Perfluoropolyether with narrow molecular weight distribution as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of organic fluorine polymer synthesis, and discloses perfluoropolyether with narrow molecular weight distribution and a preparation method and application thereof.The method comprises the steps that in an aprotic polar solvent, phosphazene organic super base and anhydrous hydrogen fluoride or perfluoroalcohol are mixed according to the molar ratio of 1: 0.5-1: 1.5, and a mixture is obtained; forming in situ a non-metallic active initiation complex containing large-volume counter cations; at the temperature of-50 DEG C to 10 DEG C, introducing a hexafluoropropylene oxide monomer into the initiation system, and carrying out anionic ring-opening polymerization until a preset number-average molecular weight is reached; after polymerization, maintaining a liquid phase, directly adding a perfluoroalkyl sulfonate end-capping reagent, and reacting at 20-80 DEG C to convert an active end group into an inert perfluoroalkyl ether end group; and performing post-treatment to obtain the perfluoropolyether product. The invention solves the problems of wide molecular weight distribution, low safety and high equipment cost in the traditional process, and the product is suitable for semiconductor vacuum pump oil and precise electronic cleaning agent, and has obvious industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of organofluorine polymer synthesis technology, specifically relating to a perfluoropolyether with a narrow molecular weight distribution, its preparation method, and its application. Background Technology

[0002] Perfluoropolyethers (PFPEs) are a class of polymeric compounds whose main chain consists of carbon-fluorine bonds and ether bonds. Due to their excellent thermal stability, chemical inertness, low volatility, and superior lubrication properties, they have irreplaceable application value in fields such as semiconductor vacuum pump oils, precision electronic cleaning agents, and lubricants for extreme aerospace environments. Currently, the industrial synthesis of PFPEs mainly follows two technical routes: photo-oxidation and anionic polymerization, but both methods have significant technical bottlenecks. Photo-oxidation, represented by the Fomblin series and existing technologies of Shandong Dongyue (CN202111642645.1), uses tetrafluoroethylene or hexafluoropropylene as raw materials for oxidative polymerization under ultraviolet light. While this method can be industrialized, it generates a large amount of unstable peroxide intermediates during the reaction, posing a very high risk of explosion. To ensure safety, complex elimination devices and strict safety monitoring measures are required, leading to a complex production process and increased costs. More importantly, the polymerization process of photo-oxidation lacks effective control, resulting in random molecular structures and a wide molecular weight distribution (PDI typically >1.5). The presence of low molecular weight components increases the product's volatility, failing to meet the stringent requirements for material purity and stability in high-end fields such as semiconductor manufacturing.

[0003] Anionic polymerization, represented by the Krytox series, primarily utilizes metal fluorides (such as cesium fluoride) or KF to catalyze the ring-opening polymerization of HFPO in aprotic solvents. However, due to the limited solubility of metal fluorides in organic solvents, the reaction system is often heterogeneous. Metal cations (Cs...) + A strong electrostatic attraction forms between the ion and the oxygen anion at the active growth chain end, known as the "tight ion pair" effect. This tight binding severely hinders the chain growth rate and easily induces chain transfer side reactions. This results in a wide molecular weight distribution of the final product (PDI>1.3), making true controlled polymerization impossible.

[0004] Furthermore, regardless of the polymerization route, the initial products contain chemically reactive and unstable acyl fluoride (-COF) end groups. These end groups are easily hydrolyzed to form carboxyl groups (-COOH), leading to increased acid value and decreased stability of the product. Therefore, end-capping stabilization treatment is necessary. Currently, mainstream industrial stabilization technologies (such as Shandong Dongyue's patent CN202211491156.5) generally rely on high-pressure fluorine gas (F2) for treatment or employ electrochemical fluorination processes. However, elemental fluorine gas is highly toxic and extremely corrosive, placing extremely stringent requirements on the materials of the reaction equipment (usually requiring Monel alloy). This not only results in huge equipment investments but also poses serious safety hazards and environmental risks during operation. Electrochemical fluorination processes, on the other hand, suffer from high energy consumption and poor product selectivity.

[0005] Although phosphazene organic superbases have been proven to achieve "living polymerization" in hydrocarbon polymerization, their application in the synthesis of perfluoropolyethers has not been successfully reported. Existing patents mostly use cyclic phosphazenes as heat-resistant additives for finished oil products, failing to utilize their catalytic properties. Therefore, developing a perfluoropolyether preparation process that can achieve homogeneous controlled polymerization (narrow distribution), avoid the use of hazardous fluorine gas (high safety), and reduce equipment costs is a core technical challenge that urgently needs to be solved in the industry. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a perfluoropolyether with a narrow molecular weight distribution, its preparation method, and its application, aiming to overcome the problems of wide molecular weight distribution, heterogeneous reaction system, high risk of end-capping process, and high equipment cost in existing perfluoropolyether preparation technologies.

[0007] To achieve the aforementioned objectives, the technical solution adopted is as follows: A method for preparing a perfluoropolyether with a narrow molecular weight distribution includes the following steps: (1) Construction of the initiation system: In an aprotic polar solvent, phosphazene organic superbase is mixed with anhydrous hydrogen fluoride (HF) or perfluoroalcohol in a molar ratio of 1:0.5 to 1:1.5 to form a non-metallic active initiation complex containing a large-volume counteracting cation in situ, thus forming an initiation system; the cation of phosphazene organic superbase achieves high delocalization of positive charge through a multi-conjugated system and has a huge spatial volume. This special structure can effectively weaken the electrostatic interaction between the cation and the oxygen anion at the end of the growth chain, and release the highly nucleophilic "naked fluoride ion", laying the foundation for homogeneous polymerization; (2) Controlled chain growth: Hexafluoropropylene oxide (HFPO) monomer is continuously introduced into the above initiation system at a temperature of -50℃ to 10℃ to carry out anionic ring-opening polymerization until the predetermined number average molecular weight is reached. (3) In-situ liquid phase end-capping: After the polymerization reaction is completed, the system is kept in a liquid phase state. Without separation, perfluoroalkyl sulfonate end-capping agents are directly added to the system and reacted at 20℃~80℃ to convert the active groups at the end of the polymer into chemically inert perfluoroalkyl ether end groups. (4) Post-processing: Solvents and byproducts are removed by conventional means such as washing, drying, filtering and rotary evaporation to obtain high-purity perfluoropolyether.

[0008] As a further improvement of the present invention, the in-situ liquid phase sealing process described in step (3) uses chemical reagent sealing. No elemental fluorine gas (F2) is introduced for treatment during the entire preparation process, and no electrochemical fluorination device is used. The reaction conditions are mild, and the in-situ process avoids the introduction of impurities and the decrease in efficiency caused by intermediate separation.

[0009] As a further improvement of the present invention, the phosphazene organic superbase is selected from 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphinoamino]-2λ 5 ,4λ 5 -Diphosphazene ( t - This - P 4. Chemical formula: C 22 H 63 N 13 P4), 1-tert-butyl-2,2,4,4,4-penta(dimethylamino)-2λ 5 ,4λ 5 -Diphosphazene) t - This - P 2. Chemical formula: C 14 H 39 N7P2) or its homologues.

[0010] As a further improvement of the present invention, the aprotic polar solvent is at least one of hydrofluoroether (HFE), acetonitrile, and diethylene glycol dimethyl ether, which can further optimize the solubility and stability of the initiation system.

[0011] As a further improvement of the present invention, the perfluoroalkyl sulfonate end-capping agent mentioned in step (3) is selected from one of trifluoromethyl trifluoromethanesulfonate (CF3SO3CF3), pentafluoroethyl trifluoromethanesulfonate (CF3SO3C2F5) or perfluorobutyl fluorosulfonate.

[0012] As a further improvement of the present invention, the prepared perfluoropolyether has the following structural formula: CF 3 - ( OCF 2 CF ( CF 3))n - O - R f ; in, n Integers between 10 and 200 R f for CF 3 or C 2 F 5. And the product's molecular weight distribution index (PDI = M w / M n (less than 1.15)

[0013] As a further improvement of the present invention, the polymerization reaction pressure in step (2) is controlled at 0.1MPa-0.5MPa, and the mass content of water in the polymerization reaction system is controlled below 10ppm.

[0014] A perfluoropolyether prepared by any of the methods described above, wherein the perfluoropolyether has a mass loss rate of less than 0.5% at 250°C and does not contain -COF or -COOH structures in its end groups.

[0015] Application of a perfluoropolyether as described above in the preparation of semiconductor vacuum pump oil, precision electronic cleaning agent and aerospace extreme environment lubricant.

[0016] Compared with the prior art, the present invention has the following significant advantages: 1. Extremely narrow molecular weight distribution: The homogeneous quasi-living polymerization is achieved through a "large-volume cation-exposed fluoride ion" initiation system constructed by phosphazene organic superbase. The product PDI is controlled below 1.15, which is far superior to the traditional method (PDI>1.3). There are very few low molecular weight components, and the volatility is significantly reduced. It can meet the needs of high-end applications without the need for subsequent fractional distillation.

[0017] 2. High process safety: This invention completely eliminates the explosive peroxide intermediates in the photo-oxidation method and the highly toxic fluorine gas in the traditional end-capping process. Both polymerization and end-capping processes are carried out under mild conditions, greatly reducing operational risks and eliminating the need for complex safety monitoring equipment.

[0018] 3. Low equipment cost: The reaction system has no special requirements for equipment corrosion resistance and can be carried out in conventional stainless steel or enamel-lined reactors. It does not require expensive special alloy equipment resistant to fluorine gas, which greatly reduces the initial investment for industrial production.

[0019] 4. Excellent product performance: The product has an end-group conversion rate of more than 99%, an acid value of less than 0.01 mg KOH / g, and strong chemical stability; the mass loss rate at 200℃ is less than 0.5%, and the kinematic viscosity at 20℃ is 200 cSt to 400 cSt, making it suitable for high-end applications such as semiconductor vacuum pump oil and precision electronic cleaning agents. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, 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: Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0023] Example 1: Standard Narrow Distribution Perfluoropolyether Synthesis Process ( M n ≈3000) A method for preparing a perfluoropolyether with a narrow molecular weight distribution includes the following steps: In a 500 mL anhydrous high-pressure reactor equipped with a magnetic stirring and cryogenic cooling system, 100 mL of anhydrous hydrofluoroether, namely methoxynonfluorobutane (HFE-7100), and 20 mL of anhydrous acetonitrile were added under nitrogen protection.

[0024] Add 1.5 mmol t - This - P 4. (1.0M n-hexane solution), followed by slow dropwise addition of 1.6 mmol of anhydrous HF / ethyl ether complex, and stirring for 30 minutes to form an active initiating complex.

[0025] The reactor temperature was lowered to -30℃, and hexafluoropropylene oxide (HFPO) gas was continuously introduced at a rate of 10 g / h, for a total of 200 g. The reaction pressure was controlled at 0.1-0.2 MPa, and the moisture content of the system was controlled below 10 ppm.

[0026] After aeration, stirring was continued at -30°C for 1 hour. Then, 5.0 g of trifluoromethyl trifluoromethanesulfonate (CF3SO3CF3) was added, and the system was heated to 40°C and reacted for 4 hours to seal the end-capping.

[0027] After the reaction was completed, the mixture was washed with 5% NaHCO3 aqueous solution, separated, and the organic layer was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain 185g of colorless and transparent oily liquid (yield 92.5%).

[0028] Test results: GPC determination M n =3100, PDI=1.08. Infrared spectrum shows 1890cm. -1 The acyl fluoride peak at that location completely disappeared.

[0029] Application of a perfluoropolyether as described above in the preparation of semiconductor vacuum pump oil, precision electronic cleaning agent and aerospace extreme environment lubricant.

[0030] Example 2: Synthesis of high molecular weight perfluoropolyether ( M n ≈6000) Except for adjusting the amount of initiator, the other steps are the same as in Example 1.

[0031] Solvent system: 150mL HFE-7200 + 30mL tetraethylene glycol dimethyl ether.

[0032] Initiator: 0.6 mmol t - This - P 4.

[0033] Monomer: 250g of HFPO is introduced.

[0034] End capping: Add 3.0g of trifluoromethyl trifluoromethanesulfonate and react at 50℃.

[0035] A method for preparing a perfluoropolyether with a high molecular weight distribution includes the following steps: In a 500 mL anhydrous high-pressure reactor equipped with a magnetic stirring and cryogenic cooling system, 150 mL of anhydrous hydrofluoroether, namely methoxynonfluorobutane (HFE-7100), and 30 mL of tetraethylene glycol dimethyl ether were added under nitrogen protection.

[0036] Add 0.6 mmol t - This - P 4. (1.0M n-hexane solution), followed by slow dropwise addition of 1.6 mmol of anhydrous HF / ethyl ether complex, and stirring for 30 minutes to form an active initiating complex.

[0037] The reactor temperature was lowered to -30℃, and hexafluoropropylene oxide (HFPO) gas was continuously introduced at a rate of 10 g / h, for a total of 250 g. The reaction pressure was controlled at 0.1-0.2 MPa, and the moisture content of the system was controlled below 10 ppm.

[0038] After aeration, stirring was continued at -30°C for 1 hour. Then, 3.0 g of trifluoromethyl trifluoromethanesulfonate (CF3SO3CF3) was added, and the system was heated to 50°C and reacted for 4 hours to seal the end-capping.

[0039] After the reaction was completed, the mixture was washed with 5% NaHCO3 aqueous solution, separated, and the organic layer was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain 238g of colorless and transparent oily liquid (yield 95.2%).

[0040] Test results: 238g of product (yield 95.2%). M n =6200, PDI=1.10.

[0041] Example 3: Different phosphazene base catalysts ( t - This - P 2) Preparation of perfluoropolyether use t - This - P 2 replace t - This - P 4.

[0042] Solvent: 100 mL dichloropentafluoropropane (HCFC-225).

[0043] Initiator: 2.0 mmol t - This - P 2+2.2mmolHF.

[0044] Temperature: -20℃.

[0045] HFPO dosage: 150g.

[0046] End-capping agent: 6.0g of pentafluoroethyl trifluoromethanesulfonate (CF3SO3C2F5) was used.

[0047] A method for preparing a perfluoropolyether with a narrow molecular weight distribution includes the following steps: 100 mL of dichloropentafluoropropane (HCFC-225) was added to a 500 mL anhydrous high-pressure reactor equipped with a magnetic stirring and cryogenic cooling system under nitrogen protection.

[0048] Add 2.0 mmolt - This - P 2. Then, 2.2 mmol of anhydrous HF was slowly added dropwise, and the mixture was stirred for 30 minutes to form an active initiation complex.

[0049] The reactor temperature was lowered to -20℃, and hexafluoropropylene oxide (HFPO) gas was continuously introduced at a rate of 10 g / h, for a total of 150 g. The reaction pressure was controlled at 0.1-0.2 MPa, and the moisture content of the system was controlled below 10 ppm.

[0050] After aeration, stirring was continued at -20°C for 1 hour. Then, 6.0 g of pentafluoroethyl trifluoromethanesulfonate (CF3SO3C2F5) was added, and the system was heated to 40°C and reacted for 4 hours to seal the end.

[0051] After the reaction was completed, the mixture was washed with 5% NaHCO3 aqueous solution, separated, and the organic layer was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain 140g of colorless and transparent oily liquid (yield 93.3%).

[0052] Test results: GPC determination M n =2400, PDI=1.12. End group is pentafluoroethyl.

[0053] Example 4: Highly Polar Solvent System Solvent: 100 mL of pure adiponitrile.

[0054] Initiator: 1.0 mmol t - This - P 4.

[0055] HFPO: 100g.

[0056] Temperature: 0℃ (higher temperature test).

[0057] End sealing: Same as in Example 1.

[0058] Test results: 92g of product (yield 92%). M n =2800, PDI=1.14. This indicates that the catalytic system maintains good controllability even at 0℃.

[0059] A method for preparing a perfluoropolyether with a narrow molecular weight distribution includes the following steps: 100 mL of pure adiponitrile was added to a 500 mL anhydrous high-pressure reactor equipped with a magnetic stirring and cryogenic cooling system under nitrogen protection.

[0060] Add 1.0 mmol t - This - P 4. Then, slowly add 1.6 mmol of anhydrous HF / ethyl ether complex and stir for 30 minutes to form an active initiation complex.

[0061] The reactor temperature was lowered to 0℃, and hexafluoropropylene oxide (HFPO) gas was continuously introduced at a rate of 10 g / h, for a total of 100 g. The reaction pressure was controlled at 0.1-0.2 MPa, and the moisture content of the system was controlled below 10 ppm.

[0062] After aeration, stirring was continued at 0°C for 1 hour. Then, 5.0 g of trifluoromethyl trifluoromethanesulfonate (CF3SO3CF3) was added, and the system was heated to 40°C and reacted for 4 hours to seal the end.

[0063] After the reaction was completed, the mixture was washed with 5% NaHCO3 aqueous solution, separated, and the organic layer was dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain 92g of colorless and transparent oily liquid (yield 92%).

[0064] Test results: GPC determination M n =2800, PDI=1.14. This indicates that the catalytic system maintains good controllability even at 0℃.

[0065] Example 5: Verification of Quasi-living Polymerization (Secondary Feeding) In the synthesis M n Sampling analysis was conducted on a polymer system (uncapped) with a capacity of approximately 2000. M n =1950, PDI=1.06). Without quenching, 100g of HFPO was directly added to the system. After continuing the reaction for 2 hours, the reaction was capped.

[0066] Test results: final product M n =3800, PDI=1.07. The GPC curve shows a single peak shifting towards higher molecular weights, confirming the characteristics of living polymerization.

[0067] Comparative Example 1: Traditional Metal Fluoride Catalysis To verify the advantages of the phosphazene catalyst of this invention in controlling molecular weight distribution, a conventional CsF (cesium fluoride) catalyst was used for comparison.

[0068] Solvent: Tetraethylene glycol dimethyl ether.

[0069] Initiator: CsF (1.5 mmol).

[0070] Temperature: -30℃.

[0071] A method for preparing perfluoropolyethers using conventional metal fluoride catalysis includes the following steps: In the same reaction vessel as in Example 1, 1.5 mmol of CsF (cesium fluoride) was used instead of t - This - P 4. Tetraethylene glycol dimethyl ether is used as the solvent because CsF is almost insoluble in HFE. The reaction temperature is controlled at -30℃.

[0072] Results: The reaction time was significantly prolonged, and the product yield was 85%. M n =2900, PDI=1.35. The molecular weight distribution is significantly broadened, indicating that the chain transfer side effect of the metal cation is relatively large, resulting in a significantly broadened molecular weight distribution in the heterogeneous system, which cannot achieve the narrow distribution level of this invention (PDI<1.15).

[0073] Comparative Example 2: Photo-oxidation method (simulating existing technology) A method for preparing perfluoropolyethers using photo-oxidation includes the following steps: In a UV reactor, hexafluoropropylene (HFP) and oxygen are introduced at a temperature of -40°C. The product is then reduced and fluorinated.

[0074] Results: The product structure contains random -CF2O and -C3F6O- linkages. M n =3000, PDI=1.65. Furthermore, the degree of peroxide needs to be strictly monitored during the synthesis process, making the process complex.

[0075] Comparative Example 3: Traditional Fluorine Gas End-Sealing (Comparison focusing on the end-sealing stage) To verify the safety and effectiveness of the liquid phase sealing process of this invention, a comparison was made using a traditional fluorine gas sealing process.

[0076] The polymerization steps are exactly the same as in Example 1 (resulting in an uncapped, narrowly distributed intermediate).

[0077] The end-capping step is changed to: transferring the uncapped product to a specialized nickel (Monel) autoclave (simulating existing industrial technology). A mixture of F2 / N2 (volume ratio 20:80) is introduced and treated at 120°C and 0.3 MPa for 6 hours, during which gas leakage must be strictly monitored.

[0078] Results: Infrared spectroscopy showed that the end-group conversion rate reached >99%. However, the product was slightly yellow (possibly due to the carbonization of trace metal corrosion products or impurities at high temperatures), and the process involved highly toxic gas operation, posing a high safety risk and requiring extremely sophisticated equipment.

[0079] A comparison of technical performance is shown in Table 1: Table 1. Performance Comparison of the Product of this Invention with Existing Technologies As can be seen from the above embodiments and comparative examples, the preparation method provided by the present invention can efficiently synthesize perfluoropolyethers with extremely narrow molecular weight distribution and excellent performance. Moreover, the process is highly safe and the equipment cost is low. Compared with traditional technologies, it has significant technical advantages and prospects for industrial application.

[0080] This invention innovatively employs a phosphazene-based organic superbase combined with anhydrous hydrogen fluoride or perfluoroalcohol to construct an initiation system. The phosphazene cation (such as P4-t-Bu) + The large volume and highly delocalized positive charge through a multi-conjugated system effectively weaken the electrostatic interaction between the cation and the oxygen anion at the growth chain end, releasing highly nucleophilic "naked fluoride." This "large-volume counter-cation" system achieves true homogeneous polymerization, significantly increasing the chain growth rate and inhibiting chain transfer, thus realizing quasi-living polymerization. This invention innovatively applies phosphazene-based organic superbases to the synthesis of perfluoropolyethers, achieving a homogeneous, rapid polymerization process with a very narrow distribution (PDI < 1.15). In the end-capping stage, this invention abandons the traditional fluorine gas route and innovatively uses perfluoroalkyl sulfonates (such as trifluoromethyltrifluoromethanesulfonate) as liquid-phase end-capping agents. Under mild liquid-phase conditions, the active end groups are directly converted into chemically inert perfluoroalkyl ether end groups. Furthermore, this invention innovatively uses perfluoroalkyltrifluoromethanesulfonate as a liquid-phase end-capping agent, avoiding the harsh conditions of gaseous fluorination.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, component splitting or combination, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a perfluoropolyether with a narrow molecular weight distribution, characterized in that, Includes the following steps: (1) Construction of the initiation system: In an aprotic polar solvent, a phosphazene organic superbase is mixed with anhydrous hydrogen fluoride or perfluoroalcohol in a molar ratio of 1:0.5 to 1:1.5 to form a non-metallic active initiation complex containing a large volume counter cation in situ, thus forming an initiation system; (2) Controlled chain growth: Hexafluoropropylene oxide monomer is continuously introduced into the above initiation system at a temperature of -50℃ to 10℃ to carry out anionic ring-opening polymerization until the predetermined number average molecular weight is reached. (3) In-situ liquid phase end-capping: After the polymerization reaction is completed, the system is kept in a liquid phase state. Without separation, perfluoroalkyl sulfonate end-capping agents are directly added to the system and reacted at 20℃~80℃ to convert the active groups at the end of the polymer into chemically inert perfluoroalkyl ether end groups. (4) Post-processing: Remove solvent and byproducts to obtain perfluoropolyether product.

2. The method for preparing a perfluoropolyether with a narrow molecular weight distribution according to claim 1, characterized in that: The in-situ liquid-phase sealing process described in step (3) uses chemical reagents for sealing. No elemental fluorine gas is introduced for treatment during the entire preparation process, and no electrochemical fluorination device is used.

3. The method for preparing a perfluoropolyether with a narrow molecular weight distribution according to claim 1, characterized in that: said phosphazene organosuperbase is selected from the group consisting of 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phospholylamino]-2λ 5 ,4λ 5 -phosphazene, 1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2λ 5 ,4λ 5 -phosphazene) or homologues thereof.

4. The method for preparing a perfluoropolyether with a narrow molecular weight distribution according to claim 1, characterized in that: The aprotic polar solvent is at least one of hydrofluoroether, acetonitrile, and diethylene glycol dimethyl ether.

5. The method for preparing a perfluoropolyether with a narrow molecular weight distribution according to claim 1, characterized in that: The perfluoroalkyl sulfonate end-capping agent mentioned in step (3) is selected from one of trifluoromethyl trifluoromethanesulfonate, pentafluoroethyl trifluoromethanesulfonate or perfluorobutyl fluorosulfonate.

6. The method for preparing a perfluoropolyether with a narrow molecular weight distribution according to claim 1, characterized in that: The prepared perfluoropolyether has the following structural formula: CF 3 - （ OCF 2 CF （ CF 3）） n - O - R f ； in, n Integers between 10 and 200 R f for CF 3 or C 2 F 5. The molecular weight distribution index (PDI) of the product is less than 1.

15.

7. The method for preparing a perfluoropolyether with a narrow molecular weight distribution according to claim 1, characterized in that: The polymerization reaction pressure described in step (2) is controlled at 0.1MPa-0.5MPa, and the water content in the polymerization reaction system is controlled below 10ppm.

8. A perfluoropolyether prepared by the method according to any one of claims 1-7, characterized in that, The perfluoropolyether exhibits a mass loss rate of less than 0.5% at 250°C and does not contain -COF or -COOH structures in its end groups.

9. The application of a perfluoropolyether as described in claim 8 in the preparation of semiconductor vacuum pump oil, precision electronic cleaning agent and aerospace extreme environment lubricant.

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