Polar p-hydroxybenzoic acid single crystal as well as preparation method and application thereof

Abstract

The invention relates to the technical field of benzoic acid single crystal culture, in particular to a polar p-hydroxybenzoic acid single crystal as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving p-aminobenzamide in a solvent to obtain a saturated p-aminobenzamide solution; dissolving p-hydroxybenzoic acid in a solvent to obtain a saturated p-hydroxybenzoic acid solution; and mixing the saturated p-aminobenzamide solution and the saturated p-hydroxybenzoic acid solution, and standing to obtain the polar p-hydroxybenzoic acid single crystal. According to the preparation method, the structural limitation of a recrystallization method after direct dissolution of a single solvent is overcome, the p-hydroxybenzoic acid single crystal with a polar space group P21 structure is successfully obtained, the ferroelectricity of the p-hydroxybenzoic acid single crystal is changed from nothing to one, and a new way is opened up for the development of the field of ferroelectric materials.

Description

Technical Field

[0001] The present invention relates to the technical field of benzoic acid single crystal cultivation, and particularly relates to a polar p-hydroxybenzoic acid single crystal, a preparation method thereof and an application thereof. Background Art

[0002] Ferroelectric materials have been widely used in many fields due to their excellent optoelectronic properties. Designing and synthesizing complexes with polar space groups is the key prerequisite for improving the performance of ferroelectric materials. By carefully designing ligands with different structures and adopting ingenious complex assembly strategies, numerous ferroelectric compounds can be synthesized, such as various organic-inorganic hybrid ferroelectric materials.

[0003] In recent years, with the continuous exploration and in-depth research in the field of ferroelectric chemistry, pure organic ferroelectric materials have gradually become a research hotspot. In the existing preparation technologies, organic ferroelectric materials are usually prepared by directly dissolving them in a single solvent and then recrystallizing. For example, p-hydroxybenzoic acid is dissolved in ethanol, and then reacted at 150 °C under high pressure for 4 days, followed by the process of solvent evaporation and recrystallization. However, this method has the following defects: First, there is a structural limitation. By using the method of dissolving in a single solvent, reacting under high pressure and then recrystallizing, it is difficult to obtain organic ferroelectric materials with a polar space group structure, and only a non-polar P2 1 / n structure can be obtained. Second, the preparation conditions are harsh. High-pressure reactions require high experimental conditions and precise control of temperature and pressure parameters, which increases the complexity and cost of the experiment and is not conducive to large-scale production. Third, the performance of organic ferroelectric materials is unstable. Since a single solvent system cannot effectively control the crystal growth environment, it leads to defects and inhomogeneities in the crystal structure, making the performance of ferroelectric materials unstable. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a polar p-hydroxybenzoic acid single crystal, a preparation method thereof and an application thereof. By introducing a saturated p-aminobenzamide solution into a saturated p-hydroxybenzoic acid solution and using p-aminobenzamide as a regulator, the present invention significantly changes the chemical environment of the saturated p-hydroxybenzoic acid solution, thereby controlling the crystal growth process and finally successfully preparing a polar p-hydroxybenzoic acid single crystal. The preparation method of the present invention not only overcomes the defect that is not conducive to large-scale production existing in the method of directly dissolving in a single solvent and then recrystallizing; moreover, the p-hydroxybenzoic acid single crystal obtained by using the method of the present invention overcomes the structural limitation, successfully obtains a p-hydroxybenzoic acid single crystal with a polar space group P2 1 structure, reduces the defects and inhomogeneities in the crystal structure, and also realizes the ferroelectricity of the p-hydroxybenzoic acid single crystal from scratch, opening up a new path for the development of the ferroelectric material field.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The first object of the present invention is to provide a method for preparing the above-mentioned polar p-hydroxybenzoic acid single crystal, comprising the following steps: S1. Dissolve p-aminobenzamide in a solvent to obtain a saturated p-aminobenzamide solution.

[0006] S2. Dissolve p-hydroxybenzoic acid in a solvent to obtain a saturated p-hydroxybenzoic acid solution.

[0007] S3. Mix the saturated p-aminobenzamide solution and the saturated p-hydroxybenzoic acid solution, and let it stand at room temperature. During the standing process, the basic group in p-aminobenzamide and the acidic group in p-hydroxybenzoic acid form a complex through hydrogen bonding and electrostatic interaction. This interaction reduces the solubility of the saturated p-hydroxybenzoic acid and induces the directional arrangement of p-hydroxybenzoic acid molecules, obtaining a polar p-hydroxybenzoic acid single crystal.

[0008] Preferably, the molar ratio of p-aminobenzamide to p-hydroxybenzoic acid is 1:1 to 1.5.

[0009] Preferably, the solvents for dissolving p-aminobenzamide and p-hydroxybenzoic acid are the same.

[0010] Preferably, the standing condition is: standing at room temperature for 14 days to 20 days.

[0011] Preferably, the mass-volume ratio of p-aminobenzamide to methanol is 1.36 g to 1.38 g: 100 mL; wherein, when the mass-volume ratio of p-aminobenzamide to methanol is 1.36 g: 100 mL, only a small amount of p-aminobenzamide in the saturated p-aminobenzamide solution is not dissolved; while when the mass-volume ratio of p-aminobenzamide to methanol is 1.38 g: 100 mL, it is observed that more p-aminobenzamide fails to dissolve completely.

[0012] Preferably, the solvent is selected from methanol, ethanol or acetonitrile.

[0013] The second object of the present invention is to provide the polar p-hydroxybenzoic acid single crystal prepared by the above-mentioned preparation method.

[0014] Preferably, the polar p-hydroxybenzoic acid single crystal is a colorless transparent flaky crystal.

[0015] Preferably, the polar p-hydroxybenzoic acid single crystal has ferroelectricity.

[0016] The third object of the present invention is to provide the application of the above-mentioned polar p-hydroxybenzoic acid single crystal in the preparation of organic ferroelectric materials.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention provides a method for preparing a polar p-hydroxybenzoic acid single crystal. Dissolve p-aminobenzamide in a solvent to obtain a saturated p-aminobenzamide solution; dissolve p-hydroxybenzoic acid in a solvent to obtain a saturated p-hydroxybenzoic acid solution; mix the saturated p-aminobenzamide solution and the saturated p-hydroxybenzoic acid solution, and let it stand at room temperature. During the standing process, the basic group in p-aminobenzamide and the acidic group in p-hydroxybenzoic acid form a complex through hydrogen bonding and electrostatic interaction. This interaction reduces the solubility of the saturated p-hydroxybenzoic acid and induces the directional arrangement of p-hydroxybenzoic acid molecules, resulting in the formation of polar p-hydroxybenzoic acid single crystals. The present invention adopts an induced crystallization strategy. By introducing p-aminobenzamide as a regulator into the saturated p-hydroxybenzoic acid solution, the chemical environment of the saturated p-hydroxybenzoic acid solution is significantly changed. While inducing the formation of a polar lattice and reducing defects, more crystallization driving forces are provided, thereby controlling the growth process of polar p-hydroxybenzoic acid single crystals and effectively improving the structural stability and performance uniformity of organic ferroelectric materials. The preparation method of the present invention not only overcomes the structural limitations of direct recrystallization after single solvent dissolution, but also successfully obtains p-hydroxybenzoic acid single crystals with a polar space group P2 1 structure, and also realizes the emergence of ferroelectricity in p-hydroxybenzoic acid single crystals, opening up a new path for the development of the ferroelectric material field.

[0018] 2. The polar p-hydroxybenzoic acid single crystal provided by the present invention has a polar space group P2 1 structure. This structural feature endows the polar p-hydroxybenzoic acid single crystal with ferroelectric properties. Specifically, the hydroxyl group and carboxyl group in the polar p-hydroxybenzoic acid single crystal molecule act together to form a distinct polar characteristic, prompting the molecules to be orderly arranged inside the crystal, and thus generating a spontaneous polarization phenomenon. Under the action of an external electric field, the electric dipole moments of these polar molecules are directionally arranged, thereby generating a macroscopic polarization effect and exhibiting good ferroelectric properties. In addition, the polar structure of the polar p-hydroxybenzoic acid single crystal also endows the polar p-hydroxybenzoic acid single crystal with good electric domain reversibility, providing a basis for the application of ferroelectric storage, such as room temperature ferroelectricity, making it have a broader application prospect in the fields of information storage, sensors, and optoelectronics.

[0019] 3. The preparation method of the present invention is simple to operate, does not require complex equipment and harsh experimental conditions, reduces the experimental cost, and improves the repeatability of the experiment and the feasibility of large-scale application. In addition, the method of the present invention is not only applicable to the p-hydroxybenzoic acid and p-aminobenzamide system, but also can be extended to the preparation of other organic, inorganic, and hybrid ferroelectric materials, and has wide applicability. Description of the Drawings

[0020] Figure 1It is the asymmetric unit ellipsoid diagram of the polar p-hydroxybenzoic acid single crystal prepared in Example 1 of the present invention.

[0021] Figure 2 It is the XRD diagram of the polar p-hydroxybenzoic acid single crystal prepared in Example 1 of the present invention.

[0022] Figure 3 It is the infrared spectrum diagram of the polar p-hydroxybenzoic acid single crystal prepared in Example 1 of the present invention.

[0023] Figure 4 It is the P-E curve diagram of the polar p-hydroxybenzoic acid single crystal prepared in Example 1 of the present invention. Detailed implementation manners

[0024] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the data in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods.

[0026] In the prior art, the preparation of organic ferroelectric materials such as p-hydroxybenzoic acid mainly relies on direct dissolution in a single solvent followed by recrystallization. This method has many limitations in the preparation process. First, due to the single nature of the solvent system, it is difficult to effectively control the crystal growth environment, resulting in the crystal structure often being limited to non-polar space groups and the ferroelectric properties being unsatisfactory. Second, direct dissolution in a single solvent followed by recrystallization has high requirements for experimental conditions, and parameters such as temperature and pressure need to be precisely controlled. This not only increases the complexity and cost of the experiment, but also limits the large-scale application of this method. In addition, due to the insufficient control ability of the single solvent system on crystal growth, defects and inhomogeneities often exist in the obtained crystals, resulting in unstable properties of the ferroelectric materials and difficulty in meeting the requirements of practical applications.

[0027] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for preparing polar p-hydroxybenzoic acid single crystals, which includes the following steps: Dissolve p-aminobenzamide in a solvent to obtain a saturated p-aminobenzamide solution; dissolve p-hydroxybenzoic acid in a solvent to obtain a saturated p-hydroxybenzoic acid solution; mix the saturated p-aminobenzamide solution and the saturated p-hydroxybenzoic acid solution, and let it stand at room temperature. During the standing process, the basic group in p-aminobenzamide and the acidic group in p-hydroxybenzoic acid form a complex through hydrogen bonding and electrostatic interaction. This interaction reduces the solubility of the saturated p-hydroxybenzoic acid and induces the directional arrangement of p-hydroxybenzoic acid molecules, resulting in polar p-hydroxybenzoic acid single crystals.

[0028] In view of the problem that it is difficult to obtain a polar space group structure by directly dissolving and recrystallizing with a single solvent, the present invention introduces p-aminobenzamide as a regulator into the solvent system, significantly changing the chemical environment of the solvent system, and then controlling the crystal growth process, successfully obtaining p-hydroxybenzoic acid single crystals with a polar space group P2 1 structure.

[0029] In view of the problem that the traditional preparation method has high requirements for experimental conditions, resulting in increased experimental complexity and cost, the preparation method provided by the present invention is simple to operate, does not require complex equipment and harsh experimental conditions, and can obtain the required polar p-hydroxybenzoic acid single crystals only by standing at room temperature.

[0030] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific embodiments.

[0031] Example 1 A method for preparing polar p-hydroxybenzoic acid single crystals specifically includes the following steps: S1. Dissolve 138.53 g (1.01 mol) of p-hydroxybenzoic acid in methanol to obtain a saturated methanol solution of p-hydroxybenzoic acid for standby; dissolve 137.82 g (1.01 mol) of p-aminobenzamide in methanol to obtain a saturated methanol solution of p-aminobenzamide for standby.

[0032] S2. Mix 50 mL of the saturated methanol solution of p-aminobenzamide and the saturated methanol solution of p-hydroxybenzoic acid according to a volume ratio of 1:1, filter, and let it stand for 14 days. After obvious crystals are formed, filter and wash to obtain polar p-hydroxybenzoic acid single crystals. The ellipsoid diagram of its asymmetric unit is as Figure 1 shown.

[0033] Example 2 A method for preparing polar p-hydroxybenzoic acid single crystals specifically includes the following steps: S1. Dissolve 138.53 g (1.01 mol) of p-hydroxybenzoic acid in methanol to obtain a saturated methanol solution of p-hydroxybenzoic acid for standby; dissolve 137.82 g (1.01 mol) of p-aminobenzamide in methanol to obtain a saturated methanol solution of p-aminobenzamide for standby.

[0034] S2. Mix 50 mL of the saturated methanol solution of p-aminobenzamide and the saturated methanol solution of p-hydroxybenzoic acid according to a volume ratio of 1:1. After filtration, let it stand for 20 days. After obvious crystals are formed, filter and wash to obtain single crystals of polar p-hydroxybenzoic acid.

[0035] Example 3 A method for preparing single crystals of polar p-hydroxybenzoic acid specifically includes the following steps: S1. Dissolve 138.53 g (1.01 mol) of p-hydroxybenzoic acid in ethanol to obtain a saturated ethanol solution of p-hydroxybenzoic acid for standby; dissolve 137.82 g (1.01 mol) of p-aminobenzamide in ethanol to obtain a saturated ethanol solution of p-aminobenzamide for standby.

[0036] S2. Mix 50 mL of the saturated ethanol solution of p-aminobenzamide and the saturated ethanol solution of p-hydroxybenzoic acid according to a volume ratio of 1:1.5. After filtration, let it stand for 14 days. After obvious crystals are formed, filter and wash to obtain single crystals of polar p-hydroxybenzoic acid.

[0037] Example 4 A method for preparing single crystals of polar p-hydroxybenzoic acid specifically includes the following steps: S1. Dissolve 138.53 g (1.01 mol) of p-hydroxybenzoic acid in acetonitrile to obtain a saturated acetonitrile solution of p-hydroxybenzoic acid for standby; dissolve 137.82 g (1.01 mol) of p-aminobenzamide in acetonitrile to obtain a saturated acetonitrile solution of p-aminobenzamide for standby.

[0038] S2. Mix 50 mL of the saturated acetonitrile solution of p-aminobenzamide and the saturated acetonitrile solution of p-hydroxybenzoic acid according to a volume ratio of 1:1. After filtration, let it stand for 14 days. After obvious crystals are formed, filter and wash to obtain single crystals of polar p-hydroxybenzoic acid.

[0039] Example 5 A method for preparing single crystals of polar p-hydroxybenzoic acid specifically includes the following steps: S1. Dissolve 207.18 g of 1.5 mol of p-hydroxybenzoic acid in methanol to obtain a saturated methanol solution of p-hydroxybenzoic acid for standby; dissolve 137.82 g of 1.00 mol of p-aminobenzamide in methanol to obtain a saturated methanol solution of p-aminobenzamide for standby.

[0040] S2. Mix 50 mL of the saturated methanol solution of p-aminobenzamide and the saturated methanol solution of p-hydroxybenzoic acid according to a volume ratio of 1:1. After filtration, let it stand for 14 days. After obvious crystals are formed, filter and wash to obtain polar p-hydroxybenzoic acid single crystals.

[0041] Comparative Example 1 A method for preparing non-polar p-hydroxybenzoic acid single crystals specifically includes the following steps: S1. Dissolve 138.53 g of 1.01 mol of p-hydroxybenzoic acid in methanol to obtain a saturated methanol solution of p-hydroxybenzoic acid.

[0042] S2. Slowly volatilize the solvent of the above-mentioned saturated methanol solution of p-hydroxybenzoic acid at room temperature. After standing for 14 days, after obvious crystals are formed, filter and wash to obtain non-polar p-hydroxybenzoic acid single crystals.

[0043] Table 1 Data of polar p-hydroxybenzoic acid single crystals prepared in Example 1 and structure refinement parameters table

[0044] The results in Table 1 show that the polar p-hydroxybenzoic acid single crystals prepared in the present invention belong to the monoclinic system, P2 1 space group, indicating that the symmetry of the polar p-hydroxybenzoic acid single crystals of the present invention is relatively low, a = 7.9359(4) Å, b = 5.2893(3) Å, c = 8.4552(4) Å, α = γ = 90°, β = 108.774(3)°, Z = 2.

[0045] It can be obtained from Figure 2 that the XRD pattern of the polar p-hydroxybenzoic acid single crystals of the present invention, presented as a black curve, is basically consistent with the simulated XRD pattern, presented as a red curve, in the position and relative intensity of the diffraction peaks, indicating the high purity and correct crystal structure of the polar p-hydroxybenzoic acid single crystals prepared in Example 1 of the present invention.

[0046] It can be obtained from Figure 3 that through infrared spectrum analysis, the absorption peaks at 3465 cm -1 , 3323 cm -1 and 3209 cm -1 are attributed to the O-H stretching vibration, revealing the presence of hydroxyl groups (-OH) in the molecules of the polar p-hydroxybenzoic acid single crystals of the present invention. 1660 cm-1 and absorption peaks near 1615 cm -1 are attributed to the C=O stretching vibration, further confirming the presence of the carboxyl group (-COOH). Absorption peaks at 1598 cm -1 and 1563 cm -1 are related to the C=C stretching vibration of the benzene ring, reflecting the structural characteristics of the aromatic ring. Absorption peaks at 1434 cm -1 and 1394 cm -1 correspond to the bending vibration of C-H, further supporting the presence of the benzene ring. Absorption peaks at 1290 cm -1 and 1153 cm -1 are related to the C-O stretching vibration, consistent with the C-O bond in the carboxyl group. Absorption peaks at 851 cm -1 and 784 cm -1 are related to the out-of-plane bending vibration of C-H. These characteristic peaks are consistent with the molecular structure of p-hydroxybenzoic acid, verifying its chemical composition.

[0047] It is obtained from Figure 4 that it exhibits obvious non-linear characteristics, indicating that the prepared polar p-hydroxybenzoic acid single crystal of the present invention has significant ferroelectricity. As the electric field strength increases, the polarization intensity gradually increases and tends to saturate at high electric field strength, further verifying the polarization response characteristics of the polar p-hydroxybenzoic acid single crystal molecules under the action of the electric field. Specifically, the saturation polarization intensity (P s ) of this sample is 1.61 μC / cm 2 , the remanent polarization intensity (P r ) is 0.20 μC / cm 2 , and the coercive field (E c ) is 0.46 kV / cm. These parameters are all in line with the typical characteristics of ferroelectric materials.

[0048] It should be noted that when the present invention involves numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the adopted step methods are the same as those in the embodiments, in order to prevent repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concepts. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0049] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A method for preparing a polar p-hydroxybenzoic acid single crystal, characterized in that: The steps include: dissolving p-aminobenzamide in a solvent to obtain a saturated p-aminobenzamide solution; dissolving p-hydroxybenzoic acid in a solvent to obtain a saturated p-hydroxybenzoic acid solution; A saturated p-aminobenzamide solution and a saturated p-hydroxybenzoic acid solution are mixed and allowed to stand at room temperature. During the standing process, the basic groups in p-aminobenzamide and the acidic groups in p-hydroxybenzoic acid form a complex through hydrogen bonds and electrostatic effects, inducing the p-hydroxybenzoic acid molecules to be oriented and thereby obtaining polar p-hydroxybenzoic acid single crystals.

2. The method for preparing polar p-hydroxybenzoic acid single crystal according to claim 1, characterized in that: The molar ratio of p-aminobenzamide to p-hydroxybenzoic acid is 1:1~1.

5.

3. The method for preparing polar p-hydroxybenzoic acid single crystal according to claim 1, characterized in that: The solvent for dissolving p-aminobenzamide is the same as that for dissolving p-hydroxybenzoic acid.

4. The method for preparing polar p-hydroxybenzoic acid single crystal according to claim 3, characterized in that: The solvent is selected from methanol, ethanol or acetonitrile.

5. A polar p-hydroxybenzoic acid single crystal, characterized in that: The polar p-hydroxybenzoic acid single crystal is prepared by the preparation method described in any one of claims 1 to 4.

6. The polar p-hydroxybenzoic acid single crystal according to claim 5, characterized in that: Polar p-hydroxybenzoic acid single crystal is colorless and transparent flaky crystal.

7. The polar p-hydroxybenzoic acid single crystal according to claim 5, characterized in that: Polar p-hydroxybenzoic acid single crystals exhibit ferroelectricity.

8. Use of the polar p-hydroxybenzoic acid single crystal according to claim 5 in the preparation of organic ferroelectric materials.

Images