Pure organic high refractive index polyurethane and preparation method thereof

Abstract

The invention discloses a preparation method of pure organic polyurethane with a high refractive index. The preparation method specifically comprises the following steps: step 1, dissolving dimercaptothiadiazole; step 2, polymerizing the product obtained in the step 1 with diisocyanate; and step 3, washing and purifying the product obtained in the step 2. The invention also discloses pure organic high-refractive-index polyurethane. The polyurethane material prepared by the method disclosed by the invention is high in refractive index and low in cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical materials, and relates to pure organic high-refractive polyurethane, and also relates to a preparation method of the pure organic high-refractive polyurethane. BACKGROUND

[0002] At present, the competition of various optical materials is quite fierce, especially between glass materials and resin materials. Optical glass can realize the combination of high refractive index (up to 2.1) and wide Abbe number (30-85) by doping rare earth elements (such as lanthanum and neodymium) or special compounds (such as fluorophosphate), for example, the refractive index of lanthanum series glass (LaK series) is 1.69-1.81. The upper limit of the refractive index of pure organic optical resin is lower, for example, the highest refractive index of the lens of optical giant Carl Zeiss is only 1.74, and high-refractive resin is often accompanied by low Abbe number (for example, the Abbe number of resin with a refractive index of 1.64 is only about 30), which easily leads to dispersion problems such as "purple edge" and "green edge" at the edge of the picture, and multiple lens combinations are needed to compensate, which increases the complexity of the lens, and this leads to high cost of high-refractive optical resin. If it is desired to further improve the refractive index of the optical resin, nano particles such as nano titanium dioxide can be introduced in addition to structural design, but the light transmittance of the material will be reduced. Therefore, in order to realize the application of optical resin in the field of extreme optical performance and high stability in the future, it is necessary to develop high-refractive optical materials by preparing new materials. SUMMARY

[0003] The purpose of the present application is to provide a preparation method of pure organic high-refractive polyurethane, and the polyurethane material prepared by the method has high refractive index and low cost.

[0004] Another purpose of the present application is to provide pure organic high-refractive polyurethane.

[0005] The first technical solution adopted by the present application is a preparation method of pure organic high-refractive polyurethane, which specifically comprises the following steps: Step 1, dissolving dimercaptothiadiazole; Step 2, polymerizing the product obtained in step 1 with diisocyanate; Step 3, washing and purifying the product obtained in step 2.

[0006] The first technical solution of the present application is also characterized in that: The specific process of step 1 is: under a nitrogen atmosphere, dimercaptothiadiazole and a solvent are added to a flask and stirred.

[0007] In step 1, the solvent is selected from one of tetrahydrofuran, cyclohexene oxide, ethyl acetate, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone, and the mass ratio of the solvent to dimercaptothiadiazole is 4-8:1.

[0008] In step 1, the stirring time is 5-15 min, and the stirring temperature is 20-70℃.

[0009] In step 2, the specific process is: under the protection of nitrogen, the product obtained in step 1 is dropped with diisocyanate and continuously stirred, and after complete dropping, three drops of dibutyl tin dilaurate are added, and the reaction is carried out at room temperature.

[0010] In step 2, the diisocyanate is selected to be phenylene diisocyanate or isophorone diisocyanate, and the reaction time at room temperature is 6-12h.

[0011] In step 3, the specific process is: the product reacted completely in step 2 is poured into n-hexane for precipitation, filtered, washed with n-hexane, placed in an oven for vacuum drying, taken out after complete drying, and ground into powder.

[0012] In step 3, the amount of n-hexane is 300-800mL, the powder dissolution solid content is 5-30%, and the vacuum drying temperature is 50-65℃.

[0013] The second technical solution adopted by the present application is pure organic high refractive index polyurethane, which is prepared by the above-mentioned preparation method of pure organic high refractive index polyurethane.

[0014] The beneficial effects of the present application are as follows: (1) The present application selects dimercaptothiadiazole and phenylene diisocyanate or isophorone diisocyanate as raw materials, which are low in price and simple in reaction steps.

[0015] (2) The present application selects dimercaptothiadiazole, which has very high sulfur content, so that the refractive index of the product is above 1.75, belonging to high refractive index materials.

[0016] (3) The present application has a light transmittance of above 90%, which can optimize the imaging effect and restore the real information. (4) The present application adopts a simple process method to polymerize dimercaptothiadiazole and diisocyanate to prepare high refractive index materials, which provides a new idea for further development of high-performance optical materials, and has very important research significance and great prospects. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure is a synthesis route of the pure organic high refractive index polyurethane of the present application; Figure 2 The figure is a refractive index curve of the polyurethane material prepared in the preparation method 1 and example 4 of the present application at a wavelength of 400-800nm; Figure 3The ultraviolet light transmittance curves of the polyurethane materials prepared by the preparation method of pure organic high refractive index polyurethane of the present invention in Examples 1 and 4 are shown. Detailed Implementation

[0018] The following detailed description is provided in conjunction with specific implementation methods.

[0019] The present invention provides a method for preparing a pure organic high-refractive-index polyurethane, which mainly comprises two parts: the preparation of dimercaptothiadiazole and the preparation of dimercaptothiadiazole-diisocyanate polyurethane. Specifically, it includes the following steps: Step 1, dissolution of dimercaptothiadiazole; The specific process of step 1 is as follows: Under a nitrogen atmosphere, add dimercaptothiadiazole and solvent to a flask and stir.

[0020] In step 1, the solvent is selected from one of tetrahydrofuran, epoxide, ethyl acetate, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. The mass ratio of the solvent to dimercaptothiadiazole is 4-8:1. The stirring time is 5-15 min and the stirring temperature is 20-70℃.

[0021] Step 2: Polymerize the product obtained in Step 1 with diisocyanate; The specific process of step 2 is as follows: under nitrogen protection, diisocyanate is slowly added dropwise to the product obtained in step 1 while stirring continuously. After it is completely added, three drops of dibutyltin dilaurate are added and the reaction is carried out at room temperature.

[0022] In step 2, the diisocyanate is selected as phenyl diisocyanate or isophorone diisocyanate. The mass ratio of the product of step 1 to phenyl diisocyanate is 5-6:1, and the mass ratio of the product of step 1 to isophorone diisocyanate is 4-5:1. The reaction time at room temperature is 6-12 hours.

[0023] Step 3: Wash and purify the product obtained in Step 2.

[0024] The specific steps of step 3 are as follows: after the product of the reaction in step 2 is completed, it is poured into n-hexane to precipitate, filtered, washed 3 times with n-hexane, placed in an oven for vacuum drying, and after it is completely dry, it is taken out and ground into powder.

[0025] In step 3, the amount of n-hexane used is 300-800 mL, the solid content of the dissolved powder is 5-30%, the vacuum drying temperature is 50-65℃, and the drying time is 24 h.

[0026] Example 1 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 10 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.62 g of phenylenediamine diisocyanate was slowly added dropwise while continuously stirring. After the phenylenediamine diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 500 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in a vacuum oven at 50°C for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF (N,N-dimethylformamide) at a solid content of 10%, coated onto a glass plate, and dried in a vacuum oven at 120°C for 12 h.

[0027] Example 2 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 2 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 5 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.5 g of phenylene diisocyanate was slowly added dropwise with continuous stirring. After the phenylene diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 300 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in an oven at 50°C under vacuum for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF at a solid content of 10%, coated onto a glass plate, and dried in an oven at 120°C under vacuum for 12 h.

[0028] Example 3 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 8 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 15 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 1.4 g of phenylenediamine diisocyanate was slowly added dropwise while continuously stirring. After the phenylenediamine diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 800 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in an oven at 50°C under vacuum for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF at a solid content of 10%, coated onto a glass plate, and dried in an oven at 120°C under vacuum for 12 h.

[0029] Example 4 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 10 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.74 g of isophorone diisocyanate was slowly added dropwise with continuous stirring. After the isophorone diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 500 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in a vacuum oven at 50°C for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF at a solid content of 10%, coated onto a glass plate, and dried in a vacuum oven at 120°C for 12 h.

[0030] Example 5 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3g of tetrahydrofuran and 0.5g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 10 minutes until the solid dissolved. A vacuum was then created, and nitrogen gas was introduced. Under nitrogen protection, 0.5g of isophorone diisocyanate was slowly added dropwise while continuously stirring. After the isophorone diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 hours. After the reaction was complete, 500mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in a vacuum oven at 50°C for 8 hours. Once completely dry, the precipitate was ground into powder. The powder was dissolved in DMF at a solid content of 10%, coated onto a glass plate, and then dried in a vacuum oven at 120°C for 12 hours.

[0031] Example 6 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 10 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.9 g of isophorone diisocyanate was slowly added dropwise with continuous stirring. After the isophorone diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 500 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in an oven at 50°C under vacuum for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF at a solid content of 10%, coated onto a glass plate, and dried in an oven at 120°C under vacuum for 12 h.

[0032] The above embodiment 1 is a preferred embodiment of the present invention, but the embodiments of the present invention are not limited to the above embodiment. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

[0033] Comparative Example 1 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of ethyl acetate and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 10 min, 45°C for 10 min, and 65°C for 10 min. Compared to Example 1, after stirring at 25°C for 10 min, the dimercaptothiadiazole had not yet dissolved. Even after further heating, the dimercaptothiadiazole remained partially undissolved, making steps 2 and 3 impossible to continue.

[0034] Comparative Example 2 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of N,N-dimethylformamide and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 10 min, 45°C for 10 min, and 65°C for 10 min. Compared to Example 1, after stirring at 25°C for 10 min, the dimercaptothiadiazole had not yet dissolved. Even after further heating, the dimercaptothiadiazole remained partially undissolved, making steps 2 and 3 impossible to continue.

[0035] Comparative Example 3 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of N,N-dimethylacetamide and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 10 min, 45°C for 10 min, and 65°C for 10 min. Compared to Example 1, after stirring at 25°C for 10 min, the dimercaptothiadiazole had not yet dissolved. Even after further heating, the dimercaptothiadiazole remained partially undissolved, making steps 2 and 3 impossible to continue.

[0036] Comparative Example 4 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3g of N-methylpyrrolidone and 0.5g of dimercaptothiadiazole were added. The mixture was stirred at 25°C for 10 min, then at 45°C for 10 min, and finally at 45°C for 10 min. Compared to Example 1, after stirring at 25°C for 10 min, the dimercaptothiadiazole had not yet dissolved. Even after further heating, the dimercaptothiadiazole remained partially undissolved, making steps 2 and 3 impossible to continue.

[0037] Figure 2 The graphs show the refractive index of Examples 1 and 4 in the range of 400-800 nm. Example 1 has a high refractive index of 1.78, which is in the typical range of high refractive index optical materials, demonstrating excellent optical functional potential.

[0038] The refractive index of Example 4 is only 1.68, classifying it as a medium-refractive-index material. The main reasons for the difference in refractive index between the two are the different sulfur contents of the polymer monomers and whether the main chain contains aromatic rings. Example 1 has a sulfur content of 28%, while Example 4 has a sulfur content of 25%. Sulfur atoms have high polarizability, and their outer electron clouds are easily deformable. The polarizability of sulfur atoms is approximately 1.3 times that of carbon, which causes a larger electron shift in sulfur-containing materials under the influence of a light field, resulting in a higher refractive index. Simultaneously, sulfur atoms possess outer d orbitals, providing additional electron transition channels, giving sulfur atoms both a high molar refractive index (approximately 7.78-7.86 cm³ / mol) and low molecular dispersion, thus controlling dispersion while increasing the refractive index. Furthermore, the benzene ring has high electronic polarizability; under the influence of a light field, the π electron cloud of the benzene ring is easily deformed, generating a larger induced dipole moment, leading to a higher refractive index response.

[0039] Figure 3 The figures show the transmittance curves of Examples 1 and 4 at 400-800 nm. Both have transmittance of over 90%, which indicates they are high transmittance materials.

[0040] Comparative Examples 1-4 showed poor solubility in the four solvents. Even under heating conditions, some solid residue remained of dimercaptothiadiazole. Compared to tetrahydrofuran, which dissolves rapidly at room temperature, this increased the use of solvent and energy. While soluble in tetrahydrofuran (THF) and epoxide, it is insoluble in ethyl acetate, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. The key difference lies in the polarity matching, hydrogen bonding interactions, and solvation capabilities of the solute and solvent, following the "like dissolves like" principle. THF is a moderately polar solvent. Its cyclic ether structure has low steric hindrance, and the lone pair electrons of the ether oxygen atom can quickly encapsulate moderately or weakly polar solute molecules (such as some nonpolar polymers and small lipid-soluble molecules without strong hydrogen-bonding groups), forming a stable solvation layer. Simultaneously, its weak hydrogen bond acceptor properties can form weak hydrogen bonds with sterically hindrance-containing solutes containing hydroxyl / amino groups, aiding dispersion. While ethyl acetate is also moderately polar, the electron distribution and spatial structure of the ester group differ from that of the ether bond. The carbonyl oxygen is highly electrophilic, interacting weakly with the hydrophobic groups of the solute, and exhibiting stronger intermolecular dipole-dipole interactions, making it more prone to self-aggregation and difficult to disperse the solute. N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone are strongly polar solvents, with a polarity mismatch with moderately polar solutes. Their extremely strong intermolecular interactions preferentially form their own solvent networks, effectively "displacing" the solute molecules. If the solute is of the type that can bind to hydrogen bond acceptors, the strong hydrogen bond acceptor properties of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone can form excessively strong hydrogen bonds with the solute, causing the solute to aggregate. In addition, the solubilizing ability of THF can just disrupt the crystal lattice of the solute, while ethyl acetate and DMF / DMAc cannot effectively disrupt it, which further exacerbates the solubility difference. Although factors such as temperature and concentration have an impact, the above reasons play a dominant role under the same conditions.

[0041] Example 7 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of hexane oxide and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 20°C for 5 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.62 g of phenylenediamine diisocyanate was slowly added dropwise with continuous stirring. After the phenylenediamine diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 500 mL of n-hexane was added to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in a vacuum oven at 50°C for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF (N,N-dimethylformamide) at a solid content of 10%, coated onto a glass plate, and dried in a vacuum oven at 120°C for 12 h.

[0042] Example 8 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 40 °C for 7 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.62 g of phenylenediamine diisocyanate was slowly added dropwise with continuous stirring. After the phenylenediamine diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 500 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in an oven at 50 °C under vacuum for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF (N,N-dimethylformamide) at a solid content of 10%, coated onto a glass plate, and dried in an oven at 120 °C under vacuum for 12 h.

[0043] Example 9 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 60 °C for 10 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.62 g of phenylenediamine diisocyanate was slowly added dropwise while continuously stirring. After the phenylenediamine diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 500 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in an oven at 50 °C under vacuum for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF (N,N-dimethylformamide) at a solid content of 10%, coated onto a glass plate, and dried in an oven at 120 °C under vacuum for 12 h.

[0044] Example 10 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 40 °C for 12 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.62 g of phenylenediamine diisocyanate was slowly added dropwise while continuously stirring. After the phenylenediamine diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 500 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in an oven at 50 °C under vacuum for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF (N,N-dimethylformamide) at a solid content of 10%, coated onto a glass plate, and dried in an oven at 120 °C under vacuum for 12 h.

[0045] Example 11 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 60 °C for 13 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.62 g of phenylenediamine diisocyanate was slowly added dropwise while continuously stirring. After the phenylenediamine diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 500 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in an oven at 50 °C under vacuum for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF (N,N-dimethylformamide) at a solid content of 10%, coated onto a glass plate, and dried in an oven at 120 °C under vacuum for 12 h.

[0046] Example 12 In a reaction apparatus equipped with an electric stirrer and a reflux condenser, 3 g of tetrahydrofuran and 0.5 g of dimercaptothiadiazole were added. The mixture was stirred at 70 °C for 13 min until the solid dissolved. Vacuum was then applied, and nitrogen gas was introduced. Under nitrogen protection, 0.62 g of phenylenediamine diisocyanate was slowly added dropwise while continuously stirring. After the phenylenediamine diisocyanate was completely added, three drops of dibutyltin dilaurate were added, and the reaction was carried out at room temperature for 24 h. After the reaction was complete, 500 mL of n-hexane was poured in to precipitate the solids. The precipitate was filtered, washed three times with n-hexane, and then dried in an oven at 50 °C under vacuum for 8 h. After complete drying, the precipitate was ground into powder. The powder was dissolved in DMF (N,N-dimethylformamide) at a solid content of 10%, coated onto a glass plate, and dried in an oven at 120 °C under vacuum for 12 h.

Claims

1. A method for preparing pure organic high-refractive-index polyurethane, characterized in that: Specifically, the steps include the following: Step 1: Dissolve dimercaptothiadiazole; Step 2: Polymerize the product obtained in Step 1 with diisocyanate; Step 3: Wash and purify the product obtained in Step 2.

2. The method for preparing pure organic high-refractive-index polyurethane according to claim 1, characterized in that: The specific process of step 1 is as follows: under a nitrogen atmosphere, add dimercaptothiadiazole and solvent to a flask and stir.

3. The method for preparing pure organic high-refractive-index polyurethane according to claim 2, characterized in that: In step 1, the solvent is selected from one of tetrahydrofuran, ethyl acetate, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and the mass ratio of the solvent to dimercaptothiadiazole is 4-8:

1.

4. The method for preparing pure organic high-refractive-index polyurethane according to claim 2, characterized in that: In step 1, the stirring time is 5-15 minutes and the stirring temperature is 20-70℃.

5. The method for preparing pure organic high-refractive-index polyurethane according to claim 2, characterized in that: The specific process of step 2 is as follows: under nitrogen protection, diisocyanate is added dropwise to the product obtained in step 1 while stirring continuously. After it is completely added, three drops of dibutyltin dilaurate are added, and the reaction is carried out at room temperature.

6. The method for preparing pure organic high-refractive-index polyurethane according to claim 5, characterized in that: In step 2, the diisocyanate is selected as phenyl diisocyanate or isophorone diisocyanate, and the reaction time at room temperature is 6-12 hours.

7. The method for preparing pure organic high-refractive-index polyurethane according to claim 5, characterized in that: The specific process of step 3 is as follows: the product from step 2 is poured into n-hexane to precipitate, filtered, washed with n-hexane, placed in an oven for vacuum drying, and after it is completely dry, it is taken out and ground into powder.

8. The method for preparing pure organic high-refractive-index polyurethane according to claim 7, characterized in that: In step 3, the amount of n-hexane used is 300-800 mL, the solid content of the dissolved powder is 5-30%, and the vacuum drying temperature is 50-65℃.

9. A pure organic high refractive index polyurethane, prepared by the method for preparing pure organic high refractive index polyurethane as described in any one of claims 1 to 8.

Images