Polyfluorosiloxane-based polyurethane, and preparation method and application thereof, and marine protective coating

Abstract

This invention provides a polyfluorosiloxane alkyl polyurethane, its preparation method and application, and marine protective coatings, relating to the field of marine engineering protection technology. The polyfluorosiloxane alkyl polyurethane provided by this invention has a molecular chain comprising a soft segment component and a hard segment component. The soft segment component is a polylactic acid-polycarbonate copolymer with dihydroxyl-terminated ends; the hard segment component has polyfluorosiloxane side chains. Using the polyfluorosiloxane alkyl polyurethane provided by this invention, a biomimetic super-lubricating surface marine engineering protective coating with self-healing function and highly stable surface lubricant can be prepared. The chemically bonded polyfluorosiloxane side chain structure endows the coating with longer-lasting corrosion protection performance; the addition of mercapto-modified nano-silica further enhances the mechanical properties and UV aging resistance of the coating; simultaneously, the preparation method of this polyurethane is simple, and the reaction conditions are mild and efficient.

Description

Technical Field

[0001] This invention relates to the field of marine engineering protection technology, and in particular to a polyfluorosiloxane alkyl polyurethane, its preparation method and application, and marine protective coatings. Background Technology

[0002] Marine corrosion and biofouling are serious problems that severely restrict the healthy development of the marine industry. In recent years, an increasing number of major marine engineering infrastructures and large ships have been put into use. However, due to the harsh marine environment, the corrosion and deterioration of marine engineering structures and metal materials have become increasingly prominent, causing serious economic losses.

[0003] With continuous research advancements, various types of marine corrosion protection coatings have emerged, and numerous high-efficiency and environmentally friendly new coatings have been developed. However, as the demand for antifouling coatings increases, the shortcomings of existing antifouling coatings are becoming increasingly apparent, such as difficulties in maintenance and construction after coating damage, and short service life. Biomimetic (Nepenthes-like) super-slippery surfaces have attracted widespread attention due to their excellent marine corrosion protection performance. Numerous studies have shown that these coatings are free of toxic substances and can effectively inhibit marine corrosion and the adhesion of fouling organisms. However, the free lubricating oil film on these biomimetic super-slippery surfaces is prone to loss, which significantly affects their overall protective capability. Ensuring the long-term effectiveness of antifouling capabilities is a crucial technical problem that urgently needs to be solved in the practical application of biomimetic super-slippery coatings. Summary of the Invention

[0004] The purpose of this invention is to provide a polyfluorosiloxane alkyl polyurethane, its preparation method and application, and a marine protective coating. The polyfluorosiloxane alkyl polyurethane provided by this invention, when formulated into a marine protective coating, exhibits excellent surface antifouling properties and long-lasting effectiveness.

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

[0006] The present invention provides a polyfluorosiloxane alkyl polyurethane, the molecular chain of which includes a soft segment component and a hard segment component. The soft segment component is a polylactic acid polycarbonate copolymer with dihydroxyl-terminated ends; the hard segment component has polyfluorosiloxane side chains.

[0007] Preferably, the number-average molecular weight of the dihydroxyl-terminated polylactic acid polycarbonate polymer is 1×10⁻⁶. 3 ~10×10 5 g / mol; the number-average molecular weight of the polyfluorosiloxane side chains is 1×10⁻⁶ g / mol. 3 ~10×10 5 g / mol; the number-average molecular weight of the polyfluorosiloxane alkyl polyurethane is 3 × 10⁻⁶ g / mol. 3 ~30×10 5g / mol.

[0008] This invention provides a method for preparing the polyfluorosiloxane alkyl polyurethane described above, comprising the following steps:

[0009] Under inert gas protection, a first prepolymerization reaction is carried out by mixing a dihydroxyl-terminated polylactic acid polycarbonate copolymer, a diisocyanate, and a first organic solvent. A second prepolymerization reaction is carried out by adding a polyfluorosiloxane with two hydroxyl groups at one end to the first prepolymer. The second prepolymer is then subjected to a final polymerization reaction at room temperature to obtain the polyfluorosiloxane polyurethane.

[0010] Preferably, the preparation of the dihydroxyl-terminated polylactic acid polycarbonate copolymer includes: under inert gas protection, mixing lactide and trimethylene carbonate, a first small molecule diol with carbon-carbon double bonds and an organic base catalyst, and performing a copolymerization reaction to obtain the dihydroxyl-terminated polylactic acid polycarbonate copolymer.

[0011] Preferably, the first small molecule diol with carbon-carbon double bonds includes at least one selected from 2-methylene-1,3-propanediol, 3,4-dihydroxy-1-butene, 2-buten-1,4-diol, hepten-6-en-2,4-diol, and 3-hexen-1,6-diol; the molar ratio of lactide to trimethylene carbonate is 1:1.

[0012] Preferably, the preparation of the polyfluorosiloxane with two hydroxyl groups at one end comprises:

[0013] A hexane-tetrahydrofuran mixed solvent, a silane monomer, and an initiator are mixed and subjected to a homopolymerization reaction. The reaction is terminated by adding dimethylchlorosilane to the reaction system to obtain a polyfluorosiloxane with silane-hydrogen bonds at the molecular chain ends; at least one of the silane monomers is trifluoropropylmethylcyclotrisiloxane.

[0014] Under inert gas protection, a polyfluorosiloxane with a silicon-hydrogen bond at the end of its molecular chain, a second small molecule diol with a carbon-carbon double bond, a platinum catalyst, and a second organic solvent are mixed and subjected to a hydrosilylation reaction to obtain a polyfluorosiloxane with two hydroxyl groups at one end.

[0015] Preferably, the silane monomer is trifluoropropylmethylcyclotrisiloxane, or a mixture of trifluoropropylmethylcyclotrisiloxane and hexamethylcyclotrisiloxane.

[0016] Preferably, the molar ratio of hydroxyl groups to organotin catalyst in the polyfluorosiloxane with two hydroxyl groups at one end is (0.1-1000):1;

[0017] The molar ratio of the dihydroxyl-terminated polylactic acid polycarbonate copolymer to diisocyanate is (0.1–10):1;

[0018] The molar ratio of the polyfluorosiloxane with two hydroxyl groups at one end to the diisocyanate is (0.1–10):1.

[0019] This invention provides the application of the polyfluorosiloxane alkyl polyurethane described in the above-described scheme or the polyfluorosiloxane alkyl polyurethane prepared by the preparation method described in the above-described scheme in marine protective coatings.

[0020] This invention provides a marine protective coating comprising polyfluorosiloxane alkyl polyurethane and mercapto-modified nano-silica; wherein the polyfluorosiloxane alkyl polyurethane is the polyfluorosiloxane alkyl polyurethane described in the above scheme or the polyfluorosiloxane alkyl polyurethane prepared by the preparation method described in the above scheme.

[0021] The present invention provides a polyfluorosiloxane alkyl polyurethane, the molecular chain of which includes a soft segment component and a hard segment component. The soft segment component is a polylactic acid polycarbonate copolymer with dihydroxyl-terminated ends; the hard segment component has polyfluorosiloxane side chains.

[0022] Traditional biomimetic super-lubricating surfaces utilize the low interaction between lubricating oil and water molecules to achieve marine protection properties. In this invention, polyfluorosiloxane is a specialized polyfluorosiloxane with fluorine-containing groups in its molecular chain. Fluorine atoms have a strong electron-withdrawing inductive effect, which can form a strong shielding effect on the side chain groups, thereby limiting its sensitivity to van der Waals interactions and resulting in extremely low intermolecular interaction forces. Therefore, the coating surface formed by grafting polyfluorosiloxane macromolecules has extremely low intermolecular interaction forces with corrosive / fouling media, thus enabling the polyfluorosiloxane alkyl polyurethane provided by this invention to have superior marine corrosion protection capabilities compared to traditional biomimetic super-lubricating surfaces.

[0023] The marine protective coating prepared using the polyfluorosiloxane alkyl polyurethane provided by this invention adheres to the metal or concrete surface through the flowability of the polymer material to penetrate into the pores, and also achieves a strong bond between the coating and the substrate through the hydrogen bonding between the polyurethane and the hydroxyl groups on the surface of the substrate material. This solves the problem that the lubricating oil of traditional biomimetic super-lubricating coatings is easy to lose in the underwater environment, and makes the coating have a longer-lasting anti-biofouling performance.

[0024] Furthermore, the marine protective coating prepared using the polyfluorosiloxane alkyl polyurethane provided by this invention also has the function of self-repair after damage. This is because the polylactic acid polycarbonate copolymer provides reliable molecular chain flowability and molding ability to the polyurethane backbone. The molecular chain flowability drives a large number of reversible hydrogen bonds on the polyurethane molecules, providing the material with excellent self-healing properties, so that the scratches can be repaired into a smooth surface after contact.

[0025] The preparation method of polyfluorosiloxane alkyl polyurethane provided by this invention is simple, and the reaction conditions are mild and efficient.

[0026] This invention provides a marine protective coating comprising the aforementioned polyfluorosiloxane alkyl polyurethane and mercapto-modified nano-silica. In addition to the advantages of the aforementioned polyfluorosiloxane alkyl polyurethane, the marine protective coating provided by this invention, through the doping of mercapto-modified silica, achieves a strong chemical bond between the reinforcing material nano-silica and the polyurethane macromolecules via a mercapto-double bond click reaction under ultraviolet light, thereby enhancing the coating's mechanical properties and UV aging resistance. Attached Figure Description

[0027] Figure 1 The nuclear magnetic resonance spectrum of the polyfluorosiloxane alkyl polyurethane prepared in Example 1 of this invention;

[0028] Figure 2 The dynamic wettability diagram of a droplet (20 μL) on the surfaces of a polyfluorosiloxane alkyl polyurethane protective coating (PU-SSS coating), a control group concrete material, and a control group polyurethane coating (PU coating);

[0029] Figure 3 Metallurgical microscope image of a polyfluorosiloxane alkyl polyurethane protective coating that self-repaired after damage;

[0030] Figure 4 Fluorescent images of bacterial adhesion in polyfluorosiloxane alkyl polyurethane protective coating (SSS) and control concrete material after immersion in Pseudomonas alterniflora culture medium under static conditions for 3 and 14 days.

[0031] Figure 5 A comparison chart showing the water absorption rate and protective performance of polyfluorosiloxane alkyl polyurethane protective coatings and some commercially available concrete coatings.

[0032] Figure 6 This is a schematic diagram illustrating the preparation principle of the polyfluorosiloxane alkyl polyurethane protective coating of the present invention;

[0033] Figure 7 Dynamic wettability diagram of self-repair of polyfluorosiloxane alkyl polyurethane protective coating after damage;

[0034] Figure 8 The mechanical properties of polyurethane coatings formed with and without added thiol-modified nano-silica are shown in the test results. Detailed Implementation

[0035] The present invention provides a polyfluorosiloxane alkyl polyurethane, the molecular chain of which includes a soft segment component and a hard segment component. The soft segment component is a polylactic acid polycarbonate copolymer with dihydroxyl-terminated ends; the hard segment component has polyfluorosiloxane side chains.

[0036] In this invention, the number-average molecular weight of the dihydroxyl-terminated polylactic acid polycarbonate polymer is preferably 1 × 10⁻⁶. 3 ~10×10 5 g / mol, more preferably 9×10 g / mol 3 ~1×10 5 g / mol; the number-average molecular weight of the polyfluorosiloxane side chains is preferably 1×10⁻⁶ g / mol. 3 ~10×10 5 g / mol, more preferably 1×10 g / mol 4 ~1×10 5 g / mol; the preferred number-average molecular weight of the polyfluorosiloxane alkyl polyurethane is 3 × 10⁻⁶ g / mol. 3 ~30×10 5 g / mol, more preferably 1×10 g / mol 4 ~3×10 5 g / mol, further preferably 1×10 g / mol 5 ~2×10 5 g / mol.

[0037] In this invention, the structure of the polyfluorosiloxane side chain preferably includes:

[0038]

[0039] In this invention, the polyfluorosiloxane alkyl polyurethane preferably has the structure shown in any one of Formulas 1 to 3:

[0040]

[0041]

[0042] Traditional biomimetic super-lubricating surfaces utilize the low interaction between lubricating oil and water molecules to achieve marine protection properties. In this invention, polyfluorosiloxane is a specialized polyfluorosiloxane with fluorine-containing groups in its molecular chain. Fluorine atoms have a strong electron-withdrawing inductive effect, which can form a strong shielding effect on the side chain groups, thereby limiting its sensitivity to van der Waals interactions and resulting in extremely low intermolecular interaction forces. Therefore, the coating surface formed by grafting polyfluorosiloxane macromolecules has extremely low intermolecular interaction forces with corrosive / fouling media, thus enabling the polyfluorosiloxane alkyl polyurethane provided by this invention to have superior marine corrosion protection capabilities compared to traditional biomimetic super-lubricating surfaces.

[0043] This invention provides a method for preparing the polyfluorosiloxane alkyl polyurethane described above, comprising the following steps:

[0044] Under inert gas protection, a first prepolymerization reaction is carried out by mixing a dihydroxyl-terminated polylactic acid polycarbonate copolymer, a diisocyanate, and a first organic solvent. A second prepolymerization reaction is carried out by adding a polyfluorosiloxane with two hydroxyl groups at one end to the first prepolymer. The second prepolymer is then subjected to a final polymerization reaction at room temperature to obtain the polyfluorosiloxane polyurethane.

[0045] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0046] In this invention, the preparation of the dihydroxyl-terminated polylactic acid polycarbonate copolymer preferably includes: under inert gas protection, mixing lactide and trimethylene carbonate, a first small molecule diol with carbon-carbon double bonds and an organic base catalyst, and performing a copolymerization reaction to obtain the dihydroxyl-terminated polylactic acid polycarbonate copolymer.

[0047] In this invention, the lactide is preferably one or a mixture of two or more of levorotatory lactide, dextrorotatory lactide, racemic lactide, and meso lactide in any proportion. In this invention, the molar ratio of lactide to trimethylene carbonate is preferably 1:1; the first small-molecule diol with carbon-carbon double bonds preferably includes at least one of 2-methylene-1,3-propanediol, 3,4-dihydroxy-1-butene, 2-buten-1,4-diol, hepta-6-en-2,4-diol, and 3-hexen-1,6-diol; the molar ratio of the hydroxyl groups in the lactide and the first small-molecule diol with carbon-carbon double bonds is preferably (10–200):1, more preferably (50–150):1, and even more preferably (80–120):1. In this invention, the first small-molecule diol with carbon-carbon double bonds serves as an initiator.

[0048] In this invention, the organic base catalyst is preferably one or more of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). In this invention, the molar ratio of the organic base catalyst to the hydroxyl group in the first small-molecule diol with a carbon-carbon double bond is preferably (0.1–5):1, more preferably (1–4):1, and even more preferably (2–3):1.

[0049] In this invention, the mixing of lactide and trimethylene carbonate, a first small molecule diol with carbon-carbon double bonds and an organic base catalyst preferably includes: adding the first small molecule diol with carbon-carbon double bonds, lactide and trimethylene carbonate to a reaction vessel under inert gas protection, stirring at room temperature until the two solid monomers are in a eutectic state, adding the organic base catalyst, stirring continuously at room temperature for 1 minute, and then heating to the temperature of the copolymerization reaction.

[0050] In this invention, the temperature of the copolymerization reaction is preferably 55-65°C, more preferably 60-63°C, and the time is preferably 10-35h, more preferably 15-30h, and even more preferably 20-25h.

[0051] After the copolymerization reaction has reached the set time, chloroform solvent is added to the reaction system to dissolve the copolymer. Benzoic acid solution is added to the dissolved product to terminate the polymerization reaction. The product is then poured into ice-cold methanol for precipitation (to remove organic base catalyst and unreacted monomers). The solid product is collected and dried to constant weight to obtain dihydroxyl-terminated polylactic acid polycarbonate copolymer.

[0052] In this invention, the preparation of the polyfluorosiloxane with two hydroxyl groups at one end preferably includes:

[0053] A hexane-tetrahydrofuran mixed solvent, a silane monomer, and an initiator are mixed and subjected to a homopolymerization reaction. The reaction is terminated by adding dimethylchlorosilane to the reaction system to obtain a polyfluorosiloxane with silane-hydrogen bonds at the molecular chain ends; at least one of the silane monomers is trifluoropropylmethylcyclotrisiloxane.

[0054] Under inert gas protection, a polyfluorosiloxane with a silicon-hydrogen bond at the end of its molecular chain, a second small molecule diol with a carbon-carbon double bond, a platinum catalyst, and a second organic solvent are mixed and subjected to a hydrosilylation reaction to obtain a polyfluorosiloxane with two hydroxyl groups at one end.

[0055] This invention involves mixing a hexane-tetrahydrofuran mixed solvent, a silane monomer, and an initiator to carry out a homopolymerization reaction, and then adding dimethylchlorosilane to the reaction system to terminate the reaction, thereby obtaining a polyfluorosiloxane with silicon-hydrogen bonds at the ends of the molecular chain.

[0056] In this invention, the volume ratio of hexane to tetrahydrofuran in the hexane-tetrahydrofuran mixed solvent is preferably (6-7):(4-3). In this invention, the hexane is preferably n-hexane or cyclohexane.

[0057] In this invention, at least one of the silane monomers is trifluoropropylmethylcyclotrisiloxane, more preferably trifluoropropylmethylcyclotrisiloxane, or a mixture of trifluoropropylmethylcyclotrisiloxane and hexamethylcyclotrisiloxane. When the silane monomer is a mixture of trifluoropropylmethylcyclotrisiloxane and hexamethylcyclotrisiloxane, the molar ratio of trifluoropropylmethylcyclotrisiloxane to hexamethylcyclotrisiloxane is preferably 1:1. In this invention, the initiator is preferably n-butyllithium, tert-butyllithium, or sec-butyllithium.

[0058] In this invention, the molar ratio of the silane monomer to the initiator is preferably (1-10000):1, more preferably (100-9000):1, and even more preferably (1000-8000):1; the molar ratio of the silane monomer to the mixed solvent is preferably (0.001-1000):1, more preferably (0.01-100):1, and even more preferably (0.1-10):1.

[0059] In this invention, the mixing of the hexane-tetrahydrofuran mixed solvent, silane monomer, and initiator preferably includes: adding a dried hexane-tetrahydrofuran mixed solvent to a container that has undergone repeated vacuuming, baking, and nitrogen purging; then injecting the silane monomer into the mixed solvent using a sealed syringe; subsequently placing the reaction flask in a 20°C constant temperature water bath for 0.5 hours; and finally adding the initiator. In this invention, the purpose of the constant temperature water bath is to ensure that the reactants are properly mixed.

[0060] In this invention, the preferred temperature for the homopolymerization reaction is 20°C, and the preferred time is 3.5 h.

[0061] After the homopolymerization reaction is completed, the present invention adds dimethylchlorosilane to the reaction system to terminate the reaction, thereby obtaining a polyfluorosiloxane with silicon-hydrogen bonds at the end of the molecular chain.

[0062] The present invention does not have any special requirements on the specific amount of dimethylchlorosilane used; an excess amount is sufficient to terminate the reaction.

[0063] After the reaction is terminated, the present invention preferably uses anhydrous methanol for precipitation, collects the precipitated oily substance, and dries it in a vacuum oven at 40°C to constant weight to obtain a polyfluorosiloxane with silicon-hydrogen bonds at the end of the molecular chain.

[0064] After obtaining a polyfluorosiloxane with silicon-hydrogen bonds at the end of its molecular chain, the present invention, under the protection of an inert gas, mixes the polyfluorosiloxane with silicon-hydrogen bonds at the end of its molecular chain, a second small molecule diol with carbon-carbon double bonds, a platinum catalyst, and a second organic solvent to carry out a hydrosilylation reaction to obtain a polyfluorosiloxane with two hydroxyl groups at one end.

[0065] In this invention, the second small molecule diol with carbon-carbon double bonds preferably includes one or more of 2-methylene-1,3-propanediol, 1,4-butenediol, trans-2-buten-1,4-diol, and 3-buten-1,2-diol; the platinum catalyst is preferably a Karstedt catalyst and / or a Speier catalyst; the second organic solvent preferably includes one or more of dichloromethane, trichloromethane, pentane, hexane, heptane, cyclohexane, benzene, toluene, xylene, chlorobenzene, dichlorobenzene, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethyl sulfoxide, more preferably tetrahydrofuran.

[0066] In this invention, the molar ratio of the double bond in the second small molecule diol with carbon-carbon double bonds to the platinum catalyst is preferably (0.1-100000):1, more preferably (1-90000):1, further preferably (100-10000):1, and even more preferably (1000-9000):1; the molar ratio of the polyfluorosiloxane with silicon-hydrogen bonds at the end of the molecular chain to the double bond in the second small molecule diol with carbon-carbon double bonds is preferably (1-1.2):1; the molar ratio of the polyfluorosiloxane with silicon-hydrogen bonds at the end of the molecular chain to the second solvent is preferably 1:(1-100), more preferably 1:(10-80).

[0067] In this invention, the mixing of the polyfluorosiloxane with silicon-hydrogen bonds at the molecular chain end, the second small molecule diol with carbon-carbon double bonds, the platinum catalyst, and the second organic solvent under inert gas protection preferably includes: dissolving the second small molecule diol with carbon-carbon double bonds and the platinum catalyst in the second organic solvent under inert gas protection, and adding the polyfluorosiloxane with silicon-hydrogen bonds at the molecular chain end dropwise to the resulting solution.

[0068] In this invention, the preferred temperature for the hydrosilylation reaction is 55–70°C, more preferably 60–65°C, and the preferred time is 4 hours. The hydrosilylation reaction is preferably carried out under reflux conditions. In the hydrosilylation reaction of this invention, a polyfluorosiloxane with terminal silane-hydrogen bonds undergoes a hydrosilylation reaction with a small-molecule diol containing carbon-carbon double bonds, resulting in the formation of two hydroxyl groups at the original silane-hydrogen bond site, thus yielding a polyfluorosiloxane with two hydroxyl groups at one end.

[0069] After the hydrosilylation reaction is completed, most of the solvent is removed by rotary evaporation. The remaining solution is separated by chromatography column chromatography with petroleum ether as the eluent. The collected fraction is removed by rotary evaporation and then dried under vacuum at 40°C to constant weight to obtain a colorless oily liquid, which is a polyfluorosiloxane with two hydroxyl groups at one end.

[0070] After obtaining a dihydroxyl-terminated polylactic acid-polycarbonate copolymer and a polyfluorosiloxane with two hydroxyl groups at one end, this invention uses both as chain extenders to prepare polyfluorosiloxane-based polyurethanes with diisocyanate. A schematic diagram of the preparation principle is shown below. Figure 6 As shown (the diisocyanate is isophorone diisocyanate as an example).

[0071] Under inert gas protection, the present invention involves mixing a dihydroxyl-terminated polylactic acid polycarbonate copolymer, a diisocyanate, and a first organic solvent to carry out a first prepolymerization reaction. A polyfluorosiloxane with two hydroxyl groups at one end and an organotin catalyst are then added to the resulting first prepolymer to carry out a second prepolymerization reaction. The resulting second prepolymer is then subjected to a final polymerization reaction at room temperature to obtain the polyfluorosiloxane polyurethane.

[0072] In this invention, the first organic solvent preferably includes one or more of dichloromethane, trichloromethane, pentane, hexane, heptane, cyclohexane, benzene, toluene, xylene, chlorobenzene, dichlorobenzene, tetrahydrofuran, N,N-dimethylformamide, and N,N-dimethyl sulfoxide; the diisocyanate is preferably one or more of diphenylmethyl diisocyanate, isophorone diisocyanate, and 1,6-hexyl diisocyanate. In this invention, the molar ratio of the dihydroxyl-terminated polylactic acid polycarbonate copolymer to the diisocyanate is preferably (0.1–10):1, more preferably (0.5–5):1. This invention does not have special requirements on the amount of the first organic solvent used, as long as the prepolymerization reaction proceeds smoothly.

[0073] In this invention, the temperature of the first prepolymerization reaction is preferably 70–90°C, and the time is preferably 2–6 h, more preferably 3–5 h, and even more preferably 4 h. In the first prepolymerization reaction, the dihydroxyl-terminated polylactic acid-polycarbonate copolymer acts as a chain extender and reacts with diisocyanate to generate an NCO-terminated polyurethane prepolymer, i.e., the first prepolymer.

[0074] In this invention, the organotin catalyst is preferably stannous octoate and / or dibutyltin dilaurate; the molar ratio of the polyfluorosiloxane with two hydroxyl groups at one end to the diisocyanate is preferably (0.1-10):1, more preferably (1-5):1; the molar ratio of the hydroxyl group to the organotin catalyst in the polyfluorosiloxane with two hydroxyl groups at one end is (0.1-1000):1, more preferably (1-900):1, further preferably (10-850):1, and even more preferably (100-700):1.

[0075] In this invention, the polyfluorosiloxane with two hydroxyl groups at one end and the organotin catalyst are preferably added by dropwise addition.

[0076] In this invention, the temperature of the second prepolymerization reaction is preferably 110°C, and the time is preferably 1–5 h, more preferably 2–3 h. During the second prepolymerization reaction, a polyfluorosiloxane with two hydroxyl groups at one end acts as a chain extender and continues to prepolymerize with the first prepolymer.

[0077] In this invention, the time for the final polymerization reaction is preferably 12 to 20 hours, more preferably 14 to 18 hours.

[0078] After the final polymerization reaction is completed, the present invention preferably precipitates the final product in deionized water and then dries it in a vacuum oven at 80°C for 12 hours to obtain the polyfluorosiloxane alkyl polyurethane.

[0079] This invention provides the application of the polyfluorosiloxane alkyl polyurethane described in the above-described scheme or the polyfluorosiloxane alkyl polyurethane prepared by the preparation method described in the above-described scheme in marine protective coatings.

[0080] The present invention preferably coats the polyfluorosiloxane alkyl polyurethane onto a marine substrate to form a marine protective coating.

[0081] The marine protective coating prepared using the polyfluorosiloxane alkyl polyurethane provided by this invention adheres to the metal or concrete surface through the flowability of the polymer material penetrating into the pores, and also achieves a strong bond between the coating and the substrate through the hydrogen bonding between the polyurethane and the hydroxyl groups on the surface of the substrate material. This solves the problem of easy loss of lubricating oil in traditional biomimetic super-lubricating coatings in underwater environments, giving the coating a longer-lasting ability to prevent biofouling.

[0082] This invention provides a marine protective coating comprising polyfluorosiloxane alkyl polyurethane and mercapto-modified nano-silica; wherein the polyfluorosiloxane alkyl polyurethane is the aforementioned polyfluorosiloxane alkyl polyurethane.

[0083] In this invention, the mass ratio of the polyfluorosiloxane alkyl polyurethane and the mercapto-modified nano silica is not specifically limited.

[0084] In this invention, the preparation of the thiol-modified nano silica preferably includes: dispersing nano silica and 3-mercaptopropyltrimethoxysilane in an organic solvent, placing the resulting dispersion in water to settle, and drying the resulting precipitate to obtain the thiol-modified nano silica.

[0085] In this invention, the mass ratio of the nano-silica to 3-mercaptopropyltrimethoxysilane is preferably (0.01-1000):1, more preferably (0.1-900):1, even more preferably (1-800):1, and even more preferably (10-700):1.

[0086] In this invention, the organic solvent preferably includes one or more of methanol, ethanol, tetrahydrofuran, N,N-dimethylformamide and N,N-dimethyl sulfoxide.

[0087] In this invention, the dispersion is preferably carried out under ultrasonic conditions, and the ultrasonic time is preferably 1 to 6 hours.

[0088] The present invention does not have special requirements for the preparation method of the marine protective coating; it is sufficient to directly mix the polyfluorosiloxane alkyl polyurethane and the mercapto-modified nano-silica evenly. Before mixing, the mercapto-modified nano-silica is preferably ground.

[0089] In addition to the advantages of polyfluorosiloxane alkyl polyurethane mentioned above, the marine protective coating provided by this invention also achieves the chemical bonding of reinforcing nano-silica to polyurethane macromolecules through a mercapto-modified silica reaction under ultraviolet light, thereby enhancing the mechanical properties and UV aging resistance of the coating.

[0090] The following detailed description, in conjunction with embodiments, illustrates the polyfluorosiloxane alkyl polyurethane, its preparation method, its application, and marine protective coatings provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0091] Example 1

[0092] (1) Preparation of polyfluorosiloxanes with silane-hydrogen bonds at the molecular chain ends: A stir bar and 100 mL of dried hexane-tetrahydrofuran mixed solvent (Hex:THF volume ratio = 6:4) were added to a round-bottom flask that had been repeatedly evacuated, baked, and purged with nitrogen three times. Then, trifluoropropylmethylcyclotrisiloxane (21.825 g, 0.1 mol) was injected into the mixed solvent through a sealed syringe. The reaction flask was then placed in a constant temperature water bath at 20 °C for 0.5 h. Then, the initiator n-butyllithium (1 mL, 1.6 mmol) was slowly injected through a sealed syringe. After reacting at 20 °C for 3.5 h, excess dimethylchlorosilane (0.284 g, 3 mmol) was added to terminate the reaction. The obtained product was precipitated with excess anhydrous methanol to remove unreacted reactants and dried under vacuum at 40 °C to constant weight. The product was analyzed by organogel chromatography (GPC). n It is 13900 g / mol, and the PDI is 1.06.

[0093] (2) Preparation of polyfluorosiloxane with two hydroxyl groups at one end: Under the protection of inert gas argon at room temperature and pressure, 2-methylene-1,3-propanediol (0.11 g, 1.25 mmol) and the pre-prepared Speier catalyst (0.01 mL, 0.001 mmol) were dissolved in anhydrous tetrahydrofuran. The polyfluorosiloxane with silane-hydrogen bonds at the end synthesized in step (1) (13.9 g, 1 mmol) was slowly added dropwise at room temperature. After the addition was completed, the temperature was raised to 66 °C and the reaction was continued under reflux for 4 h. Most of the solvent was removed by rotary evaporation. The remaining solution was separated by chromatography column with petroleum ether as the eluent. The fraction was collected and the solvent was removed by rotary evaporation. The solution was then dried under vacuum at 40 °C to constant weight to obtain a colorless oily liquid.

[0094] (3) Preparation of dihydroxyl-terminated polylactic acid-polycarbonate copolymer: A stir bar and 2-methylene-1,3-propanediol initiator (0.0529 g, 0.6 mmol) were added to a round-bottom flask that had been repeatedly evacuated, baked, and purged with nitrogen three times. Simultaneously, L-lactide (L-LA, 2.88 g, 0.02 mol) and trimethylene carbonate (TMC, 2.04 g, 0.02 mol) were added, and the mixture was stirred at 25 °C for 30 min until the two solid monomer components were in a eutectic state. Then, the catalyst DBU (0.023 g, 0.21 mmol) was rapidly added. The reaction began after stirring at room temperature for 20 s, and after approximately 40 s (a total of 1 min), the polylactic acid component, which was formed first, began to crystallize. At this point, the reaction temperature was rapidly increased to 63 °C (above the glass transition temperature of polylactic acid), and the reaction was continued for 20 h. After the reaction is complete, chloroform solvent is added to dissolve the product, followed by the addition of a measured amount of benzoic acid solution (polymerization terminator). The resulting product is then precipitated with excess anhydrous methanol to remove the catalyst and unreacted monomers, and dried under vacuum at 40°C to constant weight. Organic gel permeation chromatography (GPC) analysis shows that product M... n It is 9200 g / mol, and the PDI is 1.07.

[0095] (4) Preparation of polyfluorosiloxane polyurethane: Dihydroxyl-terminated polylactic acid polycarbonate copolymer (Mn = 9200, 0.5 mmol) and isophorone diisocyanate (0.222 g, 1 mmol) were added to 20 mL of tetrahydrofuran and reacted at 70 °C for 4 h to obtain NCO-terminated polyurethane prepolymer. Then, polyfluorosiloxane with two hydroxyl groups at one end (10.45 g, 0.5 mmol) synthesized in step (2) and a small amount of dibutyltin dilaurate catalyst (0.006 g, 0.01 mmol) were added to a flask, and the reaction was continued for 2 h. The temperature was then lowered to room temperature and the reaction was continued for 10 h. The final product was dried in a vacuum oven at 80 °C for 12 h after precipitation with deionized water. The product was analyzed by organogel chromatography (GPC). n It is 5.67 × 10 4 g / mol, PDI is 1.22.

[0096] The polyfluorosiloxane alkyl polyurethane prepared in Example 1 has a molecular structure with polyfluorosiloxane branches, and its molecular structural formula is as follows:

[0097]

[0098] The polyurethane prepared in Example 1 was characterized by its molecular structure, such as... Figure 1 As shown, δe+f = 3.37ppm and 3.65ppm correspond to the methylene and methylene groups linked to the urethane bond, confirming the successful preparation of side-chain polyfluorosiloxane alkyl polyurethane.

[0099] Example 2

[0100] (1) Preparation of polyfluorosiloxanes with silane-hydrogen bonds at the molecular chain ends: A stir bar and 100 mL of dried n-hexane-tetrahydrofuran mixed solvent (Hex:THF volume ratio = 7:3) were added to a round-bottom flask that had been repeatedly evacuated, baked, and purged with nitrogen three times. Then, trifluoropropylmethylcyclotrisiloxane (32.738 g, 0.15 mol) was injected into the above solution through a sealed syringe. The reaction flask was then placed in a constant temperature water bath at 20 °C for 0.5 h. Then, the initiator n-butyllithium (1 mL, 1.6 mmol) was slowly injected through a sealed syringe. After reacting at 20 °C for 3.5 h, excess dimethylchlorosilane (0.284 g, 3 mmol) was added to terminate the reaction. The obtained product was precipitated with excess anhydrous methanol to remove unreacted reactants and dried under vacuum at 40 °C to constant weight. The product was analyzed by organogel chromatography (GPC). n It is 20900 g / mol, and the PDI is 1.07.

[0101] (2) Preparation of polyfluorosiloxane with two hydroxyl groups at one end: Under the protection of inert gas argon at room temperature and pressure, 1,4-butenediol (0.11 g, 1.25 mmol) and the pre-prepared Speier catalyst (0.01 mL, 0.001 mmol) were dissolved in anhydrous tetrahydrofuran. The polyfluorosiloxane with silane-hydrogen bonds at the end synthesized in step (1) (20.1 g, 1 mmol) was slowly added dropwise at room temperature. After the addition was completed, the temperature was raised to 66 °C and the reaction was continued under reflux for 4 h. Most of the solvent was removed by rotary evaporation. The remaining solution was separated by chromatography column with petroleum ether as the eluent. The fraction was collected and the solvent was removed by rotary evaporation. The solution was then dried under vacuum at 40 °C to constant weight to obtain a colorless oily liquid.

[0102] (3) Preparation of dihydroxyl-terminated polylactic acid polycarbonate copolymer: Same as in Example 1.

[0103] (4) Preparation of polyfluorosiloxane polyurethane: Dihydroxyl-terminated polylactic acid polycarbonate copolymer (Mn = 9200, 0.5 mmol) and 1,6-hexyl diisocyanate (0.168 g, 1 mmol) were added to 20 mL of N,N-dimethylformamide and reacted at 90 °C for 4 h to obtain NCO-terminated polyurethane prepolymer. Then, the mixture was heated to 110 °C, and polyfluorosiloxane with two hydroxyl groups at one end (10.45 g, 0.5 mmol) synthesized in step (2) and a small amount of stannous octoate catalyst (0.004 g, 0.01 mmol) were added to a flask. The reaction was continued for 2 h, then cooled to room temperature and continued for 10 h. The final product was dried in a vacuum oven at 80 °C for 12 h after precipitation with deionized water. The product was analyzed by organogel chromatography (GPC). n 10.22×10 4g / mol, PDI is 1.39.

[0104] The polyfluorosiloxane alkyl polyurethane prepared in Example 2 has a molecular structure with polyfluorosiloxane branches, and its molecular structural formula is as follows:

[0105]

[0106] Example 3

[0107] (1) Preparation of polyfluorosiloxane with silane-hydrogen bonds at the end of the molecular chain: Same as in Example 2.

[0108] (2) Preparation of polyfluorosiloxane with two hydroxyl groups at one end: Same as in Example 2.

[0109] (3) Preparation of dihydroxyl-terminated polylactic acid polycarbonate copolymer: Same as in Example 1.

[0110] (4) Preparation of polyfluorosiloxane polyurethane: A dihydroxyl-terminated polylactic acid-polycarbonate copolymer (Mn = 9200, 0.5 mmol) and diphenylmethyl diisocyanate (0.250 g, 1 mmol) were added to 20 mL of toluene. After reacting at 90 °C for 4 h, an NCO-terminated polyurethane prepolymer was obtained. The mixture was then heated to 110 °C, and a flask containing a single-terminated polyfluorosiloxane with two hydroxyl groups (10.45 g, 0.5 mmol) and a small amount of stannous octoate catalyst (0.004 g, 0.01 mmol) synthesized in step (2) was added. The reaction was continued for 2 h, then cooled to room temperature and continued for 10 h. The final product was precipitated with deionized water and dried in a vacuum oven at 80 °C for 12 h. Organic gel permeation chromatography (GPC) analysis showed that the product M... n It is 5.86×10 4 g / mol, PDI is 1.39.

[0111] The polyfluorosiloxane alkyl polyurethane prepared in Example 3 has a molecular structure with polydimethylsiloxane branches, and its molecular structural formula is as follows:

[0112]

[0113] Example 4

[0114] (1) Preparation of polyfluorosiloxanes with silane-hydrogen bonds at the end: Same as in Example 2.

[0115] (2) Preparation of polyfluorosiloxane with two hydroxyl groups at one end: Same as in Example 2.

[0116] (3) Preparation of dihydroxyl-terminated polylactic acid polycarbonate copolymer: Same as in Example 1.

[0117] (4) Preparation of polyfluorosiloxane polyurethane: A dihydroxyl-terminated polylactic acid polycarbonate copolymer (Mn = 9200, 0.5 mmol) and diphenylmethyl diisocyanate (0.250 g, 1 mmol) were added to 20 mL of xylene. After reacting at 90 °C for 4 h, an NCO-terminated polyurethane prepolymer was obtained. The mixture was then heated to 110 °C, and a flask containing a single-terminated polyfluorosiloxane with two hydroxyl groups synthesized in step (2) (10.45 g, 0.5 mmol) and a small amount of dibutyltin dilaurate catalyst (0.006 g, 0.01 mmol) was added. The reaction was continued for 2 h, then cooled to room temperature and continued for 10 h. The final product was precipitated with deionized water and dried in a vacuum oven at 80 °C for 12 h. Organic gel permeation chromatography (GPC) analysis showed that the product M... n It is 5.89×10 4 g / mol, PDI is 1.35.

[0118] The polyfluorosiloxane alkyl polyurethane prepared in Example 4 has a molecular structure with polyfluorosiloxane branches, and its molecular structural formula is as follows:

[0119]

[0120] Example 5

[0121] (1) Preparation of polyfluorosiloxanes with silane-hydrogen bonds at the end: Same as in Example 2.

[0122] (2) Preparation of polyfluorosiloxane with two hydroxyl groups at one end: Same as in Example 2.

[0123] (3) Preparation of dihydroxyl-terminated polylactic acid polycarbonate copolymer: Same as in Example 1.

[0124] (4) Preparation of polyfluorosiloxane polyurethane: Dihydroxyl-terminated polylactic acid polycarbonate copolymer (Mn = 9200, 0.5 mmol) and isophorone diisocyanate (0.222 g, 1 mmol) were added to 20 mL of N,N-dimethylformamide and reacted at 90 °C for 4 h to obtain NCO-terminated polyurethane prepolymer. Then, the mixture was heated to 110 °C, and polyfluorosiloxane with two hydroxyl groups at one end (10.45 g, 0.5 mmol) synthesized in step (2) and a small amount of dibutyltin dilaurate catalyst (0.006 g, 0.01 mmol) were added to a flask. The reaction was continued for 2 h, then cooled to room temperature and continued for 10 h. The final product was dried in a vacuum oven at 80 °C for 12 h after precipitation with deionized water. The product was tested by organogel chromatography (GPC) and the M... n 5.58×10 4 g / mol, PDI is 1.39.

[0125] The polyfluorosiloxane alkyl polyurethane prepared in Example 5 has a molecular structure with polyfluorosiloxane branches, and its molecular structural formula is as follows:

[0126]

[0127] Example 6

[0128] (1) Preparation of polyfluorosiloxanes with silane-hydrogen bonds at the end: Same as in Example 2.

[0129] (2) Preparation of polyfluorosiloxane with two hydroxyl groups at one end: Same as in Example 2.

[0130] (3) Preparation of polylactic acid polycarbonate copolymer: Same as in Example 1.

[0131] (4) Preparation of polyfluorosiloxane polyurethane: Dihydroxyl-terminated polylactic acid polycarbonate copolymer (Mn = 9200, 0.5 mmol) and 1,6-hexyl diisocyanate (0.168 g, 1 mmol) were added to 20 mL of N,N-dimethylformamide and reacted at 90 °C for 4 h to obtain NCO-terminated polyurethane prepolymer. Then, the mixture was heated to 110 °C, and polyfluorosiloxane with two hydroxyl groups at one end (10.45 g, 0.5 mmol) synthesized in step (2) and a small amount of dibutyltin dilaurate catalyst (0.006 g, 0.01 mmol) were added to a flask. The reaction was continued for 2 h, then cooled to room temperature and continued for 10 h. The final product was dried in a vacuum oven at 80 °C for 12 h after precipitation with deionized water. The product was tested by organogel chromatography (GPC) and the Mn-terminated polyurethane prepolymer was found to be NCO-terminated. n It is 5.35×10 4 g / mol, PDI is 1.33.

[0132] The polyfluorosiloxane alkyl polyurethane prepared in Example 6 has a molecular structure with polyfluorosiloxane branches, and its molecular structural formula is as follows:

[0133]

[0134] Comparison Example

[0135] Preparation of the control group polyurethane: Dihydroxyl-terminated polylactic acid-polycarbonate copolymer (Mn = 9200, 0.5 mmol) and isophorone diisocyanate (0.222 g, 1 mmol) were added to 20 mL of tetrahydrofuran and reacted at 70 °C for 4 h to obtain NCO-terminated polyurethane prepolymer. Then, 1,3-propanediol and a suitable amount of dibutyltin dilaurate catalyst were added to a flask, and the reaction was continued for 2 h, then cooled to room temperature and continued for 10 h. The final product was precipitated with deionized water and dried in a vacuum oven at 80 °C for 12 h. Organic gel permeation chromatography (GPC) analysis showed that product M... n 3.23×10 4g / mol, PDI 1.23. The polyurethane coating prepared in the control example applied to the surface of concrete material to form a coating is denoted as PU coating.

[0136] Performance testing:

[0137] The preparation process of thiol-modified nano silica is as follows: 1.5g of nano silica is added to an ethanol solution containing 20mL of 6% 3-mercaptopropyltrimethoxysilane. After sealing, the solution is ultrasonically stirred at room temperature for 3h. After precipitation with deionized water, the solution is naturally dried at room temperature to obtain thiol-modified nano silica.

[0138] The dried polyfluorosiloxane alkyl polyurethane prepared in Example 1 and the ground mercapto-modified nano-silica were uniformly dispersed in tetrahydrofuran at a mass ratio of 95:5. Part of the solvent was evaporated by stirring, and the mixture was then coated onto the surface of concrete material. Afterward, it was treated with ultraviolet light at room temperature until completely dry and cured to obtain a polyfluorosiloxane alkyl polyurethane protective coating. The following performance tests were performed on the obtained polyfluorosiloxane alkyl polyurethane protective coating:

[0139] The sliding property of a water droplet on an inclined protective coating surface was determined by a contact angle meter. Specifically, a water droplet (20 μL) was dropped onto the protective coating surface with an inclination of 10°, and then the distance the droplet slid on the surface for a period of time was recorded by the contact angle meter.

[0140] like Figure 2 As shown, droplets can slide off the surface of the polyfluorosiloxane alkyl polyurethane protective coating (PU-SSS coating) on ​​their own, indicating that the protective coating formed by the polyfluorosiloxane alkyl polyurethane has excellent super-slip properties. However, on the concrete surface at a 10° inclination angle and the control group polyurethane coating surface, they always remain in the initial position, confirming that the polyfluorosiloxane side chain structure is the key to the super-slip properties of the polyurethane coating, which has the protective advantage of weaker interaction between water and water.

[0141] Figure 3 This is a metallographic micrograph of a damaged polyfluorosiloxane alkyl polyurethane protective coating that self-heals. The coating surface was scratched at room temperature, and the wound healed spontaneously after 12 hours of rest. Figure 7 As shown, after scratching the surface of the polyfluorosiloxane alkyl polyurethane protective coating, the falling droplet remained at the damaged area during its sliding process; after removing the droplet, the sample was left to stand at room temperature for 12 hours, and the droplet then slid off the scratch on its own. This result confirms that the polyfluorosiloxane alkyl polyurethane protective coating of the present invention can restore its super-slippery properties after completing self-repair.

[0142] Figure 4Fluorescent images show bacterial adhesion on the surface of the polyfluorosiloxane alkyl polyurethane protective coating and the control concrete material after immersion in *Pseudomonas alterniflora* culture for 3 and 14 days under static conditions. The images show that, regardless of whether the immersion lasted 3 or 14 days, the control concrete material exhibited a large amount of bacterial adhesion, while the solid super-lubricating coating showed only a small amount of bacterial adhesion. This indicates that the protective coating effectively inhibits bacterial adhesion, thereby suppressing corrosion and degradation caused by bacterial adhesion.

[0143] Figure 5 This image compares the water absorption and protective performance of a polyfluorosiloxane-alkyl polyurethane protective coating with that of several commercially available concrete coatings. Two concrete samples (3cm x 3cm x 3cm) were coated with the experimental group's polyfluorosiloxane-alkyl polyurethane protective coating and the control group's coating, respectively. The samples were then placed in a seawater environment under static conditions and weighed at fixed intervals. The image shows that during the 30-day pre-experiment, the water absorption rate of the polyfluorosiloxane-alkyl polyurethane protective coating (Slippery Coating) was consistently lower than that of the control group concrete material (Bare Concerte), epoxy resin coating (EpoxyResin), polyurethane coating (PU Coating), and polydimethylsiloxane gel coating (PDMS Coating). This indicates that the protective coating effectively inhibits seawater erosion of the concrete substrate, thus achieving a protective effect.

[0144] Mechanical properties were tested on polyurethane coatings with added thiol-modified nano-silica and polyurethane coatings without added reinforcing materials (thiol-modified silica). The test results are as follows: Figure 8 As shown. By Figure 8 It is known that the adhesion strength of the polyurethane coating without the addition of reinforcing material (thiol-modified silica) is about 1.5 MPa. After the addition of nano silica, the mechanical strength gradually increases, and the optimal mechanical properties are achieved when the total addition is about 10%, with an adhesion strength of about 2.8 MPa.

[0145] The polyfluorosiloxane alkyl polyurethane provided by this invention achieves the self-permeation of polyfluorosiloxane from the molecular side chains to the surface through microphase separation within the polyurethane molecule and the effect of intermolecular osmotic pressure. This maintains a stable single-end grafted polyfluorosiloxane oil film on the surface, thereby giving the surface lubricant extremely reliable stability. This provides a solution to the problem of the long-term effectiveness of biomimetic super-lubricating coatings in marine biofouling protection.

[0146] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A polyfluorosiloxane alkyl polyurethane, the molecular chain comprising a soft segment component and a hard segment component, wherein the soft segment component is a dihydroxyl-terminated polylactic acid polycarbonate copolymer; and the hard segment component has polyfluorosiloxane side chains. The preparation method of the polyfluorosiloxane alkyl polyurethane includes the following steps: Under inert gas protection, a first prepolymerization reaction is carried out by mixing a dihydroxyl-terminated polylactic acid polycarbonate copolymer, a diisocyanate and a first organic solvent. A second prepolymerization reaction is carried out by adding a polyfluorosiloxane with two hydroxyl groups at one end to the first prepolymer. The second prepolymer is then subjected to a final polymerization reaction at room temperature to obtain the polyfluorosiloxane polyurethane. The preparation of the dihydroxyl-terminated polylactic acid polycarbonate copolymer includes: mixing lactide and trimethylene carbonate, a first small molecule diol with carbon-carbon double bonds and an organic base catalyst under inert gas protection, and carrying out a copolymerization reaction to obtain the dihydroxyl-terminated polylactic acid polycarbonate copolymer. The first small molecule diol with carbon-carbon double bonds includes at least one selected from 2-methylene-1,3-propanediol, 3,4-dihydroxy-1-butene, 2-butene-1,4-diol, hepten-6-en-2,4-diol, and 3-hexene-1,6-diol; the molar ratio of lactide to trimethylene carbonate is 1:

1. The preparation of the polyfluorosiloxane with two hydroxyl groups at one end includes: A hexane-tetrahydrofuran mixed solvent, a silane monomer, and an initiator are mixed and subjected to a homopolymerization reaction. The reaction is terminated by adding dimethylchlorosilane to the reaction system to obtain a polyfluorosiloxane with silane-hydrogen bonds at the molecular chain ends; at least one of the silane monomers is trifluoropropylmethylcyclotrisiloxane. Under the protection of an inert gas, the polyfluorosiloxane with a silicon-hydrogen bond at the end of the molecular chain, a second small molecule diol with a carbon-carbon double bond, a platinum catalyst, and a second organic solvent are mixed and subjected to a hydrosilylation reaction to obtain a polyfluorosiloxane with two hydroxyl groups at one end. The silane monomer is trifluoropropylmethylcyclotrisiloxane, or a mixture of trifluoropropylmethylcyclotrisiloxane and hexamethylcyclotrisiloxane.

2. The polyfluorosiloxane alkyl polyurethane according to claim 1, characterized in that, The number-average molecular weight of the dihydroxyl-terminated polylactic acid polycarbonate polymer is 1×10⁻⁶. 3 ~10×10 5 g / mol; the number-average molecular weight of the polyfluorosiloxane side chains is 1×10⁻⁶ g / mol. 3 ~10×10 5 g / mol; the number-average molecular weight of the polyfluorosiloxane alkyl polyurethane is 3 × 10⁻⁶ g / mol. 3 ~30×10 5 g / mol.

3. The method for preparing the polyfluorosiloxane alkyl polyurethane according to claim 1 or 2, characterized in that, Includes the following steps: Under inert gas protection, a first prepolymerization reaction is carried out by mixing a dihydroxyl-terminated polylactic acid polycarbonate copolymer, a diisocyanate and a first organic solvent. A second prepolymerization reaction is carried out by adding a polyfluorosiloxane with two hydroxyl groups at one end to the first prepolymer. The second prepolymer is then subjected to a final polymerization reaction at room temperature to obtain the polyfluorosiloxane polyurethane. The preparation of the dihydroxyl-terminated polylactic acid polycarbonate copolymer includes: mixing lactide and trimethylene carbonate, a first small molecule diol with carbon-carbon double bonds and an organic base catalyst under inert gas protection, and carrying out a copolymerization reaction to obtain the dihydroxyl-terminated polylactic acid polycarbonate copolymer. The first small molecule diol with carbon-carbon double bonds includes at least one selected from 2-methylene-1,3-propanediol, 3,4-dihydroxy-1-butene, 2-butene-1,4-diol, hepten-6-en-2,4-diol, and 3-hexene-1,6-diol; the molar ratio of lactide to trimethylene carbonate is 1:

1. The preparation of the polyfluorosiloxane with two hydroxyl groups at one end includes: A hexane-tetrahydrofuran mixed solvent, a silane monomer, and an initiator are mixed and subjected to a homopolymerization reaction. The reaction is terminated by adding dimethylchlorosilane to the reaction system to obtain a polyfluorosiloxane with silane-hydrogen bonds at the molecular chain ends; at least one of the silane monomers is trifluoropropylmethylcyclotrisiloxane. Under the protection of an inert gas, the polyfluorosiloxane with a silicon-hydrogen bond at the end of the molecular chain, a second small molecule diol with a carbon-carbon double bond, a platinum catalyst, and a second organic solvent are mixed and subjected to a hydrosilylation reaction to obtain a polyfluorosiloxane with two hydroxyl groups at one end. The silane monomer is trifluoropropylmethylcyclotrisiloxane, or a mixture of trifluoropropylmethylcyclotrisiloxane and hexamethylcyclotrisiloxane.

4. The preparation method according to claim 3, characterized in that, The molar ratio of hydroxyl groups to organotin catalyst in the polyfluorosiloxane with two hydroxyl groups at one end is (0.1~1000):1; The molar ratio of the dihydroxyl-terminated polylactic acid polycarbonate copolymer to diisocyanate is (0.1~10):1; The molar ratio of the polyfluorosiloxane with two hydroxyl groups at one end to the diisocyanate is (0.1~10):

1.

5. The application of the polyfluorosiloxane alkyl polyurethane according to any one of claims 1 to 2 or the polyfluorosiloxane alkyl polyurethane prepared by the preparation method according to any one of claims 3 to 4 in marine protective coatings.

6. A marine protective coating, characterized in that, It includes polyfluorosiloxane alkyl polyurethane and mercapto-modified nano silica; the polyfluorosiloxane alkyl polyurethane is the polyfluorosiloxane alkyl polyurethane according to any one of claims 1 to 2 or the polyfluorosiloxane alkyl polyurethane prepared by the preparation method according to any one of claims 3 to 4.

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