Double-cable conjugated polymer based on isoindigo and its application in electrochromic field

Abstract

The present invention relates to an isoindigo-based double-cable conjugated polymer and its application in the field of electrochromism. The isoindigo-based double-cable conjugated polymer has the following structural formula, wherein Ar is one of naphthalimide, perylene imide, benzotriazole, naphthotriazole, benzopyrrole dione, thienopyrrole dione, bisthiophene imide and derivatives of all the above structures; n is a natural number of 1 to 10,000; m is a natural number of 1 to 12; and X is C or N. The conjugated polymer has high electrochromic stability and is an excellent electrochromic functional layer.

Description

Technical Field

[0001] The invention relates to the field of organic optoelectronics, and in particular to the design and synthesis of a donor / acceptor double-cable conjugated polymer and its application in electrochromism. Background Art

[0002] Electrochromic materials refer to materials whose doping level can be regulated by changing the applied voltage, causing changes in the band structure of the material, thereby causing changes in its optical absorption properties, which visually manifests as changes in the color of the material film. As the degree of doping (oxidation) increases, electrochromic materials can form polarons and bipolaron energy levels with lower band gaps between the valence band and the conduction band. The formation of these new energy levels changes the energy required in the valence electron transition process, which manifests as changes in absorption peaks in spectroelectrochemistry. This type of material shows commercial prospects in many fields such as low-energy display devices, electronic paper, color-changing skin, information storage and display, and can be used to update and integrate functions of various wearable electronic devices.

[0003] The evaluation of electrochromic material performance is the most important issue faced. Researchers use the following parameters and indicators to evaluate electrochromic performance.

[0004] (1) Optical contrast: (ΔT) The optical transmittance (T) between the oxidized and neutral states of an electrochromic material at a single wavelength. ox and T neut。 ), which is one of the important parameters for measuring the electrochromic performance of materials. This wavelength is determined based on the absorption spectrum of the material (multiple wavelengths may appear for the same material), that is, the wavelength corresponding to the maximum absorption peak of the material in the oxidized or neutral state. The absorption spectrum of a material refers to the absorbance or transmittance curve corresponding to the material at different wavelengths. The color change of the material is measured by the size of the absorbance of the absorption spectrum. In addition, the spectroelectrochemical experiment can also react to the generation of monopolarons or bipolarons in the material according to the different voltages applied.

[0005] (2) Coloration efficiency: (CE) refers to the ratio between the change in absorbance of the electrochromic material at a specific wavelength and the charge density of the transmittance conversion that occurs when a certain amount of electricity is injected into the conductive polymer film per unit area. Generally, the coloration efficiency value of the same polymer film during the oxidation or reduction process is fixed and has nothing to do with the thickness of the film. The coloration efficiency calculation formula is:

[0006]

[0007] in, △OD Optical density change refers to the change in optical density of polymer films at a specific wavelength. λ max , the ratio of the transmittance of the oxidized state to that of the reduced state; Q d is the charge density, which refers to the amount of charge injected per unit area.

[0008] (3) Response time: (Switching time) The time required for an electrochromic material or device to complete an oxidation (coloring state) or reduction (fading state) conversion process. The oxidation (coloring) process corresponds to the coloring response time, and the reduction (fading) process corresponds to the fading response time. The response time is generally calculated using the time required for the transmittance to change by 95%. The factors that affect the switching time mainly include: the composition of the electrolytic cell (acidity and alkalinity of the solvent, ion conductivity of the supporting electrolyte), the voltage applied during the oxidation-reduction process, and the ease of diffusion of ions in the electrochromic material.

[0009] (4) Open circuit optical memory effect: (Open circuit memory) refers to the ability of electrochromic materials to maintain the color of the oxidized or reduced state when no external voltage is applied. In operation, the optical transmittance of the polymer is tested under external pressure for a certain period of time, and then the external pressure is removed to test the optical transmittance. This change is the memory of the material or device. Related applications are reflected in the fact that light-emitting diodes (LEDs) can maintain the displayed content when the power is off. It is worth pointing out that for electrochromic materials or devices that display color in solution, due to the existence of ion diffusion or exchange, the color displayed by the electrochromic material or device will fade quickly, while all-solid-state electrochromic devices have a good memory effect.

[0010] At present, the requirements for electrochromic materials and devices are mainly high optical contrast, high coloring efficiency, short response time, good memory effect, obvious color change, good stability, etc. Professor Reynolds of Georgia Institute of Technology, Professor Toppare of Turkey, Professor Xu Chunye of USTC, Professor Meng Hong of Peking University, Professor Jia Chunyang of University of Electronic Science and Technology of China, Professor Xu Jingkun of Jiangxi Science and Technology Normal University, etc. have made important contributions in the field of electrochromism. The pursuit of high-performance electrochromic materials and devices has always been an important mission of scientific researchers. On the one hand, scientific researchers optimize the performance of existing invented materials in order to achieve performance breakthroughs; on the other hand, scientific researchers continue to develop new electrochromic materials in order to obtain more efficient and stable electrochromic performance. Summary of the invention

[0011] The primary purpose of the present invention is to provide a double-cable conjugated polymer based on isoindigo.

[0012] Another object of the present invention is to provide a method for preparing the above-mentioned isoindigo-based double-cable conjugated polymer.

[0013] Another object of the present invention is to provide the application of the above-mentioned isoindigo-based double-cable conjugated polymer in the field of electrochromism.

[0014] The purpose of the present invention is achieved through the following solutions:

[0015] Based on isoindigo blue double-cable conjugated polymer and its application in the field of electrochromism, it is characterized by having the following structure:

[0016] .

[0017] Wherein, n is a natural number of 1 to 10000; m is a natural number of 1 to 12; X is C or N, and Ar is one of naphthaleneimide, peryleneimide, benzotriazole, naphthotriazole, benzopyrroledione, thienopyrroledione, bisthiopheneimide and derivatives of all the above structures.

[0018] The isoindigo-based double-cable conjugated polymer is characterized in that the conjugated unit Ar has the following structure:

[0019] .

[0020] The preparation method of the polymer material is characterized by comprising the following steps: mixing a calculated molar ratio of a brominated alkyl chain EDOT-isoindigo-EDOT monomer with a corresponding ratio of an Ar monomer having a secondary amine functional group, reacting to obtain a polymer precursor of the polymer, and subjecting the polymer precursor to electrochemical polymerization to obtain the novel isoindigo dual-cable electrochromic conjugated polymer of the present invention.

[0021] The isoindigo-based double-cable conjugated polymer is applied in the field of electrochromism.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The present invention designs and synthesizes a new type of isoindigo-based double-cable conjugated polymer.

[0024] (2) The present invention achieves electrochromic performance with excellent stability and high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The invention provides a synthetic route for the specific implementation of isoindigo-based double-cable conjugated polymers.

[0026] Figure 2 The spectroelectrochemical diagram.

[0027] Figure 3 The kinetic stability diagram. DETAILED DESCRIPTION

[0028] The present invention is further described below through specific examples, the purpose of which is to help better understand the content of the present invention, specifically including the synthesis of polymers and device preparation methods, but these specific embodiments do not limit the scope of protection of the present invention in any way.

[0029] The practice of the present invention can adopt the conventional techniques of polymer chemistry within the art. In the following examples, efforts are made to ensure the accuracy of the numbers used (including amounts, temperatures, reaction times, etc.), but some experimental errors and deviations should be considered. The temperatures used in the following examples are expressed in ° C, and the pressure is atmospheric pressure or near atmospheric pressure. The solvents used are purchased as analytical or chromatographically pure, and all reactions are carried out in a nitrogen atmosphere. Unless otherwise noted, all reagents are commercially available.

[0030] Specific implementation methods

[0031] Example 1

[0032] Preparation of isoindigo-based double-cable conjugated polymer precursor (8)

[0033] The chemical reaction process is shown below, and the specific reaction steps and reaction conditions are as follows:

[0034] .

[0035] (1) The raw materials 6-bromo-indole-2-one (1), 6-bromo-indole-2,3-dione (2) and 3,4-ethylenedioxythiophene (EDOT) described in the above reaction formula were purchased from Beijing Bailingwei Technology Co., Ltd., and perylene imide was purchased from Suzhou Nakai Technology Co., Ltd.

[0036] (2) Preparation of compound (3)

[0037] 6-Bromo-indole-2,3-dione (0.53 g, 2.30 mmol) and 6-bromo-indole-2-one (0.50 g, 2.30 mmol) were added to a two-necked flask, and glacial acetic acid (15 mL) and concentrated hydrochloric acid (0.13 mL) were used as solvents. The mixture was reacted under reflux for 24 hours. After the reaction was stopped, the reaction solution was filtered, and the filter cake was washed three times with water, ethanol, and ether in turn, and then dried in a vacuum oven. Finally, a wine-red solid [111,113] was obtained with a yield of 92%.

[0038] (3) Preparation of compound (4)

[0039] In a two-necked flask, EDOT (0.11 g, 0.8 mmol) was dissolved in refined THF (20 mL) and stirred thoroughly at -78°C. During this period, 1.6 mol / L n-butyl lithium (13 mmol) was added dropwise to the reaction system, and the reaction was continued for 3 hours after the complete addition. Then the reaction temperature was raised to -48°C and tributyltin chloride (13 mmol) solution was added dropwise. Finally, the reaction temperature was raised to room temperature and the reaction was continued for 12 hours. The whole process was in an anhydrous, oxygen-free, nitrogen-protected environment. After the reaction was completed, the crude product was filtered to remove the lithium salt generated in the reaction, and the excess solvent was removed by rotary evaporation and directly used in subsequent reactions.

[0040] (4) Preparation of compound (5)

[0041] Refined toluene solution (50 mL) and compound (3) (0.59 g, 1.0 mmol) were added to a two-necked flask, and the reaction apparatus was evacuated and protected by nitrogen. During the stirring process, 2-tinbutyl EDOT (1.72 g, 4.0 mmol) and tetrakistriphenylphosphine palladium (Pd(PPh3)4, 0.058 g, 5.0 mmol%) were injected into the reaction apparatus in sequence. The reaction was carried out at 110°C for 24 hours, with nitrogen protection throughout the process. The reaction process was monitored by TCL. After the reaction was complete, the crude product was poured into saturated brine for washing and extracted with dichloromethane. The operation was repeated three times. The extract was collected and dried over anhydrous magnesium sulfate, filtered, and rotary evaporated. Finally, the crude product was separated by silica gel chromatography to obtain a blood-red flocculent solid with a yield of 85%.

[0042] (5) Preparation of compound (6)

[0043] 40 mL of DMF, compound (5) and anhydrous potassium carbonate (0.26 g, 1.90 mmol) were added to a two-necked flask. The reaction system was evacuated and nitrogen was introduced for protection. 1,6-dibromohexane (0.80 g, 4.84 mmol) was injected into the reaction system and reacted at 110°C for 20 hours. After the reaction was complete as detected by TCL, the reaction was stopped. The reaction system was washed with saturated brine, extracted with dichloromethane and dried over anhydrous magnesium sulfate for 12 hours. The crude product was filtered and rotary evaporated to obtain a purple-black solid after separation by silica gel chromatography. The yield was 81%.

[0044] (6) Preparation of compound (7)

[0045] Weigh 30 g of imidazole in a 100 mL round-bottom flask, heat at 120 °C to melt all the imidazole into liquid, add 1 g (2.55 mmol) 3,4,9,10-perylenetetracarboxylic dianhydride (PDA), 5.36 g (6.12 mmol) 1-bromohexylamine, heat to 140 °C and stir for 4 hours. Pour the reaction solution into 300 mL methanol, stir for a period of time, and let stand to separate so that the imidazole is fully dissolved in methanol to remove the imidazole and precipitate the product. Vacuum filter to obtain a precipitate, and place the precipitate in a 40 °C vacuum drying oven to dry to remove all methanol. Then perform column chromatography (dichloromethane: petroleum ether, 1:6) to obtain an orange solid (yield 95%).

[0046] (7) Preparation of compound (8)

[0047] Compound (6) (2.08 g, 2.92 mmol) and compound (7) (1.00 g, 1.27 mmol), potassium carbonate (0.53 g, 3.81 mmol) were added to a reaction flask, and 50 mL of DMF solution was added. The reaction mixture was stirred at 80 °C for 36 h and then cooled to room temperature. Chloroform (100 mL) and water (100 mL) were added to the organic layer, respectively, and the organic layer was separated, washed with brine, and the solvent was evaporated. The obtained solid was purified by silica gel chromatography (dichloromethane: ethyl acetate, v / v = 100: 1 as eluent) to give M compound (8) as a black solid (1.02 g, 38.6%).

[0048] Example 2

[0049] Electrochemical polymerization of isoindigo blue double-cable conjugated polymer precursor into the corresponding polymer (P1)

[0050] The chemical reaction process is shown below, and the specific reaction steps and reaction conditions are as follows:

[0051] .

[0052] (1) The electrochemical polymerization supporting electrolyte tetrabutylammonium phosphorus hexafluoride was purchased from Beijing Bailingwei Technology Co., Ltd.

[0053] (2) Under nitrogen protection, the isoindigocyanine double-cable conjugated polymer precursor was dissolved in dichloromethane at a concentration of 1 M and polymerized into the isoindigocyanine double-cable conjugated polymer P1 by electrochemical cyclic voltammetry.

[0054] Example 3

[0055] Take the polymer material P1 obtained in Example 2 as an example and apply it to electrochromic

[0056] The following examples will illustrate the isoindigo blue double-cable conjugated polymer provided by the present invention and its application process in the field of electrochromism, but the present invention is not limited to the examples given.

[0057] (1) Spectroelectrochemistry

[0058] The polymer film deposited on the ITO conductive glass prepared in Example 2 was placed in a three-electrode electrolytic cell, in which there was an acetonitrile solution containing tetrabutylammonium phosphorus hexafluoride; the working electrode was the ITO conductive glass with the polymer film attached, the counter electrode was a platinum sheet, and the reference electrode was an Ag / AgCl electrode. The constant potential method was used to adjust the voltage applied to the working electrode through an electrochemical workstation, and at the same time, a UV-visible spectrometer was used to record the variation trend of the absorption spectrum of the polymer at different voltages, and the spectral electrochemical spectrum of the polymer was obtained. Figure 2 . The spectroelectrochemical graph shows three absorption peaks at 540nm, 800nm ​​and 1500nm, which are the absorption peak of perylene imide, the π-π* absorption peak of isoindigo-EDOT and the polaron absorption peak of the material. As the voltage increases, the intensity of the first two absorption peaks of the polymer weakens or even disappears, and a new absorption peak generated by polaron absorption gradually appears in the near-infrared region. The isosbestic point of the spectrum is around 900nm, which shows that the polymer can switch back and forth between the oxidized state and the reduced state without hindrance, and has good redox performance.

[0059] (2) Study on the dynamic stability of polymer films

[0060] UV-visible spectrophotometer is used to measure the transmittance of the oxidized and reduced states of the polymer film at a specific wavelength under square wave potential, so as to calculate the optical contrast, impact time, etc. The UV-visible spectrophotometer records the time-transmittance curve, and the electrochemical workstation records the time-current curve. The coloring efficiency can also be calculated based on these two curves. Figure 3 This is the kinetic stability study spectrum of P1 at 800 nm, with a square wave potential interval of 10 seconds. The transmittance value of P1 is about 34%, and after scanning for 450 seconds, its transmittance still remains at 34%, showing relatively good kinetic stability.

[0061] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. Based on isoindigo blue double cable type conjugated polymer, characterized in that, It has the following structure: Wherein, n is a natural number of 1 to 10000; m is a natural number of 1 to 12; X is C or N, and Ar has one or more coupled structures of the following structures: Wherein R is selected from H, C1~C50 straight chain alkyl or branched chain alkyl.

2. The preparation method based on isoindigo blue double-cable conjugated polymer according to claim 1, characterized in that: The specific steps are as follows: a calculated molar ratio of bromoalkyl chain EDOT-isoindigo-EDOT monomer is mixed with a corresponding ratio of Ar monomer having a secondary amine functional group, and the reaction is carried out to obtain a polymerization precursor of the polymer, and the polymerization precursor is subjected to an electrochemical polymerization method to obtain the isoindigo double-cable conjugated polymer.

3. The isoindigo blue double-cable conjugated polymer according to any one of claims 1 to 2 is used in the field of electrochromism.

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