Small molecule organic piezoelectric materials based on phenylalanine derivatives and their preparation methods

Abstract

The present invention provides a small molecule organic piezoelectric material based on phenylalanine derivatives, a preparation method and an application. The preparation method includes the following steps: dissolving an organic small molecule of a phenylalanine derivative in an alcohol solvent to obtain a mixed solution; adding acids of different types and molar ratios to the mixed solution to dope the organic small molecule; and volatilizing the solvent and assembling the organic small molecule to obtain an organic piezoelectric material with different piezoelectric coefficients. The organic small molecule assembly synthesized by the present invention has piezoelectric properties, and the piezoelectric performance can be adjusted by means of acid doping. The preparation method is simple, efficient and environmentally friendly. The piezoelectric device prepared by the method can effectively monitor human movement and can be used in the fields of electronic skin, soft robots, health monitoring, motion monitoring, wearable devices and the like.

Description

Technical Field

[0001] The present invention belongs to the field of organic small molecule materials / electronic devices. Specifically, it relates to a small molecule organic piezoelectric material based on phenylalanine derivatives, its preparation method and application. Background Art

[0002] Materials with piezoelectric effects are collectively referred to as piezoelectric materials, which can be divided into the direct piezoelectric effect (applying pressure to the piezoelectric material generates a potential difference) and the inverse piezoelectric effect (applying voltage to the piezoelectric material generates mechanical stress). Since the piezoelectric effect was discovered by the Curie brothers in 1880, it has been widely used in fields such as piezoelectric sensing, energy harvesting, and filter transducers. Therefore, the design and synthesis of a new type of piezoelectric material are of great significance for both its basic research and practical applications.

[0003] Piezoelectric materials can be roughly divided into inorganic piezoelectric materials (such as lead zirconate titanate piezoelectric ceramics), organic piezoelectric materials (such as polyvinylidene fluoride), and composite piezoelectric materials. However, the preparation processes of these materials require high temperature or melt quenching techniques, long processing times, and other stimuli such as stretching and high-voltage polarization, consuming a large amount of energy. In addition, several of these materials cause serious harm to the environment due to their toxic heavy metal content, so they cannot be used in wearable electronic devices or implantable devices. These drawbacks require the development of new environmentally friendly piezoelectric materials through reasonable design of raw materials and manufacturing methods. Organic small molecule piezoelectric materials are a new type of piezoelectric materials because of their simple and efficient synthesis method, environmental friendliness, and adjustable structure, and can be used in fields such as electronic skin, soft robots, health monitoring, motion monitoring, and wearable devices. Summary of the Invention

[0004] Aiming at the defects in the prior art, the purpose of the present invention is to provide a small molecule organic piezoelectric material based on phenylalanine derivatives, its preparation method and application.

[0005] The purpose of the present invention is achieved through the following solutions:

[0006] The present invention provides a preparation method of a small molecule organic piezoelectric material based on phenylalanine derivatives, including the following steps:

[0007] Step 1: Dissolve the organic small molecule substance of phenylalanine derivatives in an alcohol solvent to obtain a mixed solution;

[0008] Step 2: Add an acidic substance to the mixed solution to perform acid doping on the organic small molecule;

[0009] Step 3: Volatilize the solvent, and the organic small molecules are assembled to obtain an organic piezoelectric material with different piezoelectric coefficients.

[0010] In the said step 1, the structural formula of the organic small molecule substance of phenylalanine derivative is shown as formula Ⅰ or formula Ⅱ:

[0011]

[0012] Among them, R1 is diphenylamine and R2 is a hydrogen atom.

[0013] In the organic small molecule of structural formula Ⅰ, the molar ratio of the doped acid is 1:n, and the said n is 0.5 - 2.

[0014] In the organic small molecule of structural formula Ⅱ, the molar ratio of the doped acid is 1:m, and the said m is 0.5 - 1.5.

[0015] In step 2, the acids used for doping include one or more of hydrochloric acid, hydrobromic acid, hydroiodic acid, and chloropropionic acid.

[0016] The said alcohol solvents include one or several of hexafluoroisopropanol, isopropanol, trifluoroethanol, ethanol, and n-butanol.

[0017] As another embodiment of the present invention, the preparation method of the small molecule organic piezoelectric material based on phenylalanine derivative includes the following steps:

[0018] (1) Dissolve the organic small molecule of phenylalanine derivative in alcohol solvents such as hexafluoroisopropanol;

[0019] (2) Add an acidic substance to dope the organic small molecule, and after the solvent volatilizes, the organic small molecule assembles to obtain a piezoelectric assembly with different piezoelectric coefficients.

[0020] The small molecule organic piezoelectric material based on phenylalanine derivative prepared by the above-mentioned preparation method also belongs to the protection scope of the present invention.

[0021] The application of the said small molecule organic piezoelectric material based on phenylalanine derivative in piezoelectric devices also belongs to the protection scope of the present invention.

[0022] The said piezoelectric device includes an electrode, a PDMS protective layer, an organic small molecule assembly, and a Kapton protective layer. The preparation method of the said piezoelectric device is as follows:

[0023] (1) Use a metal sheet as the bottom electrode;

[0024] (2) Adopt the dip-coating method to assemble the organic small molecule assembly on the said substrate;

[0025] (3) Encapsulate with PDMS to obtain a PDMS protective layer covering the organic small molecule assembly;

[0026] (4) Another metal sheet is used as the top electrode and covered on the PDMS protective layer, and Kapton glue is used for sealing to form a Kapton protective layer, thus fabricating a device with piezoelectric properties.

[0027] This device can be used as a piezoelectric sensor, which can sensitively sense subtle environmental stresses and reflect them in the form of electrical signals. The specific usage method is to load the device onto a finger, which can sensitively and completely record the movement cycle and amplitude of the finger, and can also distinguish the hardness of the touched object.

[0028] The said piezoelectric device can be applied to flexible electronic fields such as human motion detection and electronic skin.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The small molecule organic piezoelectric material based on phenylalanine derivatives in the present invention has simple composition, abundant and non-toxic raw materials, adjustable molecular structure, and environmentally friendly preparation process;

[0031] (2) The organic small molecules used in the small molecule organic piezoelectric material based on phenylalanine derivatives in the present invention can adjust the piezoelectric properties of the material by acid doping, with a simple system and good repeatability;

[0032] (3) The application of the small molecule organic piezoelectric material based on phenylalanine derivatives in the present invention: the piezoelectric device based on this material can be used to monitor human activities and distinguish the hardness of the contacted materials;

[0033] (4) The doping of acid in the present invention can improve the piezoelectric properties. The performance is optimal when the ratio of acid to organic molecule is 1:1. The piezoelectric coefficient first increases with acid doping and reaches the maximum value when the organic molecule:acid = 1:1. Continuing doping results in a decrease in the piezoelectric coefficient. Description of the Drawings

[0034] By reading the detailed description of the non-restrictive embodiments with reference to the following drawings, other features, purposes and advantages of the present invention will become more obvious:

[0035] Figure 1 It is an exploded view of the device in Example 1;

[0036] Figure 2 It is a physical diagram of Example 1;

[0037] Figure 3 It is a photo of the D-2AD organic small molecule assembly on copper in Example 1 ( Figure 3 a) and a scanning electron microscope image ( Figure 3 b);

[0038] Figure 4It is a graph showing the linear relationship between the PFM amplitude and the applied voltage of the D-2AD organic small molecule assembly doped with hydrochloric acid at different molar ratios in Example 1;

[0039] Figure 5 For the open-circuit voltage V of the device when the molar ratio of D-2AD:HCl is 1:1 in Example 1 OC and the short-circuit current I SC Signal diagram;

[0040] Figure 6 For the open-circuit voltage V of the device when the molar ratio of D-2AD:HCl is 1:(0-2) summarized in Example 1 OC and the short-circuit current I SC Signal diagram;

[0041] Figure 7 It is a diagram of a finger-shaped flexible piezoelectric sensor prepared with a molar ratio of D-2AD:HCl of 1:1;

[0042] Figure 8 It is a diagram of the electrical signal generated by the finger movement recorded by the flexible piezoelectric device;

[0043] Figure 9 It is a diagram of the electrical signal generated by the finger contacting different hardness materials recorded by the flexible piezoelectric device;

[0044] Figure 10 It is a graph showing the linear relationship between the PFM amplitude and the applied voltage of the D-2AD organic small molecule assembly doped with different kinds of acids (hydrochloric acid, hydrobromic acid, hydroiodic acid) in Example 2;

[0045] Figure 11 It is a graph showing the linear relationship between the PFM amplitude and the applied voltage of the D-2AD organic small molecule assembly doped with different chiral acids (R-chloropropionic acid, S-chloropropionic acid) in Example 3;

[0046] Figure 12 It is a graph showing the linear relationship between the PFM amplitude and the applied voltage of the D-AD organic small molecule assembly doped with hydrochloric acid at different molar ratios in Example 4;

[0047] Figure 13 For Comparative Example 1, it is a graph showing the linear relationship between the PFM amplitude and the applied voltage of the D-2An organic small molecule assembly with or without the addition of hydrochloric acid. Detailed implementation manners

[0048] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0049] Example 1

[0050] 1. In this example, the reaction process of the organic small molecule with piezoelectric properties based on phenylalanine derivatives is shown in the following formula (1):

[0051]

[0052] 2. The piezoelectric device includes an electrode, a PDMS protective layer, an organic small molecule assembly, and a Kapton protective layer. The preparation method of the small molecule organic piezoelectric material device based on phenylalanine derivatives includes the following steps:

[0053] (1). Dissolve the above-mentioned organic small molecule D-2AD in hexafluoroisopropanol to prepare a 10 mg / ml (0.0126 mol / L) mixed solution;

[0054] (2). Add hydrochloric acid for acid doping in the mixed solution at different molar ratios. Among them, the molar ratios of organic small molecule D-2AD:hydrochloric acid are 1:0, 1:0.5, 1:1, and 1:2 respectively;

[0055] (3). Use copper as the substrate and bottom electrode,

[0056] (4). Adopt the dip-coating method to assemble the organic small molecules on the substrate, and let the solvent naturally volatilize at room temperature to end the self-assembly process; As Figure 3 shown is the morphology diagram of the assembled body with piezoelectric performance.

[0057] As Figure 4 shown is the linear relationship between the PFM amplitude and the applied voltage of the D-2AD organic small molecule assembly doped with hydrochloric acid at different molar ratios. The effective piezoelectric coefficient of this assembly changes with the doping acid ratio and can be measured by a piezoresponse force microscope. For the four conditions of D-2AD, D-2AD:HCl = 1:0.5, D-2AD:HCl = 1:1, and D-2AD:HCl = 1:2, the effective piezoelectric coefficients of the assembled bodies are 8.5, 24.5, 38.5, and 20.2 pm V -1 .

[0058] (5) Encapsulate with PDMS to obtain a PDMS protective layer covering the organic small molecule assembly;

[0059] (6) Cover another metal sheet as the top electrode on the PDMS protective layer, and seal it with Kapton glue to form a Kapton protective layer, thus fabricating a device with piezoelectric performance in a sandwich structure, as Figure 1 shown. Among them, Figure 2 is the physical picture of this device.

[0060] The open-circuit voltage and short-circuit current of the devices prepared by doping the D-2AD organic small molecule assembly with hydrochloric acid at different molar ratios in step (4) were tested, and the test results are as follows:

[0061] When the molar ratio of D-2AD:HCl is 1:1, the open-circuit voltage V OC and short-circuit current I SC signals are as Figure 5 shown.

[0062] When the molar ratio of D-2AD:HCl is 1:(0 - 2), the open-circuit voltage V OC and short-circuit current I SC signals are summarized as Figure 6 shown.

[0063] Based on the assembly of D-2AD:HCl = 1:1, a finger-shaped flexible piezoelectric sensor can be prepared, as Figure 7 shown. The electrical signals generated by the finger movement recorded by this flexible piezoelectric device are as Figure 8 shown and can be used for motion monitoring. The electrical signals generated by the finger contacting materials with different hardnesses recorded by this flexible piezoelectric device are as Figure 9 shown and can be used to distinguish the materials with different hardnesses contacted.

[0064] Example 2

[0065] The organic small molecule with piezoelectric properties based on phenylalanine derivatives used is still D-2AD in Example 1.

[0066] The organic small molecule with piezoelectric properties D-2AD was dissolved in hexafluoroisopropanol at a concentration of still 10 mg / ml (0.0126 mol / L) and doped and modified with an acid. The molar ratio of the organic small molecule D-2AD: the doped acid was 1:1, but the doped acid was replaced with hydrobromic acid or hydroiodic acid respectively to obtain an assembly with piezoelectric performance. The effective piezoelectric coefficient of this assembly varies with the different doped acids and can be measured by a piezoresponse force microscope, as Figure 10 shown. For the assemblies under the three conditions of D-2AD:HCl = 1:1, D-2AD:HBr = 1:1, and D-2AD:HI = 1:1, the effective piezoelectric coefficients are 38.5, 29.0, and 12.44 pm V -1 .

[0067] Example 3

[0068] The organic small molecule with piezoelectric properties based on phenylalanine derivatives used is still D-2AD in Example 1.

[0069] Dissolve the organic small molecule D-2AD with piezoelectric properties in hexafluoroisopropanol and modify it by acid doping. The molar ratio of the organic small molecule D-2AD to the doped acid is 1:1. However, replace the doped acid hydrochloric acid with chiral acids S-chloropropionic acid or R-chloropropionic acid respectively to obtain an assembly with piezoelectric properties. The effective piezoelectric coefficient of this assembly varies with the different doped acids and can be measured by a piezoresponse force microscope. As Figure 11 shown, the effective piezoelectric coefficients of the assemblies under the two conditions of D-2AD:S-CPA = 1:1 and D-2AD:R-CPA = 1:1 are 18.4 and 13.8 pm V respectively -1 .

[0070] Example 4

[0071] The reaction process of an organic small molecule with piezoelectric properties based on phenylalanine derivatives is shown in the following formula (2)

[0072]

[0073] Dissolve the organic small molecule D-AD with piezoelectric properties in hexafluoroisopropanol with a concentration still of 0.0126 mol / L and dope it with hydrochloric acid. The molar ratios of the organic small molecule D-AD to hydrochloric acid are 1:0, 1:0.5, 1:1, and 1:1.5 respectively to obtain an assembly with piezoelectric properties. The effective piezoelectric coefficient of this assembly varies with the proportion of the doped acid and can be measured by a piezoresponse force microscope. As Figure 12 shown, the effective piezoelectric coefficients of the assemblies under the four conditions of D-AD, D-AD:HCl = 1:0.5, D-AD:HCl = 1:1, and D-AD:HCl = 1:1.5 are 11.0, 14.6, 16.1, and 12.5 pm V respectively -1 .

[0074] Comparative Example 1

[0075] This comparative example involves an organic small molecule with piezoelectric properties. The specific preparation steps are basically the same as those in Example 1, except that: the molecular structure is different and lacks doping sites. The specific structure of this organic small molecule is shown in Formula III. Configure this small molecule D-2An into a 0.0126 mol / L hexafluoroisopropanol solution and add hydrochloric acid. The molar ratios of D-2An to hydrochloric acid are 1:0 and 1:1 respectively. Test the molecules in this comparative example with a piezoresponse force microscope. As Figure 13 shown, the effective piezoelectric coefficients under these two conditions are almost the same, about 11.0 pm V -1 . Experiments show that due to the lack of doping sites in this molecule, the introduction of hydrochloric acid cannot increase its piezoelectric coefficient.

[0076]

[0077] The doping of the acid in the present invention can improve the piezoelectric performance. The performance is optimal when the ratio of the acid to the organic molecule is 1:1. Through Figure 4 and Figure 12 As can be seen from the measured piezoelectric coefficients, the piezoelectric coefficient first increases with the acid doping and reaches the maximum value when the organic molecule: acid = 1:1. The piezoelectric coefficient decreases when further doped. This can also be seen from Figure 6 it.

[0078] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A preparation method of a small molecule organic piezoelectric material based on phenylalanine derivatives, characterized in that, The method includes the following steps: Step 1: Dissolve the organic small molecule substance of phenylalanine derivative in an alcohol solvent to obtain a mixed solution; Step 2: Add an acidic substance to the mixed solution to perform acid doping on the organic small molecule; Step 3: Evaporate the solvent, and the organic small molecules can be assembled to obtain an organic piezoelectric material with different piezoelectric coefficients; The organic small molecule substance of phenylalanine derivative is D-2AD or D-AD; The structural formula of D-2AD is as follows: ； The structural formula of D-AD is as follows: 。 2. The preparation method of the small molecule organic piezoelectric material based on phenylalanine derivatives according to claim 1, wherein, In Step 2, the acid used for doping includes one or more of hydrochloric acid, hydrobromic acid, hydroiodic acid, and chloropropionic acid.

3. The preparation method of the small molecule organic piezoelectric material based on phenylalanine derivatives according to claim 1, characterized in that, In Step 1, the alcohol solvent includes one or several of hexafluoroisopropanol, isopropanol, trifluoroethanol, ethanol, and n-butanol.

4. A small molecule organic piezoelectric material based on phenylalanine derivative prepared by the preparation method according to any one of claims 1-3.

5. An application of the small molecule organic piezoelectric material based on phenylalanine derivative according to claim 4 in a piezoelectric device.

6. The application according to claim 5, wherein The piezoelectric device includes an electrode, a PDMS protective layer, an organic small molecule assembly, and a Kapton protective layer. The preparation method of the piezoelectric device is as follows: (1) Use a metal sheet as the substrate and the bottom electrode; (2) Adopt the dip-coating method to assemble the organic small molecule assembly on the substrate; (3) Encapsulate with PDMS to obtain a PDMS protective layer covering the organic small molecule assembly; (4) Use another metal sheet as the top electrode to cover the PDMS protective layer, and seal with Kapton glue to form a Kapton protective layer, thereby assembling a device with piezoelectric performance.

7. The application according to claim 6, characterized in that The piezoelectric device is applied to the fields of human motion detection or electronic skin flexible electronics.

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