Preparation method of green and environmentally friendly chitosan modified polyimide substrate

Abstract

The present invention discloses a method for preparing a green and environmentally friendly chitosan-modified polyimide substrate, which specifically comprises the following steps: step 1, preparing an imide compound containing an aldehyde group; and step 2, preparing a polyimide substrate according to the product obtained in step 1. The present invention adopts biomass-based chitosan to modify polyimide, so that the prepared polyimide substrate has degradability and excellent photophysical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials and relates to a method for preparing a green and environmentally friendly chitosan modified polyimide substrate. Background Art

[0002] Polyimide has been widely used in coatings, electronic circuits, optoelectronic devices, membrane separation, and aerospace. Due to the unique "donor-acceptor" molecular structure of polyimide, it has excellent thermal stability, mechanical properties, and photophysical properties; however, due to the molecular structure of polyimide, it has problems such as dark color, high cost, and difficulty in degradation. With the development of flexible electronic technology, the application of polyimide substrates has also expanded to biomedicine, medical and other fields, and higher requirements have been put forward for polyimide substrates, such as colorless and transparent, low cost, environmentally friendly and degradable. Therefore, it is necessary to modify the existing polyimide substrates. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing a green and environmentally friendly chitosan-modified polyimide substrate, which adopts biomass-based chitosan to modify polyimide, so that the prepared polyimide substrate has degradability and excellent photophysical properties.

[0004] The technical solution adopted by the present invention is a method for preparing a green and environmentally friendly chitosan-modified polyimide substrate, which specifically comprises the following steps:

[0005] Step 1, preparing an imide compound containing an aldehyde group;

[0006] Step 2: preparing a polyimide substrate according to the product obtained in step 1.

[0007] The present invention is also characterized in that:

[0008] The specific process of step 1 is:

[0009] Step 1.1, dissolve 1.21g-2.42g of p-aminobenzaldehyde in 25mL-75mL of m-cresol solution, add 0.62g-1.24g of ethylene glycol, and stir at 50 o C-100 o C overnight, add 1.09 g to 2.18 g of pyromellitic anhydride, and purge with nitrogen for 30 to 60 min;

[0010] Step 1.2, gradually add 10-15 mL of m-cresol solution to the solution obtained in step 1.1, and heat to 100-120°C and maintain for 0.5-1h, then heat to 150-160°C and react for 3-6h, after the reaction is completed, cool to room temperature, add hydrochloric acid solution, and react for 12-24h;

[0011] Step 1.3, the solution obtained in step 1.2 is purified by column separation to obtain an aldehyde-containing imide compound.

[0012] The specific process of step 2 is:

[0013] Step 2.1, dispersing 0.5 g to 1 g of chitosan in 50 mL to 100 mL of methanol solution, swelling overnight, to obtain a mixed solution A;

[0014] Step 2.2, dissolving 2.12 g to 4.24 g of the aldehyde-containing imide compound in 50 mL to 100 mL of a methanol solution to obtain a mixed solution B;

[0015] Step 2.3, mixing the mixed solution A obtained in step 2.1 and the mixed solution B obtained in step 2.2 and stirring for 30-60 min, purging with nitrogen for 30-60 min, and heating to 60°C-80°C for 6h-12h, and cooling to room temperature after the reaction is completed;

[0016] Step 2.4, adding 0.2 g to 0.4 g of ethylenediamine to the solution obtained in step 2.3, stirring overnight at room temperature, and dialyzing to obtain a white solid powder;

[0017] Step 2.5, take 50 mg-100 mg of white solid powder, disperse it in 20 mL-30 mL of m-cresol solution, let it stand overnight, put it into a polytetrafluoroethylene mold, and vacuum dry it to form a film.

[0018] The m-cresol solution in step 1.2 contains 0.1 g to 0.2 g of isoquinoline.

[0019] The eluent formula used for column separation in step 1.3 is: ethyl acetate, cyclohexane, and methanol are mixed in a volume ratio of 2:10:1.

[0020] The beneficial effect of the present invention is that the present invention utilizes green, environmentally friendly, colorless and transparent chitosan to modify polyimide, and finally constructs a biomass-based flexible substrate with low cost, which has high light transmittance and degradability. The chitosan component dissolves and degrades in an alkaline solution; the chitosan and polyimide are connected by a carbon-nitrogen double bond, mainly because amines and aldehydes undergo a Schiff base reaction, and the reaction conditions are mild. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a comparison chart of substrate haze values ​​under different conditions in Example 1 and Comparative Example 1 in the method for preparing a green and environmentally friendly chitosan-modified polyimide substrate of the present invention;

[0022] Figure 2A comparison chart of light transmittance tests of Example 1 and Comparative Example 1 in the method for preparing a green and environmentally friendly chitosan modified polyimide substrate of the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] The method for preparing the green and environmentally friendly chitosan-modified polyimide substrate of the present invention specifically comprises the following steps:

[0025] Step 1, synthesis of an aldehyde-containing imide compound, specifically:

[0026] Take 1.21g-2.42g of p-aminobenzaldehyde and dissolve it in 25mL-75mL of m-cresol, add 0.62g-1.24g of ethylene glycol, and o C-100 o C overnight, further add 1.09g-2.18g of pyromellitic anhydride; nitrogen purge for 30min-60min, then gradually add 10mL-15mL of m-cresol solution (containing 0.1g-0.2g of isoquinoline), and the addition is completed in 20min-30min, and the temperature is raised to 100℃-120℃ for 0.5h-1h, and then raised to 150℃-160℃ for 3h-6h. After the reaction is completed, it is cooled to room temperature, and 20mL of hydrochloric acid solution with a pH of 1 is added to react for 12-24h. Finally, column separation (eluent is ethyl acetate, cyclohexane, methanol, volume ratio is 2:10:1) is used to purify the imide compound containing aldehyde group.

[0027] Step 2, preparation of a polyimide substrate, specifically:

[0028] First, 0.5g-1g chitosan was dispersed in 50mL-100mL methanol solution and swelled overnight. 2.12g-4.24g aldehyde-containing imide compound was dissolved in (50mL-100mL) methanol solution, the methanol solution containing aldehyde-containing imide compound and the methanol solution containing chitosan were mixed and stirred for 30min-60min, purged with nitrogen for 30min-60min, and heated to 60℃-80℃ for 6h-12h. Secondly, after the reaction solution was lowered to room temperature, 0.2g-0.4g of ethylenediamine was added and stirred overnight at room temperature. A 7000Da dialysis bag was used to dialyze the catalyst, unreacted small molecular monomers and high boiling point solvents to obtain a white solid powder; finally, 50mg-100mg of white solid powder was dispersed in 20mL-30mL of m-cresol solution, and after standing overnight, it was placed in a polytetrafluoroethylene mold and 45 o C conditions and vacuum dried to form a film.

[0029] Example 1

[0030] Step 1: Dissolve 1.21 g of p-aminobenzaldehyde in 25 mL of m-cresol, add 0.62 g of ethylene glycol, and heat at 50 o C overnight, and further add 1.09 g of pyromellitic anhydride; nitrogen purge for 30 min. Then gradually add 10 mL of m-cresol solution (containing 0.1 g of isoquinoline) dropwise, and the addition is completed in 20 min, and the temperature is raised to 100 ° C for 0.5 h, and then raised to 150 ° C for 3 hours. After the reaction is completed, the temperature is cooled to room temperature, and 20 mL of hydrochloric acid solution with a pH of 1 is added, and the reaction is continued for 12 h. Finally, column separation (eluent is ethyl acetate, cyclohexane, methanol, volume ratio is 2:10:1) is used to purify the imide compound containing aldehyde group.

[0031] Step 2, first, disperse 0.5g of chitosan in 50 mL of methanol solution and swell overnight. Dissolve 2.12g of aldehyde-containing imide compound in (50 mL) methanol solution, mix the obtained methanol solution and the above methanol solution containing chitosan and stir for 30 minutes, purge with nitrogen for 30 minutes, and heat to 60 °C for 6 hours. Secondly, after the reaction solution is cooled to room temperature, continue to add 0.2g of ethylenediamine and stir overnight at room temperature. Use a 7000Da dialysis bag to dialyze to remove the catalyst, unreacted small molecular monomers and high boiling point solvents to obtain a white solid powder; finally, take 50 mg of white solid powder, disperse it in 20mL of m-cresol solution, let it stand overnight, put it into a polytetrafluoroethylene grinder, and grind it at 45 o C conditions and vacuum dried to form a film.

[0032] Comparative Example 1 (the substrate is not added with chitosan, other conditions remain unchanged, the substrate is not easy to degrade, and the substrate color is dark)

[0033] Step 1: Dissolve 1.21 g of p-aminobenzaldehyde in 25 mL of m-cresol, add 0.62 g of ethylene glycol, and heat at 50 o C overnight, and further add 1.09 g of pyromellitic anhydride; nitrogen purge for 30 min. Then gradually add 10 mL of m-cresol solution (containing 0.1 g of isoquinoline) dropwise, and the addition is completed in 20 min, and the temperature is raised to 100 ° C for 0.5 h, and then raised to 150 ° C for 3 hours. After the reaction is completed, the temperature is cooled to room temperature, and 20 mL of hydrochloric acid solution with a pH of 1 is added, and the reaction is continued for 12 h. Finally, column separation (eluent is ethyl acetate, cyclohexane, methanol, volume ratio is 2:10:1) is used to purify the imide compound containing aldehyde group.

[0034] Step 2, dissolving 2.12 g of the aldehyde-containing imide compound in (50 mL) methanol solution, purging the obtained methanol solution with nitrogen for 30 min, adding 0.2 g of ethylenediamine and stirring overnight at room temperature, dialyzing the unreacted small molecular monomers and high boiling point solvents using a 7000Da dialysis bag to obtain a white solid powder; finally, taking 50 mg of the yellow solid powder, dispersing it in 20 mL of m-cresol solution, standing it overnight, placing it in a polytetrafluoroethylene grinder, and sieving it at 45 o C conditions and vacuum dried to form a film.

[0035] Comparative Example 2 (During the synthesis of the aldehyde-containing imide compound, ethylene glycol was not added and the target product was not obtained)

[0036] Take 1.21-2.42g of p-aminobenzaldehyde and dissolve it in 25-75mL of m-cresol at 50-100 o C overnight, further add 1.09-2.18g of pyromellitic anhydride; nitrogen purge for 30-60 min. Then gradually add 10-15 mL of m-cresol solution (containing 0.1-0.2g of isoquinoline) dropwise, and the addition is completed in 20-30 min, and the temperature is raised to 100-120 ℃ and maintained for 0.5-1h, and then raised to 150-160 ℃ for reaction for 3-6 hours. After the reaction is completed, the temperature is cooled to room temperature, 20 mL of hydrochloric acid solution with a pH of 1 is added, and the reaction is carried out for 12-24 h. The target product (imide compound containing aldehyde group) was not obtained, and the final product was p-aminobenzaldehyde self-polymer.

[0037] Results and Discussion:

[0038] Chitosan is widely used in the biomedical field due to its low toxicity, biocompatibility and environmental protection. In this patent, chitosan and polyimide are connected through the Schiff base C=N double bond. The chitosan in Example 1 is well dissolved and degraded under acidic conditions; while under alkaline conditions, the Schiff base C=N double bond connecting chitosan and polyimide is hydrolyzed, which is conducive to its degradation. Thanks to the introduction of chitosan, the substrate in Example 1 can be degraded under both acidic and alkaline conditions.

[0039] The substrates of Example 1 and Comparative Example 1 were soaked in water, acetic acid solution (Ph = 3), and sodium hydroxide solution (Ph = 10) for 12 hours, respectively. Example 1 and Comparative Example 1 were relatively stable in water, and both showed changes. Since Example 1 contained chitosan, the substrate was partially corroded in the acetic acid solution, mainly due to the dissolution and degradation of chitosan. The substrate changed from colorless and transparent to white, and at the same time, the haze of the substrate increased significantly, such as Figure 1After the substrate of Example 1 was immersed in sodium hydroxide solution, the haze value increased slightly. The main reason was that the Schiff base in chitosan and polyimide was hydrolyzed under alkaline conditions. The characteristic absorption peak of the C=N double bond of the Schiff base in Example 1 was found to be 1690 cm -1 After alkali treatment, the infrared characteristic absorption peak disappears. The main reason is that the C=N double bond of the Schiff base undergoes hydrolysis reaction after alkali treatment.

[0040] On the contrary, Comparative Example 1 shows good stability under acidic conditions. After being soaked in acid, no obvious changes occur, and the substrate cannot be degraded. Under alkaline conditions, the substrate haze changes slightly. The following Table 1 shows the corrosion of the substrate under different conditions:

[0041] Table 1

[0042]

[0043] like Figure 2 As shown, chitosan was added in Example 1, and its light absorption in the wavelength range of 400-500 nm was weak, and the substrate showed better transparency. On the contrary, chitosan was not added in Comparative Example 1, and its absorption in the wavelength range of 400-500 nm was strong, and the color of the substrate was light yellow. It was also found that the light transmittance of Example 1 at a wavelength of 550 nm (87%) was higher than that of Comparative Example 1 (83%).

[0044] Example 2

[0045] Step 1: Dissolve 2.42 g of p-aminobenzaldehyde in 75 mL of m-cresol, add 1.24 g of ethylene glycol, and heat at 100 °C. o C overnight, and further add 2.18g of pyromellitic anhydride; nitrogen purge for 60 min. Then gradually add 15 mL of m-cresol solution (containing 0.2g of isoquinoline) dropwise, and the addition is completed in 30 min, and the temperature is raised to 120℃ and maintained for 1h, and then raised to 160℃ for reaction for 6 hours. After the reaction is completed, the temperature is cooled to room temperature, 20 mL of hydrochloric acid solution with a pH of 1 is added, and the reaction is continued for 24 h. Finally, column separation (eluent is ethyl acetate, cyclohexane, methanol, volume ratio is 2:10:1) is used to purify the imide compound containing aldehyde group.

[0046] Step 2. First, disperse 1g of chitosan in 100mL of methanol solution and swell overnight. Dissolve 4.24g of aldehyde-containing imide compound in (100mL) methanol solution, mix the obtained methanol solution and the above methanol solution containing chitosan and stir for 60min, purge with nitrogen for 60min, and heat to 80℃ for 12h. Secondly, after lowering the reaction solution to room temperature, continue to add 0.4g of ethylenediamine and stir overnight at room temperature. Use a 7000Da dialysis bag to dialyze to remove the catalyst, unreacted small molecular monomers and high boiling point solvents to obtain a white solid powder; finally, take 100mg of white solid powder, disperse it in 30mL of m-cresol solution, let it stand overnight, put it into a polytetrafluoroethylene grinder, and grind it at 45 o C conditions and vacuum dried to form a film.

[0047] Example 3

[0048] Step 1: Dissolve 2.12 g of p-aminobenzaldehyde in 55 mL of m-cresol, add 0.84 g of ethylene glycol, and heat at 80 o C overnight, and further add 1.84 g of pyromellitic anhydride; nitrogen purge for 50 min. Then gradually add 12 mL of m-cresol solution (containing 0.15 g of isoquinoline) dropwise, and the addition is completed in 25 min, and the temperature is raised to 110 ° C for 0.8 h, and then raised to 155 ° C for 5 hours. After the reaction is completed, the temperature is cooled to room temperature, and 20 mL of hydrochloric acid solution with a pH of 1 is added, and the reaction is continued for 20 h. Finally, column separation (eluent is ethyl acetate, cyclohexane, methanol, volume ratio is 2:10:1) is used to purify the imide compound containing aldehyde group.

[0049] Step 2. First, disperse 0.8g of chitosan in 80mL of methanol solution and swell overnight. Dissolve 3.24g of aldehyde-containing imide compound in (80mL) methanol solution, mix the obtained methanol solution and the above methanol solution containing chitosan and stir for 50min, purge with nitrogen for 50min, and heat to 70℃ and maintain for 10h. Secondly, after lowering the reaction solution to room temperature, continue to add 0.3g of ethylenediamine and stir overnight at room temperature. Use a 7000Da dialysis bag to dialyze to remove the catalyst, unreacted small molecular monomers and high boiling point solvents to obtain a white solid powder; finally, take 80 mg of white solid powder, disperse it in 25mL of m-cresol solution, let it stand overnight, put it into a polytetrafluoroethylene grinder, and grind it at 45 o C conditions and vacuum dried to form a film.

Claims

1. Preparation method of green and environmentally friendly chitosan modified polyimide substrate, Features: The specific steps include: Step 1, preparing an imide compound containing an aldehyde group; The specific process of step 1 is as follows: Step 1.1, dissolve 1.21g-2.42g of p-aminobenzaldehyde in 25mL-75mL of m-cresol solution, add 0.62g-1.24g of ethylene glycol, and stir at 50 o C-100 o C overnight, add 1.09 g to 2.18 g of pyromellitic anhydride, and purge with nitrogen for 30 to 60 min; Step 1.2, gradually add 10-15 mL of m-cresol solution to the solution obtained in step 1.1, and heat to 100-120°C and maintain for 0.5-1h, then heat to 150-160°C and react for 3-6h, after the reaction is completed, cool to room temperature, add hydrochloric acid solution, and react for 12-24h; Step 1.3, separating and purifying the solution obtained in step 1.2 by column separation to obtain an aldehyde-containing imide compound; Step 2, preparing a polyimide substrate according to the product obtained in step 1; The specific process of step 2 is as follows: Step 2.1, dispersing 0.5 g to 1 g of chitosan in 50 mL to 100 mL of methanol solution, swelling overnight, to obtain a mixed solution A; Step 2.2, dissolving 2.12 g to 4.24 g of the aldehyde-containing imide compound in 50 mL to 100 mL of a methanol solution to obtain a mixed solution B; Step 2.3, mixing the mixed solution A obtained in step 2.1 and the mixed solution B obtained in step 2.2 and stirring for 30-60 min, purging with nitrogen for 30-60 min, and heating to 60°C-80°C for 6h-12h, and cooling to room temperature after the reaction is completed; Step 2.4, adding 0.2 g to 0.4 g of ethylenediamine to the solution obtained in step 2.3, stirring overnight at room temperature, and dialyzing to obtain a white solid powder; Step 2.5, take 50 mg-100 mg of white solid powder, disperse it in 20 mL-30 mL of m-cresol solution, let it stand overnight, put it into a polytetrafluoroethylene mold, and vacuum dry it to form a film.

2. The method for preparing the green and environmentally friendly chitosan modified polyimide substrate according to claim 1, Features: The m-cresol solution in step 1.2 contains 0.1 g to 0.2 g of isoquinoline.

3. The method for preparing the green and environmentally friendly chitosan modified polyimide substrate according to claim 1, Features: The eluent formula used for column separation in step 1.3 is: ethyl acetate, cyclohexane, and methanol are mixed in a volume ratio of 2:10:1.

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