High-voltage, low-modulus polymer alloy and method of making

Abstract

The application relates to the technical field of organic functional material preparation, and provides a high piezoelectricity low modulus polymer alloy and a preparation method, the preparation method comprises the following steps: S1, dissolving dimers P(VDF-TrFE) and trimers P(VDF-TrFE-CFE) with different proportions into a polar solvent to form a mixed solution; S2, forming a thin film of the mixed solution on a substrate, crystallizing and annealing to obtain a piezoelectric polymer alloy; and S3, polarizing the piezoelectric polymer alloy by using a strong electric field, thereby obtaining the high piezoelectricity low modulus polymer alloy. The two organic polymer molecules are compatible at the molecular level, the crystallization temperature and the annealing temperature are controlled, the molecular chain conformation and the phase structure are regulated by using components and a polarization electric field, the morphotropic phase boundary is induced, the high piezoelectricity and the low Young's modulus of the polymer alloy are realized, and the foundation is laid for constructing high-performance piezoelectric devices. The material system used by the application is simple and controllable, the manufacturing cost is low, and the application has great commercial value and practical significance.

Description

Technical Field

[0001] This invention relates to the field of organic functional material preparation technology, and in particular to a high-voltage low-modulus polymer alloy and its preparation method. Background Technology

[0002] Organic piezoelectric materials are indispensable materials in electromechanical systems and have been used in medical ultrasound imaging, wearable sensors, underwater sonar, and actuators. To meet the increasing performance demands of piezoelectric devices, especially high-frequency medical ultrasound imaging and wearable ultra-low voltage sensing, there is an urgent need for high-performance organic materials. However, most organic piezoelectric materials have low quasi-static piezoelectric coefficients (dp). 33 <Approximately -25 pC / N).

[0003] Currently, there are two main methods to improve piezoelectric properties. One method is to increase the content of polar phases through directional stretching, annealing, or doping with polar materials, thereby increasing piezoelectric properties. However, this method reduces the number of molecular conformations in organic materials, increases crystallinity, or enhances the interaction between molecular chains, resulting in a high Young's modulus (>1 GPa). A high Young's modulus leads to poor mechanical compatibility between organic piezoelectric materials and the substrate, significantly hindering their application, especially in wearable devices and bioelectronics. This is because mechanical compatibility with human tissue requires materials with a low Young's modulus (<400 MPa) to ensure long-term biointegration and reduce foreign body reactions.

[0004] Another approach is to induce biphasic competing quasi-isomorphic phase boundaries (MPBs) in organic piezoelectric materials through compositional differences. Due to the unstable polarization states at the MPBs, the polarization direction is easily reversed by external electric fields or stresses, resulting in high piezoelectric properties. However, MPBs have not yet been achieved in other organic piezoelectric materials besides dimer P(VDF-TrFE) (49 / 51 mol%), because the molecular conformation of organic piezoelectric materials is easily altered under an external electric field, with two phases of similar energy directly transforming into a single phase. Therefore, preparing high-performance organic materials without significantly increasing Young's modulus remains an unprecedented challenge. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-voltage, low-modulus polymer alloy and its preparation method. By achieving molecular-level compatibility and molecular chain conformation control of P(VDF-TrFE) (polyvinylidene fluoride-trifluoroethylene) and P(VDF-TrFE-CFE) (polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene), a high-voltage, low-modulus polymer alloy with quasi-isomorphic phase boundaries is prepared.

[0006] The present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a method for preparing a high-voltage low-modulus polymer alloy, comprising:

[0008] S1. Dissolve dimer P (VDF-TrFE) and trimer P (VDF-TrFE-CFE) in different ratios in a polar solvent to form a mixed solution;

[0009] S2. The mixed solution obtained in step S1 is used to form a thin film on a substrate, crystallized and annealed to obtain a piezoelectric polymer alloy.

[0010] S3. Polarize the piezoelectric polymer alloy obtained in step S2 with a strong electric field to obtain the high-voltage low-modulus polymer alloy.

[0011] In addition to any of the possible implementations described above, another implementation is provided in which, in step S1, the TrFE content in dimer P (VDF-TrFE) is 20 mol% to 70 mol%; and the CFE content in trimer P (VDF-TrFE-CFE) is 6 mol% to 12 mol%.

[0012] In addition to any of the possible implementations described above, an implementation is further provided in which, in step S1, the mass fraction of dimer P(VDF-TrFE) in both dimer P(VDF-TrFE) and trimer P(VDF-TrFE-CFE) is 10 wt% to 50 wt%.

[0013] It should be noted that when the TrFE content in dimer P (VDF-TrFE) and the CFE content in trimer P (VDF-TrFE-CFE) are not within the above range, quasi-isomorphic phase boundaries (MPB) cannot be generated, and the performance of the piezoelectric polymer alloy cannot be effectively improved.

[0014] In addition to any of the possible implementations described above, another implementation is provided in which, in step S1, the polar solvent is one of hexamethylphosphoric triamine, tetrahydrofuran, dimethyl sulfoxide, acetonitrile, dimethylformamide, nitromethane, acetone, and pyridine.

[0015] In addition to any of the possible implementations described above, a further implementation is provided in which, in step S1, the dimer P (VDF-TrFE) and trimer P (VDF-TrFE-CFE) are molecularly compatible. Molecularly compatible means that each molecular chain of the two polymers is dispersed together. The criterion for judging molecularly compatibleness is whether the two polymers form a single glass transition temperature. If there is only one glass transition temperature, molecularly compatibleness is achieved. Achieving molecularly compatibleness requires strong interactions between the polymer molecular chains.

[0016] In addition to any of the possible implementations described above, another implementation is provided in which the crystallization temperature in step S2 is 40–100°C and the crystallization time is 2–48 h.

[0017] In addition to any of the possible implementations described above, another implementation is provided in which, in step S2, the annealing temperature is 90–150°C and the annealing time is 10 min–48 h; the resulting piezoelectric polymer alloy has only one glass transition temperature Tg.

[0018] It should be noted that if the crystallization temperature and annealing temperature exceed the above range, the piezoelectric polymer alloy will not crystallize well, and its performance will be difficult to improve effectively.

[0019] In addition to any of the possible implementations described above, another implementation is provided in which, after polarization in step S3, the high-voltage low-modulus polymer alloy has two phases coexisting: a fully trans phase (β phase) and a 3 / 1-helical phase, forming a quasi-isomorphic phase boundary.

[0020] On the other hand, the present invention also provides a high-voltage low-modulus polymer alloy, which is prepared by the above-described method for preparing high-voltage low-modulus polymer alloy.

[0021] In addition to any of the possible implementations described above, a further implementation is provided in which the piezoelectric low-modulus polymer alloy has a piezoelectric coefficient greater than 32 pC / N and a Young's modulus as low as 200 MPa.

[0022] The beneficial effects of this invention are as follows: By achieving molecular-level compatibility between two organic polymers and controlling the crystallization and annealing temperatures, a polymer alloy is prepared; by utilizing composition and polarization electric fields to regulate the molecular chain conformation and phase structure, quasi-isomorphic phase boundaries are induced, achieving high piezoelectricity and low Young's modulus in the polymer alloy, laying the foundation for constructing high-performance piezoelectric devices. The material system used in this invention is simple and controllable, with low manufacturing costs, possessing significant commercial value and practical significance. Attached Figure Description

[0023] Figure 1 Glass transition temperature based on P(VDF-TrFE)(80 / 20mol%) high-voltage low-modulus polymer alloy.

[0024] Figure 2 Phase structure based on P(VDF-TrFE)(80 / 20mol%) high voltage low modulus polymer alloy.

[0025] Figure 3 The piezoelectric coefficient of a P(VDF-TrFE) (80 / 20mol%) high-voltage low-modulus polymer alloy.

[0026] Figure 4Stress-strain curves of P(VDF-TrFE) (80 / 20mol%) high-voltage low-modulus polymer alloys (Young's modulus can be calculated from the slope of the curves).

[0027] Figure 5 Phase structure based on P(VDF-TrFE)(55 / 45mol%) high voltage low modulus polymer alloy.

[0028] Figure 6 The piezoelectric coefficient of a P(VDF-TrFE) (55 / 45mol%) high-voltage low-modulus polymer alloy.

[0029] Figure 7 Stress-strain curves based on P(VDF-TrFE) (55 / 45mol%) high-voltage low-modulus polymer alloy. Detailed Implementation

[0030] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered in isolation, but can be combined with each other to achieve better technical effects.

[0031] The inventors discovered in their experiments that adding dimer P (VDF-TrFE) to trimer P (VDF-TrFE-CFE) induces a phase transition in the trimer, generating quasi-isomorphic phase boundaries (MPBs) and increasing its piezoelectric properties. The large intermolecular distance and abundant phase structure at the MPBs result in a low Young's modulus. Adding other materials to trimer P (VDF-TrFE-CFE) prevents the formation of MPBs and thus fails to improve the polymer alloy's properties.

[0032] This invention discloses a method for preparing a high-voltage, low-modulus polymer alloy. By achieving molecular-level compatibility between two organic polymers and controlling the crystallization and annealing temperatures, a polymer alloy is prepared. By utilizing the composition and polarization electric field to regulate the molecular chain conformation and phase structure, and inducing quasi-isomorphic phase boundaries, the high-voltage electrical properties and low Young's modulus of the polymer alloy are achieved.

[0033] The preparation method includes the following steps:

[0034] S1. Dissolve dimer P (VDF-TrFE) and trimer P (VDF-TrFE-CFE) in different ratios in a polar solvent to form a mixed solution;

[0035] S2. The mixed solution obtained in step S1 is used to form a thin film on a substrate, crystallized and annealed to obtain a piezoelectric polymer alloy.

[0036] S3. Polarize the piezoelectric polymer alloy obtained in step S2 with a strong electric field to obtain the high-voltage low-modulus polymer alloy.

[0037] Example 1

[0038] Preparation based on P(VDF-TrFE) (80 / 20 mol%) high-voltage low-modulus polymer alloy:

[0039] S1. Dissolve 0.05g P(VDF-TrFE) (80 / 20mol%) and 0.25g P(VDF-TrFE-CFE) (64.8 / 27.4 / 7.8mol%) in 2.5ml N,N-dimethylformamide, stir for 24h and sonicate for 5min to make it uniformly dissolved and form a mixed solution;

[0040] S2. After removing air bubbles from the homogeneously dissolved mixed solution in a vacuum drying oven at room temperature, a film is formed on a glass slide using a casting device. The film is then placed in a forced-air drying oven at 70°C for 24 hours to crystallize, followed by annealing at 110°C for 30 minutes to obtain a piezoelectric polymer alloy with only one glass transition temperature (e.g., ...). Figure 1 (as shown);

[0041] S3. Using a corona polarization device, the piezoelectric polymer alloy is polarized under a 24KV electric field. This piezoelectric polymer alloy forms a dual-phase system consisting of a β phase and a 3 / 1-helical phase, constituting a quasi-isomorphic phase boundary (e.g., ...). Figure 2 As shown), a high piezoelectric coefficient and low Young's modulus were obtained, with a piezoelectric coefficient of -33 pC / N and a Young's modulus as low as 180 MPa (as shown). Figure 3 and 4 (As shown).

[0042] Example 2

[0043] Preparation based on P(VDF-TrFE) (55 / 45 mol%) high-voltage low-modulus polymer alloy:

[0044] S1. Dissolve 0.08g P(VDF-TrFE) (55 / 45mol%) and 0.22g P(VDF-TrFE-CFE) (64.8 / 27.4 / 7.8mol%) in 2.5ml of tetrahydrofuran, stir for 28h and sonicate for 3min to make it uniformly dissolved and form a mixed solution.

[0045] S2. After removing air bubbles from the uniformly dissolved mixed solution in a vacuum drying oven at room temperature, the film is formed on a glass slide using a casting device, and then placed in a forced-air drying oven at 60°C for 24 hours to crystallize, and then annealed at 120°C for 24 hours to obtain a piezoelectric polymer alloy.

[0046] S3. Using a corona polarization device, the piezoelectric polymer alloy is polarized under a 20KV electric field. This piezoelectric polymer alloy forms a dual-phase system consisting of a β phase and a 3 / 1-helical phase, constituting a quasi-isomorphic phase boundary (e.g., ...). Figure 5 As shown), a high piezoelectric coefficient and low Young's modulus were obtained, with a piezoelectric coefficient of -30 pC / N and a Young's modulus as low as 120 MPa (e.g. Figure 6 and 7 (As shown).

[0047] This invention prepares polymer alloys by achieving molecular-level compatibility between two organic polymers and controlling the crystallization and annealing temperatures. By utilizing the composition and polarization electric field to regulate the molecular chain conformation and phase structure, quasi-isomorphic phase boundaries are induced, thereby achieving high voltage conductivity and low Young's modulus in the polymer alloys.

[0048] While several embodiments of the present invention have been provided herein, those skilled in the art should understand that modifications can be made to these embodiments without departing from the spirit of the invention. The above embodiments are merely exemplary and should not be construed as limiting the scope of the invention.

Claims

1. A method for preparing a high-voltage low-modulus polymer alloy, characterized in that, The preparation method includes: S1. Dissolve dimer P (VDF-TrFE) and trimer P (VDF-TrFE-CFE) in a polar solvent to form a mixed solution; wherein the content of TrFE in the dimer P (VDF-TrFE) is 20 mol% to 70 mol%, the content of CFE in the trimer P (VDF-TrFE-CFE) is 6 mol% to 12 mol%, and the mass fraction of the dimer P (VDF-TrFE) is 10 wt% to 50 wt%. S2. The mixed solution obtained in step S1 is used to form a thin film on a substrate, crystallized and annealed to obtain a piezoelectric polymer alloy; crystallized at 40~100℃ for 2~48h, and then annealed at 90~150℃ for 10min~48h to obtain a piezoelectric polymer alloy; the piezoelectric polymer alloy has only one glass transition temperature Tg; S3. The piezoelectric polymer alloy obtained in step S2 is polarized with a strong electric field to obtain the high-voltage low-modulus polymer alloy. After polarization, the high-voltage low-modulus polymer alloy has two phases, an all-inverse phase and a 3 / 1 spiral phase, coexisting and forming a quasi-isomorphic phase boundary.

2. The method for preparing the high-voltage low-modulus polymer alloy as described in claim 1, characterized in that, In step S1, the polar solvent is one of hexamethylphosphoric triamine, tetrahydrofuran, dimethyl sulfoxide, acetonitrile, dimethylformamide, nitromethane, acetone, and pyridine.

3. The method for preparing the high-voltage low-modulus polymer alloy as described in claim 1, characterized in that, In step S1, dimer P (VDF-TrFE) and trimer P (VDF-TrFE-CFE) are compatible at the molecular level.

4. A high-voltage, low-modulus polymer alloy, characterized in that, The high-voltage low-modulus polymer alloy is prepared by the preparation method of the high-voltage low-modulus polymer alloy as described in any one of claims 1-3.

5. The high-voltage low-modulus polymer alloy as described in claim 4, characterized in that, The piezoelectric low-modulus polymer alloy has a piezoelectric coefficient greater than 32 pC / N and a Young's modulus as low as 200 MPa.

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