosidic bonds to form maltotriose units, which are then linked by α-(1→6) glycosidic bonds to form a high molecular chain structure. Each glucose unit retains multiple hydroxyl groups, exhibiting good water solubility, dispersibility, and film-forming properties. Its aqueous solution has low viscosity, does not easily form colloids, and is a neutral solution with strong adhesion. It has good solubility, dissolving rapidly in cold water, and the solution is stable over a long period without aging, and is not easily affected by pH or various salts.
[0024] The concept of this invention lies in introducing pullulan into the components of polyvinylidene fluoride (PVDF). The piezoelectricity of PVDF originates from its β phase (all-trans TTTT configuration), while pure PVDF, during conventional NIPS film formation, often forms a non-piezoelectric α phase (TGTG' configuration). Each glucose unit of pullulan contains three hydroxyl groups, which can form dense OH···FC hydrogen bonds along the -CF2- backbone of PVDF. This multi-point hydrogen bonding forces the PVDF molecular chains to extend, adopting the more energy-favorable all-trans conformation, thus directly nucleating into the β phase during crystallization, rather than the α phase. Furthermore, the water solubility and highly compliant segments of pullulan result in more uniform dispersion and a higher nucleation density. In other words, the long chains of pullulan extensively entangle with PVDF, forming a physical cross-linking network through hydrogen bonds, greatly restricting the mobility of the PVDF molecular chains and "locking" the formed β phase conformation, preventing it from relaxing back to the α phase. This stabilizing effect ensures that a high content of the β phase is retained in the final material.
[0025] Accordingly, on the one hand, the present invention provides a polyvinylidene fluoride piezoelectric material, the raw materials of which include, by mass, 1-1.5 parts of polyvinylidene fluoride and 0-0.3 parts of pullulan, wherein the endpoint 0 is unavailable.
[0026] In some preferred embodiments, the raw materials also include 0-0.2 parts by weight of a surfactant, wherein endpoint 0 is unavailable.
[0027] In some preferred embodiments, the surfactant is sodium dodecyl sulfate (SDS).
[0028] Sodium dodecyl sulfate, as a small-molecule surfactant, can rapidly migrate to the interface to form micelles, thus creating pores in the initial stage. Pullulan, due to its high viscosity and macromolecular characteristics, acts as a stabilizer and connecting bridge for these pores, preventing the collapse of the pore structure in the later stages and forming a homogeneous, interconnected network.
[0029] On the other hand, the present invention provides a method for preparing a polyvinylidene fluoride piezoelectric material, comprising, by weight, Dissolve 1-1.5 parts of polyvinylidene fluoride and 0-0.3 parts of pullulan in 8-9 parts of solvent to obtain a casting solution. The endpoint 0 of pullulan cannot be obtained. After degassing and aging the casting solution, it is cast and uniformly dispersed on the substrate surface. Then it is transferred to a phase separating agent, and the insoluble matter is collected to obtain polyvinylidene fluoride piezoelectric material.
[0030] As some preferred embodiments, the dissolution includes stirring at a temperature of 40-80°C and a rotation speed of 200-600 rpm for 2-8 hours.
[0031] As some preferred embodiments, the curing process includes sealing and standing at a temperature of 40-80°C for 6-13 hours.
[0032] The material of the substrate is not strictly limited, as long as it has at least one flat and smooth surface. Examples include glass, stainless steel, and silicon wafers.
[0033] The main mechanisms involved in the preparation of this product using PVDF and pullulan as raw materials are as follows: All-trans conformation induced by hydrogen bonds: Each glucose unit of pullulan contains three hydroxyl groups, which can form dense OH···FC hydrogen bonds along the -CF2- backbone of PVDF. This multi-point hydrogen bonding forces the PVDF molecular chain to extend and adopt the more energy-favorable all-trans conformation, thus directly nucleating into the β phase during crystallization, rather than the α phase. Furthermore, the water solubility and highly compliant segments of pullulan result in more uniform dispersion and a higher nucleation density.
[0034] Physical cross-linking inhibition: The long chains of pullulan become extensively entangled with PVDF and form a physical cross-linking network through hydrogen bonds, which greatly restricts the mobility of PVDF molecular chains and "locks" the formed β-phase conformation, preventing it from relaxing back to the α-phase. This stabilizing effect ensures that a high content of the β-phase is retained in the final dry film.
[0035] Delayed phase separation and promoted crystallization: Pullulan significantly increases the viscosity of the casting solution. When immersed in the coagulation bath (even just pure water or ethanol solution), it simultaneously reduces the rate of inward diffusion of non-solvents (such as water) and the rate of outward diffusion of solvents, thus achieving delayed phase separation. Delayed phase separation provides PVDF molecular chains with more time for conformational adjustment and regular arrangement, which is beneficial for the full growth of β-phase crystals in a homogeneous solution, rather than rapid freezing into amorphous or α-phase microcrystals. This is completely different from the case of instantaneous liquid-liquid phase separation, which forms finger-like macropores and has a low β-phase content. Pullulan helps to form a dense or sponge-like structure rich in spherulites, and the interior of the spherulites is precisely the enriched region of the β-phase.
[0036] As some preferred embodiments, the solvent includes at least one selected from N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone.
[0037] As some preferred embodiments, the phase separating agent includes at least one of water, salt solution, alcohol, and alcohol solution.
[0038] As some preferred embodiments, 0-0.2 parts by weight of a surfactant are added during the mixing and dissolution process, wherein endpoint 0 is unavailable.
[0039] The main mechanisms involved in the preparation of this product using PVDF, pullulan, and surfactants are as follows: The combination of instantaneous phase separation and liquid-solid phase separation: Conventional PVDF / solvent / phase separation systems mostly involve instantaneous liquid-liquid phase separation, which easily forms finger-like macropores and a dense skin layer, hindering the full formation of the β phase (electroactive phase). The introduction of pullulan alters the thermodynamic stability of the casting solution. Its numerous hydroxyl groups have a strong affinity for water (non-solvent), accelerating the inward diffusion of non-solvent when immersed in a salt-containing ethanol coagulation bath, while simultaneously slowing the outward diffusion of solvent due to its large molecular chain entanglement. This asymmetric mass transfer process, combined with the enrichment of pullulan molecules in specific regions acting as a physical template, promotes the formation of sponge-like or spherulite-like stacked structures. This three-dimensional continuous network provides more space for the PVDF molecular chains to extend, which is beneficial for crystallization into the β phase conformation (all-trans TTTT conformation).
[0040] SDS-mediated pore formation: As a small-molecule surfactant, SDS can rapidly migrate to the interface to form micelles, thus initiating pore formation. Pullulan, due to its high viscosity and macromolecular characteristics, acts as a stabilizer and bridge for these pores, preventing the pore structure from collapsing in the later stages of solvent exchange and forming a homogeneous, interconnected network. The charged sulfate root group of SDS generates a strong ion-dipole interaction with the -CF2- dipole of PVDF, forcing the PVDF molecular chain to crystallize in an all-trans (TTTT) conformation. Each sugar unit on the pullulan molecular chain has three hydroxyl groups, which can form multiple OH···FC hydrogen bonds with the -CF2- groups of PVDF on the basis of the β-phase rudimentary structure induced by SDS.
[0041] In some preferred embodiments, the phase separating agent also contains inorganic ions, which, upon entering the matrix, undergo complex interfacial adsorption with pullulan and SDS. Anions may preferentially adsorb around the hydrophilic end of SDS, while cations complex with pullulan through ion-dipole interactions. This forms an organic-inorganic composite microcapacitor network with pullulan / SDS as the framework and inorganic salt ions as charge carriers. This spontaneous polarization enables the material to exhibit excellent piezoelectricity.
[0042] The present invention will be further described in detail below through specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.
[0043] Example 1 A method for preparing a polyvinylidene fluoride piezoelectric material includes the following steps: (1) Mix 0.3g pullulan polysaccharide with 8.5g N,N-dimethylacetamide and stir at 400rpm for 6h at 60℃. During this period, add 1.2g polyvinylidene fluoride in batches to obtain casting solution.
[0044] (2) After vacuum degassing the casting solution, it is sealed and left to stand for 5 hours at 50°C to obtain a bubble-free casting solution.
[0045] (3) At room temperature, the bubble-free casting solution is cast onto a clean glass plate surface and uniformly dispersed on the glass plate using a scraper with a gap of 200 μm. Then, the glass plate is placed flat and immersed in a 0.1% ethanol solution at room temperature, resulting in non-solvent phase separation.
[0046] (4) After the solvent is completely exchanged, the material is naturally peeled off from the glass plate and transferred to deionized water for 24 hours. The water is changed every 12 hours during this period to remove the residual solvent. Finally, it is dried to obtain polyvinylidene fluoride piezoelectric material.
[0047] Example 2 A method for preparing a polyvinylidene fluoride piezoelectric material includes the following steps: (1) Mix 0.3g pullulan polysaccharide with 8.5g N,N-dimethylacetamide and stir at 400rpm for 6h at 60℃. During this period, add 1.2g polyvinylidene fluoride in batches to obtain casting solution.
[0048] (2) After vacuum degassing the casting solution, it is sealed and left to stand for 5 hours at 50°C to obtain a bubble-free casting solution.
[0049] (3) At room temperature, the bubble-free casting solution is cast onto a clean glass plate surface and uniformly dispersed on the glass plate using a scraper with a gap of 200 μm. Then, the glass plate is placed flat and immersed in a 0.1% ethanol solution containing 5 g / L sodium chloride at room temperature, resulting in non-solvent phase separation.
[0050] (4) After the solvent is completely exchanged, the material is naturally peeled off from the glass plate and transferred to deionized water for 24 hours. The water is changed every 12 hours during this period to remove the residual solvent. Finally, it is dried to obtain polyvinylidene fluoride piezoelectric material.
[0051] Example 3 A method for preparing a polyvinylidene fluoride piezoelectric material includes the following steps: (1) Mix 0.3g pullulan polysaccharide and 0.02g sodium dodecyl sulfate with 8.48g N,N-dimethylacetamide and stir at 400rpm for 6h at 60℃. During the stirring, add 1.2g polyvinylidene fluoride in batches to obtain casting solution.
[0052] (2) After vacuum degassing the casting solution, it is sealed and left to stand for 5 hours at 50°C to obtain a bubble-free casting solution.
[0053] (3) At room temperature, the bubble-free casting solution is cast onto a clean glass plate surface and uniformly dispersed on the glass plate using a scraper with a gap of 200 μm. Then, the glass plate is placed flat and immersed in a 0.1% ethanol solution containing 5 g / L sodium chloride at room temperature, resulting in non-solvent phase separation.
[0054] (4) After the solvent is completely exchanged, the material is naturally peeled off from the glass plate and transferred to deionized water for 24 hours. The water is changed every 12 hours during this period to remove the residual solvent. Finally, it is dried to obtain polyvinylidene fluoride piezoelectric material.
[0055] Examples 4-7 The difference from Example 3 is that the amount of sodium dodecyl sulfate used in step (1) is 0.05g, 0.1g, 0.15g and 0.2g, respectively, while the amount of N,N-dimethylacetamide is 8.45g, 8.4g, 8.35g and 8.3g, respectively.
[0056] Comparative Example 1 A method for preparing polyvinylidene fluoride (PVDF) material includes the following steps: (1) Mix 8.5g of N,N-dimethylacetamide and stir at 400rpm for 6h at 60℃, during which 1.5g of polyvinylidene fluoride is added in batches to obtain casting solution.
[0057] (2) After vacuum degassing the casting solution, it is sealed and left to stand for 5 hours at 50°C to obtain a bubble-free casting solution.
[0058] (3) At room temperature, the bubble-free casting solution is cast onto a clean glass plate surface and uniformly dispersed on the glass plate using a scraper with a gap of 200 μm. Then, the glass plate is placed flat and immersed in a 0.1% ethanol solution at room temperature, resulting in non-solvent phase separation.
[0059] (4) After the solvent is completely exchanged, the material is naturally peeled off from the glass plate and transferred to deionized water for 24 hours. The water is changed every 12 hours during this period to remove the residual solvent. Finally, it is dried to obtain polyvinylidene fluoride material.
[0060] Test case Infrared spectroscopy was used to characterize the chemical bond types and functional group compositions of the materials prepared in the examples and comparative examples, such as... Figure 1 As shown in the figure, P0 represents Comparative Example 1, and PNO-PN2 represent Examples 2-7, respectively. It can be seen that in the system formed by polyvinylidene fluoride, pullulan, sodium dodecylbenzenesulfonate, and solvent, adding sodium dodecylbenzenesulfonate in different mass proportions is beneficial to reducing the formation of the α phase.
[0061] The relative proportions of the active phase in Comparative Example 1 and Examples 2-7 were also tested, such as... Figure 2 As shown, in the system formed by polyvinylidene fluoride, pullulan, sodium dodecylbenzenesulfonate, and solvent, it can be seen that when the proportion of sodium dodecylbenzenesulfonate is 0.2% (Example 3), further increasing the amount of sodium dodecylbenzenesulfonate does not significantly change the proportion of the relative active phase. These results also indicate that the method of the present invention can effectively promote the formation of the β phase of polyvinylidene fluoride.
[0062] ZJ-3AN type quasi-static D33 The measuring instrument measures the piezoelectric constant D of the piezoelectric materials obtained in the examples and comparative examples. 33 Tests were conducted; a 10N reciprocating force was applied to the piezoelectric materials obtained in the examples and comparative examples, and their open-circuit voltage was tested; the surface potential of the materials obtained in the examples and comparative examples was detected using Kelvin probe force microscopy (KPFM) under different applied electric fields. These test results are shown in Table 1.
[0063] Table 1 D of piezoelectric materials 33 Open-circuit voltage and surface potential results
[0064] As can be seen from the test results in Table 1, this invention can construct a piezoelectric material using pullulan and polyvinylidene fluoride (PVDF). This is due to the extensive entanglement of the long chains of pullulan with PVDF and the formation of a physical cross-linking network through hydrogen bonds, which greatly restricts the mobility of the PVDF molecular chains and "locks" the formed β-phase conformation, preventing it from relaxing back to the α-phase. This stabilizing effect ensures that a high content of the β-phase is retained in the final material, thereby improving the piezoelectric performance. Compared to Example 1, Example 2 uses a 0.1% ethanol solution containing 5 g / L sodium chloride instead of a 0.1% ethanol solution as the phase separating agent, and its piezoelectric response is also significantly improved, exhibiting a higher open-circuit voltage. This is because the phase separating agent also contains inorganic ions, which, after entering the membrane matrix, will form complex interfacial adsorption with pullulan and SDS. Anions may preferentially adsorb around the hydrophilic end of SDS, while cations complex with pullulan through ion-dipole interactions, forming an organic-inorganic composite microcapacitor network with inorganic salt ions as charge carriers, thereby significantly improving the piezoelectric performance. Compared to Comparative Example 2, Example 3 also included sodium dodecylbenzenesulfonate. SDS, as a small-molecule surfactant, rapidly migrates to the interface to form micelles, initially creating pores. Pullulan, due to its high viscosity and macromolecular characteristics, acts as a stabilizer and bridge for these pores, preventing the pore structure from collapsing in the later stages of solvent exchange, thus forming a homogeneous, interconnected network. The charged sulfate root group of SDS generates a strong ion-dipole interaction with the -CF2- dipole of PVDF, forcing the PVDF molecular chain to crystallize in an all-trans (TTTT) conformation. Each sugar unit on the pullulan molecular chain has three hydroxyl groups, which can form multiple OH···FC hydrogen bonds with the -CF2- groups of PVDF on the basis of the SDS-induced β-phase rudimentary structure. Ultimately, an organic-inorganic composite microcapacitor network with pullulan / SDS as the backbone and inorganic salt ions as charge carriers is formed, further improving the piezoelectric properties of the material.
[0065] In summary, the introduction of pullulan into the polyvinylidene fluoride (PVDF) composition, with each glucose unit containing three hydroxyl groups, allows for the formation of dense OH···FC hydrogen bonds along the -CF2- backbone of PVDF. This multi-point hydrogen bonding forces the PVDF molecular chains to extend, adopting the more energy-favorable all-trans conformation, thus directly nucleating into the β phase during crystallization, rather than the α phase. Furthermore, the water solubility and highly compliant segments of pullulan result in more uniform dispersion and higher nucleation density. In other words, the long chains of pullulan extensively entangle with PVDF, forming a physical cross-linking network through hydrogen bonds, significantly restricting the mobility of the PVDF molecular chains and "locking" the formed β-phase conformation, preventing it from relaxing back to the α phase. This stabilizing effect ensures a high content of the β phase in the final material, thereby improving its piezoelectric properties. In addition, the addition of sodium dodecyl sulfate and the organic ions in the phase separating agent can form with pullulan, significantly enhancing the piezoelectric properties of the material.
[0066] Furthermore, the polyvinylidene fluoride piezoelectric material of the present invention has a simple composition, and the pullulan polysaccharide used is a special microbial polysaccharide, which gives it good biodegradability and broad application prospects.
[0067] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A polyvinylidene fluoride piezoelectric material, characterized in that, Its raw materials, by weight, include 1-1.5 parts polyvinylidene fluoride and 0-0.3 parts pullulan, wherein the endpoint 0 is unavailable.
2. The polyvinylidene fluoride piezoelectric material according to claim 1, characterized in that, Its raw materials also include 0-0.2 parts by weight of surfactant, wherein endpoint 0 is unavailable.
3. The polyvinylidene fluoride piezoelectric material according to claim 2, characterized in that, The surfactant is sodium dodecyl sulfate.
4. A method for preparing a polyvinylidene fluoride piezoelectric material, characterized in that, Included by weight parts, Dissolve 1-1.5 parts of polyvinylidene fluoride and 0-0.3 parts of pullulan in 8-9 parts of solvent to obtain a casting solution. The endpoint 0 of pullulan cannot be obtained. After degassing and aging the casting solution, it is cast and uniformly dispersed on the substrate surface. Then it is transferred to a phase separating agent, and the insoluble matter is collected to obtain polyvinylidene fluoride piezoelectric material.
5. The method for preparing polyvinylidene fluoride piezoelectric material according to claim 4, characterized in that, The dissolution process includes stirring at a temperature of 40-80°C and a speed of 200-600 rpm for 2-8 hours.
6. The method for preparing polyvinylidene fluoride piezoelectric material according to claim 4, characterized in that, The aging process includes sealing and standing at a temperature of 40-80℃ for 6-13 hours.
7. The method for preparing polyvinylidene fluoride piezoelectric material according to claim 4, characterized in that, The solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and acetone.
8. The method for preparing polyvinylidene fluoride piezoelectric material according to claim 4, characterized in that, The phase separating agent includes at least one of water, salt solution, alcohol, and alcohol solution.
9. The method for preparing polyvinylidene fluoride piezoelectric material according to claim 4, characterized in that, During the mixing and dissolution process, 0-0.2 parts by mass of surfactant are added, wherein endpoint 0 is unavailable.
10. A piezoelectric power generation device, characterized in that, The polyvinylidene fluoride piezoelectric material comprising any one of claims 1-3.