Fluorine-containing polyurethane with low refractive index and preparation method thereof

Abstract

The invention discloses fluorine-containing polyurethane with a low refractive index and a preparation method thereof, and belongs to the technical field of optical materials.Fluorine-containing polyether polyurethane is prepared from a fluorine-containing epoxy compound as a raw material through an isocyanate chain extension method, so that the prepared fluorine-containing polyurethane has excellent light transmission and mechanical properties and low refractive index. Besides, the problems of insufficient mechanical strength and wear resistance of polyurethane are overcome through a cross-linking technology, a functional material system with optical properties and mechanical properties is formed, and the application range of the material is expanded.

Description

Technical Field

[0001] This invention belongs to the field of optical materials technology, and particularly relates to a fluorinated polyurethane with low refractive index and its preparation method. Background Technology

[0002] Low-refractive-index materials have been widely used in various optical and optoelectronic fields due to their ability to significantly reduce light reflection at interfaces, increase light transmittance, and provide good chemical and mechanical stability. These applications primarily include anti-reflective coatings, solar photovoltaics, display and touch panels, optical components and lenses, and protective and weather-resistant coatings. For example, in camera lenses, low-refractive-index materials can reduce surface reflection, improving imaging and contrast. Adding low-refractive-index materials to fiber optic cladding or integrated waveguides can reduce refractive index differences, lower mode coupling loss, and improve the reliability of long-distance transmission.

[0003] Currently, common low-refractive-index materials mainly include inorganic nanoparticles, magnesium fluoride, calcium fluoride, polytetrafluoroethylene, and fluorinated polyimide. Although they exhibit excellent optical properties, they still have limitations in terms of flexible processing, weather resistance, and mechanical strength. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a fluorinated polyurethane with a low refractive index and its preparation method. This invention prepares a fluorinated polymer using a specific fluorinated epoxy compound as a raw material and then uses an isocyanate chain extension method to prepare the fluorinated polyurethane, thereby resulting in a fluorinated polyether polyurethane that possesses excellent light transmittance, mechanical properties, and refractive index.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a fluorinated polyurethane with a low refractive index, which is an uncrosslinked linear polyurethane or a crosslinked polyurethane, and the general structural formula of the uncrosslinked linear polyurethane is as follows:

[0007] ,

[0008] The general structural formula of the crosslinked polyurethane is as follows:

[0009]

[0010] Where, R1= , , , or R2= or R3 = , , or n = 5~8, preferably n = 5, 6 or 8.

[0011] The present invention also provides a method for preparing the above-mentioned fluorinated polyurethane with low refractive index, comprising the following steps:

[0012] Fluorinated polyether diols or fluorinated polyether polyols are prepared by ring-opening polymerization of fluorinated epoxy compounds in a first organic solvent.

[0013] Polyether-type polyurethane is prepared by an addition reaction of diisocyanate, the fluorinated polyether diol and / or the fluorinated polyether polyol in a second organic solvent, which is the fluorinated polyurethane with low refractive index.

[0014] The synthetic route for the fluorinated polyurethane with low refractive index of this invention is as follows:

[0015] Synthetic route of fluorinated polyether diols: ;

[0016] Synthetic routes for fluorinated polyether polyols: ;

[0017] Synthetic route of uncrosslinked linear polyurethane:

[0018]

[0019] Synthetic route of crosslinked polyurethane:

[0020]

[0021] Compared with existing technologies, this invention reduces the polarizability of materials by introducing high-fluorine-content groups (such as perfluoroalkyl and trifluoromethyl groups) into the molecular chain, thereby achieving the preparation of low-refractive-index polyurethane. Simultaneously, the fluorinated polyurethane backbone contains numerous urethane groups, giving it both the general properties of elastomers and the excellent solvent resistance and heat resistance of fluorinated polymers. Furthermore, by introducing fluorinated polyether diols and / or fluorinated polyether polyols, the fluorinated polyurethane forms a three-dimensional cross-linked network after heat treatment, further enhancing the hardness of films prepared from these materials. This allows the fluorinated polyurethane to maintain flexible processing while meeting the mechanical strength requirements of high-end optical applications, forming a functional material system that combines optical performance and weather resistance. In summary, the low-refractive-index fluorinated polyurethane of this invention has potential application value in optical fiber inner layer coating materials, low-refractive-index components of camera optical lenses, and flexible optical devices.

[0022] Furthermore, the molecular weight of the fluorinated polyether diol is 500-4000, and the molecular weight of the fluorinated polyether polyol is 500-4000.

[0023] Furthermore, the fluorinated epoxy compound is selected from 1,1,1-trifluoro-2,3-epoxypropane, 2,2-bis(trifluoromethyl)epoxyethylene, decafluoro-1,2-epoxycyclohexane, or 2-(perfluorobutyl)epoxyethylene.

[0024] Furthermore, the diisocyanate is selected from isophorone diisocyanate, toluene-2,4-diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, or hexamethylene diisocyanate.

[0025] Furthermore, an initiator and a catalyst were also added during the ring-opening polymerization reaction;

[0026] The molar ratio of the catalyst, initiator and fluorinated epoxy compound is 1:(200~600):2000.

[0027] Furthermore, when carrying out the ring-opening polymerization reaction, the initiator is selected from 1,4-butanediol, 1,4-benzyldiethanol or 1,1,1-trimethylolethane; the catalyst is selected from phosphazene ligand P4-tert-butyl (t-Bu-P4) or phosphazene ligand P2-tert-butyl (t-Bu-P2).

[0028] Furthermore, the first organic solvent is selected from tetrahydrofuran, 1,4-dioxane, diethoxymethane, or ethylene glycol dimethyl ether; the second organic solvent is N,N-dimethylformamide.

[0029] Furthermore, the ring-opening polymerization reaction is carried out at a temperature of 25~150 °C for a time of 24~48 h; preferably, the ring-opening polymerization reaction is carried out at a temperature of 80 °C for a time of 24~48 h.

[0030] Furthermore, the addition reaction is carried out at a temperature of 50-80 °C for 4-8 h; preferably, the addition reaction is carried out at a temperature of 80 °C for 4 h.

[0031] Furthermore, an organotin catalyst was added during the preparation of the polyether-type polyurethane via an addition reaction.

[0032] Furthermore, the amount of the organotin catalyst added is 0.5 to 2% of the mass of the fluorinated polyether diol or the fluorinated polyether polyol, preferably 0.5%.

[0033] For example, the organotin catalyst is dibutyltin dilaurate.

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] This invention introduces fluorine atoms into polyurethane, thereby producing a polyether-type polyurethane that possesses excellent light transmittance, mechanical properties, and a low refractive index. Furthermore, crosslinking technology overcomes the shortcomings of insufficient mechanical strength and abrasion resistance in polyurethane, forming a functional material system that combines optical properties and mechanical strength, thus expanding the material's application range. For example, the fluorinated polyurethane with a low refractive index prepared by this invention can be used as an inner cladding material for optical fibers, a low refractive index component in camera optical lenses, and in flexible optical devices. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0037] Figure 1 The image shows the 1H NMR spectrum of the fluorinated polyether diol prepared in Example 1.

[0038] Figure 2 The refractive index curve of the fluorinated polyurethane prepared in Example 1 is shown.

[0039] Figure 3 The image shows a comparison of the tensile strength and elongation at break of the fluorinated polyurethane prepared in Example 2 after multiple processing steps.

[0040] Figure 4 The transmittance curve of the crosslinked fluorinated polyurethane prepared in Example 3. Detailed Implementation

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0044] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0045] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0046] Embodiments of the present invention provide a fluorinated polyurethane with a low refractive index, which is an uncrosslinked linear polyurethane or a crosslinked polyurethane, and the general structural formula of the uncrosslinked linear polyurethane is as follows:

[0047] ,

[0048] The general structural formula of the crosslinked polyurethane is as follows:

[0049]

[0050] Where, R1= , , , or R2= or R3 = , , , n=5~8, preferably n=5, 6 or 8.

[0051] Embodiments of the present invention also provide a method for preparing the above-mentioned fluorinated polyurethane with low refractive index, comprising the following steps:

[0052] Fluorinated polyether diols or fluorinated polyether polyols are prepared by ring-opening polymerization of fluorinated epoxy compounds in a first organic solvent.

[0053] Polyether-type polyurethanes with low refractive index are prepared by addition reaction of diisocyanate, fluorinated polyether diol and / or fluorinated polyether polyol in a second organic solvent.

[0054] In a preferred embodiment of the present invention, the mass ratio of diisocyanate, fluorinated polyether diol, and / or fluorinated polyether polyol is (0.8~1.1):(1.1~2). That is, in the present invention, polyether-type polyurethane is prepared by addition reaction using diisocyanate and at least one of fluorinated polyether diol and fluorinated polyether polyol as raw materials.

[0055] In a preferred embodiment of the present invention, when preparing polyether-type polyurethane by addition reaction using diisocyanate, fluorinated polyether diol and fluorinated polyether polyol as raw materials, the mass ratio of fluorinated polyether diol to fluorinated polyether polyol is 7:48.

[0056] In a preferred embodiment of the present invention, the molecular weight of the fluorinated polyether diol is 500-4000, and the molecular weight of the fluorinated polyether polyol is 500-4000.

[0057] In a preferred embodiment of the present invention, the fluorinated epoxy compound is selected from 1,1,1-trifluoro-2,3-epoxypropane, 2,2-bis(trifluoromethyl)epoxyethylene, decafluoro-1,2-epoxycyclohexane, or 2-(perfluorobutyl)epoxyethylene, preferably 1,1,1-trifluoro-2,3-epoxypropane. These fluorinated epoxy compounds balance low cost with the high reactivity required for ring-opening polymerization and addition reactions. Compared to other fluorinated epoxy compounds, the epoxy compounds selected in this invention can effectively reduce the refractive index of polyurethane while maintaining a moderate degree of phase separation, which is more conducive to ensuring the excellent overall performance of fluorinated polyurethane.

[0058] In a preferred embodiment of the present invention, the diisocyanate is selected from isophorone diisocyanate, toluene-2,4-diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, or hexamethylene diisocyanate.

[0059] In a preferred embodiment of the present invention, an initiator and a catalyst are also added during the ring-opening polymerization reaction;

[0060] The molar ratio of catalyst, initiator and fluorinated epoxy compound is 1:(200~600):2000.

[0061] In a preferred embodiment of the present invention, when carrying out the ring-opening polymerization reaction, the initiator is selected from 1,4-butanediol, 1,4-benzenedimethanol or 1,1,1-trimethylolethane; the catalyst is selected from phosphazene ligand P4-tert-butyl (t-Bu-P4) or phosphazene ligand P2-tert-butyl (t-Bu-P2).

[0062] In a preferred embodiment of the present invention, the first organic solvent is selected from tetrahydrofuran, 1,4-dioxane, diethoxymethane, or ethylene glycol dimethyl ether; the second organic solvent is N,N-dimethylformamide.

[0063] In a preferred embodiment of the present invention, the ring-opening polymerization reaction is carried out at a temperature of 25~150 °C for 24~48 h; preferably, the ring-opening polymerization reaction is carried out at a temperature of 80 °C for 24~48 h.

[0064] In a preferred embodiment of the present invention, the temperature of the addition reaction is 50~80 °C and the time is 4~8 h; preferably, the temperature of the addition reaction is 80 °C and the time is 4 h.

[0065] In a preferred embodiment of the present invention, when preparing polyether polyurethane by addition reaction, the amount of the second organic solvent added is 100 to 300% of the mass of fluorinated polyether diol and / or fluorinated polyether polyol.

[0066] In a preferred embodiment of the present invention, an organotin catalyst is also added when preparing polyether polyurethane by addition reaction.

[0067] In a preferred embodiment of the present invention, the amount of organotin catalyst added is 0.5 to 2% of the mass of fluorinated polyether diol or fluorinated polyether polyol, preferably 0.5%.

[0068] For example, the organotin catalyst is dibutyltin dilaurate.

[0069] In preparing fluorinated polyether diols or polyether polyols via ring-opening polymerization, the molecular weight and molecular weight distribution of the resulting polyether diols or polyether polyols can be precisely controlled by adjusting the ratio of the fluorinated epoxy compound to the initiator (see Examples 1-3). Different structures of polyether polyols can also be obtained by changing the type of initiator (see Example 4). For example, when the molar ratio of the fluorinated epoxy compound to the initiator is 10:1, a polyether diol with a molecular weight of 1852 can be obtained (molecular weight determined by GPC testing). Further increasing the amount of initiator, when the molar ratio of the fluorinated epoxy compound to the initiator is 5:1, a polyether diol with a molecular weight of 1483 can be obtained (molecular weight determined by GPC testing). Therefore, reducing the ratio of the fluorinated epoxy compound to the initiator can reduce the molecular weight of the resulting polyether diol, and this rule also applies to polyether polyols. Replacing the initiator with 1,4-butanediol yields branched polyether polyols, which can then be used to prepare cross-linked fluorinated polyurethanes.

[0070] This invention uses fluorinated polyether diols or fluorinated polyether polyols as soft segments and diisocyanates as hard segments. Through covalent bonds, intramolecular and intermolecular hydrogen bonds, it retains the flexibility of the polyether segments while introducing the rigidity of the diisocyanate. Furthermore, the mixed use of fluorinated polyether diols, fluorinated polyether polyols, and diisocyanates provides additional crosslinking points for the fluorinated polyurethane, further improving its tensile strength (up to 15.62 MPa) while maintaining a low refractive index. Compared to the fluorinated polyurethane acrylate in CN111057462A (tensile strength 2.4 MPa, elongation at break 35%), the fluorinated polyurethane prepared by this invention combines a lower refractive index with good mechanical properties. The fluorinated epoxy resin polymers disclosed in CN114907290A are formed by introducing fluorine atoms into epoxy resins and reacting them with difunctional or multifunctional organic amines to form a crosslinked network. The fluorinated polyurethane (with a minimum refractive index of 1.420) prepared by this invention has a lower refractive index compared to previous fluorinated epoxy resin materials (with a refractive index of 1.440), and also exhibits good flexibility. The uncrosslinked linear polyurethane can be melted and further processed. Furthermore, compared to the preparation method of fluorinated epoxy resin polymers disclosed in CN114907290A, the fluorinated epoxy compounds used in this invention are readily available, requiring no complex synthesis process, resulting in lower synthesis costs and milder reaction conditions, which is more conducive to further large-scale production.

[0071] In the following embodiments and comparative examples of the present invention, the performance testing method for polyurethane is as follows:

[0072] 1. Mechanical properties: Samples were prepared and tested according to ASTM D882 at a test speed of 50 mm / min.

[0073] 2. Refractive index: Measured using a SE-VE-L type ellipsometer, with a test wavelength range of 400~1000 nm.

[0074] 3. Transmittance: Tested by ultraviolet spectrophotometer, the sample thickness is 0.3 mm.

[0075] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0076] All raw materials used in the embodiments of this invention were purchased commercially. As an example, t-Bu-P4 was purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., and t-Bu-P2 was purchased from Aladdin.

[0077] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0078] The technical solution of the present invention will be further illustrated by the following embodiments.

[0079] Example 1

[0080] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0081] 11 g (0.10 mol) of 1,1,1-trifluoro-2,3-epoxypropane, 0.9 g (0.01 mol) of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:200:2000) were added to a 120 mL pressure-resistant bottle. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number-average molecular weight was 1852 as determined by GPC (its 1H NMR spectrum is shown in [reference needed]). Figure 1 ); Take 4 g of the above-mentioned fluorinated polyether diol into a 50 mL side-necked flask, and add 8 g of N,N-dimethylformamide, 0.92 g of isophorone diisocyanate and 20 mg of dibutyltin dilaurate sequentially under a nitrogen atmosphere. After stirring and reacting at 80 °C for 4 h, pour the mixture into a polytetrafluoroethylene plate, and then place it in a 50 °C forced-air oven for curing for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. The number-average molecular weight of the polyurethane prepared in this example is 26.5 kDa, as determined by GPC. The structural formula is as follows:

[0082] ,

[0083] The mechanical properties of the product prepared according to ASTM D882 were tested at a speed of 50 mm / min. The tensile strength of the fluorinated polyurethane with low refractive index prepared in this example was 8.96 MPa, and the elongation at break was 1190%.

[0084] The refractive index of the prepared product was measured using a SE-VE-L type ellipsometer, with a test wavelength range of 400~1000 nm. The refractive index curve of the fluorinated polyurethane with low refractive index prepared in this example is shown in [reference needed]. Figure 2 It can be seen that the fluorinated polyurethane has a low refractive index, and its refractive index shows a monotonically decreasing trend with increasing wavelength; the fluorinated polyurethane with low refractive index prepared in this embodiment has a refractive index of 1.420 at a wavelength of 589 nm.

[0085] The transmittance of the product was measured by ultraviolet spectrophotometer. The sample thickness was 0.3 mm. The visible light transmittance of the fluorinated polyurethane with low refractive index prepared in this example was 91% at 800 nm.

[0086] Example 2

[0087] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0088] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this embodiment is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1483 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were reacted with stirring at 80 °C for 4 h, and then poured into a polytetrafluoroethylene plate. The plate was then cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. The number-average molecular weight of the polyurethane prepared in this example was 37.9 kDa, and the structural formula was the same as that in Example 1.

[0089] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 11.39 MPa and an elongation at break of 670%; a refractive index of 1.433 at a wavelength of 589 nm; and a visible light transmittance of 92% at 800 nm when the sample thickness is 0.3 mm.

[0090] To further verify the reprocessability of the low-refractive-index fluorinated polyurethane prepared in this embodiment, the prepared fluorinated polyurethane was cut into pieces and re-hot-pressed (hot-pressing temperature: 100 ℃, processing pressure: 10 MPa, processing time: 10 min), and mechanical property tests were performed. This process was repeated multiple times. Specific experimental results can be found in [link to experimental results]. Figure 3 It can be seen that after repeated processing, the tensile strength and elongation at break of the fluorinated polyurethane with low refractive index prepared in this embodiment did not change significantly, indicating that the fluorinated polyurethane with low refractive index has good reprocessability.

[0091] Example 3

[0092] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0093] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 2.7 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this embodiment is 1:600:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1274 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 2.2 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were stirred and reacted at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. The number average molecular weight of the polyurethane prepared in this example was 25.5 kDa, and the structural formula was the same as that in Example 1.

[0094] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 8.35 MPa and an elongation at break of 550%; a refractive index of 1.436 at a wavelength of 589 nm; and a visible light transmittance of 85% at 800 nm when the sample thickness is 0.3 mm.

[0095] Example 4

[0096] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0097] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 3.6 g of 1,1,1-trimethylolethane, 62.5 μL of a 0.8 mol / L t-Bu-P4 solution in n-hexane, and 60 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:600:2000) were added. The reaction was carried out in a closed system at 80 °C for 48 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed with n-hexane, and excess 1,1,1-trimethylolethane was removed by alumina column chromatography. The product was then dried in a forced-air oven at 50 °C to obtain a fluorinated polyether polyol, the number average molecular weight of which was determined to be 1602 by GPC. 0.28 g of the product was then taken. In Example 2, 1.92 g of the fluorinated polyether diol (Mn = 1483) and the above-mentioned fluorinated polyether polyol were placed in a 50 mL side-necked flask. Under a nitrogen atmosphere, 8 g of N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were added sequentially. After stirring and reacting at 80 °C for 4 h, the mixture was poured into a polytetrafluoroethylene plate and then cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. Since the polyurethane obtained in this example has a cross-linked structure, its number-average molecular weight cannot be obtained. The structural formula of the fluorinated polyurethane prepared in this example is as follows:

[0098] ,

[0099] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 15.62 MPa and an elongation at break of 596%; its refractive index at 589 nm is 1.427; and the transmittance curve of the fluorinated polyurethane with low refractive index prepared in this embodiment at a sample thickness of 0.3 mm is shown in the figure. Figure 4 The visible light transmittance at 800 nm is 93%.

[0100] Example 5

[0101] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0102] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 3.6 g of 1,1,1-trimethylolethane, 62.5 μL of a 0.8 mol / L t-Bu-P4 solution in n-hexane, and 60 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:600:2000) were added. The reaction was carried out in a closed system at 80 °C for 48 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed with n-hexane, and excess 1,1,1-trimethylolethane was removed by alumina column chromatography. The product was then dried in a forced-air oven at 50 °C to obtain a fluorinated polyether polyol, the number average molecular weight of which was determined to be 1602 by GPC. 0.28 g of the product was then taken. The fluorinated polyether diol (M) prepared in Example 2 n = 1483) and 1.92 g of the above-mentioned fluorinated polyether polyol were placed in a 50 mL side-necked flask. Under a nitrogen atmosphere, 8 g of N,N-dimethylformamide, 1.6 g of isophorone diisocyanate and 20 mg of dibutyltin dilaurate were added sequentially. After stirring and reacting at 80 °C for 4 h, the mixture was poured into a polytetrafluoroethylene plate and then placed in a 50 °C forced-air oven for curing for 48 h to obtain a polyether polyurethane, which is a fluorinated polyurethane with a low refractive index. Since the polyurethane obtained in this example has a cross-linked structure, its number-average molecular weight cannot be obtained. The structural formula of the fluorinated polyurethane prepared in this example is the same as that in Example 4.

[0103] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 7.20 MPa and an elongation at break of 663%; a refractive index of 1.423 at a wavelength of 589 nm; and a visible light transmittance of 87% at 800 nm when the sample thickness is 0.3 mm.

[0104] Example 6

[0105] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0106] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 3.6 g of 1,1,1-trimethylolethane, 62.5 μL of a 0.8 mol / L t-Bu-P4 solution in n-hexane, and 60 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:600:2000) were added. The reaction was carried out in a closed system at 80 °C for 48 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed with n-hexane, and excess 1,1,1-trimethylolethane was removed by alumina column chromatography. The product was then dried in a forced-air oven at 50 °C to obtain a fluorinated polyether polyol, the number average molecular weight of which was determined to be 1602 by GPC. 0.28 g of the product was then taken. The fluorinated polyether diol (Mn = 14834) prepared in Example 2 and the above-mentioned 1.92 g of fluorinated polyether polyol were placed in a 50 mL side-necked flask. Under a nitrogen atmosphere, 8 g of N,N-dimethylformamide, 2.0 g of isophorone diisocyanate and 20 mg of dibutyltin dilaurate were added sequentially. After stirring and reacting at 80 °C for 4 h, the mixture was poured into a polytetrafluoroethylene plate and then cured in a 50 °C forced-air oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. Since the polyurethane obtained in this example has a cross-linked structure, its number-average molecular weight cannot be obtained. The structural formula of the fluorinated polyurethane prepared in this example is the same as that in Example 4.

[0107] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 11.17 MPa and an elongation at break of 509%; a refractive index of 1.425 at a wavelength of 589 nm; and a visible light transmittance of 86% at 800 nm when the sample thickness is 0.3 mm.

[0108] Example 7

[0109] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0110] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 3.6 g of 1,1,1-trimethylolethane, 62.5 μL of a 0.8 mol / L t-Bu-P4 solution in n-hexane, and 60 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:600:2000) were added. The reaction was carried out in a closed system at 80 °C for 48 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed with n-hexane, and excess 1,1,1-trimethylolethane was removed by alumina column chromatography. The product was then dried in a forced-air oven at 50 °C to obtain a fluorinated polyether polyol, the number average molecular weight of which was determined to be 1602 by GPC. 0.28 g of the product was then taken. The fluorinated polyether diol (Mn = 1852) prepared in Example 1 and 1.92 g of the above-mentioned fluorinated polyether polyol were placed in a 50 mL side-necked flask. Under a nitrogen atmosphere, 8 g of N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were added sequentially. After stirring and reacting at 80 °C for 4 h, the mixture was poured into a polytetrafluoroethylene plate and then cured in a 50 °C forced-air oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. Since the polyurethane obtained in this example has a cross-linked structure, its number-average molecular weight cannot be obtained. The structural formula of the fluorinated polyurethane prepared in this example is as follows:

[0111] ,

[0112] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 10.25 MPa and an elongation at break of 590%; a refractive index of 1.424 at a wavelength of 589 nm; and a visible light transmittance of 88% at 800 nm when the sample thickness is 0.3 mm.

[0113] Example 8

[0114] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0115] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 3.6 g of 1,1,1-trimethylolethane, 62.5 μL of a 0.8 mol / L t-Bu-P4 solution in n-hexane, and 60 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:600:2000) were added. The reaction was carried out in a closed system at 80 °C for 48 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed with n-hexane, and excess 1,1,1-trimethylolethane was removed by alumina column chromatography. The product was then dried in a forced-air oven at 50 °C to obtain a fluorinated polyether polyol, the number average molecular weight of which was determined to be 1602 by GPC. 0.28 g of the product was then taken. The fluorinated polyether diol (Mn = 1274) prepared in Example 3 and 1.92 g of the above-mentioned fluorinated polyether polyol were placed in a 50 mL side-necked flask. Under a nitrogen atmosphere, 8 g of N,N-dimethylformamide, 1.8 g of isophorone diisocyanate and 20 mg of dibutyltin dilaurate were added sequentially. After stirring and reacting at 80 °C for 4 h, the mixture was poured into a polytetrafluoroethylene plate and then cured in a 50 °C forced-air oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. Since the polyurethane obtained in this example has a cross-linked structure, its number-average molecular weight cannot be obtained. The structural formula of the fluorinated polyurethane prepared in this example is as follows:

[0116] ,

[0117] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 11.46 MPa and an elongation at break of 605%; a refractive index of 1.426 at a wavelength of 589 nm; and a visible light transmittance of 89% at 800 nm when the sample thickness is 0.3 mm.

[0118] Example 9

[0119] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0120] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this embodiment is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1483 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 0.67 g hexamethylene diisocyanate, and 20 mg dibutyltin dilaurate were reacted at 80 °C for 4 h with stirring, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. GPC testing showed that the number-average molecular weight of the polyurethane prepared in this example was 24.0 kDa, and its structural formula is as follows:

[0121] ,

[0122] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 6.5 MPa and an elongation at break of 1200%; a refractive index of 1.435 at a wavelength of 589 nm; and a visible light transmittance of 87% at 800 nm when the sample thickness is 0.3 mm.

[0123] Example 10

[0124] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0125] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this embodiment is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1483 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 0.69 g toluene-2,4-diisocyanate, and 20 mg dibutyltin dilaurate were reacted at 80 °C for 4 h with stirring, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. GPC testing showed that the number-average molecular weight of the polyurethane prepared in this example was 26.8 kDa, and its structural formula is as follows:

[0126] ,

[0127] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 10.0 MPa and an elongation at break of 650%; a refractive index of 1.439 at a wavelength of 589 nm; and a visible light transmittance of 86% at 800 nm when the sample thickness is 0.3 mm.

[0128] Example 11

[0129] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0130] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this embodiment is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1483 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 1.05 g of dicyclohexylmethane diisocyanate, and 20 mg of dibutyltin dilaurate were reacted with stirring at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. GPC testing showed that the number-average molecular weight of the polyurethane prepared in this example was 36.5 kDa, and its structural formula is as follows:

[0131] ,

[0132] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 11.50 MPa and an elongation at break of 615%; a refractive index of 1.437 at a wavelength of 589 nm; and a visible light transmittance of 90% at 800 nm when the sample thickness is 0.3 mm.

[0133] Example 12

[0134] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0135] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this embodiment is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1483 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 1.0 g of diphenylmethane diisocyanate, and 20 mg of dibutyltin dilaurate were reacted with stirring at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. GPC testing showed that the number-average molecular weight of the polyurethane prepared in this example was 24.8 kDa, and its structural formula is as follows:

[0136] ,

[0137] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 6.0 MPa and an elongation at break of 470%; a refractive index of 1.436 at a wavelength of 589 nm; and a visible light transmittance of 88% at 800 nm when the sample thickness is 0.3 mm.

[0138] Example 13

[0139] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0140] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 2.8 g of 1,4-benzenedimethanol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1375 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were reacted with stirring at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. GPC testing showed that the number-average molecular weight of the polyurethane prepared in this example was 27.1 kDa, and its structural formula is as follows:

[0141] ,

[0142] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 10.05 MPa and an elongation at break of 480%; a refractive index of 1.431 at a wavelength of 589 nm; and a visible light transmittance of 88% at 800 nm when the sample thickness is 0.3 mm.

[0143] Example 14

[0144] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0145] In a 120 mL pressure-resistant bottle, 18 g of 2,2-bis(trifluoromethyl)ethylene oxide, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 in n-hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 2,2-bis(trifluoromethyl)ethylene oxide had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with n-hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number-average molecular weight was determined to be 1525 by GPC. 4 g of the above fluorinated polyether diol was taken into a 50 mL side-necked flask, and 8 g of N,N-dimethylformamide, 1.8 g of 1,4-butanediol, and 1.8 μL of t-Bu-P4 in n-hexane solution were added sequentially under a nitrogen atmosphere. g of isophorone diisocyanate and 20 mg of dibutyltin dilaurate were reacted with stirring at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate, and then cured in a 50 °C forced-air oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. The number average molecular weight of the polyurethane prepared in this example was 28.3 kDa according to GPC testing, and the structural formula is as follows:

[0146] ,

[0147] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 9.6 MPa and an elongation at break of 660%; a refractive index of 1.423 at a wavelength of 589 nm; and a visible light transmittance of 86% at 800 nm when the sample thickness is 0.3 mm.

[0148] Example 15

[0149] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0150] In a 120 mL pressure-resistant bottle, 28 g of decafluoro-1,2-epoxycyclohexane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 n-hexane solution, and 10 mL of tetrahydrofuran (i.e., in this example, the molar ratio of catalyst, initiator, and fluorinated epoxy compound is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added decafluoro-1,2-epoxycyclohexane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with n-hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number-average molecular weight was determined to be 1485 by GPC. 4 g of the above fluorinated polyether diol was taken into a 50 mL side-necked flask, and 8 g of N,N-dimethylformamide, 1.8 g of 1,4-butanediol, and 1.8 μL of tetrahydrofuran were added sequentially under a nitrogen atmosphere. g of isophorone diisocyanate and 20 mg of dibutyltin dilaurate were reacted with stirring at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate, and then cured in a 50 °C forced-air oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. The number average molecular weight of the polyurethane prepared in this example was 27.5 kDa according to GPC testing, and the structural formula is as follows:

[0151] ,

[0152] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 16.5 MPa and an elongation at break of 440%; a refractive index of 1.425 at a wavelength of 589 nm; and a visible light transmittance of 90% at 800 nm when the sample thickness is 0.3 mm.

[0153] Example 16

[0154] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0155] In a 120 mL pressure-resistant bottle, 26 g of 2-(perfluorobutyl)ethylene oxide, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 in n-hexane solution, and 10 mL of tetrahydrofuran (i.e., in this example, the molar ratio of catalyst, initiator, and fluorinated epoxy compound is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 2-(perfluorobutyl)ethylene oxide had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with n-hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number-average molecular weight was determined to be 1465 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of N,N-dimethylformamide, 1.8 g of 1,4-butanediol, and 1.8 μL of t-Bu-P4 in n-hexane solution were added sequentially under a nitrogen atmosphere. g of isophorone diisocyanate and 20 mg of dibutyltin dilaurate were reacted with stirring at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate, and then cured in a 50 °C forced-air oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. The number average molecular weight of the polyurethane prepared in this example was 26.7 kDa according to GPC testing, and the structural formula is as follows:

[0156] ,

[0157] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 9.05 MPa and an elongation at break of 560%; a refractive index of 1.421 at a wavelength of 589 nm; and a visible light transmittance of 85% at 800 nm when the sample thickness is 0.3 mm.

[0158] Example 17

[0159] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0160] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of 1,4-dioxane (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1490 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of [unspecified substance] was added sequentially under a nitrogen atmosphere. N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were stirred and reacted at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. The number average molecular weight of the polyurethane prepared in this example was 28.5 kDa, and the structural formula was the same as that in Example 1.

[0161] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 10.80 MPa and an elongation at break of 485%; a refractive index of 1.430 at a wavelength of 589 nm; and a visible light transmittance of 90% at 800 nm when the sample thickness is 0.3 mm.

[0162] Example 18

[0163] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0164] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of diethoxymethane (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane was completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1458 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of [unspecified substance] was added sequentially under a nitrogen atmosphere. N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were stirred and reacted at 80 °C for 4 h. The mixture was then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. The number-average molecular weight of the polyurethane prepared in this example was 27.8 kDa, as determined by GPC. The structural formula is the same as that in Example 1.

[0165] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 10.40 MPa and an elongation at break of 595%; a refractive index of 1.428 at a wavelength of 589 nm; and a visible light transmittance of 89% at 800 nm when the sample thickness is 0.3 mm.

[0166] Example 19

[0167] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0168] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of ethylene glycol dimethyl ether (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1469 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of [unspecified substance] was added sequentially under a nitrogen atmosphere. N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were stirred and reacted at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. The number average molecular weight of the polyurethane prepared in this example was 25.9 kDa, and the structural formula was the same as that in Example 1, according to GPC testing.

[0169] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 9.90 MPa and an elongation at break of 560%; a refractive index of 1.429 at a wavelength of 589 nm; and a visible light transmittance of 92% at 800 nm when the sample thickness is 0.3 mm.

[0170] Example 20

[0171] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0172] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:400:2000) were added. The reaction was carried out in a closed system at 25 °C for 48 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1478 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were reacted with stirring at 80 °C for 4 h, and then poured into a polytetrafluoroethylene plate. The plate was then cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. The number-average molecular weight of the polyurethane prepared in this example was 36.6 kDa, and the structural formula was the same as that in Example 1.

[0173] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 11.30 MPa and an elongation at break of 650%; a refractive index of 1.428 at a wavelength of 589 nm; and a visible light transmittance of 91% at 800 nm when the sample thickness is 0.3 mm.

[0174] Example 21

[0175] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0176] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this example is 1:400:2000) were added. The reaction was carried out in a closed system at 150 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1480 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were stirred and reacted at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. The number average molecular weight of the polyurethane prepared in this example was 36.1 kDa, and the structural formula was the same as that in Example 1, according to GPC testing.

[0177] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 11.0 MPa and an elongation at break of 630%; a refractive index of 1.427 at a wavelength of 589 nm; and a visible light transmittance of 88% at 800 nm when the sample thickness is 0.3 mm.

[0178] Example 22

[0179] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0180] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this embodiment is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1483 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were stirred and reacted at 50 °C for 8 h. The mixture was then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. The number-average molecular weight of the polyurethane prepared in this example was 36.3 kDa, as determined by GPC. The structural formula was the same as that in Example 1.

[0181] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 11.20 MPa and an elongation at break of 620%; a refractive index of 1.425 at a wavelength of 589 nm; and a visible light transmittance of 85% at 800 nm when the sample thickness is 0.3 mm.

[0182] Example 23

[0183] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0184] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 62.5 μL of 0.8 mol / L t-Bu-P4 hexane solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this embodiment is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1483 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of... N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were stirred and reacted at 80 °C for 8 h. The mixture was then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with a low refractive index. The number-average molecular weight of the polyurethane prepared in this example was 36.2 kDa, as determined by GPC. The structural formula was the same as that in Example 1.

[0185] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 11.15 MPa and an elongation at break of 615%; a refractive index of 1.424 at a wavelength of 589 nm; and a visible light transmittance of 89% at 800 nm when the sample thickness is 0.3 mm.

[0186] Example 24

[0187] A method for preparing a fluorinated polyurethane with a low refractive index, comprising the following steps:

[0188] In a 120 mL pressure-resistant bottle, 11 g of 1,1,1-trifluoro-2,3-epoxypropane, 1.8 g of 1,4-butanediol, 25 μL of 2.0 mol / L t-Bu-P2 tetrahydrofuran solution, and 10 mL of tetrahydrofuran (i.e., the molar ratio of catalyst, initiator, and fluorinated epoxy compound in this embodiment is 1:400:2000) were added. The reaction was carried out in a closed system at 80 °C for 24 h. After ensuring that the added 1,1,1-trifluoro-2,3-epoxypropane had completely reacted, 0.5 mL of acetic acid was added dropwise to terminate the polymerization reaction. After cooling to room temperature, the product was washed three times with n-hexane and dried in a forced-air oven at 50 °C to obtain a fluorinated polyether diol. The number average molecular weight was determined to be 1470 by GPC. 4 g of the above fluorinated polyether diol was placed in a 50 mL side-necked flask, and 8 g of [unspecified substance] was added sequentially under a nitrogen atmosphere. N,N-dimethylformamide, 1.8 g of isophorone diisocyanate, and 20 mg of dibutyltin dilaurate were stirred and reacted at 80 °C for 4 h, then poured into a polytetrafluoroethylene plate and cured in a 50 °C oven for 48 h to obtain a polyether-type polyurethane, which is a fluorinated polyurethane with low refractive index. The number average molecular weight of the polyurethane prepared in this example was 37.6 kDa according to GPC testing, and the structural formula was the same as that in Example 1.

[0189] The fluorinated polyurethane with low refractive index prepared in this embodiment has a tensile strength of 11.25 MPa and an elongation at break of 650%; a refractive index of 1.432 at a wavelength of 589 nm; and a visible light transmittance of 91% at 800 nm when the sample thickness is 0.3 mm.

[0190] Comparative Example 1

[0191] A method for preparing a fluorine-free polyether polyurethane, comprising the following steps:

[0192] Compared with Example 2, the only difference is that 1,1,1-trifluoro-2,3-epoxypropane is replaced with an equimolar amount of propylene oxide.

[0193] The fluorine-free polyurethane prepared in this comparative example has a tensile strength of 4.16 MPa, an elongation at break of 380%, a refractive index of 1.491 at a wavelength of 589 nm, and a visible light transmittance of 96% at 800 nm when the sample thickness is 0.3 mm.

[0194] Compared to polyether-type polyurethanes with introduced fluorine atoms, the polyurethane prepared in this comparative example has a lower CH bond energy than the CF bond energy and a higher segment electronic polarization ability. At the same time, the polyurethane segments without fluorine have lower rigidity, resulting in the refractive index of the fluorinated polyurethane prepared in Example 2 being significantly lower than that of the fluorine-free polyurethane in Comparative Example 1.

[0195] Comparative Example 2

[0196] A method for preparing a fluorine-free polyether polyurethane, comprising the following steps:

[0197] Compared to Example 12, the only difference is that 2,2-bis(trifluoromethyl)ethylene oxide is replaced with an equimolar amount of methyl propylene oxide.

[0198] The fluorine-free polyurethane prepared in this comparative example has a tensile strength of 4.25 MPa, an elongation at break of 400%, a refractive index of 1.485 at a wavelength of 589 nm, and a visible light transmittance of 91% at 800 nm when the sample thickness is 0.3 mm.

[0199] Comparative Example 3

[0200] A method for preparing a fluorine-free polyether polyurethane, comprising the following steps:

[0201] Compared with Example 13, the only difference is that decafluoro-1,2-epoxycyclohexane is replaced with an equimolar amount of 1,2-epoxycyclohexane.

[0202] The fluorine-free polyurethane prepared in this comparative example has a tensile strength of 4.20 MPa, an elongation at break of 395%, a refractive index of 1.488 at a wavelength of 589 nm, and a visible light transmittance of 89% at 800 nm when the sample thickness is 0.3 mm.

[0203] Comparative Example 4

[0204] A method for preparing a fluorine-free polyether polyurethane, comprising the following steps:

[0205] Compared to Example 14, the only difference is that 2-(perfluorobutyl)ethylene oxide is replaced with an equimolar amount of 1,2-epoxyhexane.

[0206] The fluorine-free polyurethane prepared in this comparative example has a tensile strength of 3.50 MPa, an elongation at break of 415%, a refractive index of 1.493 at a wavelength of 589 nm, and a visible light transmittance of 95% at 800 nm when the sample thickness is 0.3 mm.

[0207] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A fluorinated polyurethane with a low refractive index, characterized in that, It is either uncrosslinked linear polyurethane or crosslinked polyurethane, and the general structural formula of the uncrosslinked linear polyurethane is as follows: ， The general structural formula of the crosslinked polyurethane is as follows: ， Where, R1= , , , or R2= or R3 = , , or n = 5~8.

2. A method for preparing a fluorinated polyurethane with a low refractive index as described in claim 1, characterized in that, Includes the following steps: Fluorinated polyether diols or fluorinated polyether polyols are prepared by ring-opening polymerization of fluorinated epoxy compounds in a first organic solvent. Polyether-type polyurethane is prepared by an addition reaction of diisocyanate, the fluorinated polyether diol and / or the fluorinated polyether polyol in a second organic solvent, which is the fluorinated polyurethane with low refractive index.

3. The method for preparing fluorinated polyurethane with low refractive index according to claim 2, characterized in that, The fluorinated epoxy compound is selected from 1,1,1-trifluoro-2,3-epoxypropane, 2,2-bis(trifluoromethyl)epoxyethylene, decafluoro-1,2-epoxycyclohexane, or 2-(perfluorobutyl)epoxyethylene.

4. The method for preparing fluorinated polyurethane with low refractive index according to claim 2, characterized in that, The diisocyanate is selected from isophorone diisocyanate, toluene-2,4-diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, or hexamethylene diisocyanate.

5. The method for preparing fluorinated polyurethane with low refractive index according to claim 2, characterized in that, Initiator and catalyst were also added during the ring-opening polymerization reaction; The molar ratio of the catalyst, initiator and fluorinated epoxy compound is 1:(200~600):2000.

6. The method for preparing fluorinated polyurethane with low refractive index according to claim 5, characterized in that, The initiator is selected from 1,4-butanediol, 1,4-benzyl alcohol, or 1,1,1-trimethylolethane; And / or, the catalyst is selected from phosphazene ligand P4-tert-butyl or phosphazene ligand P2-tert-butyl.

7. The method for preparing fluorinated polyurethane with low refractive index according to claim 2, characterized in that, The first organic solvent is selected from tetrahydrofuran, 1,4-dioxane, diethoxymethane, or ethylene glycol dimethyl ether; And / or, the second organic solvent is N,N-dimethylformamide.

8. The method for preparing fluorinated polyurethane with low refractive index according to claim 2, characterized in that, The ring-opening polymerization reaction is carried out at a temperature of 25~150 ℃.

9. The method for preparing fluorinated polyurethane with low refractive index according to claim 2, characterized in that, The addition reaction is carried out at a temperature of 50-80 °C for 4-8 h.

10. The method for preparing fluorinated polyurethane with low refractive index according to claim 2, characterized in that, When preparing the polyether-type polyurethane via an addition reaction, an organotin catalyst was also added.

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