Anti-crease elastic adhesive and preparation method thereof

Abstract

The invention discloses a preparation method of an anti-crease elastic adhesive. The preparation method specifically comprises the following steps: step 1, synthesizing an imidazolyl acrylic monomer; step 2, preparing imidazolyl acrylic resin according to a product obtained in the step 1; step 3, preparing imidazole modified polydimethylsiloxane; step 4, preparing imidazole modified nano cellulose; and 5, preparing the elastic adhesive according to products obtained in the steps 2-4. The invention further discloses an elastic adhesive for preventing creases, the elastic adhesive is used in the OLED flexible substrate, and the problems that the creases are easy to form when the existing OLED flexible substrate is folded and the anti-creases effect is poor due to the fact that stress generated by bending and folding of the substrate cannot be really released are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and relates to an elastic adhesive for preventing creases. The present invention also relates to a preparation method of the elastic adhesive for preventing creases. Background Art

[0002] As the OLED (organic light-emitting diode) screen gradually changes from the original flat panel to a flexible one. The flexible screen poses higher requirements on the substrate, such as the number of folds, bending curvature, bending duration, etc. With the increase in the number of folds, bending curvature, and bending time, the substrate will undergo a certain degree of irreversible deformation, which will manifest as obvious creases on the OLED screen. The appearance of creases on the OLED screen not only affects the overall picture perception but also affects the service life of the screen. Currently, the proposed methods for preventing creases are to increase the thickness of the flexible substrate and add foam cotton under the substrate. However, the increase in the substrate thickness not only increases the production cost but also reduces the light transmittance and bending curvature of the substrate. Adding elastic foam cotton under the substrate as a buffer can relieve the creases of the flexible screen to a certain extent, but the effect is limited because it cannot truly release the energy (stress) generated by the bending and folding of the substrate. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of an elastic adhesive for preventing creases. When this elastic adhesive is used in an OLED flexible substrate, it solves the problems that the existing OLED flexible substrate is prone to form creases during folding and the poor crease prevention effect caused by the inability to truly release the stress generated by the bending and folding of the substrate.

[0004] Another purpose of the present invention is to provide an elastic adhesive for preventing creases.

[0005] The first technical solution adopted by the present invention is a preparation method of an elastic adhesive for preventing creases, which specifically includes the following steps:

[0006] Step 1, synthesize imidazolyl acrylic monomers;

[0007] Step 2, prepare imidazolyl acrylic resin according to the product obtained in Step 1;

[0008] Step 3, prepare imidazole-modified polydimethylsiloxane;

[0009] Step 4, prepare imidazole-modified nanocellulose;

[0010] Step 5, prepare an elastic adhesive according to the products obtained in Steps 2 - 4.

[0011] The characteristics of the first technical solution adopted by the present invention are further as follows:

[0012] The specific process of Step 1 is:

[0013] Step 1.1: Take 6.8 - 13.6 g of imidazole and dissolve it in 50 - 100 mL of tetrahydrofuran solvent. Then add 2.4 - 4.8 g of sodium hydride and stir at room temperature for 30 - 60 minutes.

[0014] Step 1.2: Dropwise add 8 - 16 g of 2 - chloroethanol to the product obtained in Step 1.1. After complete addition, continue to stir at room temperature for 30 - 60 minutes. Rotate evaporate the resulting reaction solution to obtain a pale yellow liquid, and purify it by column chromatography to obtain hydroxylated imidazole.

[0015] Step 1.3: Dissolve 5.6 - 11.2 g of hydroxylated imidazole in 35 - 70 mL of dichloromethane solvent. Then add 3.6 - 7.2 g of acrylic acid and 0.2 - 0.4 mL of concentrated sulfuric acid, and react at 40 - 45 °C for 8 - 16 h. After the reaction is completed, cool the temperature to room temperature and purify it by column chromatography to obtain colorless imidazolyl acrylic acid monomer.

[0016] In Step 1.2 and Step 1.3, the eluent used for column chromatography purification is a mixed solution of ethyl acetate and n - hexane.

[0017] The specific process of Step 2 is as follows:

[0018] Take 1.6 - 3.2 g of imidazolyl acrylic acid monomer, 0.5 - 1.0 g of isooctyl acrylate, 0.8 - 1.6 g of triethylene glycol methyl ether methacrylate, and 0.1 - 0.2 g of ethylene glycol diacrylate. After mixing evenly, add 15 - 20 mg of azobisisobutyronitrile and stir evenly. Heat the temperature to 60 - 80 °C and react for 30 - 60 minutes. After the reaction is completed, cool to room temperature to obtain imidazolyl acrylic acid resin.

[0019] The specific process of Step 3 is as follows:

[0020] Take 1.4 - 2.8 g of 1-(2 - isocyanatoethyl)-1H - imidazole and add it to 2 - 4 mL of dimethyl sulfoxide solution. After mixing evenly, introduce it into 12 - 24 g of [α,ω - bis(6 - hydroxyethoxypropyl)polydimethylsiloxane, and stir at room temperature for 14 - 28 h. After the reaction is completed, dialyze using a dialysis bag. The solution used for dialysis is 200 - 400 mL of ethanol, and repeat three times to obtain imidazole - modified polydimethylsiloxane.

[0021] The specific process of Step 4 is as follows:

[0022] Step 4.1: Take 0.1 - 0.2 g of cellulose nanofibers and disperse them in 50 - 100 mL of dimethyl sulfoxide solution, then ultrasonicate for 30 - 60 min. Next, add 0.15 - 0.3 mL of bromoacetyl chloride and stir at room temperature for 1 - 2 h. After the reaction, dialyze with a 7000 Da dialysis bag and 200 - 400 mL of ethanol to remove the excess bromoacetyl chloride and the generated HCl. Repeat three times to obtain brominated cellulose nanofibers;

[0023] Step 4.2: Disperse the brominated cellulose nanofibers obtained in Step 4.1 in 30 - 60 mL of dimethyl sulfoxide solution and ultrasonically disperse for 30 - 60 min to obtain a brominated cellulose nanofiber solution;

[0024] Step 4.3: Take 1.1 - 2.2 g of imidazole and dissolve it in 10 - 20 mL of tetrahydrofuran solvent, then add 0.4 - 0.8 g of sodium hydride and stir at room temperature for 30 - 60 min to obtain a deprotonated imidazole solution; Step 4.4: Dropwise add the deprotonated imidazole solution obtained in Step 4.3 to the brominated cellulose nanofiber solution obtained in Step 4.2 over 30 - 60 min. After the addition, continue to stir at room temperature for 1 - 2 h. Dialyze the resulting reaction solution with a 7000 Da dialysis bag and 200 - 400 mL of ethanol, repeat three times, and dry the collected solid powder at 45 - 60 °C overnight to obtain imidazole - modified nanocellulose.

[0025] The specific process of Step 5 is as follows:

[0026] Take 0.5 - 1 g of tetramethyldivinyldisiloxane, 0.5 - 1 g of glycidyl acrylate, and 2 - 4 g of imidazole - based acrylic resin, stir at room temperature for 1 - 2 h. Subsequently, add 30 - 60 mg of tetrabutyl titanate and 15 - 30 mg of azobisisobutyronitrile, raise the temperature to 60 - 80 °C and react for 30 - 60 min. After the reaction, add 0.1 - 0.2 g of imidazole - modified nanocellulose and 2.5 - 5 g of imidazole - modified polydimethylsiloxane, stir at room temperature for 30 - 60 min, and then add 0.14 - 0.28 g of zinc dichloride and continue to stir for 1 - 2 h to obtain an elastic adhesive.

[0027] The second technical solution adopted in the present invention is an elastic adhesive for preventing creases, which is prepared by using the above - mentioned preparation method of the elastic adhesive for preventing creases.

[0028] The beneficial effects of the present invention are as follows

[0029] The elastic adhesive prepared by the present invention is an elastic OCA optical adhesive, which can be used as a mechanical deformation buffer material for flexible substrates during folding and bending; and a reversible dynamic coordination bond is introduced into the molecular structure of the OCA optical adhesive, so that the energy generated during the folding and bending of the substrate is dissipated through the formation and breaking of the reversible-dynamic coordination bond, thereby improving the anti-crease performance of the OCA optical adhesive of the material. The OCA optical adhesive can be directly coated on the surface of a flexible substrate (polyethylene terephthalate: PET). The OCA optical adhesive not only has good light transmittance, but also has good elasticity, and can be used as a buffer material for mechanical deformation during the bending and folding of the substrate; nano-cellulose is used to replace fillers such as nano-calcium carbonate and carbon black to ensure its excellent light transmittance and low haze. Description of the Drawings

[0030] Figure 1 It is the stress-strain curve of the elastic adhesive coating in Example 1 and Comparative Examples 1-5 of the present invention. Detailed Description of the Invention

[0031] The following is a detailed description in conjunction with the specific embodiments.

[0032] The preparation method of the elastic adhesive for anti-crease of the present invention specifically includes the following steps:

[0033] Step 1, synthesis of imidazolyl acrylic acid monomer, specifically:

[0034] Take 6.8 - 13.6 g of imidazole and dissolve it in 50 - 100 mL of tetrahydrofuran solvent, then add 2.4 - 4.8 g of sodium hydride, and stir at room temperature for 30 - 60 min. Further, 8 - 16 g of 2-chloroethanol is added dropwise, the dropping time is 20 - 40 min, after all the dropping is completed, continue to stir at room temperature for 30 - 60 min. The obtained reaction solution is rotary evaporated (dried at 60 - 65 °C for 1 - 2 h) to obtain a light yellow liquid, and is purified by column separation (the eluent is ethyl acetate: n-hexane, volume ratio is 1:2) to obtain hydroxylated imidazole. Take 5.6 - 11.2 g of hydroxylated imidazole and dissolve it in 35 - 70 mL of dichloromethane solvent, then add 3.6 - 7.2 g of acrylic acid and 0.2 - 0.4 mL of concentrated sulfuric acid (concentration is 98.3%), heat to 40 - 45 °C and react for 8 - 16 h. After the reaction is completed, the temperature is lowered to room temperature, and is purified by column separation (the eluent is ethyl acetate: n-hexane, volume ratio is 1:10) to obtain a colorless imidazolyl acrylic acid monomer. The synthesis route is as follows:

[0035]

[0036] Step 2, preparation of imidazolyl acrylic resin, specifically:

[0037] Take 1.6 - 3.2 g of imidazolyl acrylic acid monomer, 0.5 - 1.0 g of isooctyl acrylate, 0.8 - 1.6 g of triethylene glycol methyl ether methacrylate, and 0.1 - 0.2 g of ethylene glycol diacrylate. After mixing evenly, add 15 - 20 mg of azobisisobutyronitrile and stir for 15 - 30 min. Heat the temperature to 60 - 80 °C and react for 30 - 60 min. After the reaction is completed, cool it to room temperature to obtain imidazolyl acrylic resin, and store the obtained imidazolyl acrylic resin in a refrigerator at 0 °C.

[0038] Step 3, prepare imidazole-modified polydimethylsiloxane, specifically:

[0039] Take 1.4 - 2.8 g of 1-(2-isocyanatoethyl)-1H-imidazole and add it to 2 - 4 mL of dimethyl sulfoxide solution. After mixing evenly, introduce it into 12 - 24 g of [α,ω-bis(6-hydroxyethoxypropyl) polydimethylsiloxane (molecular weight 8000 - 12000). Stir at room temperature for 14 - 28 h. After the reaction is completed, dialyze using a dialysis bag with a molecular weight cut-off of 7000 Da. The dialysis solution is 200 - 400 mL of ethanol, and repeat three times to obtain imidazole-modified polydimethylsiloxane. The synthesis route is as follows:

[0040]

[0041] Step 4, prepare imidazole-modified nanocellulose, specifically:

[0042] Take 0.1 - 0.2 g of cellulose nanofibers (diameter 10 - 20 nm, length 100 - 500 nm) and disperse them in 50 - 100 mL of dimethyl sulfoxide solution and sonicate for 30 - 60 min. Then add 0.15 - 0.3 mL of bromoacetyl chloride and stir at room temperature for 1 - 2 h. After the reaction is completed, dialyze using a dialysis bag with a molecular weight cut-off of 7000 Da and 200 - 400 mL of ethanol to remove excess bromoacetyl chloride and generated HCl, and repeat three times to obtain brominated cellulose nanofibers. Then, take 1.1 - 2.2 g of imidazole and dissolve it in 10 - 20 mL of tetrahydrofuran solvent, then add 0.4 - 0.8 g of sodium hydride and stir at room temperature for 30 - 60 min to obtain a deprotonated imidazole solution. Subsequently, disperse the obtained brominated cellulose nanofibers in 30 - 60 mL of dimethyl sulfoxide solution and sonicate for 30 - 60 min to obtain a brominated cellulose nanofiber solution; finally, slowly drop the deprotonated imidazole solution into the brominated cellulose nanofiber solution, and the dropping time is 30 - 60 min. After the dropping is completed, continue to stir at room temperature for 1 - 2 h. Dialyze the obtained reaction solution using a dialysis bag with a molecular weight cut-off of 7000 Da and 200 - 400 mL of ethanol, and repeat three times. The collected solid powder is dried overnight at 45 - 60 °C to obtain imidazole-modified nanocellulose.

[0043] Step 5, preparation of the elastic adhesive, specifically:

[0044] Take 0.5 - 1 g of tetramethyldivinyldisiloxane, 0.5 - 1 g of glycidyl acrylate, and 2 - 4 g of imidazolyl acrylate resin, stir at room temperature for 1 - 2 h. Further add 30 - 60 mg of tetrabutyl titanate and 15 - 30 mg of azobisisobutyronitrile thereto, raise the temperature to 60 - 80 °C and react for 30 - 60 min. After the reaction is completed, further add 0.1 - 0.2 g of imidazole - modified nanocellulose and 2.5 - 5 g of imidazole - modified polydimethylsiloxane, stir at room temperature for 30 - 60 min, and then add 0.14 - 0.28 g of zinc dichloride and continue stirring for 1 - 2 h to obtain the elastic adhesive.

[0045] PET Surface Coating Treatment and Performance Testing

[0046] Take a 10 cm x 10 cm PET substrate material, coat the elastic adhesive on the surface of the PET substrate, and the coating thickness is 200 - 300 μm. Then put the coated PET substrate into an oven at 60 - 80 °C and bake for 3 - 6 h. In order to study the elasticity and dynamic reversible self - healing performance of the elastic adhesive coating, spray a layer of release agent on the PET surface, keep other process parameters unchanged, peel the coated PET substrate and the elastic adhesive coating to obtain the elastic adhesive coating for coating performance testing.

[0047] Example 1

[0048] Step 1, synthesis of imidazolyl acrylate monomer, specifically:

[0049] Take 6.8 g of imidazole and dissolve it in 50 mL of tetrahydrofuran solvent, then add 2.4 g of sodium hydride, stir at room temperature for 30 min. Further add 8 g of 2 - chloroethanol dropwise, and the dropping time is 20 min. After all the addition is completed, continue stirring at room temperature for 30 min. Carry out rotary evaporation (evaporate to dryness at 60 °C for 2 h) on the obtained reaction solution to obtain a pale yellow liquid, and purify it by column separation (the eluent is ethyl acetate: n - hexane, volume ratio 1:2) to obtain hydroxylated imidazole. Take 5.6 g of hydroxylated imidazole and dissolve it in 35 mL of dichloromethane solvent, then add 3.6 g of acrylic acid and 0.2 mL of concentrated sulfuric acid (concentration 98.3%), heat to 40 °C and react for 8 h. After the reaction is completed, cool the temperature to room temperature, and purify it by column separation (the eluent is ethyl acetate: n - hexane, volume ratio 1:10) to obtain a colorless imidazolyl acrylate monomer.

[0050] Step 2, preparation of imidazolyl acrylate resin, specifically:

[0051] Take 1.6 g of imidazolyl acrylic monomer, 0.5 g of isooctyl acrylate, 0.8 g of triethylene glycol methyl ether methacrylate, and 0.1 g of ethylene glycol diacrylate. After mixing evenly, add 15 mg of azobisisobutyronitrile and stir for 15 min. Heat the temperature to 60 °C and react for 30 min. After the reaction is completed, cool it to room temperature to obtain imidazolyl acrylic resin, and store the obtained imidazolyl acrylic resin in a refrigerator at 0 °C.

[0052] Step 3, prepare imidazole-modified polydimethylsiloxane, specifically:

[0053] Take 1.4 g of 1-(2-isocyanatoethyl)-1H-imidazole and add it to 2 mL of dimethyl sulfoxide solution. After mixing evenly, introduce it into 12 g of [α,ω-bis(6-hydroxyethoxypropyl) polydimethylsiloxane (molecular weight 8000 - 12000). Stir at room temperature for 14 h. After the reaction is completed, dialyze using a dialysis bag with a molecular weight cut-off of 7000 Da. The dialysis solution is 200 mL of ethanol, and repeat three times to obtain imidazole-modified polydimethylsiloxane.

[0054] Step 4, prepare imidazole-modified nanocellulose, specifically:

[0055] Take 0.1 g of cellulose nanofibers (diameter 10 - 20 nm, length 100 - 500 nm) and disperse them in 50 mL of dimethyl sulfoxide solution and sonicate for 30 min. Then add 0.15 mL of bromoacetyl chloride and stir at room temperature for 1 h. After the reaction is completed, dialyze using a 7000 Da dialysis bag and 200 mL of ethanol to remove excess bromoacetyl chloride and the generated HCl, and repeat three times to obtain brominated cellulose nanofibers. Then, take 1.1 g of imidazole and dissolve it in 10 mL of tetrahydrofuran solvent, and then add 0.4 g of sodium hydride and stir at room temperature for 30 min to obtain a deprotonated imidazole solution. Subsequently, disperse the obtained brominated cellulose nanofibers in 30 mL of dimethyl sulfoxide solution and sonicate for 30 min to obtain a brominated cellulose nanofiber solution; dropwise add the deprotonated imidazole solution to the brominated cellulose nanofiber solution, and the dropping time is 30 min. After the dropping is completed, continue to stir at room temperature for 1 h. Dialyze the obtained reaction solution using a 7000 Da dialysis bag and 200 mL of ethanol, repeat three times, and dry the collected solid powder overnight at 45 °C to obtain imidazole-modified nanocellulose.

[0056] Step 5, preparation of elastic adhesive, specifically:

[0057] Take 0.5 g of tetramethyldivinyldisiloxane, 0.5 g of glycidyl acrylate, and 2 g of imidazolyl acrylate resin, stir at room temperature for 1 h, further add 30 mg of tetrabutyl titanate and 15 mg of azobisisobutyronitrile, raise the temperature to 60 °C and react for 30 min. After the reaction is completed, further add 0.1 g of imidazole-modified nanocellulose and 2.5 g of imidazole-modified polydimethylsiloxane, stir at room temperature for 30 min, then add 0.14 g of zinc dichloride and continue stirring for 1 h to obtain the elastic adhesive.

[0058] PET Surface Coating Treatment and Performance Testing

[0059] Take a 10 cm x 10 cm PET substrate material, coat the elastic adhesive on the surface of the PET substrate, and the coating thickness is 200 μm. Then place the coated PET substrate in an oven at 60 °C and bake for 3 h. In order to study the elasticity and dynamic reversible self-healing performance of the elastic adhesive coating, spray a layer of release agent on the PET surface, keep other process parameters unchanged, peel the coated substrate PET and the elastic adhesive coating, and use the obtained elastic adhesive coating for coating performance testing.

[0060] Comparative Example 1 (No zinc dichloride is added to the elastic adhesive, dynamic-reversible coordination bonds cannot be formed, energy cannot be dissipated, and creases are obvious)

[0061] Step 1, Synthesis of imidazolyl acrylic monomer, specifically:

[0062] Take 6.8 g of imidazole and dissolve it in 50 mL of tetrahydrofuran solvent, then add 2.4 g of sodium hydride, stir at room temperature for 30 min, further dropwise add 8 g of 2-chloroethanol dropwise over 20 min. After all the addition is completed, continue stirring at room temperature for 30 min. Perform rotary evaporation on the obtained reaction solution (evaporate to dryness at 60 °C for 2 h) to obtain a pale yellow liquid, and purify it by column chromatography (the eluent is ethyl acetate: n-hexane, volume ratio 1:2) to obtain hydroxylated imidazole. Take 5.6 g of hydroxylated imidazole and dissolve it in 35 mL of dichloromethane solvent, then add 3.6 g of acrylic acid and 0.2 mL of concentrated sulfuric acid (concentration 98.3%), heat to 40 °C and react for 8 h. After the reaction is completed, cool the temperature to room temperature and purify it by column chromatography (the eluent is ethyl acetate: n-hexane, volume ratio 1:10) to obtain a colorless imidazolyl acrylic monomer.

[0063] Step 2, Preparation of imidazolyl acrylate resin, specifically:

[0064] Take 1.6 g of imidazolyl acrylic monomer, 0.5 g of isooctyl acrylate, 0.8 g of triethylene glycol methyl ether methacrylate, and 0.1 g of ethylene glycol diacrylate. After mixing evenly, add 15 mg of azobisisobutyronitrile and stir for 15 min. Heat the temperature to 60 °C and react for 30 min. After the reaction is completed, cool it to room temperature to obtain imidazolyl acrylic resin, and store the obtained imidazolyl acrylic resin in a refrigerator at 0 °C.

[0065] Step 3, prepare imidazole-modified polydimethylsiloxane, specifically:

[0066] Take 1.4 g of 1-(2-isocyanatoethyl)-1H-imidazole and add it to 2 mL of dimethyl sulfoxide solution. After mixing evenly, introduce it into 12 g of [α,ω-bis(6-hydroxyethoxypropyl) polydimethylsiloxane (molecular weight 8000 - 12000). Stir at room temperature for 14 h. After the reaction is completed, dialyze with a dialysis bag of 7000 Da. The dialysis solution is 200 mL of ethanol, and repeat three times to obtain imidazole-modified polydimethylsiloxane.

[0067] Step 4, prepare imidazole-modified nanocellulose, specifically:

[0068] Take 0.1 g of cellulose nanofibers (diameter 10 - 20 nm, length 100 - 500 nm) and disperse them in 50 mL of dimethyl sulfoxide solution and ultrasonicate for 30 min. Then add 0.15 mL of bromoacetyl chloride and stir at room temperature for 1 h. After the reaction is completed, dialyze with a 7000 Da dialysis bag and 200 mL of ethanol to remove excess bromoacetyl chloride and generated HCl, and repeat three times to obtain brominated cellulose nanofibers. Then, take 1.1 g of imidazole and dissolve it in 10 mL of tetrahydrofuran solvent, then add 0.4 g of sodium hydride and stir at room temperature for 30 min to obtain a deprotonated imidazole solution. Subsequently, disperse the obtained brominated cellulose nanofibers in 30 mL of dimethyl sulfoxide solution and ultrasonically disperse for 30 min to obtain a brominated cellulose nanofiber solution; dropwise add the deprotonated imidazole solution to the brominated cellulose nanofiber solution dropwise for 30 min. After the dropwise addition, continue to stir at room temperature for 1 h. Dialyze the obtained reaction solution with a 7000 Da dialysis bag and 200 mL of ethanol, repeat three times, and dry the collected solid powder overnight at 45 °C to obtain imidazole-modified nanocellulose.

[0069] Step 5, preparation of elastic adhesive, specifically:

[0070] Take 0.5 g of tetramethyldivinyldisiloxane, 0.5 g of glycidyl acrylate, and 2 g of imidazolyl acrylate resin, stir at room temperature for 1 h, further add 30 mg of tetrabutyl titanate and 15 mg of azobisisobutyronitrile, and raise the temperature to 60 °C for reaction for 30 min. After the reaction, further add 0.1 g of imidazole-modified nanocellulose and 2.5 g of imidazole-modified polydimethylsiloxane, and stir at room temperature for 30 min to obtain an elastic adhesive.

[0071] PET Surface Coating Treatment and Performance Testing

[0072] Take a 10 cm x 10 cm PET substrate material, coat the elastic adhesive on the surface of the PET substrate, and the coating thickness is 200 μm. Then place the coated PET substrate in an oven at 60 °C and bake for 3 h. In order to study the elasticity and dynamic reversible self-healing performance of the elastic adhesive coating, spray a layer of release agent on the PET surface, keep other process parameters unchanged, peel the coated substrate PET and the elastic adhesive coating, and use the obtained elastic adhesive coating for coating performance testing.

[0073] Comparative Example 2 (Nano calcium carbonate and carbon black are commonly used as reinforcing fillers for elastic materials. Replace the imidazole-modified nanocellulose with nano calcium carbonate, and the coating haze is large)

[0074] Step 1, Synthesis of imidazolyl acrylate monomer, specifically:

[0075] Take 6.8 g of imidazole and dissolve it in 50 mL of tetrahydrofuran solvent, then add 2.4 g of sodium hydride, stir at room temperature for 30 min, further dropwise add 8 g of 2-chloroethanol dropwise over 20 min. After all the addition, continue to stir at room temperature for 30 min. Rotate evaporate the obtained reaction solution (evaporate to dryness at 60 °C for 2 h) to obtain a pale yellow liquid, and purify it by column separation (the eluent is ethyl acetate: n-hexane, volume ratio 1:2) to obtain hydroxylated imidazole. Take 5.6 g of hydroxylated imidazole and dissolve it in 35 mL of dichloromethane solvent, then add 3.6 g of acrylic acid and 0.2 mL of concentrated sulfuric acid (concentration 98.3%), heat to 40 °C and react for 8 h. After the reaction, cool the temperature to room temperature, and purify it by column separation (the eluent is ethyl acetate: n-hexane, volume ratio 1:10) to obtain a colorless imidazolyl acrylate monomer.

[0076] Step 2, Preparation of imidazolyl acrylate resin, specifically:

[0077] Take 1.6 g of imidazolyl acrylic monomer, 0.5 g of isooctyl acrylate, 0.8 g of triethylene glycol methyl ether methacrylate, and 0.1 g of ethylene glycol diacrylate. After mixing evenly, add 15 mg of azobisisobutyronitrile and stir for 15 min. Heat the temperature to 60 °C and react for 30 min. After the reaction is completed, cool it to room temperature to obtain the imidazolyl acrylic resin, and store the obtained imidazolyl acrylic resin in a refrigerator at 0 °C.

[0078] Step 3, prepare imidazole-modified polydimethylsiloxane, specifically:

[0079] Take 1.4 g of 1-(2-isocyanatoethyl)-1H-imidazole and add it to 2 mL of dimethyl sulfoxide solution. After mixing evenly, introduce it into 12 g of [α,ω-bis(6-hydroxyethoxypropyl) polydimethylsiloxane (molecular weight 8000 - 12000). Stir at room temperature for 14 h. After the reaction is completed, dialyze with a dialysis bag of 7000 Da. The dialysis solution is 200 mL of ethanol, and repeat three times to obtain imidazole-modified polydimethylsiloxane.

[0080] Step 4, preparation of the elastic adhesive, specifically:

[0081] Take 0.5 g of tetramethyldivinyldisiloxane, 0.5 g of glycidyl acrylate, and 2 g of imidazolyl acrylic resin, stir at room temperature for 1 h, further add 30 mg of tetrabutyl titanate and 15 mg of azobisisobutyronitrile, raise the temperature to 60 °C and react for 30 min. After the reaction is completed, add 0.1 g (20 - 50 nm) of nano calcium carbonate and 2.5 g of imidazole-modified polydimethylsiloxane, stir at room temperature for 30 min, and then add 0.14 g of zinc dichloride and continue to stir for 1 h to obtain the elastic adhesive.

[0082] PET surface coating treatment and performance testing

[0083] Take a 10 cm x 10 cm PET substrate material, coat the elastic adhesive on the surface of the PET substrate, and the coating thickness is 200 μm. Then put the coated PET substrate into an oven at 60 °C and bake for 3 h. In order to study the elasticity and dynamic reversible self-healing performance of the elastic adhesive coating, spray a layer of release agent on the PET surface, keep other process parameters unchanged, peel the coated PET substrate and the elastic adhesive coating, and use the obtained elastic adhesive coating for coating performance testing.

[0084] Comparative Example 3 (Nano calcium carbonate and carbon black are commonly used as reinforcing fillers for elastic materials. Replace imidazole-modified nano cellulose with carbon black, and the coating haze increases and the light transmittance decreases)

[0085] Step 1, synthesis of imidazolyl acrylic monomer, specifically:

[0086] Dissolve 6.8 g of imidazole in 50 mL of tetrahydrofuran solvent, then add 2.4 g of sodium hydride, stir at room temperature for 30 min, and further dropwise add 8 g of 2-chloroethanol over 20 min. After complete addition, continue to stir at room temperature for 30 min. Rotavaporize the resulting reaction solution (evaporate to dryness at 60 °C for 2 h) to obtain a pale yellow liquid, and purify it by column chromatography (the eluent is ethyl acetate:n-hexane, volume ratio 1:2) to obtain hydroxylated imidazole. Dissolve 5.6 g of hydroxylated imidazole in 35 mL of dichloromethane solvent, then add 3.6 g of acrylic acid and 0.2 mL of concentrated sulfuric acid (concentration 98.3%), and react at 40 °C for 8 h. After the reaction is completed, cool the temperature to room temperature, and purify it by column chromatography (the eluent is ethyl acetate:n-hexane, volume ratio 1:10) to obtain colorless imidazolylacrylic acid monomer.

[0087] Step 2, preparation of imidazolylacrylic acid resin, specifically:

[0088] Take 1.6 g of imidazolylacrylic acid monomer, 0.5 g of isooctyl acrylate, 0.8 g of triethylene glycol methyl ether methacrylate, and 0.1 g of ethylene glycol diacrylate, mix them evenly, then add 15 mg of azobisisobutyronitrile and stir for 15 min. Heat the temperature to 60 °C and react for 30 min. After the reaction is completed, cool to room temperature to obtain imidazolylacrylic acid resin, and store the obtained imidazolylacrylic acid resin in a 0 °C refrigerator.

[0089] Step 3, preparation of imidazole-modified polydimethylsiloxane, specifically:

[0090] Take 1.4 g of 1-(2-isocyanatoethyl)-1H-imidazole and add it to 2 mL of dimethyl sulfoxide solution. After mixing evenly, introduce it into 12 g of [α,ω-bis(6-hydroxyethoxypropyl) polydimethylsiloxane (molecular weight 8000 - 12000). Stir at room temperature for 14 h. After the reaction is completed, dialyze using a 7000 Da dialysis bag. The dialysis solution is 200 mL of ethanol, and repeat three times to obtain imidazole-modified polydimethylsiloxane.

[0091] Step 4, preparation of elastic adhesive, specifically:

[0092] Take 0.5 g of tetramethyldivinyldisiloxane, 0.5 g of glycidyl acrylate, and 2 g of imidazolylacrylic acid resin, stir at room temperature for 1 h, add 30 mg of tetrabutyl titanate and 15 mg of azobisisobutyronitrile, raise the temperature to 60 °C and react for 30 min. After the reaction is completed, add 0.1 g of carbon black and 2.5 g of imidazole-modified polydimethylsiloxane, stir at room temperature for 30 min, and then add 0.14 g of zinc dichloride and continue to stir for 1 h to obtain elastic adhesive.

[0093] PET Surface Coating Treatment and Performance Testing

[0094] Take a PET substrate material of 10 cm x 10 cm, coat the surface of the PET substrate with an elastic adhesive, and the coating thickness is 200 μm. Then put the coated PET substrate into an oven at 60 °C and bake for 3 h. In order to study the elasticity and dynamic reversible self-healing performance of the elastic adhesive coating, spray a layer of release agent on the PET surface, keep other process parameters unchanged, peel the coated PET substrate and the elastic adhesive coating, and use the obtained elastic adhesive coating for coating performance testing.

[0095] Comparative Example 4 (Among all components of the elastic adhesive, there is no imidazole structural unit, so dynamic-reversible coordination bonds cannot be formed, energy cannot be dissipated, and obvious creases appear)

[0096] Step 1, Preparation of acrylic resin, specifically:

[0097] Take 1.6 g of ethyl acrylate, 0.5 g of isooctyl acrylate, 0.8 g of triethylene glycol methyl ether methacrylate, and 0.1 g of ethylene glycol diacrylate. After mixing evenly, add azobisisobutyronitrile for 15 min. Heat the temperature to 60 °C and react for 30 min. After the reaction is completed, cool to room temperature to obtain acrylic resin. Put the obtained acrylic resin into a refrigerator at 0 °C for storage and standby.

[0098] Step 2, Preparation of ethyl-modified polydimethylsiloxane, specifically:

[0099] Take 1.4 g of ethyl isocyanate and add it to 2 mL of dimethyl sulfoxide solution. After mixing evenly, introduce it into 12 g of [α,ω-bis(6-hydroxyethoxypropyl) polydimethylsiloxane (molecular weight 8000 - 12000). Stir at room temperature for 14 h. After the reaction is completed, dialyze with a 7000 Da dialysis bag, and the dialysis solution is 200 mL of ethanol. Repeat three times to obtain ethyl-modified polydimethylsiloxane.

[0100] Step 3, Preparation of bromine-modified nanocellulose, specifically:

[0101] Take 0.1 g of cellulose nanofibers (diameter 10 - 20 nm, length 100 - 500 nm) and disperse them in 50 mL of dimethyl sulfoxide solution and sonicate for 30 min. Then add 0.15 mL of bromoacetyl chloride and stir at room temperature for 1 h. After the reaction is completed, dialyze with a 7000 Da dialysis bag and 200 mL of ethanol to remove excess bromoacetyl chloride and generated HCl. Repeat three times to obtain brominated cellulose nanofibers.

[0102] Step 4, Preparation of elastic adhesive, specifically:

[0103] Take 0.5 g of tetramethyldivinyldisiloxane, 0.5 g of glycidyl acrylate, and 2 g of acrylic resin, stir at room temperature for 1 h, add 30 mg of tetrabutyl titanate and 15 mg of azobisisobutyronitrile. Then, raise the temperature to 60 °C and react for 30 min. After the reaction, add 0.1 g of bromine-modified nanocellulose and 2.5 g of ethyl-modified polydimethylsiloxane, stir at room temperature for 30 min, and then add 0.14 g of zinc dichloride and continue stirring for 1 h to obtain the elastic adhesive.

[0104] PET Surface Coating Treatment and Performance Testing

[0105] Take a 10 cm x 10 cm PET substrate material, coat the elastic adhesive on the surface of the PET substrate, and the coating thickness is 200 μm. Then, place the coated PET substrate in an oven at 60 °C and bake for 3 h. To study the elasticity and dynamic reversible self-healing performance of the elastic adhesive coating, spray a release agent on the PET surface, keep other process parameters unchanged, peel the coated PET substrate and the elastic adhesive coating, and use the obtained elastic adhesive coating for coating performance testing.

[0106] Comparative Example 5 (No reinforcing filler imidazole-modified nanocellulose is added to the elastic adhesive, and there are creases when the material is folded)

[0107] Step 1, Synthesis of imidazolyl acrylic acid monomer, specifically:

[0108] Take 6.8 g of imidazole and dissolve it in 50 mL of tetrahydrofuran solvent. Then, add 2.4 g of sodium hydride and stir at room temperature for 30 min. Further, dropwise add 8 g of 2-chloroethanol drop by drop over 20 min. After all the addition, continue stirring at room temperature for 30 min. Rotate evaporate the obtained reaction solution (evaporate to dryness at 60 °C for 2 h) to obtain a light yellow liquid, and purify it by column separation (the eluent is ethyl acetate: n-hexane, volume ratio 1:2) to obtain hydroxylated imidazole. Take 5.6 g of hydroxylated imidazole and dissolve it in 35 mL of dichloromethane solvent. Then, add 3.6 g of acrylic acid and 0.2 mL of concentrated sulfuric acid (concentration 98.3%) and heat to 40 °C to react for 8 h. After the reaction, cool the temperature to room temperature and purify it by column separation (the eluent is ethyl acetate: n-hexane, volume ratio 1:10) to obtain a colorless imidazolyl acrylic acid monomer.

[0109] Step 2, Preparation of imidazolyl acrylic resin, specifically:

[0110] Take 1.6 g of imidazolyl acrylic monomer, 0.5 g of isooctyl acrylate, 0.8 g of triethylene glycol methyl ether methacrylate, and 0.1 g of ethylene glycol diacrylate. After mixing evenly, add 15 mg of azobisisobutyronitrile and stir for 15 min. Heat the temperature to 60 °C and react for 30 min. After the reaction is completed, cool it to room temperature to obtain the imidazolyl acrylic resin, and store the obtained imidazolyl acrylic resin in a refrigerator at 0 °C.

[0111] Step 3, prepare imidazole-modified polydimethylsiloxane, specifically:

[0112] Take 1.4 g of 1-(2-isocyanatoethyl)-1H-imidazole and add it to 2 mL of dimethyl sulfoxide solution. After mixing evenly, introduce it into 12 g of [α,ω-bis(6-hydroxyethoxypropyl) polydimethylsiloxane (molecular weight 8000 - 12000). Stir at room temperature for 14 h. After the reaction is completed, dialyze with a dialysis bag of 7000 Da. The dialysis solution is 200 mL of ethanol, and repeat three times to obtain imidazole-modified polydimethylsiloxane.

[0113] Step 4, prepare the elastic adhesive, specifically:

[0114] Take 0.5 g of tetramethyldivinyldisiloxane, 0.5 g of glycidyl acrylate, and 2 g of imidazolyl acrylic resin, stir at room temperature for 1 h, add 30 mg of tetrabutyl titanate and 15 mg of azobisisobutyronitrile, raise the temperature to 60 °C and react for 30 min. After the reaction is completed, add 2.5 g of imidazole-modified polydimethylsiloxane, stir at room temperature for 30 min, and then add 0.14 g of zinc dichloride and continue to stir for 1 h to obtain the elastic adhesive.

[0115] PET surface coating treatment and performance testing

[0116] Take a 10 cm x 10 cm PET substrate material, coat the elastic adhesive on the surface of the PET substrate, and the coating thickness is 200 μm. Then put the coated PET substrate into an oven at 60 °C and bake for 3 h. In order to study the mechanical properties and dynamic reversible self-healing properties of the elastic adhesive coating, spray a layer of release agent on the PET surface, and keep other process parameters unchanged. Peel the coated PET substrate and the elastic adhesive coating, and use the obtained elastic adhesive coating for coating performance testing.

[0117] The following Table 1 shows the performance test results of the elastic adhesives prepared in Example 1 and Comparative Examples 1 - 5:

[0118] Table 1

[0119]

[0120] The crease test is to bend the surface-coated PET through 90° at a bending speed of 5 seconds each time. After folding 10,000 times, unfold it and let it stand for 12 hours to check whether there are creases.

[0121] Results and Discussion

[0122] As shown in Table 1 and Figure 1 As shown, the elongation at break in Example 1 and Comparative Examples 2-3 is relatively low; while Comparative Example 1 lacks a dynamic-reversible coordination bond, and Comparative Examples 4-5 lack a reinforcing filler and other forces that resist deformation, making it easy for the polymer chains in the coating to slide.

[0123] The light transmittance of Comparative Example 3 is the lowest, which is mainly caused by the light absorption of carbon black itself. In contrast, the reinforcing materials in Example 1 and Comparative Examples 1-2, 4-5 are all nanometer-sized and have low light absorption and high light transmittance.

[0124] The haze of Comparative Examples 2-3 is relatively high because nano-calcium carbonate and carbon black are dispersed in the elastic adhesive coating, resulting in internal haze light scattering.

[0125] For Comparative Examples 1 and 4, after 10,000 90° folds, the creases are obvious mainly due to the lack of dynamic-reversible coordination bonds, and the energy generated by the bending cannot be dissipated. For Comparative Example 5, the lack of reinforcement material leads to insufficient mechanics and easy creases.

[0126] There are no creases in Example 1. The main reason is that the substrate is coated with an elastic adhesive, which can play a buffering role when the substrate is bent. At the same time, the energy dissipation is not smooth when the substrate is folded, which is one of the important reasons for the creases. The present invention utilizes the formation and breaking of dynamic reversible coordination bonds in the elastic adhesive to achieve energy dissipation and reduce creases.

[0127] The curling rate is mainly to curl the substrate with a cylinder having a diameter of r = 0.5 cm. The curling rate is η = 1 / r. By curling the substrate in Example 1, it is found that the substrate can be curled with or without the elastic adhesive, and can be freely restored to flatness after curling.

[0128] Table 2 below shows the performance test results of the elastic adhesives prepared in Example 1 and Comparative Examples 1-5:

[0129] Table 2

[0130] Breaking strength (MPa) Breaking strength after repair (MPa) Repair rate (%) Example 1 5.2 4.1 79 Comparative Example 1 3.8 1.1 29 Comparative Example 2 5.1 3.1 61 Comparative Example 3 4.9 3.0 61 Comparative Example 4 3.6 1.2 33 Comparative Example 5 3.1 1.8 58

[0131] The repair rate is (repaired fracture strength ÷ fracture strength) x 100%. The fracture strength test after repair is to cut the elastic adhesive coating with a blade, then splice the cuts together, heat press at 50℃ and 10N for 30 minutes, and then measure its fracture strength with a tensile machine.

[0132] As shown in Table 2 andFigure 1 As shown in the figure, the fracture strength in Example 1 and Comparative Examples 2-3 is relatively large because the coating contains a reinforcing material and a dynamic-reversible coordination bond; while Comparative Examples 1, 4-5 lack a reinforcing filler or a dynamic-reversible coordination bond, resulting in a small force to resist deformation and a low fracture strength.

[0133] The fracture strength after repair of Comparative Examples 1 and 4 is the lowest, mainly lacking a dynamic-reversible coordination bond, and the self-healing rate is only 29-33%.

[0134] The repair rate in Example 1 is relatively high, indicating that the dynamic-reversible coordination bond is more likely to form again after fracture. Therefore, the excellent coordination bond fracture and formation performance in Example 1 endow the elastic adhesive coating with better energy dissipation performance, which is beneficial to preventing creases.

[0135] Example 2

[0136] Step 1, synthesis of imidazolyl acrylic acid monomer, specifically:

[0137] Take 12.5 g of imidazole and dissolve it in 80 mL of tetrahydrofuran solvent, then add 3.6 g of sodium hydride, stir at room temperature for 40 min, and further dropwise add 12 g of 2-chloroethanol dropwise over 30 min. After all the addition is completed, continue to stir at room temperature for 40 min. Rotate evaporate the obtained reaction solution (evaporate to dryness at 62 °C for 1.5 h) to obtain a light yellow liquid, and purify it by column chromatography (the eluent is ethyl acetate: n-hexane, volume ratio 1:2) to obtain hydroxylated imidazole. Take 8.8 g of hydroxylated imidazole and dissolve it in 58 mL of dichloromethane solvent, then add 4.8 g of acrylic acid and 0.3 mL of concentrated sulfuric acid (concentration 98.3%), and react at 42 °C for 12 h. After the reaction is completed, cool the temperature to room temperature, and purify it by column chromatography (the eluent is ethyl acetate: n-hexane, volume ratio 1:10) to obtain a colorless imidazolyl acrylic acid monomer.

[0138] Step 2, preparation of imidazolyl acrylic resin, specifically:

[0139] Take 2.4 g of imidazolyl acrylic acid monomer, 0.8 g of isooctyl acrylate, 1.2 g of triethylene glycol methyl ether methacrylate, and 0.15 g of ethylene glycol diacrylate, mix them evenly, then add 18 mg of azobisisobutyronitrile and stir for 20 min, and heat to 70 °C for reaction for 50 min. After the reaction is completed, cool to room temperature to obtain imidazolyl acrylic resin, and store the obtained imidazolyl acrylic resin in a 0 °C refrigerator.

[0140] Step 3, preparation of imidazole-modified polydimethylsiloxane, specifically:

[0141] 2.4 g of 1-(2-isocyanatoethyl)-1H-imidazole was added to 3 mL of dimethyl sulfoxide solution. After mixing evenly, it was introduced into 18 g of [α,ω-bis(6-hydroxyethoxypropyl)polydimethylsiloxane (molecular weight 8000 - 12000). Stir at room temperature for 18 h. After the reaction, dialysis was carried out using a dialysis bag with a molecular weight cut-off of 7000 Da. The dialysis solution was 300 mL of ethanol. Repeat three times to obtain imidazole-modified polydimethylsiloxane.

[0142] Step 4, preparation of imidazole-modified nanocellulose, specifically:

[0143] 0.15 g of cellulose nanofibers (diameter 10 - 20 nm, length 100 - 500 nm) was dispersed in 80 mL of dimethyl sulfoxide solution and ultrasonicated for 40 min. Then 0.2 mL of bromoacetyl chloride was added and stirred at room temperature for 1.5 h. After the reaction, dialysis was carried out using a 7000 Da dialysis bag and 300 mL of ethanol to remove excess bromoacetyl chloride and generated HCl. Repeat three times to obtain brominated cellulose nanofibers. Then, 1.8 g of imidazole was dissolved in 15 mL of tetrahydrofuran solvent, and then 0.6 g of sodium hydride was added and stirred at room temperature for 40 min to obtain a deprotonated imidazole solution. Subsequently, the obtained brominated cellulose nanofibers were dispersed in 40 mL of dimethyl sulfoxide solution and ultrasonicated for 40 min to obtain a brominated cellulose nanofiber solution; the deprotonated imidazole solution was added dropwise to the brominated cellulose nanofiber solution over 40 min. After the addition, continue to stir at room temperature for 1.5 h. The resulting reaction solution was dialyzed using a 7000 Da dialysis bag and 300 mL of ethanol, repeated three times, and the collected solid powder was dried overnight at 55 °C to obtain imidazole-modified nanocellulose.

[0144] Step 5, preparation of elastic adhesive, specifically:

[0145] 0.8 g of tetramethyldivinyldisiloxane, 0.8 g of glycidyl acrylate and 3 g of imidazole-based acrylic resin were taken and stirred at room temperature for 1.5 h. Further, 40 mg of tetrabutyl titanate and 20 mg of azobisisobutyronitrile were added, and the temperature was raised to 70 °C and reacted for 40 min. After the reaction, 0.15 g of imidazole-modified nanocellulose and 4 g of imidazole-modified polydimethylsiloxane were further added and stirred at room temperature for 40 min. Then 0.24 g of zinc dichloride was added and stirred for 1.5 h to obtain the elastic adhesive.

[0146] PET surface coating treatment and performance testing

[0147] Take a 10 cm x 10 cm PET substrate material, coat an elastic adhesive on the surface of the PET substrate with a coating thickness of 260 μm. Then place the coated PET substrate in an oven at 70 °C and bake for 4 h. In order to study the elasticity and dynamic reversible self-healing performance of the elastic adhesive coating, spray a release agent on the PET surface, keep other process parameters unchanged, peel the coated PET substrate and the elastic adhesive coating, and use the obtained elastic adhesive coating for coating performance testing.

[0148] Example 3

[0149] Step 1, synthesis of imidazolyl acrylic acid monomer, specifically:

[0150] Take 13.6 g of imidazole and dissolve it in 100 mL of tetrahydrofuran solvent, then add 4.8 g of sodium hydride, stir at room temperature for 60 min, and further dropwise add 16 g of 2-chloroethanol dropwise over 40 min. After all the addition is completed, continue to stir at room temperature for 60 min. Rotate evaporate the obtained reaction solution (evaporate to dryness at 65 °C for 2 h) to obtain a pale yellow liquid, and purify it by column chromatography (the eluent is ethyl acetate: n-hexane, volume ratio 1:2) to obtain hydroxylated imidazole. Take 11.2 g of hydroxylated imidazole and dissolve it in 70 mL of dichloromethane solvent, then add 7.2 g of acrylic acid and 0.4 mL of concentrated sulfuric acid (concentration 98.3%), heat to 45 °C and react for 16 h. After the reaction is completed, cool the temperature to room temperature, and purify it by column chromatography (the eluent is ethyl acetate: n-hexane, volume ratio 1:10) to obtain a colorless imidazolyl acrylic acid monomer.

[0151] Step 2, preparation of imidazolyl acrylic resin, specifically:

[0152] Take 3.2 g of imidazolyl acrylic acid monomer, 1.0 g of isooctyl acrylate, 1.6 g of triethylene glycol methyl ether methacrylate, and 0.2 g of ethylene glycol diacrylate, mix them evenly, add 20 mg of azobisisobutyronitrile and stir for 30 min, heat to 80 °C and react for 60 min. After the reaction is completed, cool to room temperature to obtain imidazolyl acrylic resin, and store the obtained imidazolyl acrylic resin in a refrigerator at 0 °C.

[0153] Step 3, preparation of imidazole-modified polydimethylsiloxane, specifically:

[0154] 2.8 g of 1-(2-isocyanatoethyl)-1H-imidazole was added to 4 mL of dimethyl sulfoxide solution. After mixing evenly, it was introduced into 24 g of [α,ω-bis(6-hydroxyethoxypropyl)polydimethylsiloxane (with a molecular weight of 8000 - 12000). Stir at room temperature for 28 h. After the reaction, dialysis was carried out using a dialysis bag with a molecular weight cut-off of 7000 Da. The dialysis solution was 400 mL of ethanol, and this was repeated three times to obtain imidazole-modified polydimethylsiloxane.

[0155] Step 4, preparation of imidazole-modified nanocellulose, specifically:

[0156] 0.2 g of cellulose nanofibers (with a diameter of 10 - 20 nm and a length of 100 - 500 nm) was dispersed in 100 mL of dimethyl sulfoxide solution and sonicated for 60 min. Then, 0.3 mL of bromoacetyl chloride was added, and the mixture was stirred at room temperature for 2 h. After the reaction, dialysis was carried out using a 7000 Da dialysis bag and 400 mL of ethanol to remove the excess bromoacetyl chloride and the generated HCl, and this was repeated three times to obtain brominated cellulose nanofibers. Then, 2.2 g of imidazole was dissolved in 20 mL of tetrahydrofuran solvent, and then 0.8 g of sodium hydride was added, and the mixture was stirred at room temperature for 60 min to obtain a deprotonated imidazole solution. Subsequently, the obtained brominated cellulose nanofibers were dispersed in 60 mL of dimethyl sulfoxide solution and sonicated for 60 min to obtain a brominated cellulose nanofiber solution; the deprotonated imidazole solution was added dropwise to the brominated cellulose nanofiber solution over a period of 60 min. After the addition, stirring was continued at room temperature for 2 h. The resulting reaction solution was dialyzed using a 7000 Da dialysis bag and 400 mL of ethanol, repeated three times, and the collected solid powder was dried overnight at 60 °C to obtain imidazole-modified nanocellulose.

[0157] Step 5, preparation of the elastic adhesive, specifically:

[0158] 1 g of tetramethyldivinyldisiloxane, 1 g of glycidyl acrylate, and 4 g of imidazole-based acrylic resin were taken and stirred at room temperature for 2 h. Further, 60 mg of tetrabutyl titanate and 30 mg of azobisisobutyronitrile were added, and the temperature was raised to 80 °C and reacted for 60 min. After the reaction, 0.2 g of imidazole-modified nanocellulose and 5 g of imidazole-modified polydimethylsiloxane were further added, and the mixture was stirred at room temperature for 60 min. Then, 0.28 g of zinc dichloride was added and stirring was continued for 2 h to obtain the elastic adhesive.

[0159] PET surface coating treatment and performance testing

[0160] Take a PET substrate material of 10 cm x 10 cm, coat the surface of the PET substrate with an elastic adhesive, and the coating thickness is 300 um. Then put the coated PET substrate into an oven at 80 °C and bake for 6 h. In order to study the elasticity and dynamic reversible self-healing performance of the elastic adhesive coating, spray a layer of release agent on the PET surface, keep other process parameters unchanged, peel the coated substrate PET and the elastic adhesive coating, and use the obtained elastic adhesive coating for coating performance testing.

[0161] Example 4

[0162] Compared with Example 1, in Step 1, the amount of sodium hydride used is 2.8 g, and the remaining steps are the same as those in Example 1.

[0163] Example 5

[0164] Compared with Example 1, in Step 2, the amount of imidazolyl acrylic monomer used is 1.8 g, and the remaining steps are the same as those in Example 1.

[0165] Example 6

[0166] Compared with Example 1, in Step 3, the amount of 1-(2-isocyanatoethyl)-1H-imidazole used is 1.8 g, and the remaining steps are the same as those in Example 1.

[0167] Compared with the prior art, since the flexible substrate is expensive, by increasing the substrate thickness, the amount of substrate material used will be increased, thus increasing the cost. At the same time, the increase in thickness will also extend the movement path of light in the substrate, thereby reducing the light transmittance. Meanwhile, the increase in substrate thickness will increase the stiffness of the substrate, resulting in a decrease in the substrate's curl rate. The elastic adhesive prepared in the present invention is used for the flexible substrate without adding foam cotton or increasing the substrate thickness. By utilizing the formation and fracture of the dynamic reversible bonds of the elastic adhesive, energy dissipation is achieved, and the anti-crease performance of the substrate is improved.

Claims

1. A method for preparing an elastic adhesive for preventing creases, characterized in that: The specific steps include: Step 1, synthesizing imidazole acrylic acid monomer; Step 2, preparing an imidazole acrylic resin according to the product obtained in step 1; Step 3, preparing imidazole-modified polydimethylsiloxane; Step 4, preparing imidazole-modified nanocellulose; Step 5, preparing an elastic adhesive according to the products obtained in steps 2 to 4.

2. The method for preparing the crease-proof elastic adhesive according to claim 1, characterized in that: The specific process of step 1 is as follows: Step 1.1, dissolve 6.8-13.6 g of imidazole in 50-100 mL of tetrahydrofuran solvent, then add 2.4-4.8 g of sodium hydride, and stir at room temperature for 30-60 minutes; Step 1.2, add 8-16 g of 2-chloroethanol dropwise to the product obtained in step 1.1, continue stirring at room temperature for 30-60 min after all the addition is complete, perform rotary evaporation on the obtained reaction solution to obtain a light yellow liquid, and separate and purify it by column to obtain hydroxylated imidazole; Step 1.3, dissolve 5.6-11.2 g of hydroxylated imidazole in 35-70 mL of dichloromethane solvent, then add 3.6-7.2 g of acrylic acid and 0.2-0.4 mL of concentrated sulfuric acid, heat to 40-45° C. and react for 8-16 hours. After the reaction is completed, the temperature is lowered to room temperature, and purified by column separation to obtain a colorless imidazole acrylic acid monomer.

3. The method for preparing the crease-proof elastic adhesive according to claim 2, characterized in that: In the steps 1.2 and 1.3, the eluent used for column separation and purification is a mixture of ethyl acetate and n-hexane.

4. The method for preparing the crease-proof elastic adhesive according to claim 2, characterized in that: The specific process of step 2 is: Take 1.6-3.2g of imidazole acrylic acid monomer, 0.5-1.0g of isooctyl acrylate, 0.8-1.6g of triethylene glycol methyl ether methacrylate and 0.1-0.2g of ethylene glycol diacrylate, mix them evenly, add 15-20mg of azobisisobutyronitrile, stir evenly, heat the temperature to 60-80℃ and react for 30-60min, cool to room temperature after the reaction is completed, and obtain imidazole acrylic acid resin.

5. The method for preparing the crease-proof elastic adhesive according to claim 4, characterized in that: The specific process of step 3 is as follows: Take 1.4-2.8g of 1-(2-isocyanateethyl)-1H-imidazole and add it to 2-4mL of dimethyl sulfoxide solution. After mixing evenly, introduce it into 12-24g of [α,ω-bis(6-hydroxyethoxypropyl)polydimethylsiloxane] and stir at room temperature for 14-28h. After the reaction is completed, dialyze with a dialysis bag. The solution used for dialysis is 200-400mL of ethanol. Repeat three times to obtain imidazole-modified polydimethylsiloxane.

6. The method for preparing the elastic adhesive for preventing creases according to claim 5, characterized in that: The specific process of step 4 is as follows: Step 4.1, 0.1-0.2 g of cellulose nanofibers are dispersed in 50-100 mL of dimethyl sulfoxide solution and ultrasonicated for 30-60 min, then 0.15-0.3 mL of bromoacetyl chloride is added, and stirred at room temperature for 1-2 h. After the reaction is completed, dialyze with a 7000 Da dialysis bag and 200-400 mL of ethanol to remove excess bromoacetyl chloride and generated HCl, and repeat three times to obtain brominated cellulose nanofibers; Step 4.2, dispersing the brominated cellulose nanofibers obtained in step 4.1 in 30-60 mL of dimethyl sulfoxide solution, and ultrasonically dispersing for 30-60 min to obtain a brominated cellulose nanofiber solution; Step 4.3, dissolving 1.1-2.2 g of imidazole in 10-20 mL of tetrahydrofuran solvent, then adding 0.4-0.8 g of sodium hydride, stirring at room temperature for 30-60 min to obtain a deprotonated imidazole solution; Step 4.4, adding the deprotonated imidazole solution obtained in step 4.3 dropwise to the brominated cellulose nanofiber solution obtained in step 4.2, the dropping time being 30-60 min, stirring at room temperature for 1-2 h after the dropping is completed, dialyzing the obtained reaction solution using a 7000 Da dialysis bag and 200-400 mL of ethanol, repeating three times, and drying the collected solid powder at 45-60 ° C overnight to obtain imidazole-modified nanocellulose.

7. The method for preparing the elastic adhesive for preventing creases according to claim 6, characterized in that: The specific process of step 5 is as follows: Take 0.5-1g of tetramethyldivinyldisiloxane, 0.5-1g of glycidyl acrylate and 2-4g of imidazole acrylic resin, stir at room temperature for 1-2h, then add 30-60mg of tetrabutyl titanate and 15-30mg of azobisisobutyronitrile, raise the temperature to 60-80℃ and react for 30-60min. After the reaction, add 0.1-0.2g of imidazole-modified nanocellulose and 2.5-5g of imidazole-modified polydimethylsiloxane, stir at room temperature for 30-60min, then add 0.14-0.28g of zinc dichloride and continue stirring for 1-2h to obtain an elastic adhesive.

8. An elastic adhesive for preventing creases, prepared by the method for preparing an elastic adhesive for preventing creases as claimed in any one of claims 1 to 7.

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