A polymer containing carboxyl Schiff base units and its preparation method and application

Abstract

A polymer containing a carboxyl Schiff base unit, its preparation method and application, the present invention is to solve the problem that the electrochromic performance of existing conductive polymers needs to be improved. Preparation method: 4-(bis(4-(5-formylthiophene-2-yl)phenyl)amino)benzoic acid and 1,5-diaminonaphthalene are added to an organic solvent, heated to a temperature of 80-140°C under inert gas conditions for reaction, the mixture in the reaction flask is poured into a mixture of ice methanol and ice water, the precipitated solid phase is collected, and a polymer containing a carboxyl Schiff base unit is obtained from the solid phase by a solid-liquid extraction method. The carboxyl group in the polymer containing a carboxyl Schiff base unit of the present invention contains active hydrogen and can form a dual ion structure with triphenylamine in the system, thereby changing the redox process of the original poly Schiff base system and improving the electrochromic performance. At the same time, the carboxyl group also forms hydrogen bonds with the molecules of the substrate material, increasing the structural stability between the electrochromic layer and the substrate.

Description

Technical Field

[0001] The invention relates to a polymer containing a carboxyl Schiff base unit and a preparation method thereof, as well as application of the polymer material containing the carboxyl Schiff base unit in electrochromism. Background Art

[0002] Electrochromic technology involves the stable and reversible change in color and transparency of a material's optical properties caused by the injection and efflux of charge carriers under an applied electric field. Electrochromic materials have applications in a wide range of fields, including architecture, automotive, aerospace, information technology, energy, and military. Compared to inorganic electrochromic materials, organic electrochromic materials offer advantages such as a wide variety, low raw material costs, fast response times, excellent stability, and ease of modification. Depending on the material type, they are categorized into organic small molecule and conductive polymer electrochromic materials. Examples of organic small molecules include triphenylamine and its derivatives, viologen, phenothiazine, and carbazole and its derivatives. These small molecules generate cationic or anionic free radicals during redox reactions. These free radicals have relatively high molar absorption coefficients, resulting in distinct color changes. However, during prolonged redox reactions, the intermediate free radicals may react with solvents, oxygen, and other factors, resulting in poor cyclic stability. Conductive polymer electrochromic materials include polyaniline, polythiophene, polycarbazole, polytriarylamine, and polySchiff bases. These polymers containing conjugated π bonds offer numerous advantages, including ease of processing, modifiability, a wide range of color variations, and excellent stability. They hold broad application prospects and are currently the most researched type of electrochromic material.

[0003] Poly-Schiff bases have a wide range of applications in pharmacy, catalysis, corrosion and electrochromism. The functional group C=N in its molecule can increase the effective conjugation length of the system, reduce the energy band gap and enhance the electrochromic performance. Summary of the Invention

[0004] The present invention aims to solve the problem that the electrochromic performance of existing conductive polymers needs to be improved, and provides a polymer containing a carboxyl Schiff base unit, a preparation method and an application thereof.

[0005] The molecular structural formula of the polymer containing carboxyl Schiff base units of the present invention is:

[0006]

[0007] Where n is a positive integer.

[0008] The preparation method of the polymer containing carboxyl Schiff base units of the present invention is achieved by the following steps:

[0009] 4-(bis(4-(5-formylthiophen-2-yl)phenyl)amino)benzoic acid and 1,5-diaminonaphthalene are added to an organic solvent in a molar ratio of 1:(1-1.8), stirred until the solid is dissolved, and reacted at 80-140°C for 70-75 hours under inert gas conditions. After the reaction is completed, the mixture is naturally cooled, and the mixture in the reaction flask is poured into a mixture of ice methanol and ice water. The precipitated solid phase is collected, and a polymer containing carboxyl Schiff base units is obtained from the solid phase by a solid-liquid extraction method.

[0010] The synthetic reaction formula of the polymer containing carboxyl Schiff base unit of the present invention is as follows:

[0011]

[0012] The application of the polymer containing carboxyl Schiff base units of the present invention is to use the polymer containing carboxyl Schiff base units as an organic electrochromic material.

[0013] The polymer backbone containing carboxyl Schiff base units in the present invention is a conjugated system, resulting in excellent electrical conductivity. Its molecular structure maintains the advantages of existing Schiff base unit-containing polymers, such as distinct color change, fast response time, and good cyclic stability. Furthermore, because the carboxyl groups in the system contain active hydrogen, they can form a dual-ion structure with triphenylamine in the system, altering the redox process of the existing poly-Schiff base system and improving electrochromic performance. Furthermore, the carboxyl groups can also form hydrogen bonds with molecules in the substrate material of the electrochromic device, increasing the structural stability between the electrochromic layer and the substrate, slowing the delamination of the polymer layer, and further improving the actual operating efficiency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 1 is the hydrogen nuclear magnetic resonance spectrum of the polymer containing carboxyl Schiff base units synthesized in the examples;

[0015] Figure 2 IR spectrum of the polymer containing carboxyl Schiff base unit synthesized in the examples;

[0016] Figure 3 1 is a cyclic voltammogram of a polymer containing a carboxyl Schiff base unit synthesized in the examples;

[0017] Figure 4 This is an electrochromic diagram of the polymer containing carboxyl Schiff base units synthesized in the examples. DETAILED DESCRIPTION

[0018] Specific embodiment 1: The molecular structure of the polymer containing carboxyl Schiff base units in this embodiment is:

[0019]

[0020] Where n is a positive integer.

[0021] Specific embodiment 2: The preparation method of the polymer containing carboxyl Schiff base units in this embodiment is implemented according to the following steps:

[0022] 4-(bis(4-(5-formylthiophen-2-yl)phenyl)amino)benzoic acid and 1,5-diaminonaphthalene are added to an organic solvent in a molar ratio of 1:(1-1.8), stirred until the solid is dissolved, and reacted at 80-140°C for 70-75 hours under inert gas conditions. After the reaction is completed, the mixture is naturally cooled, and the mixture in the reaction flask is poured into a mixture of ice methanol and ice water. The precipitated solid phase is collected, and a polymer containing carboxyl Schiff base units is obtained from the solid phase by a solid-liquid extraction method.

[0023] Specific embodiment three: This embodiment differs from specific embodiment two in that 4-(bis(4-(5-formylthiophen-2-yl)phenyl)amino)benzoic acid and 1,5-diaminonaphthalene are added to the organic solvent in a molar ratio of 1:(1.5-1.6).

[0024] Specific embodiment 4: This embodiment is different from specific embodiment 2 or 3 in that the organic solvent is N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) or N-methylpyrrolidone (NMP).

[0025] Specific embodiment 5: This embodiment differs from any one of specific embodiments 3 to 4 in that the volume ratio of the amount of 4-(bis(4-(5-formylthiophen-2-yl)phenyl)amino)benzoic acid to the organic solvent is 1 mmol:(30 mL to 60 mL).

[0026] Specific embodiment 6: This embodiment is different from any one of specific embodiments 3 to 5 in that the inert gas is nitrogen or argon.

[0027] Specific embodiment 7: This embodiment differs from any one of specific embodiments 3 to 6 in that the reaction is carried out at 120° C. for 70 to 75 hours under inert gas conditions.

[0028] Specific embodiment eight: This embodiment differs from any one of specific embodiments three to seven in that the solid-liquid extraction method is to extract the solid phase using methanol, hexane and chloroform as solvents in sequence through a Soxhlet extractor to obtain a polymer containing carboxyl Schiff base units.

[0029] Example: The preparation method of the polymer containing carboxyl Schiff base units in this example is implemented according to the following steps:

[0030] To a 100 mL round-bottom flask were added 4-(bis(4-(5-formylthiophen-2-yl)phenyl)amino)benzoic acid (0.66 g, 1.3 mmol) and 1,5-diaminonaphthalene (0.32 g, 2.0 mmol), followed by the addition of 50 mL of N,N-dimethylformamide (DMF) and stirring until the solid dissolved. The reaction was carried out at 120°C under nitrogen for 3 days. After completion of the reaction, the mixture was naturally cooled and poured into a mixture of icy methanol and ice water. The precipitated solid was collected and extracted with methanol, hexane, and chloroform via a Soxhlet extractor. A dark yellow solid containing a carboxyl Schiff base unit (0.53 g, 83%) was obtained from the solid.

[0031] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the polymer containing carboxyl Schiff base units prepared in this example. 1 H NMR (400 MHz, DMSO-d6) δ 8.81 (d, J = 36.1 Hz,2H), 7.95 (s, 2H), 7.75 (s,4H), 7.53 (dd, J = 17.1, 7.5 Hz, 6H), 7.10 (s, 9H).

[0032] Figure 2 This is the infrared spectrum of the polymer containing carboxyl Schiff base units prepared in this example. It can be seen from the figure that FT-IR (KBr, ν, cm -1 ) 1620-1590 cm -1 The spectral band is related to the stretching vibration of C=N, and the appearance of the C=N characteristic peak fully proves the successful synthesis of poly Schiff base. -1 and 3150 cm -1 The absorption peaks that appear are the CH stretching vibrations of the thiophene group and the benzene ring. The characteristic absorption peaks corresponding to the C=C stretching vibrations of the thiophene group and the aromatic ring are at 1510 cm -1 and 1530 cm -1 nearby.

[0033] pass Figure 1 and Figure 2 It can be proved that the structural formula of the conjugated polymer containing carboxyl Schiff base units prepared in this example is as follows:

[0034]

[0035] Where n is a positive integer.

[0036] Figure 3The cyclic voltammogram of the polymer containing carboxyl Schiff base units prepared in this example. Cyclic voltammetry is a method of electrochemical measurement based on electrode reactions. As the scanning potential changes, the active substance on the working electrode undergoes oxidation / reduction reactions, thereby obtaining information on the electrochemical properties of the active substance. This method requires the use of a prepared ITO with poly Schiff base film as the working electrode, Ag / AgCl as the reference electrode, and a platinum wire as the counter electrode to form a three-electrode system. 0.1 mol L -1 TBAP / ACN was used as the electrolyte, and the scan rate was 50 mV s -1 The cycling potential was applied from 0 V to 2 V, and the electrochemical activity data of poly Schiff base were obtained at 0.98 / 1.61 V (PTTB-6), which can be regarded as a quasi-reversible reaction, which is attributed to the conversion of TPA to TPA in the polymer. + The onset oxidation potential of the polymer is 0.89 V.

[0037] Figure 4 The electrochromic diagram of the polymer containing carboxyl Schiff base units prepared in this example was obtained. A UV spectrometer and a chemical workstation were used to perform spectroelectrochemical tests to further analyze the electrochromic behavior of the polymer during the redox process. -1 The electronic absorption spectra of the polymers were measured using a TBAP / ACN solution as the electrolyte and a gradient voltage. In the neutral state, the polymers exhibited varying shades of yellow. As the applied voltage increased from 0 V to 1.2 V, the polymers oxidized and generated new absorption peaks at 430 nm. The polymers exhibited a distinct electrochromic phenomenon, with the film color changing from yellow in the neutral state to purple in the oxidized state. This color change is attributed to the formation of nitrogen-centered cationic free radicals in the polymers.

Claims

1. A polymer containing carboxyl Schiff base units, characterized in that The molecular structural formula of the polymer containing carboxyl Schiff base units is: Where n is a positive integer.

2. The method for preparing a polymer containing a carboxyl Schiff base unit as claimed in claim 1, wherein The preparation method of the polymer containing carboxyl Schiff base units is achieved by the following steps: 4-(bis(4-(5-formylthiophen-2-yl)phenyl)amino)benzoic acid and 1,5-diaminonaphthalene are added to an organic solvent in a molar ratio of 1:(1-1.8), stirred until the solid is dissolved, and reacted at 80-140°C for 70-75 hours under inert gas conditions. After the reaction is completed, the mixture is naturally cooled and poured into a mixture of ice methanol and ice water. The precipitated solid phase is collected, and a polymer containing carboxyl Schiff base units is obtained from the solid phase by a solid-liquid extraction method.

3. The method for preparing a polymer containing a carboxyl Schiff base unit according to claim 2, wherein 4-(bis(4-(5-formylthiophen-2-yl)phenyl)amino)benzoic acid and 1,5-diaminonaphthalene are added to an organic solvent in a molar ratio of 1:(1.5-1.6).

4. The method for preparing a polymer containing a carboxyl Schiff base unit according to claim 2, wherein The organic solvent is N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone.

5. The method for preparing a polymer containing a carboxyl Schiff base unit according to claim 2, wherein The volume ratio of the amount of the 4-(bis(4-(5-formylthiophen-2-yl)phenyl)amino)benzoic acid to the organic solvent is 1 mmol: (30 mL to 60 mL).

6. The method for preparing a polymer containing a carboxyl Schiff base unit according to claim 2, wherein The inert gas is nitrogen or argon.

7. The method for preparing a polymer containing a carboxyl Schiff base unit according to claim 2, wherein Under inert gas conditions, react at 120°C for 70-75 hours.

8. The method for preparing a polymer containing a carboxyl Schiff base unit according to claim 2, wherein The solid-liquid extraction method is to sequentially use methanol, hexane and chloroform as solvents to extract the solid phase through a Soxhlet extractor to obtain a polymer containing carboxyl Schiff base units.

9. The use of a polymer containing a carboxyl Schiff base unit as claimed in claim 1, characterized in that The polymer containing the carboxyl Schiff base unit is used as an organic electrochromic material.

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