Organic ferroelectric material with adjustable polarization property and preparation method and application thereof

Abstract

The invention discloses an organic ferroelectric material with an adjustable polarization property and a preparation method and application thereof. The organic ferroelectric material is prepared from (1) an amide tri-substituted phenyl derivative; or (2) preparing the amide tri-substituted phenyl derivative amide and the amide tetra-substituted phenyl derivative. The preparation method comprises the following steps: preparing a solution containing an amide tri-substituted phenyl derivative or a mixed solution containing the amide tri-substituted phenyl derivative and an amide tetra-substituted phenyl derivative; and after standing, adding ion exchange resin and purifying to obtain the organic ferroelectric. According to the invention, the organic ferroelectric material of which the polarization property can be regulated and controlled on the nanoscale is prepared by regulating and controlling the mixing ratio of the amide tri-substituted phenyl derivative and the amide tetra-substituted phenyl derivative.

Description

Technical Field

[0001] The invention relates to the technical field of organic electronic materials and information storage devices, and in particular to an organic ferroelectric material with adjustable polarization properties and a preparation method and application thereof. Background Art

[0002] Dielectric energy storage capacitors are known for their ultra-high power density, high temperature stability and ultra-fast charge and discharge capabilities. Ferroelectric materials have a unique hysteresis phenomenon and show great potential in the fields of information storage, energy harvesting, photoelectric detection, etc. Ferroelectric materials mainly include inorganic ferroelectric ceramics, ferroelectric polymers and molecular ferroelectrics, among which inorganic ferroelectric ceramics occupy the mainstream of application, but inorganic ferroelectrics have factors such as toxicity, high price and lack of flexibility. Organic ferroelectrics have gradually begun to develop and play a good role in the preparation of non-volatile data storage devices. Ferroelectric liquid crystal refers to liquid crystal materials with ferroelectricity. The centers of positive and negative charges in the ferroelectric crystal unit cell do not coincide. Because of the electric dipole moment, the electric dipole moment will spontaneously polarize below the Curie temperature. Under the action of an external electric field, the spontaneous polarization of the ferroelectric can change or even reverse direction. In addition, ferroelectric materials can maintain their polarization even without an external electric field, thus achieving non-volatility and can be used to prepare non-volatile data storage devices.

[0003] Materials with adjustable polarization properties can bring significant advantages in many applications. For example, by adjusting the polarization properties, the dielectric constant, dielectric strength, piezoelectric properties and ferroelectric properties of the material can be improved, making it better adaptable in applications such as sensors, actuators and memories. The polarization properties of the material can also be adjusted according to application requirements, so that the same material can optimize its performance under different conditions (such as temperature, frequency, etc.) and improve flexibility.

[0004] One-dimensional columnar liquid crystal ferroelectric materials can be used to manufacture high-density non-volatile organic memory devices due to their dense structure. Therefore, the nanoscale effect of one-dimensional columnar liquid crystal ferroelectric materials is one of the important parameters in manufacturing memory devices. However, the current microstructure analysis of this type of material is not sufficient, and the failure analysis of ferroelectric to paraelectric materials requires further analysis. Summary of the invention

[0005] In view of the above technical problems, the present invention provides an organic ferroelectric material with adjustable polarization properties, a preparation method and application thereof. The present invention provides an organic ferroelectric material which is a mixed columnar assembly of multi-chain benzene derivatives. By adjusting the mixing ratio of amide tri-substituted phenyl derivatives and amide tetra-substituted phenyl derivatives, through its phase transition behavior, molecular assembly structure, and dielectric response, the nanoscale effect of the collective reversal of one-dimensional NH···O= hydrogen bond interaction is clarified, and a nanoscale flexible organic liquid crystal ferroelectric material is prepared.

[0006] In one aspect, the present invention provides an organic ferroelectric material with adjustable polarization properties, which is prepared from ① an amide tri-substituted phenyl derivative; or ② an amide tri-substituted phenyl derivative amide and an amide tetra-substituted phenyl derivative;

[0007] Wherein, the structure of the tri-substituted phenyl derivative of amide is shown in formula (I); the structure of the tetra-substituted phenyl derivative of amide is shown in formula (II);

[0008]

[0009] In formula (I), n=8-12; m=8-12.

[0010] In some specific embodiments, n=8, 9, 10, 11, 12.

[0011] In some specific embodiments, m=8, 9, 10, 11, 12.

[0012] In the technical solution of the present invention, -C n H 2n+1 It is a straight chain structure; -C m H 2m+1 It is a straight chain structure.

[0013] As a preferred embodiment, the molar ratio of the amide tri-substituted phenyl derivative amide to the amide tetra-substituted phenyl derivative is ≥10:1.

[0014] In any embodiment, the organic ferroelectric material has a polarization greater than zero.

[0015] In one embodiment, the polarization strength of the organic ferroelectric material can reach 0.85 μC / cm 2 .

[0016] In any embodiment, the organic ferroelectric material has a size of 40 to 600 nm and exhibits ferroelectricity at 40 to 600 nm.

[0017] In any embodiment, the organic ferroelectric is a one-dimensional columnar crystal or a mixed crystal.

[0018] In the technical scheme of the present invention, the tri-amide substituted phenyl derivative contains an odd number of amide substituents, the net dipole moment is not zero in the most stable structural state, and the number of substituents is greater than 2 and is mutually distributed in the meta position, and is easy to form a one-dimensional columnar self-assembled stack under the dual effects of π-π stacking and hydrogen bonding, and the direction of the intermolecular NH···O= hydrogen bond is reversed along the collective dipole of the π stacking column under the action of an external electric field, showing ferroelectric hysteresis behavior and showing a small ferroelectric loss; and the tetra-amide substituted phenyl derivative is also easy to form a one-dimensional columnar self-assembled stack, but because the number of substituents is an even number, the substituents are in a symmetrical structure in the most stable state, so that the dipole moments cancel each other out to zero, and can show antiferroelectric behavior under the action of an external electric field. The one-dimensional columns formed by these two types of compounds are of similar size and can form hydrogen bonds with each other after mixing to achieve miscibility.

[0019] In another aspect, the present invention provides a method for preparing the above-mentioned organic ferroelectric material, comprising the following steps:

[0020] Step 1) preparing a solution containing an amide tri-substituted phenyl derivative or a mixed solution containing an amide tri-substituted phenyl derivative and an amide tetra-substituted phenyl derivative;

[0021] Step 2) After the solution or mixed solution prepared in step 1 is allowed to stand, an ion exchange resin is added to purify the organic ferroelectric.

[0022] In any embodiment, in step 1), the concentration of the solution or the mixed solution is not particularly limited as long as all of the amide tri-substituted phenyl derivatives and amide tetra-substituted phenyl derivatives are dissolved.

[0023] As a preferred embodiment, in step 1), the organic solvent is selected from at least one of dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, toluene, N,N-dimethylformamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone.

[0024] In any embodiment, in step 2), the standing time is ≥ 15 min.

[0025] In any embodiment, in step 2), the ion exchange resin is added and stirred to mix evenly; the rotation speed and time of the stirring are not particularly limited, and specifically, the stirring speed can be 1000 rpm for 30 minutes.

[0026] In any embodiment, in step 2), the ion exchange resin is added, stirred and then allowed to stand; the standing time is ≥ 15 min;

[0027] As a preferred embodiment, in step 2), the ion exchange resin is selected from any one of strongly acidic cationic analytical grade AG50W resin, AG MP-50 macroporous resin and biotechnology grade AG 50W resin.

[0028] As a preferred embodiment, step 2) further includes post-treatment; the post-treatment includes washing, filtering and rotary evaporation drying.

[0029] In certain specific embodiments, the washing is an ethyl acetate wash.

[0030] In another aspect, the present invention provides the use of the above-mentioned organic ferroelectric material with adjustable polarization properties in the preparation of a dielectric energy storage capacitor.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention prepares ferroelectric materials through the self-assembly reaction of amide tri-substituted phenyl derivatives or dopes a small amount of amide tetra-substituted phenyl derivatives into amide tri-substituted phenyl derivatives to prepare ferroelectric materials through self-assembly reaction. The present invention adjusts the correlation length of ferroelectric nano-columns in organic ferroelectric materials by controlling the ratio of two phenyl derivatives, thereby realizing the controllable polarization properties. Among them, the amide tetra-substituted phenyl derivatives can form pinning potential sites in the nano-columns of amide tri-substituted phenyl derivatives to inhibit dipole reversal. By controlling the ratio of the two phenyl derivatives, the minimum columnar nano-size that can show ferroelectric properties is obtained on the basis of the nano effect, which provides an important reference for the preparation of nano-level flexible storage devices and is conducive to the development of dielectric storage devices towards miniaturization, high-density storage and low-voltage operation.

[0033] In the present invention, by regulating the doping amount of the tetra-substituted phenyl derivative of amide, the domain separation state between the columnar aggregates of (tri-substituted phenyl derivative of amide)∞ and (tetra-substituted phenyl derivative of amide)∞ that form intermolecular hydrogen bonds can be used to form ferroelectric isolation, thereby exhibiting ferroelectricity and antiferroelectricity.

[0034] The method provided by the invention has a simple preparation process and is easy to operate, and is suitable for large-scale production and preparation. The prepared organic ferroelectric has good performance and good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a surface morphology of a one-dimensional fiber of a mixed crystal organic ferroelectric material prepared in Example 2 of the present invention;

[0036] Figure 2 This is a surface morphology of a one-dimensional fiber of a mixed-crystal organic ferroelectric material prepared in Example 8 of the present invention. DETAILED DESCRIPTION

[0037] The following embodiments are only some embodiments of the present invention, rather than all embodiments. Therefore, the detailed description in the embodiments of the present invention provided below is not intended to limit the scope of the present invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the protection scope of the present invention.

[0038] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments are all conventional methods in the art unless otherwise specified.

[0039] Examples 1 to 10

[0040] In this embodiment, the tetra-substituted phenyl derivative of amide is N1, N2, N4, N5-tetraoctylbenzene-1, 2, 4, 5-tetracarboxamide (as shown in Formula 1); the tri-substituted phenyl derivative of amide in this embodiment is N1, N3, N5-tri-octylbenzene-1, 3, 5-tricarboxamide (as shown in Formula 2); In this embodiment, the ferroelectric material is prepared according to the molar proportion of the tetra-substituted phenyl derivative of amide in the tetra-substituted phenyl derivative of amide and the tri-substituted phenyl derivative of amide as shown in Table 1, and the preparation method is as follows:

[0041] Step 1: Dissolve N1, N2, N4, N5-tetraoctylbenzene-1, 2, 4, 5-tetracarboxamide and N1, N3, N5-trioctylbenzene-1, 3, 5-tricarboxamide in dichloromethane as shown in Table 1 to prepare a mixed solution 1 with a total concentration of 5 mg / mL;

[0042] Step 2: Mixed solution 1 was stirred thoroughly and then allowed to stand for 15 minutes, then strong acidic cationic analytical grade AG 50W resin was added, stirred at 1000 rpm for 30 minutes, and then allowed to stand for 25 minutes to obtain mixed solution 2;

[0043] Step 3: The mixed solution 2 obtained in step 2 is washed with ethyl acetate, filtered to remove the solid, and then rotary evaporated and dried to obtain a white mixed crystal ferroelectric.

[0044]

[0045] 2. Dielectric performance test:

[0046] Take 2 pieces with 1cm in the middle 2 The organic ferroelectric material obtained in the embodiment is heated to a liquid crystal state, sandwiched between two pieces of ITO glass, and connected in series with gold foil to form a dielectric measurement unit with an average electrode gap of 2 μm; the dielectric constant is measured at 1 kHz at 25°C and 0.5 V. The test results are shown in Table 1.

[0047] 3. Ferroelectric performance test:

[0048] Take 2 pieces with 1cm in the middle 2 The mixed crystal obtained in the embodiment is heated to a liquid crystal state, sandwiched between two pieces of ITO glass, and connected in series with gold foil to form a dielectric measurement unit with an average electrode gap of 2 μm; the ferroelectric response behavior at 0.5 Hz is measured at 25°C and 5 V. The test results are shown in Table 1.

[0049] Table 1

[0050]

[0051] Examples 11-12

[0052] The ferroelectric material is prepared according to the molar proportion of the amide tetra-substituted phenyl derivative in the amide tetra-substituted phenyl derivative and the amide tri-substituted phenyl derivative shown in Table 2. The preparation method is as follows:

[0053] Step 1: dissolving an amide tri-substituted phenyl derivative and an amide tetra-substituted phenyl derivative in ethyl acetate to prepare a mixed solution 1 with a total concentration of 5 mg / mL, wherein the molar ratio of the amide tri-substituted phenyl derivative to the amide tetra-substituted phenyl derivative in the mixed solution 1 is 6:0.01;

[0054] Step 2: The mixed solution 1 was stirred thoroughly and then allowed to stand for 30 minutes, and then a strongly acidic cationic analytical grade AG MP-50 macroporous resin was added, and the mixture was stirred at 1000 rpm for 30 minutes and then allowed to stand for 40 minutes to obtain a mixed solution 2;

[0055] Step 3: The mixed solution 2 obtained in step 2 is washed with ethyl acetate, filtered to remove the solid, and then rotary evaporated and dried to obtain a white mixed crystal ferroelectric.

[0056] The test methods for the dielectric properties and ferroelectric properties of the organic ferroelectric material prepared in this example are the same as those in Example 1. The test results are shown in Table 2.

[0057] Table 2

[0058]

[0059] In Table 2, the structure of N1, N3, N5-trinonylbenzene-1, 3, 5-tricarboxamide is:

[0060]

[0061] In Table 2, the structure of N1, N2, N4, N5-tetranonylbenzene-1, 2, 4, 5-tetracarboxamide is:

[0062]

[0063] In Table 2, the structure of N1, N3, N5-tridecylbenzene-1, 3, 5-tricarboxamide is:

[0064]

[0065] In Table 2, the structure of N1, N2, N4, N5-tetradecylbenzene-1, 2, 4, 5-tetracarboxamide is:

[0066]

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 1 is that an amide-substituted phenyl derivative N-octylbenzamide (structure shown in Formula 3) is used to replace N1, N2, N4, N5-tetraoctylbenzene-1,2,4,5-tetracarboxamide.

[0069] The test results show that the dielectric constant of the organic ferroelectric material prepared in Comparative Example 1 at 1000 Hz is 2.14 (real part) and 0.19 (imaginary part), and at 0.5 Hz, it exhibits non-ferroelectric behavior.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is that an amide hexasubstituted phenyl derivative N1,N2,N3,N4,N5,N6-hexaoctylbenzene-1,2,3,4,5,6-hexacarboxamide (structure as shown in Formula 4) is used to replace N1,N2,N4,N5-tetraoctylbenzene-1,2,4,5-tetracarboxamide.

[0072] The test results show that the organic ferroelectric material prepared in Comparative Example 2 has a dielectric constant of 1.06 (real part) and 0.16 (imaginary part) at 1000 Hz, and exhibits non-ferroelectric behavior at 0.5 Hz.

[0073]

[0074] The dielectric constant determines the freedom of movement of polar structural units in molecular assembly, and the degree of polarization and coercive electric field show the information storage capacity of ferroelectric materials and the stability of the polarization state under the action of an external electric field. It can be seen from the above test results that the polarization performance of the (amide trisubstituted phenyl derivative)∞ and (amide tetrasubstituted phenyl derivative)∞ mixed crystal systems is closely related to the composition ratio. Example 8 Since the doping amount of the amide tetrasubstituted phenyl derivative is large, the increase in the area of ​​the antiferroelectric phase causes the domain separation state between the columnar aggregates, making the nanometer size of the effective ferroelectric phase smaller than the critical value, so it is impossible to show ferroelectric behavior under the same electric field, frequency and temperature as Examples 1 to 7, affecting the polarization performance of the mixed crystal. The longer the carbon chain of the substituent means the higher the molecular softness, the polar structural unit has a higher degree of freedom of movement, and can provide more energy for the electric dipole moment reversal in the high-temperature liquid crystal state. Therefore, Examples 11 to 12 show a higher dielectric constant and a smaller coercive electric field.

[0075] Microscopic morphology observation:

[0076] The organic ferroelectric of Example 2 was prepared into a thin film sample on a mica plate, and the surface micromorphology of the film material was observed using an atomic force microscope (AFM) (see Figure 1 ) found that continuous one-dimensional fibers can be formed between mixed crystals, proving that when the doping amount of amide tetrasubstituted phenyl derivatives is large, amide trisubstituted phenyl derivatives with ferroelectric phase dominate and no obvious domain separation occurs.

[0077] The mixed crystal of Example 8 was prepared into a thin film sample on a mica plate, and the surface micromorphology of the film material was measured by AFM (see Figure 2 ) observations found that the surface morphology of the molecular assembly of the mixed crystal changed into discontinuous fragmented nanofibers, proving that when the doping amount of the amide tetrasubstituted phenyl derivative is large, an obvious domain separation state can be produced between the columnar aggregates of (amide trisubstituted phenyl derivative)∞ and (amide tetrasubstituted phenyl derivative)∞ that form intermolecular hydrogen bonds.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An organic ferroelectric material with adjustable polarization properties, characterized in that: Prepared from ① an amide trisubstituted phenyl derivative; or ② an amide trisubstituted phenyl derivative amide and an amide tetrasubstituted phenyl derivative; Wherein, the structure of the tri-substituted phenyl derivative of amide is shown in formula (I); the structure of the tetra-substituted phenyl derivative of amide is shown in formula (II); In formula (I), n=8-12; in formula (II), m=8-12.

2. The organic ferroelectric material according to claim 1, characterized in that In formula (I), -C n H 2n+1 is a straight chain structure; in formula (II), -C m H 2m+1 It is a straight chain structure.

3. The organic ferroelectric material according to claim 1, characterized in that The molar ratio of the amide tri-substituted phenyl derivative amide to the amide tetra-substituted phenyl derivative is ≥10:

1.

4. The method for preparing the organic ferroelectric material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1) preparing a solution containing an amide tri-substituted phenyl derivative or a mixed solution containing an amide tri-substituted phenyl derivative and an amide tetra-substituted phenyl derivative; Step 2) After the solution or mixed solution prepared in step 1 is allowed to stand, an ion exchange resin is added to purify the organic ferroelectric.

5. The preparation method according to claim 4, characterized in that: In step 1), the organic solvent is selected from at least one of dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, toluene, N,N-dimethylformamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone.

6. The preparation method according to claim 4, characterized in that: In step 2), the standing time is ≥ 15 min; Preferably, in step 2), the ion exchange resin is added and stirred to mix evenly; Preferably, in step 2), the ion exchange resin is added, stirred, and then allowed to stand; the standing time is ≥ 15 min.

7. The preparation method according to claim 4, characterized in that: In step 2), the ion exchange resin is selected from any one of strongly acidic cationic analytical grade AG 50W resin, AG MP-50 macroporous resin and biotechnology grade AG 50W resin.

8. The preparation method according to claim 4, characterized in that: The method further includes post-processing after step 2); the post-processing includes washing, filtering and rotary evaporation drying.

9. The preparation method according to claim 8, characterized in that: The washing is ethyl acetate washing.

10. Use of the organic ferroelectric material according to any one of claims 1 to 3 in the preparation of a dielectric energy storage capacitor.

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