WO2023235189A1

WO2023235189A1 - Bifunctional perfluoropolyether compositions based on hexafluoropropylene oxide, purification, and uses thereof

Info

Publication number: WO2023235189A1
Application number: PCT/US2023/023283
Authority: WO
Inventors: Robert Daniel LOUSENBERG
Original assignee: Vistasol Technologies, Llc
Priority date: 2022-05-28
Filing date: 2023-05-23
Publication date: 2023-12-07

Abstract

This invention discloses a poly (hexafluoropropylene oxide) (HFPO) mixture that contains a bifunctional and a monofunctional poly (HFPO) component. A process utilizing liquid or supercritical fluid chromatography may be used to separate the bifunctional from the monofunctional poly (HFPO) component. The bifunctional poly (HFPO) component that is separated is useful for coating the surface of an article wherein the coating may function as a lubricant for magnetic recording media, an anti-fingerprint coating for a touch screen display, or a coating for another article having a surface made of glass, metal, ceramic, or metal oxide.

Description

BIFUNCTIONAL PERFLUOROPOLYETHER COMPOSITIONS BASED ON HEXAFLUOROPROPYLENE OXIDE, PURIFICATION, AND USES THEREOF

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application 63/346,834, filed on May 28^th, 2022.

BACKGROUND

[0002] Perfluoropolyethers (PFPEs) are notable for their high thermal and chemical stability, and low glass transition temperatures. Most PFPEs are liquids over a wide temperature range and because of their unique properties they are used in demanding surface coating applications such as for high-performance lubricants for aerospace applications, for low surface-energy coatings on magnetic recording media, and for anti-fingerprint coatings on touchscreen displays. Three general classes of PFPEs are commercially manufactured and include Fomblin® (Solvay Solexis), Demnum® (Daikin), Aflunox® (Nippon Mektron), and Krytox® (Chemours). Fomblin® or Demnum® have -(CF2O)m-(CF2CF2O)_P- or -(CF2CF2CF2O)_n- repeating unit structures, respectively, while Aflunox® and Krytox® are based on poly (hexafluoropropylene oxide) and have a -(CF(CF3)CF2O)_n- repeating unit structure. Poly (hexafluoropropylene oxide) or poly (HFPO) may provide a coating that has a relatively lower surface-energy due to the CF3 group in the repeating unit structure.

[0003] Commercial poly (HFPO) is an inherently monofunctional material having a carboxyl group at one terminal end while Fomblin® and Demnum® are inherently bifunctional with a carboxyl group at both terminal ends. The carboxyl group may be chemically modified for increased surface adherence in various coating applications. Accordingly, Fomblin® and Demnum® are the incumbent PFPEs for magnetic recording media and for anti-fingerprint coating applications due to their bifunctional nature and better adherence. Synthesis routes to a bifunctional poly (HFPO) were known. For example, U.S. Patent No. 3,847,978 disclosed bifunctional poly (HFPO)- like PFPEs from radical polymerization of hexafluoropropylene in the presence of oxygen. A minor product, HOC(O)CF(CF3)-O-(C3F6O)n-CF(CF3)CO2H, wherein n was an integer between 1 and 50, and having two identical carboxyl end groups was disclosed. The corresponding and simultaneously identical acyl halide, ester, amide, nitrile, or carboxylate-salt end-groups were also disclosed.

[0004] Other bifunctional poly (HFPO) syntheses, such as those in U.S. Patent. No. 3,250,807 and U.S. Patent No. 3,660,315, disclosed anionic polymerization of hexafluoropropylene oxide (HFPO) using a perfluorodialkoxide initiator, which was prepared from a perfluorodialkanoyl fluoride. The perfluorodialkoxide initiator (I) was bi-reactive in that it reacted twice with HFPO and the resulting initiator fragment then being randomly distributed in the backbone of the bifunctional poly (HFPO) as represented by the following structural formula: F(O)CCF(CF3)-x(OCF2(CF3)CF)-l- (CF(CF3)CF2O)y-CF(CF3)C(O)F. The initiator fragment structure was different from the HFPO repeating unit structure. Furthermore, the HFPO repeating unit structure was non-uniform and reversed on either side of the initiator fragment. A non-uniform repeating unit structure could conceivably affect packing efficiency and may not be suitable for demanding surface coating applications.

SUMMARY

[0005] U.S. Patent No. 4,390,720 disclosed reacting hexafluoropropylene oxide (HFPO) with a fluoroalkoxide that also incorporated an ester group, and was prepared from reaction of methyl trifluoropyruvate (methyl 3,3,3-trifluoro-2- oxopropanoate) with a fluoride ion at temperatures from ambient to 60°C. The reaction of the fluoroalkoxide with HFPO yielded a bifunctional HFPO adduct, incorporating the ester group and a carbonyl fluoride, and was represented by the following structural formula: ROC(O)CF(CF₃)O-(CF(CF₃)CF₂O)n-CF(CF₃)C(O)F, wherein R was an alkyl group and n was 0 or an integer from 1 to 3, “preferably 0 or 1 ” for subsequent conversion to vinyl ether monomers and copolymers therefrom. Herein, a bifunctional poly (HFPO) was prepared from the fluoroalkoxide and related ester-containing fluoroalkoxides that were used as initiators for an anionic polymerization of HFPO at conditions that facilitate a higher number of repeating units (n > 4) or degree of polymerization. This included polymerization temperatures less than 0°C and a solvent mixture comprising a fluorinated solvent for the fluorinated and growing poly (HFPO) backbone. The bifunctional poly (HFPO) after further derivatization and purification may be used for coatings in low surface-energy applications.

[0006] In an aspect herein, a poly (HFPO) mixture is provided that comprises a bifunctional poly(HFPO) component, incorporating a carboxyl end-group at each terminal end, and is represented by the following structural formula: R¹OC(O)-R^F-O- (CF(CF₃)CF2O)_n-CF(CF₃)C(O)Y; R¹ comprises an alkyl group, R^F is a fluoroalkyl group including CFCF₃, CF(CF₃)CF2, CF2CF2, or CF2CFCI, n is an integer between 4 and 50 that defines the number or repeating units, and Y is F, OH, or OR²; wherein R² comprises an alkyl group. Surprisingly, the poly (HFPO) mixture also comprises at least some of a monofunctional poly (HFPO) component having a single carboxyl end-group at one terminal end but also having a similar number or repeating units as the bifunctional poly (HFPO). The monofunctional poly (HFPO) is represented by the following structural formula: CF₃CF2CF2-O-(CF(CF₃)CF2O)m-CF(CF₃)C(O)Y; wherein m is an integer between 4 and 50, and Y is as defined above.

[0007] In an embodiment of another aspect, a reduction reaction of carboxyl end- groups such as esters (R¹OC(O), Y = OR²) in the poly (HFPO) mixture to an alcohol end-group may be used to form the corresponding alcohol end-group derivative of the bifunctional and monofunctional poly (HFPO) components and are represented by the following structural formulas, respectively: HOCH2-R^F-O-(CF(CF₃)CF2O)n- CF(CF₃)CH₂OH and CF₃CF₂CF₂-O-(CF(CF₃)CF₂O)_m-CF(CF₃)CH₂OH ; wherein R^F comprises a fluoroalkyl group that includes CFCF₃, CF(CF₃)CF2, CF2CF2, or CF2CFCI, and m and n are integers between 4 and 50. The alcohol end-group in the derivative is relatively polar and can be advantageous in another aspect herein for a liquid chromatography separation of the bifunctional from the monofunctional poly (HFPO) component. In another embodiment, the alcohol end-group derivative may be transformed to other end-group derivatives that include diol end-groups, polyol end-groups, siloxane end-groups, and polysiloxane end-groups. In some embodiments, the other end-group derivatives may be used for a liquid chromatography separation of the bifunctional from the monofunctional poly (HFPO) component but are particularly useful in other embodiments for coating and adherence of the bifunctional poly (HFPO) to the surface of an article that includes magnetic recording media wherein the bifunctional poly (HFPO) functions as a in a low-surface energy lubricant, a touch screen display wherein the bifunctional poly (HFPO) functions as an anti-fingerprint coating, or a coating for another article that may have a surface made of glass, metal, ceramic, or metal oxide.

[0008] This summary of the invention has introduced aspects and some of the embodiments of the invention and is not intended to be limiting. As used herein, an aspect is a defining characteristic of the invention as may be recited in an independent claim and further disclosed in the detailed description. An embodiment may be viewed as a variation, or one implementation of an aspect as may be recited in a dependent claim and further disclosed in the detailed description. Certain exemplary embodiments are described herein and are only for purposes of illustrating the invention and should not be interpreted as limiting the scope of the invention. Alternate embodiments, including certain modifications, combinations, and improvements of the described embodiments will occur to those skilled in the art and all such alternate embodiments are within the scope of the invention.

[0009] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials that are similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, suitable methods and materials are described herein. The materials, methods, and examples are illustrative only and not intended to be limiting. The following definitions are provided for several commonly used terms and for the sake of clarity:

[0010] A terminal end is one of two ends of the backbone of the bifunctional or monofunctional poly (HFPO) component and does not include the end of a pendant (i.e., CF3) group in the repeating unit structure.

[0011] A carboxyl end-group consists of a carbonyl (C=O) group in combination with another atom or atomic group such fluorine (F) to form a carbonyl fluoride or hydroxyl (OH) to form a carboxylic acid end-group. Carboxyl end-groups also include ester and amide groups.

[0012] An inert solvent is a solvent for the bifunctional or monofunctional poly(HFPO) component or derivative that does not irreversibly react or complex with the bifunctional poly(HFPO). Preferred inert solvents include hydrofluorocarbons (HFCs) such as Vertrel® solvents containing HFC-4310mee, hydrofluoroethers (HFEs) such as 1 ,1 ,1 ,3,3,3-hexafluoro-2-methoxypropane, Novec® fluids including Novec® HFE-7100 and Novec® HFE-7200, Opteon® SF-10, Solstice® fluids including HCFO-1233zd, and carbon dioxide.

BRIEF DESCRIPTION OF THE DRAWING

[0013] Fig. 1 shows the relevant ¹⁹F NMR resonances with respect to a CFCh internal standard for the bifunctional and monofunctional poly(HFPO) component structures in a representative poly(HFPO) mixture from using a fluoroalkoxide initiator that was formed from methyl 3,3,3-trifluoro-2-oxopropanoate.

DETAILED DESCRIPTION

[0014] The poly (HFPO) mixture herein comprises a bifunctional poly (HFPO) component and can be synthesized by anionic polymerization of hexafluoropropylene oxide (HFPO) monomer using a fluoroalkoxide initiator that also incorporates an ester group and is represented by the following structure: R¹OC(O)R^FO^_ M⁺; wherein R¹ comprises a hydrocarbon group, R^F comprises a fluoroalkyl group and includes CF(CF3)CF2, CF2CFCI, CF2CF2, CF(CFs), and M⁺ is an alkali-metal cation. A preferred fluoroalkoxide initiator may be prepared by a reaction of fluoride ion with an initiator precursor such as a fluorocarbonyl- or oxo- fluoropropanoate ester, which are shown in scheme (1 ). Methyl 2,2,3-trifluoro-3- oxopropanoate and methyl 3,3,3-trifluoro-2-oxopropanoate are commercially available and may be preferred initiator precursors. Methyl 3,3,3-trifluoro-2- oxopropanoate may be more preferred as the structure of the carboxyl group and R^F (i.e. , CF(CFs)) at one terminal end of the bifunctional poly (HFPO) component therefrom is similar to the structure of the carbonyl fluoride group at the other terminal end after termination of the anionic polymerization and reaction to an ester.

methyl 2,3,3,3-tetrafluoro-2-(fluorocarbonyl)propanoate

methyl 2-chloro-2,3-difluoro-3-oxopropanoate

methyl 2,2,3-trifluoro-3-oxopropanoate

methyl 3,3,3-trifluoro-2-oxopropanoate

(1 )

[0015] The fluoroalkoxide initiator may be prepared in advance by the reaction of the initiator precursor with a fluoride ion prior to starting the anionic polymerization with HFPO. An alkali-metal fluoride salt such as potassium or cesium fluoride may be used as the source of the fluoride ion. The reaction to form the fluoroalkoxide initiator is an equilibrium reaction and may be preferably carried out using an excess of the initiator precursor to the alkali-metal fluoride salt in order to shift the equilibrium toward the fluoroalkoxide initiator. The molar ratio of the initiator precursor to the alkali-metal fluoride salt is preferably greater than 1 and may be at least 2 or in the range of 2 to 10. Formation of the fluoroalkoxide initiator may be carried out in an aprotic oligoether solvent such as tetraethylene glycol dimethyl ether (tetraglyme) such that the alkal-metal fluoride salt dissolves as it reacts with the initiator precursor to form a solution of the fluoroalkoxide initiator. A diluent may then be added to the solution of the fluoroalkoxide initiator to form a polymerization reaction mixture.

[0016] The diluent functions as a solvent for the growing backbone of the bifunctional poly (HFPO) component, can prevent phase separation, and can reduce the viscosity of the polymerization reaction mixture. Preferred diluents are fluorinated solvents that are miscible with the initiator precursor, fluoroalkoxide initiator, and the aprotic oligoether solvent. Preferred diluents include Novec® fluids such as HFE-7100 or HFE-7200, and hydrofluorocarbons such as 1 ,1 ,1 ,3,3- pentafluorobutane. The polymerization reaction mixture can be chilled prior to the addition of diluent and the HFPO monomer to further shift the equilibrium toward the fluoroalkoxide initiator. The anionic polymerization can then be carried out at temperatures between -40°C and 0°C, preferably -20°C to 0°C. The anionic polymerization, having “living” characteristics, continues as long as HFPO monomer is added to the reaction mixture as outlined in figure 1 ; therein exemplified using the fluoroalkoxide initiator from reaction of methyl 3,3,3-trifluoro-2-oxopropanoate with fluoride ion, and wherein (n) defines the number of HFPO repeating units

(i.e., -(CF(CF3)CF2O)n-) representing the degree of polymerization (DP) and is at least 4 and up to 50.

[0017] The number of repeating units (n > 4) and corresponding molecular weight of the bifunctional poly (HFPO) can be controlled by the reaction stoichiometry of the total amount of HFPO monomer to initiator precursor added to the anionic polymerization. Slow and continuous addition of HFPO monomer over a period of 1 to 24 hours, preferably 2 to 6 hours, can help to maintain a low concentration of HFPO monomer in the reaction mixture and can further help to reduce but does not eliminate an adventitious chain transfer reaction of the fluoride ion to the HFPO monomer and formation of the monofunctional poly (HFPO) component, which is also shown in figure 1 . Therein (m) defines the number of HFPO repeating units in the monofunctional poly (HFPO) component and is between 4 and 50 in the poly (HFPO) mixture.

[0018] Upon completion of the HFPO monomer addition and the anionic polymerization, the polymerization reaction mixture may be warmed to ambient room temperature or higher. Volatile components in the polymerization reaction mixture may be removed at this stage by evaporation (i.e. , vacuum distillation) to concentrate the poly (HFPO) mixture. Alternatively in another embodiment, carbonyl fluoride end groups (Y = F) in the poly (HFPO) mixture may be reacted before an evaporation step, such as with water to form a carboxylic acid group (Y = OH), or preferably with a lower alcohol, such as methanol, ethanol, or isopropanol, to form an ester group (Y = OR²), wherein R² is an alkyl group that may be the same or different from R¹. The poly (HFPO) mixture can then be isolated from the polymerization reaction mixture and can include washing with water to extract the tetraglyme and fluoride ion, drying, and vacuum distillation to remove volatile and low molecular weight components such as the diluent. The ester group may also be advantageous in some embodiments for a partial separation by high-vacuum distillation of low molecular weight species of both the monofunctional and bifunctional poly (HFPO) components from the poly (HFPO) mixture. Therein a limiting enrichment of the remaining bifunctional poly (HFPO) up to approximately 90 to 95 mole percent in the poly (HFPO) mixture may be achieved in some embodiments.

[0019] The fraction of the bifunctional with respect to the monofunctional poly (HFPO) component in the poly (HFPO) mixture may be characterized using ¹⁹F NMR spectroscopy from a dilute solution or dispersion of the poly (HFPO) mixture in deuterated chloroform or deuterated acetone. For example, figure 2 shows the structure of the bifunctional poly (HFPO) that is formed using the methyl 3,3,3- trifluoro-2-oxopropanoate initiator precursor, the monofunctional poly (HFPO) that was co-produced, and the relevant ¹⁹F NMR resonances with respect to a CFCI3 standard. The fraction of bifunctional poly (HFPO) component (% BF) as a mole percentage in the poly (HFPO) mixture can be calculated from the integral areas for the fluoro-methine ICF) resonance at -131 .5 ppm, next to an ester group for both components, and the difluoro-methylene (/CFS) resonance at -129.7 ppm, in the center of the perfluoropropyl ether group at a terminal end of the monofunctional poly(HFPO) component as follows: % BF = 1/[1 + /CF₂ / CF ^> ^CFZ /²)] ^X 100%. The degree of polymerization (DP) as an average of both n and m for the bifunctional and monofunctional poly (HFPO) component, may also be calculated from ¹⁹F NMR and the integral area for the fluoro-methine resonance (IcFn) in the HFPO repeating unit (i.e., -(CF(CF3)CF2O)_n-) at -144.3 ppm as follows: DP = 21_CFn/(I_CF + I_CFZ).

[0020] Purification and separation of the bifunctional from the monofunctional poly (HFPO) component in the poly (HFPO) mixture may be achieved using a chromatography process that takes advantage of the difference in end-group polarity. End-groups that have a relatively high polarity can facilitate a better interaction of the bifunctional poly (HFPO) component with a stationary phase and separation from the monofunctional poly (HFPO) component having only one polar end-group and a relatively non-polar perfluoropropyl end-group. For example, ester end-groups that include (R¹O(CO)) and Y = OR² may be hydrolyzed to a carboxylic acid wherein a bifunctional poly (HFPO) component can be represented by the following structural formula: HOC(O)-R^F-O-(CF(CF3)CF2O)n-CF(CF3)CO2H; wherein R^F comprises a fluoroalkyl group including the previously defined structures, and n is an integer between 4 and 50. In another embodiment ester end-groups may be reacted with an amine to an amide group and a bifunctional poly (HFPO) component can be represented by the following structural formula: R⁴R⁴’NC(O)-R^F-O- (CF(CF3)CF2O)n-CF(CF3)C(O)NR⁴R⁴’; wherein R⁴ and R⁴’ are independently H or comprise an alkyl group, and R^F comprises a fluoroalkyl group including the previously defined structures, and n is an integer between 4 and 50.

[0021] In another embodiment, carboxyl end-groups that include esters (R¹OC(O), Y = OR²) in the poly (HFPO) mixture can be transformed through a reduction reaction to an alcohol end-group derivative, which is relatively polar, useful for a chromatographic separation, and advantageous for a subsequent transformation reaction into other end-group compositions. A corresponding alcohol-end group derivative of the bifunctional and monofunctional poly (HFPO) components can be represented by the following structural formulas, respectively: HOCH2-R^F-O- (CF(CF₃)CF2O)n-CF(CF3)CH2OH and CF₃CF2CF2-O-(CF(CF3)CF₂O)m- CF(CFS)CH2OH ; wherein and R^F comprises a fluoroalkyl group including the previously defined structures, and n and m are integers between 4 and 50. The reduction reaction may be carried using a reducing agent such as sodium borohydride in a liquid medium that can include tetrahydrofuran or a lower alcohol, such as isopropanol. ¹H NMR spectroscopy may be used to follow the extent of the reduction reaction and the poly (HFPO) mixture comprising the alcohol end-group derivatives may be isolated from the liquid medium as a crude viscous oil.

[0022] Chromatography processes that include liquid and supercritical-fluid chromatography processes may be used for separation and purification of the bifunctional from the monofunctional poly (HFPO) component. In an embodiment, the chromatography process can be a normal phase chromatography process. Chromatography techniques for a liquid or supercritical-fluid chromatography process can include high-performance liquid chromatography (HPLC) or high- performance supercritical-fluid chromatography (HPSFC), preparative HPLC or preparative SFC, and flash chromatography. A chromatography apparatus for the liquid or supercritical fluid chromatography process at least includes a mobile phase, a chromatography column that incorporates a polar stationary phase such as high- surface-area silica gels. A detector such as an evaporative light-scattering detector (ELSD) may also be used to identify the bifunctional and monofunctional poly (HFPO) component. The poly (HFPO) mixture may be diluted in advance with the mobile phase or used as a neat liquid. The mobile phase is preferably an inert solvent or fluid that includes Vertrel® XF (i.e . , HFC-431 Omee), a Novec® fluid that includes HFE-7100 or HFE-7200, liquid or supercritical carbon dioxide, and can dissolve one or both the monofunctional and bifunctional poly (HFPO) component in the poly (HFPO) mixture.

[0023] In an embodiment for a separation using the chromatography process, the poly (HFPO) mixture is eluted with the mobile phase through the chromatography column of the chromatography apparatus. The mobile phase may include a gradient component that may be a minor component of the mobile phase and is added during the elution of the poly (HFPO) mixture. The gradient component should be miscible with the mobile phase, the poly (HFPO) mixture, and can be used to change the polarity of the mobile phase with respect to the polar stationary phase, improving the separation efficiency. Gradient components may include lower alcohols such as methanol, ethanol, or isopropanol. A first solution comprising a majority of the monofunctional poly (HFPO) component is eluted from the chromatography column and is isolated from the chromatography apparatus. A second solution comprising a majority of the bifunctional poly (HFPO) component is eluted from the chromatography column and is isolated from the chromatography apparatus. The second solution is enriched (concentrated) in the bifunctional poly (HFPO) component with respect to the monofunctional poly (HFPO) component. The bifunctional poly (HFPO) component in the second solution may be greater than 99 mole percent with respect to the monofunctional poly (HFPO) component after liquid chromatography separation. The bifunctional poly (HFPO) component may be concentrated from the second solution by evaporation of the mobile phase. In some embodiments, the mobile phase may also be recovered, purified, and recycled to the chromatography process.

[0024] The alcohol end-group derivative can be transformed into other end-group derivatives through chemical reactions before but preferably after a liquid or supercritical-fluid chromatography separation of the poly (HFPO) mixture. The other end-group derivatives include but are not limited to diol groups, polyol groups, siloxane groups, and polysiloxane groups. For example, a transformation reaction of an alcohol end-group derivative to a diol end-group derivative may be carried out as described by T urri et al. in Journal of Polymer Science: Part A: Polymer Chemistry, 1996, 34, pp 3263-3275, or by Scicchitano et al. in Die Angewandte Makromolekulare Chemie 231 (1995) 47-60. Transformation of an alcohol end- group derivative to a siloxane or polysiloxane end-group derivative may be carried out as described by Brown in U.S. Patent Application No. 20150218044.

[0025] A diol end-group derivative of the bifunctional poly (HFPO) component may be particularly useful and improve adherence of the bifunctional poly (HFPO) component to the surface of an article that includes magnetic recording media wherein the backbone of the bifunctional poly (HFPO) component functions as a low- surface-energy lubricant. Siloxane end-group derivatives may be particularly useful and can help with adherence to the surface of an article that includes touch screen displays, which are typically made of glass, and wherein the backbone of the bifunctional poly (HFPO) component functions as an anti-fingerprint coating. The alcohol end-group derivative and exemplary diol or siloxane end-group derivatives therefrom for the bifunctional and monofunctional poly (HFPO) component are exemplified by the following structural formulas, respectively: R³OCH2-R^F-O- (CF(CF₃)CF2O)n-CF(CF3)CH2OR³ and CF₃CF2CF2-O-(CF(CF₃)CF₂O)m- CF(CF₃)CH₂OR³ and; wherein R⁴ is H, CH2CH(OH)CH₂OH or CH2CH₂Si(OCH₃)3; R^F comprises a fluoroalkyl group including the previously defined structures, and n and m are integers between 4 and 50.

[0026] Magnetic recording media, touchscreen displays, or other articles having surfaces made of glass, metal, ceramic, or another metal oxide may be coated (contacted) with a bifunctional poly (HFPO) using any practical coating method known in the art. The coating method can include spraying, dip coating (dipping), roll coating, extrusion coating, Meyer rod coating, and casting. In a process for coating the article, the bifunctional poly (HFPO) may be dissolved in an inert solvent to form a solution. The surface of the article is contacted with the solution using the coating method and the inert solvent may be removed from the surface of the article. The surface of the article may be heated during the coating process to improve the speed of the coating or the surface coating properties such as the uniformity.

EXAMPLES

Example 1

[0027] HFPO polymerization with methyl 3,3,3-trifluoro-2-oxopropanoate and fluoride ion at a 1.2:1 ratio with stepwise HFPO addition. A 100-mL stainless- pressure reactor with mechanical stirring was loaded with 0.628-g (4.13 mmol) of cesium fluoride. The reactor was evacuated and 2.05-g of anhydrous tetraglyme and 0.75-g (4.8 mmol) of methyl 3,3,3-trifluoro-2-oxopropanoate was added to the evacuated reactor by cannula transfer needle. The reactor was chilled to -33°C and anhydrous Novec® HFE-7100 (3.01 -g) was transferred to the reactor. 9.25-g of HFPO was initially added followed by another 12.8-g (25.6-g total, 154 mmol) at 12 hours. The reactor was stirred at temperature for an additional 12 hours before allowing the reactor to warm to ambient room temperature, addition of 5-mL of ethanol, then backfilling with nitrogen. The reactor contents were poured into a 250- mL separation funnel containing 100-mL of water. The bottom organic layer was removed, and the reactor and aqueous layer were extracted with 40-mL of HFE- 7100. The extract and product were combined and rotary evaporated. The poly (HFPO) mixture was viscous, transparent, and the yield was 25.8-g. The fraction of the bifunctional poly (HFPO) component in the poly (HFPO) mixture was calculated as described in the specification and was 33 mole percent. The degree of polymerization was 5.2.

Example 2

[0028] HFPO polymerization with methyl 3,3,3-trifluoro-2-oxopropanoate to fluoride ion at a 2.8:1 ratio and stepwise HFPO addition. A 100-mL stainless-pressure reactor with mechanical stirring was loaded with 0.700-g (4.61 mmol) of cesium fluoride. The reactor was evacuated and 2.23-g of anhydrous tetraglyme and 2.02-g (12.9 mmol) of methyl 3,3,3-trifluoro-2-oxopropanoate was added to the evacuated reactor by cannula transfer needle. The reactor was chilled to -30°C and anhydrous Novec® HFE-7100 (6.17-g) was transferred to the reactor. 9.25-g of HFPO was initially added followed by another 9.25-g (18.5-g total, 111 mmol) at 12 hours. The reactor was stirred at temperature for an additional 12 hours before allowing the reactor to warm to ambient room temperature, addition od 5-mL of methanol, then backfilling with nitrogen. The reactor contents were poured into a 250-mL separation funnel containing 100-mL of water. The bottom organic layer was removed, and the reactor and aqueous layer were extracted with 40-mL of HFE-7100. The extract and product were combined and rotary evaporated. The poly (HFPO) mixture was viscous, transparent, and the yield was 18-g. The fraction of the bifunctional poly (HFPO) component in the poly (HFPO) mixture was calculated as described in the specification and was 28 mole percent. The degree of polymerization was 7.2.

Example 3

[0029] HFPO polymerization with a 4:1 methyl 3,3,3-trifluoro-2-oxopropanoate to fluoride ion ratio and continuous HFPO addition. A 250-mL 3-neck RB flask was assembled with magnetic stirring, a heating mantle, a gas inlet port on one of the side necks, a thermocouple well on the other side neck, and a dry ice condenser on the center neck. The top of the dry ice condenser is connected to a dual nitrogenvacuum manifold. 0.54-g (9.6 mmol) of powdered potassium fluoride (KF) is added to the RB flask under nitrogen. The KF and RB flask are dried under high vacuum while heating the RB flask to an internal temperature of 150°C for 1 hour. The RB flask is then cooled to ambient temperature under nitrogen and the heating mantle is replaced with a shallow Dewar flask and a magnetic stirrer on a lab jack. Anhydrous tetraglyme (~6.6-mL) is transferred to the dry RB flask through the gas inlet port followed by 6.00-g (38.4 mmol) of the methyl 3,3,3-trifluoro-2-oxopropanoate, both using dry-material handling techniques with syringes and needles. Anhydrous Novec® HFE-7100 (20-mL) is transferred to the RB flask through the gas inlet port using a syringe and needle. The gas addition port is subsequently connected with 1/16” OD PFA tubing to a calibrated rotameter with integral needle valve, which in turn is connected to a cylinder on a balance, containing the HFPO. With magnetic stirring, the internal temperature is lowered with a dry ice/acetone bath and maintained between -10 and -20°C with careful adjustment of the bath height using the lab jack. 55-g of HFPO (331 mmol) is slowly and steadily added over 6 hours at ~0.15-g/min through the rotameter. After completing the HFPO addition, stirring at temperature is continued for an additional hour before allowing the flask contents to slowly warm to ambient room temperature. Methanol (30-mL) is added to the flask with a notable reaction exotherm. The flask contents are poured into a 1 -L separation funnel containing 500-mL of water. The bottom organic layer is removed, and the aqueous layer is extracted with 40-mL of HFE-7100. The extract and product are combined, rotary evaporated to remove volatile components. The crude poly (HFPO) mixture is viscous, transparent, and the yield is greater than 50-g. The fraction of the bifunctional poly (HFPO) component in the crude product mixture is calculated as described in the specification and is 85 mole percent. The degree of polymerization is 7.8. The corresponding molecular weight is approximately 1650 g/mole. The poly (HFPO) mixture is further distilled under high vacuum (<0.01 mmHg) and a fraction (~ 10 to 15% v/v) is removed. The fraction of the bifunctional poly (HFPO) component after high-vacuum distillation is re-calculated as described in the specification and is 93 mole percent.

Example 4 [0030] HFPO Polymerization with a 4:1 methyl 2,3,3-trifluoro-3-oxopropanoate to fluoride ion ratio and continuous HFPO addition. A fluoroalkoxide initiator solution is prepared as generally described in example 3 using 0.54-g (9.6 mmol) of potassium fluoride and 6.00-g (38.4 mmol) of methyl 2,2,3-trifluoro-3-oxopropanoate.

Anhydrous Novec® HFE-7100 (20-mL) is transferred to the RB flask through the gas inlet port using a syringe and needle. The gas addition port is subsequently connected with 1/16” OD PFA tubing to a calibrated rotameter with integral needle valve, which in turn is connected to a cylinder on a balance, containing the HFPO. The internal temperature is lowered with a dry ice/acetone bath and maintained between -10 and -20°C with careful adjustment of the bath height using the lab jack. 55-g of HFPO (331 mmol) is slowly and steadily added over 6 hours at ~0.15-g/min through the rotameter. After completing the HFPO addition, stirring at temperature is continued for an additional hour before allowing the flask contents to slowly warm to ambient room temperature. Methanol (30-mL) is added to the flask with a notable exothermic reaction. The flask contents are poured into a 1 -L separation funnel containing 500-mL of water. The bottom organic layer is removed, and the aqueous layer is extracted with 40-mL of HFE-7100. The extract and product are combined and rotary evaporated to remove volatile components. The crude poly (HFPO) mixture is viscous, transparent, and the yield is greater than 50-g. The fraction of the bifunctional poly (HFPO) component in the poly (HFPO) mixture is calculated as % BF = 1/[1 + 1_CF2/ 21_CF - 1_CF2)] x 100% and is 83 mole percent. The degree of polymerization is 7.6.

Example 5

[0031] Formation of an alcohol end-group derivative in the poly (HFPO) mixture. A 250-mL 3-neck RB flask is assembled with mechanical stirring, a heating mantle, a reflux condenser connected to dry nitrogen, and a thermocouple well. 1 .50-g (39.7 mmol) of sodium borohydride is quickly added to the RB flask under nitrogen followed by 20-mL of tetrahydrofuran. With stirring at room temperature, 30-g (~36 mmol of ester end groups) of the poly (HFPO) mixture of example 3 is added by syringe. The reaction mixture is heated and stirred at a gentle reflux (~67°C) until the reaction is complete as indicated by ¹H NMR spectroscopy and the absence of the ester CHs resonance The reaction mixture is cooled to room temperature and the excess sodium borohydride is deactivated by careful addition of 60 ml_ of 20% ammonium chloride. The alcohol end-group derivative of the poly (HFPO) mixture as a lower oil layer is washed with a 50:50 acetone/5% aqueous saline solution in a separatory funnel and then drawn off and isolated.

Example 6

[0032] Liquid chromatography separation and purification of the alcohol end-group derivatives of example 5. A preparative HPLC system is used to separate alcohol end-group derivatives of the bifunctional poly (HFPO) component from a monofunctional poly (HFPO) component. The preparative HPLC system comprises a high-pressure binary gradient pump (40-mL/min), manual injection valve with 2 mL sample loop, silica-gel preparative column (125A, 10 pm, 30 mm X 300 mm), column heater (40°C), a fraction collector, and an evaporative light scattering detector (ELSD). A stream splitter connected to the column outlet is used to send approximately 2-3% of the volumetric flow rate from the column to the ELSD with the remaining going to the fraction collector or to waste. 1 -mL of the crude alcohol end- group derivative of the poly (HFPO) mixture of example 5 is injected into the preparative HPLC system and eluted, starting with a 100% Vertrel® XF mobile phase. A gradient component of ethanol is added starting at 5 minutes at 2% (v/v)/minute to a maximum of 30% (v/v). A solution of the monofunctional poly (HFPO) component elutes first predominantly between 8 to 13 minutes. A solution of the bifunctional poly (HFPO) then elutes, predominantly between 18 to 27 minutes. The separation process may be repeated to increase the amount of bifunctional poly (HFPO) component that is separated from the monofunctional poly (HFPO) component. The solutions of the separated bifunctional poly (HFPO) component are combined, and the mobile phase is removed by evaporation to concentrate and isolate the bifunctional poly (HFPO) component that was separated. The fraction of the bifunctional poly (HFPO) component that was separated is re-calculated from ¹⁹F NMR as described in the specification and is greater 99 mole percent with respect to the monofunctional poly (HFPO) component.

Example 7 [0033] Reaction of an alcohol end-group to a diol end-group. 10-g of the separated bifunctional poly (HFPO) component of example 6, 5-mL of anhydrous THF, and 1 .2 mL of 1 M potassium tert-butoxide in THF (approximately 10 mole % with respect to alcohol end-groups in the purified bifunctional poly(HFPO) component) are added to a 50-mL three-neck RB flask under nitrogen. With magnetic stirring, the mixture is heated to 70°C. Freshly distilled glycidol (0.90-g, 12.1 mmol, approximately 1 equivalent) is added over 2 hours. The reaction is stopped after 4 hours by acidification with 25 mL of 0.1 M HCL The lower phase is separated, diluted to approximately 5% w/w with Vertrel® XF, washed 2X with deionized water, dried with magnesium sulfate, and syringe filtered through 1 pm glass microfiber. The conversion to diol end-groups is measured using ¹H NMR spectroscopy and is at least 95%.

Example 8

[0034] Article coating with the bifunctional poly (HFPO) component. A 0.5-g sample of the solution of the diol-end-group deriviatve of the bifunctional poly (HFPO) component of example 8 is quantitatively diluted to 0.1% with additional Vertrel® XF and the solution is re-syringe filtered through 1 pm glass microfiber into a 50-mL glass vial. A glass microscope slide is pre-cleaned with isopropyl alcohol and Vertrel® XF. The glass microscope slide is immersed in the solution and slowly withdrawn. After drying at ambient temperature for a few minutes, the glass microscope slide is analyzed by FTIR spectroscopy using a horizontal attenuated total reflectance kit. The FTIR spectrum shows an absorbance peak at approximately 1200 cm'¹ and is indicative of the CF vibration of the bifunctional poly (HFPO) component that is coating the glass microscope slide.

Claims

CLAIMS What is claimed is:

1 . A poly (hexafluoropropylene oxide) (HFPO) mixture comprising a bifunctional and a monofunctional poly (HFPO) component represented by the following structural formulas, respectively: R¹OC(O)-R^F-O-(CF(CF₃)CF2O)n- CF(CF₃)C(O)Y and CF₃CF2CF2-O-(CF(CF₃)CF₂O)_m-CF(CF₃)C(O)Y; wherein R¹ comprises an alkyl group, R^F comprises a fluoroalkyl group selected from CFCF₃, CF(CF₃)CF2, CF2CF2, or CF2CFCI, n and m are integers between 4 and 50, and Y is F, OH, or OR² wherein R² comprises an alkyl group.

2. A poly (hexafluoropropylene oxide) (HFPO) mixture comprising an end-group derivative of a bifunctional and a monofunctional poly (HFPO) component represented by the following structural formulas, respectively: R³OCH₂-R^F-O- (CF(CF₃)CF₂O)_n-CF(CF₃)CH₂OR³and CF₃CF₂CF₂-O-(CF(CF₃)CF₂O)_n- CF(CF₃)CH₂OR³; wherein R³ is H, CH₂CH(OH)CH₂OH, or CH2CH₂Si(OCH₃)₃; R^F comprises a fluoroalkyl group selected from CFCF₃, CF(CF₃)CF₂, CF2CFCI, or CF2CF2, and n and m are integers between 4 and 50.

3. The poly (hexafluoropropylene oxide) HFPO mixture of claim 2, wherein the end-group derivative of the bifunctional poly (HFPO) component is greater than 99 mole percent with respect to the end-group derivative of the monofunctional poly (HFPO) component.

4. A liquid or supercritical-fluid chromatography process for separating a poly (hexafluoropropylene oxide) (HFPO) mixture comprising a bifunctional and a monofunctional poly (HFPO) component; the process comprising a chromatography technique, and; a) elution of the poly (HFPO) mixture with a mobile phase using a chromatography apparatus comprising a chromatography column incorporating a polar stationary phase; and b) elution of a first solution comprising a majority of the monofunctional poly (HFPO) component from the chromatography column and isolation from the chromatography apparatus; and c) elution of a second solution comprising a majority of the bifunctional poly (HFPO) component from the chromatography column and isolation from the chromatography apparatus. The process of claim 4, wherein the bifunctional and monofunctional poly (HFPO) component are end-group derivatives represented by the following structural formulas, respectively: R³OCH₂-R^F-O-(CF(CF₃)CF2O)n- CF(CF₃)CH₂OR³ and CF₃CF₂CF2-O-(CF(CF₃)CF₂O)m-CF(CF₃)CH₂OR³; wherein R³ is H CH₂CH(OH)CH₂OH, or CH₂CH₂Si(OCH₃)₃; R^F comprises a fluoroalkyl group selected from CFCF₃, CF(CF₃)CF₂, CF₂CFCI, or CF₂CF₂, and n and m are integers between 4 and 50. The process of claim 4, wherein the bifunctional poly (hexafluoropropylene oxide) (HFPO) component in the poly (HPO) mixture comprises a polar end- group selected from a carboxylic acid or an amine and is represented by the following structural formulas, respectively: HOC(O)-R^F-O-(CF(CF₃)CF₂O)n- CF(CF₃)CO₂H or R⁴R⁴’NC(O)-R^F-O-(CF(CF₃)CF₂O)n-CF(CF₃)C(O)NR⁴R⁴’; wherein R^F is selected from CFCF₃, CF(CF₃)CF₂, CF2CFCI, or CF2CF2R⁴; R⁴ and R⁴’ are independently H or comprise an alkyl group, and n is an integer between 4 and 50. The process of claim 4, wherein the bifunctional poly (hexafluoropropylene oxide) (HFPO) component in the second solution is greater than 99 mole percent with respect to the monofunctional poly (HFPO) component. The process of claim 4, wherein the mobile phase comprises Vertrel® XF, a Novec® fluid including HFE-7100 or HFE-7200, liquid carbon dioxide, or supercritical carbon dioxide. The process of claim 4, wherein a chromatography technique is selected from high-performance liquid chromatography (HPLC), high-performance supercritical-fluid chromatography (HPSFC), preparative HPLC, preparative SFC, or flash chromatography. The process of claim 4, wherein the polar stationary phase comprises a high- surface-area silica gel. A process for coating the surface of an article; the process comprising dissolving the poly (hexafluoropropylene oxide) (HFPO) mixture of claim 3 in an inert solvent to form a solution; contacting the surface of the article with the solution using a coating method, and removal of the inert solvent from the surface of the article. The process of claim 11 , wherein the surface of the article is heated. The process of claim 11 , wherein the coating method comprises spraying the solution on the article or dipping the article in the solution. The process of claim 11 , wherein the article is selected from magnetic recording media, a touch screen display, or another article having a surface made of glass, metal, ceramic, or other metal oxide. The article of claim 14.