Alkyl-substituted free radical polymer based on 3, 4-dimethoxythiophene and preparation method thereof

Abstract

The invention discloses an alkyl-substituted free radical polymer based on 3, 4-dimethoxythiophene and a preparation method of the alkyl-substituted free radical polymer. The preparation method comprises the following steps: dissolving 3, 4-dimethoxythiophene in an organic solvent A, adding an aldehyde substance and boron trifluoride diethyl etherate, heating to 50-120 DEG C, and reacting for 2-20 hours; after the reaction is finished, quenching, extracting with an organic solvent B which is immiscible with water, collecting an organic phase, concentrating, purifying, and filtering, washing and drying the obtained product to obtain a polymer intermediate; dissolving the polymer intermediate in an organic solvent E, stirring at normal temperature, adding boron tribromide, and reacting for 0.5-12 hours; and after the reaction, quenching, filtering, washing and drying. The polymer disclosed by the invention has a strong free radical effect, is beneficial to improving the ionic conductivity and mobility, and can be applied to the fields of coating layers of organic photoelectric devices and lithium ion battery positive electrode materials and the like.

Description

Technical Field

[0001] This invention relates to the field of free radical polymer technology, and more particularly to alkyl-substituted free radical polymers based on 3,4-dimethoxythiophene and their preparation methods. Background Technology

[0002] In the fields of organic electronics, thermoelectric devices, and transparent electrodes, the core research goal is to develop polymer materials that combine high conductivity, excellent solution processability, and environmental stability. Currently, the two most representative conductive polymers are poly(3-hexylthiophene) (P3HT) and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). P3HT and PEDOT:PSS are among the most widely used organic semiconductor polymers. P3HT, with its hexyl side chain on the thiophene ring, possesses high solubility, good solution processability, and high crystallinity; researchers have designed various strategies to enhance the charge transport properties of P3HT. However, because P3HT is a closed-shell polymer, its charge carriers originate from thermal or photoexcitation, intrinsically lacking a high concentration of intrinsic charge carriers, resulting in extremely low conductivity in its undoped state. Although conductivity can be improved through chemical doping, achieving high conductivity in P3HT derivatives still faces challenges such as complex doping processes and poor stability.

[0003] Compared to P3HT, PEDOT:PSS exhibits very high conductivity due to the cationic radical structure formed in the PEDOT backbone through PSS doping. However, this doped system also brings inherent drawbacks: firstly, the inherent strong acidity of its aqueous dispersion can corrode the metal electrodes and functional layers in the device; secondly, the hygroscopic PSS component may lead to decreased device stability; furthermore, its relatively simple work function limits its application in certain high-performance optoelectronic devices. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide an alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene that combines the advantages of P3HT and PEDOT:PSS while avoiding their shortcomings.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] An alkyl open-shell substituted radical polymer based on 3,4-dimethoxythiophene has the following structural formula (1): Equation (1);

[0008] C n H 2n For alkyl chains with different carbon numbers, n ranges from 1 to 20.

[0009] To further achieve the objectives of this invention, preferably, the molecular weight of the alkyl open-shell substituted free radical polymer based on 3,4-dimethoxythiophene is 2000 Da to 10000 Da.

[0010] The preparation method of the alkyl-substituted open-shell free radical polymer based on 3,4-dimethoxythiophene is as follows: 3,4-dimethoxythiophene is dissolved in organic solvent A, aldehydes and boron trifluoride diethyl ether are added, and the mixture is heated to 50-120℃ and reacted for 2-20 h; after the reaction is completed, the mixture is quenched, extracted with an organic solvent B that is immiscible with water, the organic phase is collected, concentrated and purified, and the obtained product is filtered, washed and dried to obtain a polymer intermediate; the polymer intermediate is dissolved in organic solvent E, stirred at room temperature, and boron tribromide is added and reacted for 0.5-12 h; after the reaction is quenched, the mixture is filtered, washed and dried to obtain the alkyl-substituted free radical polymer based on 3,4-dimethoxythiophene; the molar ratio of 3,4-dimethoxythiophene to aldehydes is controlled to be 1:1.

[0011] Preferably, the amount of raw material used, in molar parts, is:

[0012] 1-100 parts of boron trifluoride diethyl ether

[0013] 1-100 parts of boron tribromide.

[0014] Preferably, the aldehyde is a C1-C20 aliphatic aldehyde.

[0015] Preferably, the organic solvent A is one or more of chloroform, dichloromethane, tetrahydrofuran, 1,4-dioxane, and acetonitrile; each gram of 3,4-dimethoxythiophene is dissolved in 10 to 100 mL of organic solvent A.

[0016] Preferably, the quenching is achieved by adding water or an alkaline aqueous solution; the purification is achieved by recrystallization.

[0017] Preferably, the recrystallization involves dissolving the concentrate in a good solvent C, and then adding a poor solvent D to precipitate the product.

[0018] Preferably, the good solvent C is tetrahydrofuran, acetone, dichloromethane, or chloroform; the bad solvent D is petroleum ether, n-hexane, methyl tert-butyl ether, or water.

[0019] Preferably, the water-immiscible organic solvent B is one or more of dichloromethane, chloroform, ethyl acetate, methyl tert-butyl ether, and n-hexane;

[0020] The organic solvent E is dichloromethane, chloroform, toluene, tetrahydrofuran, or acetonitrile;

[0021] The boron tribromide has a purity of 99%.

[0022] Compared with the prior art, the polymer and preparation method of the present invention have the following advantages and beneficial effects:

[0023] (1) This invention effectively disrupts the rigid stacking and strong π-π interactions of polymer molecular chains by introducing alkyl chains with adjustable length and structure into the polymer backbone, thereby enabling it to exhibit good solubility in common organic solvents such as N-methylpyrrolidone (NMP), tetrahydrofuran (THF), and chloroform. This characteristic lays the foundation for the preparation of high-quality films through low-cost and easily scalable solution processes (such as spin coating, spray coating, and dip coating).

[0024] (2) By selecting aldehyde monomers with different carbon chain lengths (C1-C20), the present invention can precisely design and control the alkyl side chain, thereby achieving "on-demand customization" of polymer solubility, film-forming properties, conductivity and free basic properties to meet the specific requirements of different application scenarios for material performance;

[0025] (3) The preparation method provided by the present invention is simple, the reaction conditions are mild and controllable, the raw materials used are cheap and readily available, the post-processing purification steps are simple, the product yield is high and the reproducibility is good, and it has the advantage of scaling up from laboratory to industrial production. Attached Figure Description

[0026] Figure 1 This is a synthetic route diagram of the polymer in Example 1;

[0027] Figure 2 The above are the 1H NMR spectra of the polymers obtained in Examples 1, 3, and 5 of this invention.

[0028] Figure 3 The image shows the infrared spectra of the polymer obtained in Example 1 of this invention before and after demethylation.

[0029] Figure 4 This is an infrared spectrum comparing the polymer obtained in Example 3 of the present invention before and after demethylation.

[0030] Figure 5 This is an infrared spectrum comparing the polymer obtained in Example 5 of the present invention before and after demethylation.

[0031] Figure 6The image shows the UV absorption spectra of the polymer obtained in Example 1 before and after demethylation.

[0032] Figure 7 The images shown are electron paramagnetic resonance (ESR) spectra of Examples 1, 3 and 5 of this invention. Detailed Implementation

[0033] To better understand the present invention, it will be further described below with reference to the accompanying drawings and specific embodiments. However, the implementation of the present invention is not limited thereto. The described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In view of the problems existing in the P3HT and PEDOT:PSS technologies, there is an urgent need in the field for a new type of conductive polymer that can simultaneously meet the following requirements: (1) Like P3HT, it can achieve excellent solubility and solution processability through alkyl chain design and can be synthesized using inexpensive and simple processes; (2) Like PEDOT:PSS, it has a high concentration of intrinsic charge carriers to achieve high conductivity, but does not depend on strong acid or hygroscopic dopants, thereby maintaining the neutrality, stability and high work function of the material.

[0035] Therefore, this invention provides an open-shell radical polymer based on 3,4-dimethoxythiophene. Its unique open-shell radical properties result in high carrier concentration during device operation, providing a material structure basis for achieving high intrinsic conductivity without external doping. By introducing tunable alkyl chains onto the thiophene units, its solubility and processability can be effectively controlled, similar to P3HT. This develops a class of neutral radical polymers that can be synthesized easily and possess both high conductivity and excellent processability, overcoming the inherent acidic defects of PEDOT:PSS and providing a superior material choice for next-generation organic electronic devices.

[0036] Specifically, the present invention discloses an alkyl open-shell substituted radical polymer based on 3,4-dimethoxythiophene, having the following structural formula (1): Equation (1);

[0037] Structural formula (1) C n H 2n This represents alkyl chains with different carbon numbers, where n ranges from 1 to 20.

[0038] The present invention can control the molecular weight of the alkyl open-shell substituted free radical polymer based on 3,4-dimethoxythiophene suitable for the purposes of the present invention by controlling the degree of polymerization, preferably with a molecular weight of 2000 Da to 10000 Da.

[0039] like Figure 1 As shown, the present invention relates to a method for preparing an alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene: 3,4-dimethoxythiophene is dissolved in organic solvent A, aldehydes and boron trifluoride diethyl ether are added, and the mixture is heated to 50-120°C and reacted for 2-20 h; after the reaction is completed, the mixture is quenched, extracted with an organic solvent B that is immiscible with water, the organic phase is collected, concentrated and purified, and the obtained product is filtered, washed and dried to obtain a polymer intermediate; the polymer intermediate is dissolved in organic solvent E, stirred at room temperature, and boron tribromide is added and reacted for 0.5-12 h; after the reaction is quenched, the mixture is filtered, washed and dried to obtain an alkyl-substituted radical polymer based on 3,4-dimethoxythiophene; the molar ratio of 3,4-dimethoxythiophene to aldehydes is controlled to be 1:1. In this method, the selection of quenching, extraction, filtration, washing, drying, and various solvents can be based on the solubility of the raw material solute and the purpose of the invention; the amount of the main raw materials is mainly controlled by ensuring that the molar amounts of 3,4-dimethoxythiophene and aldehydes are the same; as for boron trifluoride ether and boron tribromide, they can be adjusted within a wide range.

[0040] Preferably, the amount of raw material used, in molar parts, is:

[0041] 1-100 parts of boron trifluoride diethyl ether

[0042] 1-100 parts of boron tribromide.

[0043] As a preferred embodiment of the present invention, the aldehydes are selected as C1-C20 aliphatic aldehydes.

[0044] As a preferred embodiment of the present invention, organic solvent A is selected from one or more of chloroform, dichloromethane, tetrahydrofuran, 1,4-dioxane, and acetonitrile; each gram of 3,4-dimethoxythiophene is dissolved in 10 to 100 mL of organic solvent A.

[0045] As a preferred embodiment of the present invention, the good solvent C is selected from tetrahydrofuran, acetone, dichloromethane or chloroform.

[0046] As a preferred embodiment of the present invention, the undesirable solvent D is selected from petroleum ether, n-hexane, methyl tert-butyl ether, or water.

[0047] As a preferred embodiment for achieving the purpose of this invention, the organic solvent B that is immiscible with water is selected from one or more of dichloromethane, chloroform, ethyl acetate, methyl tert-butyl ether and n-hexane.

[0048] As a preferred embodiment of the present invention, the organic solvent E is selected from dichloromethane, chloroform, toluene, tetrahydrofuran, or acetonitrile.

[0049] As a preferred embodiment of the present invention, quenching is achieved by adding water or an alkaline aqueous solution; purification is achieved by recrystallization. Recrystallization involves dissolving the concentrate in a good solvent C, then adding a poor solvent D to precipitate the product. The purity of boron tribromide is preferably 99%.

[0050] Example 1

[0051] 1.0 g of 3,4-dimethoxythiophene was dissolved in 20 mL of organic solvent A (chloroform), followed by the addition of 528 mg of an aldehyde substrate (dimethoxymethane) and 1.75 mL of boron trifluoride diethyl ether. The reaction mixture was heated to 90 °C and stirred at this temperature for 12 hours. After the reaction was complete, the reaction mixture was cooled to room temperature and quenched with 20 mL of deionized water. Subsequently, the mixture was extracted with 20 mL of water-immiscible organic solvent B (dichloromethane), and the organic phase was separated and collected. The organic phase was concentrated to obtain a crude product. The crude product was purified by recrystallization. Specifically, the crude product was dissolved in a suitable amount of good solvent C (dichloromethane), and then a poor solvent D (petroleum ether) was slowly added until the polymer intermediate was completely precipitated. The solid was collected by filtration, washed with petroleum ether and deionized water, and dried under vacuum to obtain a methyl-substituted polymer intermediate based on 3,4-dimethoxythiophene. The dried intermediate was dissolved in 20 mL of organic solvent E (dichloromethane) and stirred at room temperature. Then, 1.0 mL of boron tribromide was slowly added dropwise to the solution while stirring. After the addition was complete, the reaction was continued at room temperature for 1 hour. After the reaction was completed, 20 mL of deionized water was added to the system to quench the reaction. The solid product was collected by filtration and washed thoroughly with water and methanol. Finally, it was dried in a vacuum oven to obtain the final target product—a methyl-substituted free radical polymer based on 3,4-dimethoxythiophene, with n=1 in structural formula (1).

[0052] Example 2

[0053] 1.0 g of 3,4-dimethoxythiophene was dissolved in 25 mL of organic solvent A (chloroform), followed by the addition of 403 mg of an aldehyde substrate (propionaldehyde) and 1.75 mL of boron trifluoride diethyl ether. The reaction mixture was heated to 90 °C and stirred at this temperature for 15 hours. After the reaction was complete, the reaction mixture was cooled to room temperature and quenched with 20 mL of deionized water. Subsequently, the mixture was extracted with 20 mL of water-immiscible organic solvent B (dichloroform), and the organic phase was separated and collected. The organic phase was concentrated and purified by recrystallization. Specifically, the concentrate was dissolved in a suitable amount of good solvent C (acetone), and then the poor solvent D (n-hexane) was slowly added until the polymer intermediate was completely precipitated. The solid was collected by filtration, washed with n-hexane, and dried under vacuum to obtain the polymer intermediate.

[0054] The dried intermediate was dissolved in 30 mL of organic solvent E (chloroform) and stirred at room temperature. Then, 1.2 mL of boron tribromide was slowly added dropwise to the solution while stirring. After the addition was complete, the reaction was continued at room temperature for 2 hours. After the reaction was completed, 30 mL of deionized water was added to the system to quench the reaction. The solid product was collected by filtration and washed thoroughly with water and ethanol. Finally, it was dried in a vacuum oven to obtain the final target product—an ethyl-substituted free radical polymer based on 3,4-dimethoxythiophene, with n=2 in structural formula (1).

[0055] Example 3

[0056] 1.0 g of 3,4-dimethoxythiophene was dissolved in 20 mL of organic solvent A (chloroform), followed by the addition of 988 mg of an aldehyde substrate (nonanal) and 2.18 mL of boron trifluoride diethyl ether. The reaction mixture was heated to 110 °C and stirred at this temperature for 15 hours. After the reaction was complete, the reaction mixture was cooled to room temperature and quenched with 30 mL of deionized water. Subsequently, the mixture was extracted with 30 mL of water-immiscible organic solvent B (dichloroform), and the organic phase was separated and collected. The organic phase was concentrated and purified by recrystallization. Specifically, the concentrate was dissolved in a suitable amount of good solvent C (dichloroform), and then poor solvent D (methanol) was slowly added until the polymer intermediate was completely precipitated. The solid was collected by filtration, washed with methanol, and dried under vacuum to obtain the polymer intermediate. The dried intermediate was dissolved in 25 mL of organic solvent E (toluene) and stirred at room temperature. Subsequently, 2.0 mL of boron tribromide was slowly added dropwise to the solution under stirring. After the addition was complete, the reaction system was heated to 50 °C and reacted for 4 hours. After the reaction was completed, the system was cooled to room temperature, and 50 mL of deionized water was added to quench the reaction. The solid product was collected by filtration and washed thoroughly with water and methanol. Finally, it was dried in a vacuum oven to obtain the final target product—an octyl-substituted free radical polymer based on 3,4-dimethoxythiophene, with n=8 in structural formula (1).

[0057] Example 4

[0058] 1.0 g of 3,4-dimethoxythiophene was dissolved in 25 mL of organic solvent A (chloroform), followed by the addition of 793 mg of an aldehyde substrate (heptanal) and 2.18 mL of boron trifluoride diethyl ether. The reaction mixture was heated to 110 °C and stirred at this temperature for 12 hours. After the reaction was completed, the reaction mixture was cooled to room temperature and quenched with 25 mL of deionized water. Subsequently, the mixture was extracted with 25 mL of water-immiscible organic solvent B (ethyl acetate), and the organic phase was separated and collected. The organic phase was concentrated and purified by recrystallization. Specifically, the concentrate was dissolved in a suitable amount of good solvent C (chloroform), and then a poor solvent D (methyl tert-butyl ether) was slowly added until the polymer intermediate was completely precipitated. The solid was collected by filtration, washed with methyl tert-butyl ether, and dried under vacuum to obtain the polymer intermediate. The dried intermediate was dissolved in 40 mL of organic solvent E (tetrahydrofuran) and stirred at room temperature. Subsequently, 1.5 mL of boron tribromide was slowly added dropwise to the solution under stirring. After the addition was complete, the reaction was continued at room temperature for 6 hours. After the reaction was completed, 40 mL of deionized water was added to the system to quench the reaction. The solid product was collected by filtration and washed thoroughly with water and ethanol. Finally, it was dried in a vacuum oven to obtain the final target product—a hexyl-substituted free radical polymer based on 3,4-dimethoxythiophene, with n=6 in structural formula (1).

[0059] Example 5

[0060] 1.0 g of 3,4-dimethoxythiophene was dissolved in 20 mL of organic solvent A (chloroform), followed by the addition of 598 mg of an aldehyde substrate (pentanal) and 2.18 mL of boron trifluoride diethyl ether. The reaction mixture was heated to 110 °C and stirred at this temperature for 12 hours. After the reaction was complete, the reaction mixture was cooled to room temperature and quenched and washed with 20 mL of saturated sodium bicarbonate solution. Subsequently, the mixture was extracted with 20 mL of water-immiscible organic solvent B (dichloroform), and the organic phase was separated and collected. The organic phase was concentrated and purified by recrystallization. Specifically, the concentrate was dissolved in a suitable amount of good solvent C (tetrahydrofuran), and then the poor solvent D (water) was slowly added until the polymer intermediate was completely precipitated. The solid was collected by filtration, washed with water, and dried under vacuum to obtain the polymer intermediate. The dried intermediate was dissolved in 15 mL of organic solvent E (acetonitrile) and stirred at room temperature. Subsequently, 0.8 mL of boron tribromide was slowly added dropwise to the solution under stirring. After the addition was complete, the reaction was continued at room temperature for 0.5 hours. After the reaction was completed, 30 mL of deionized water was added to the system to quench the reaction. The solid product was collected by filtration and washed thoroughly with water and methanol. Finally, it was dried in a vacuum oven to obtain the final target product—a butyl-substituted free radical polymer based on 3,4-dimethoxythiophene, with n=4 in structural formula (1).

[0061] Example 6

[0062] 1.0 g of 3,4-dimethoxythiophene was dissolved in 30 mL of organic solvent A (chloroform), followed by the addition of 1.42 g of an aldehyde substrate (tridecylaldehyde) and 2.18 mL of boron trifluoride diethyl ether. The reaction mixture was heated to 100 °C and stirred at this temperature for 18 hours. After the reaction was complete, the reaction mixture was cooled to room temperature and quenched and washed with 30 mL of saturated sodium bicarbonate solution. Subsequently, the mixture was extracted with 30 mL of water-immiscible organic solvent B (ethyl acetate), and the organic phase was separated and collected. The organic phase was concentrated and purified by recrystallization. Specifically, the concentrate was dissolved in a suitable amount of good solvent C (acetone), and then a poor solvent D (methanol) was slowly added until the polymer intermediate completely precipitated. The solid was collected by filtration, washed with methanol, and dried under vacuum to obtain the polymer intermediate. The dried intermediate was dissolved in 40 mL of organic solvent E (toluene) and stirred at room temperature. Subsequently, 1.8 mL of boron tribromide was slowly added dropwise to the solution under stirring. After the addition was complete, the reaction system was heated to 60 °C and reacted for 3 hours. After the reaction was completed, the system was cooled to room temperature, and 50 mL of deionized water was added to quench the reaction. The solid product was collected by filtration and washed thoroughly with water and ethanol. Finally, it was dried in a vacuum oven to obtain the final target product—a dodecyl-substituted free radical polymer based on 3,4-dimethoxythiophene, with n=12 in structural formula (1).

[0063] Example 7

[0064] 1.0 g of 3,4-dimethoxythiophene was dissolved in 35 mL of organic solvent A (chloroform), followed by the addition of 1.98 g of an aldehyde substrate (nonadecanal) and 2.50 mL of boron trifluoride diethyl ether. The reaction system was heated to 120 °C and stirred at this temperature for 20 hours. After the reaction was completed, the reaction mixture was cooled to room temperature and quenched and washed with 40 mL of saturated sodium bicarbonate solution. Subsequently, the mixture was extracted with 40 mL of water-immiscible organic solvent B (dichloroform), and the organic phase was separated and collected. The organic phase was concentrated and purified by recrystallization. Specifically, the concentrate was dissolved in a suitable amount of good solvent C (chloroform), and then a poor solvent D (ethanol) was slowly added until the polymer intermediate was completely precipitated. The solid was collected by filtration, washed with ethanol, and dried under vacuum to obtain the polymer intermediate. The dried intermediate was dissolved in 50 mL of organic solvent E (tetrahydrofuran) and stirred at room temperature. Subsequently, 2.2 mL of boron tribromide was slowly added dropwise to the solution under stirring. After the addition was complete, the reaction was continued at room temperature for 8 hours. After the reaction was completed, 60 mL of deionized water was added to the system to quench the reaction. The solid product was collected by filtration and washed thoroughly with water and methanol. Finally, it was dried in a vacuum oven to obtain the final target product—an octadecyl-substituted free radical polymer based on 3,4-dimethoxythiophene, with n=18 in structural formula (1).

[0065] The 1H NMR spectra of the polymers obtained in Examples 1, 3, and 5 above are shown below. Figure 2 As shown, by Figure 2 It can be seen that none of the products exhibited the characteristic peak of the proton on the thiophene ring at approximately 6.8-7.2 ppm, while the multiple peaks appearing in the high-field region (0.8-2.5 ppm) belonged to the protons on the alkyl side chains (-CH2-, -CH3), corresponding to the presence of the alkyl chain structure. Notably, the sharp singlet peak of the methoxy group (-OCH3) in the starting material 3,4-dimethoxythiophene (approximately 3.8-4.0 ppm) essentially disappeared in the final product, proving that boron tribromide successfully removed the methyl group, forming the catechol or quinone structural environment required for the target radical structure.

[0066] The infrared spectra of the polymer obtained in Example 1 before and after demethylation are shown below. Figure 3 As shown. From Figure 3 As can be seen in the spectrum, skeletal vibration peaks of the thiophene ring and CH stretching vibration peaks of the alkyl chain are observed. Similarly, the peaks at 2960-2870 cm⁻¹ are also present. -1 The characteristic absorption peak of COC (methoxy) was significantly weakened or disappeared, indicating that the methyl group had been completely removed, which is consistent with the NMR results.

[0067] The infrared spectra of the polymer obtained in Example 3 above before and after demethylation are shown in the figure. Figure 4 As shown. From Figure 4 As can be seen in the spectrum, skeletal vibration peaks of the thiophene ring and CH stretching vibration peaks of the alkyl chain are observed. Similarly, the peaks at 2960-2870 cm⁻¹ are also present. -1 The characteristic absorption peak of COC (methoxy) was significantly weakened or disappeared, indicating that the methyl group had been completely removed, which is consistent with the NMR results.

[0068] The infrared spectra of the polymer obtained in Example 5 above before and after demethylation are shown in the figure. Figure 5 As shown in Figure 5, the spectrum reveals skeletal vibration peaks of the thiophene ring and CH stretching vibration peaks of the alkyl chain. Similarly, the peaks at 2960-2870 cm⁻¹ are also observed. -1 The characteristic absorption peak of COC (methoxy) was significantly weakened or disappeared, indicating that the methyl group had been completely removed, which is consistent with the NMR results.

[0069] The UV absorption spectra of the polymer obtained in Example 1 above before and after demethylation are as follows: Figure 6 As shown. From Figure 6 It can be seen that the ultraviolet absorption has shifted significantly from 800nm ​​to around 1300nm.

[0070] The electron paramagnetic resonance (ESR) spectra of Examples 1, 3, and 5 above are as follows: Figure 7 As shown. From Figure 7 As can be seen, all the products of the examples exhibited strong, symmetrical EPR single-peak signals at room temperature, with g values ​​around 2.0030, which is typical of organic conjugated radicals. This signal demonstrates the presence of unpaired electrons on the thiophene ring conjugated backbone, indicating the successful acquisition of the target radical polymer.

[0071] Equation (1);

[0072] Wherein, n is the number of carbon atoms in the alkyl chain (e.g., Example 1: -CH2; Example 2: -C2H5; Example 3: -C8H). 16 Example 4: -C6H 12 Example 5: -C4H8), this structure is a resonance hybrid, and its quinone resonance configuration can stably contain unpaired electrons (·), thus exhibiting open-shell radical characteristics. This polymer consists of alternating 3,4-dioxothiophene and alkyl chains, with hydrogen atoms at both ends of the structure.

[0073] As shown in the examples, all products are soluble in common organic solvents. The fundamental reason for this is the alkyl chain (-C) introduced onto the side chain. n H 2nAlkyl groups (such as alkyl groups) act as "molecular spacers," effectively disrupting the strong π-π stacking interactions between the polymer backbone, thereby significantly improving solubility. Longer alkyl chains (such as the octyl group in Example 3) generally result in better solubility.

[0074] The polymers obtained in Examples 1-5 underwent key performance tests on solubility and conductivity, and were compared with conventional materials on the market. The specific results are as follows:

[0075] 1. Solubility Test: At room temperature (25°C), 10 mg of polymer sample was taken and 1 mL of a specific organic solvent was added stepwise. The complete dissolution to form a homogeneous and stable solution was observed visually and under UV light. The test results showed that all products of the examples exhibited good solubility in three common organic solvents: N-methylpyrrolidone (NMP), tetrahydrofuran (THF), and chloroform (solubility > 5 mg / mL), which provides a solid foundation for their solution processing.

[0076] 2. Conductivity Test: The polymer powder was pressed into standard discs under a pressure of 10 MPa, and its intrinsic conductivity was measured using the four-probe method. The test results showed that the conductivity of Examples 1, 3, and 5 was 5.2 × 10⁻ ... 4 S / cm, 3.8 × 10⁻³ S / cm, 6.4 × 10⁻³ S / cm. The conductivity of the product of this invention is significantly higher than that of undoped P₃HT (<10⁻³ S / cm). 5 The conductivity of PEDOT:PSS (> 1 S / cm) directly demonstrates the effectiveness of its open-shell radical structure as an intrinsic carrier source. Although its conductivity is lower than that of doped PEDOT:PSS (> 1 S / cm), it is precisely this moderate and tunable conductivity, combined with its neutral characteristics, that makes it more advantageous in certain specific applications.

[0077] The alkyl-substituted free radical polymer based on 3,4-dimethoxythiophene provided by this invention successfully combines excellent solution processability with moderate intrinsic conductivity. Its neutral and stable properties make it more balanced and reliable than P3HT and PEDOT:PSS in application scenarios that require both conductivity and interfacial stability, filling a gap in the existing material system.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An alkyl open-shell substituted free radical polymer based on 3,4-dimethoxythiophene, characterized in that... It has the following structural formula as shown in formula (1): Equation (1); n can be 1 to 20.

2. The alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene as described in claim 1, characterized in that, The molecular weight of the alkyl open-shell substituted free radical polymer based on 3,4-dimethoxythiophene is 2000 Da to 10000 Da.

3. The method for preparing the alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene according to claim 1 or 2, characterized in that: 3,4-Dimethoxythiophene was dissolved in organic solvent A, and aldehydes and boron trifluoride diethyl ether were added. The mixture was heated to 50-120℃ and reacted for 2-20 h. After the reaction was completed, the mixture was quenched and extracted with organic solvent B, which is immiscible with water. The organic phase was collected, concentrated, and purified. The obtained product was filtered, washed, and dried to obtain a polymer intermediate. The polymer intermediate was dissolved in organic solvent E, stirred at room temperature, and boron tribromide was added and reacted for 0.5-12 h. After the reaction was quenched, the mixture was filtered, washed, and dried to obtain an alkyl-substituted free radical polymer based on 3,4-dimethoxythiophene. The molar ratio of 3,4-dimethoxythiophene to aldehydes was controlled to be 1:

1.

4. The method for preparing the alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene as described in claim 3, characterized in that, The amount of raw materials used, in molar parts, is: 1-100 parts of boron trifluoride diethyl ether 1-100 parts of boron tribromide.

5. The method for preparing the alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene as described in claim 3, characterized in that, The aldehydes are C1-C20 aliphatic aldehydes.

6. The method for preparing the alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene as described in claim 3, characterized in that, The organic solvent A is one or more of chloroform, dichloromethane, tetrahydrofuran, 1,4-dioxane, and acetonitrile; each gram of 3,4-dimethoxythiophene is dissolved in 10 to 100 mL of organic solvent A.

7. The method for preparing the alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene as described in claim 3, characterized in that, The quenching is achieved by adding water or an alkaline aqueous solution; the purification is achieved by recrystallization.

8. The method for preparing the alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene as described in claim 7, characterized in that, The recrystallization process involves dissolving the concentrate in a good solvent C, then adding a poor solvent D to precipitate the product.

9. The method for preparing the alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene as described in claim 8, characterized in that, The good solvent C is tetrahydrofuran, acetone, dichloromethane, or chloroform; the bad solvent D is petroleum ether, n-hexane, methyl tert-butyl ether, or water.

10. The method for preparing the alkyl-substituted open-shell radical polymer based on 3,4-dimethoxythiophene as described in claim 3, characterized in that, The organic solvent B that is immiscible with water is one or more of dichloromethane, chloroform, ethyl acetate, methyl tert-butyl ether, and n-hexane; The organic solvent E is dichloromethane, chloroform, toluene, tetrahydrofuran, or acetonitrile; The boron tribromide has a purity of 99%.

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