Fluoropolymer composition with improved adhesion

Abstract

The invention relates to a composition comprising at least one fluoropolymer and from 0.005 to 5.0 wt.-%, relative to the weight of the at least one fluoropolymer, of at least one APA additive, characterized in that the at least one APA additive is a polymer comprising repeating units derived from methyl methacrylate and at least one graftable functional group arranged at at least one end of its polymer chain. The invention also relates to a process for producing a fluoropolymer-based coating on a substrate, to such a coating on a substrate, to a device comprising such a polymer coating on a substrate, and to a use.

Description

Technical Field

[0001] This invention relates to the field of adhesion of fluoropolymers to surfaces, particularly metal or polymer surfaces. More particularly, this invention relates to compositions comprising a fluoropolymer and additives designed to improve the adhesion of said fluoropolymer to a surface.

[0002] The present invention also relates to a method for manufacturing a coating on a surface starting from an added composition. The present invention further relates to a composite material comprising a coating adhered to a surface. The present invention also relates to an electronic device comprising the composite material. Finally, the present invention relates to the use of the additive for improving the adhesion of fluoropolymers to surfaces. Background Technology

[0003] Fluoropolymers, such as those based on vinylidene fluoride (VDF) CF2=CH2, particularly PVDF and VDF-containing copolymers, are known to offer excellent mechanical stability, very high chemical inertness, and good aging resistance. These qualities are used in a wide variety of applications. In particular, certain VDF-based fluoropolymers, such as P(VDF-TrFE), P(VDF-TrFE-CTFE), or P(VDF-TrFE-CFE), are used due to their electroactive properties, especially in electronic devices.

[0004] However, due to their high chemical inertness, fluoropolymers suffer from adhesion problems to substrates, especially metal substrates, which can be particularly problematic for some applications. In fact, if a fluoropolymer separates or delaminates from the surface of the substrate in direct contact with it, it can no longer perform its original function (for the conversion of physical quantities in transducers, for adhesives in electrodes, for protective coatings, for thermal insulation, etc.).

[0005] For example, if a fluoropolymer separates or delaminates, or even partially separates or delaminates, from its electrodes, a transducer formed by an electroactive fluoropolymer disposed between the two electrodes will no longer function or will function poorly. It should be remembered that a polymer is said to be electroactive if it exhibits a response (deformation, temperature change, etc.) during the application of an electric field and / or if stress (mechanical, thermal, etc.) induces an electrical response within the material.

[0006] Several solutions have been proposed in the prior art that enable improved adhesion of fluoropolymers to substrates, particularly metal substrates. Three main methods can be mentioned:

[0007] The first approach involves adding adhesion-promoting monomers to the polymer chain of the fluoropolymer. This has been described, for example, in WO2017 / 129881. This patent document specifically describes a terpolymer composed of repeating units generated from vinylidene fluoride (VDF), trifluoroethylene (TrFE), and adhesion-promoting monomers selected from dialkyl vinylphosphonates, vinylphosphonic acid, and 2-(trifluoromethyl)acrylic acid. This method exhibits the disadvantage of requiring modification of the fluoropolymer chain structure, which in some cases may negatively impact its useful properties, particularly its mechanical properties and / or, if appropriate, its electroactive properties. Furthermore, such polymers are currently not available on an industrial scale and require more or less significant modifications to the manufacturing methods of industrially produced fluoropolymers.

[0008] The second method involves inserting a primer layer between the fluoropolymer and the substrate. This has been described, for example, in the following publication: “Whang, WT and Cheng, WH (1995), A study on interfacial adhesion of poly(vinylidene fluoride) with substrates in a multilayer structure, Polymer Engineering & Science, 35(8), 666-672”. In this method, the compound 3-aminopropyltriethoxysilane (3-APS) is used as the adhesive primer for PVDF on aluminum or silicon substrates. The disadvantage of this method is that an additional stage of applying the primer layer between the fluoropolymer and its substrate is required. This additional stage can be cumbersome to implement and, in all cases, represents a significant additional cost at the industrial level (manufacturing time) compared to applying the fluoropolymer directly to its substrate.

[0009] The third method, chosen for carrying out the invention, is to add additives to the fluoropolymer. This solution has the advantage of overcoming the two disadvantages mentioned above: the chemical composition of the polymer chain of the intended fluoropolymer for the specific application does not need to be modified, and the method for manufacturing the fluoropolymer coating on the substrate involves fewer restrictive modifications.

[0010] Therefore, there is a need to provide fluoropolymer compositions that enable improved adhesion of the fluoropolymer to a substrate, while altering the useful properties of the fluoropolymer and / or the method of forming the polymer coating on the substrate as little as possible. Summary of the Invention

[0011] The object of the present invention is to provide a composition comprising a fluoropolymer that makes it possible to improve the adhesion of the fluoropolymer to a substrate while altering the useful properties of the fluoropolymer as little as possible.

[0012] According to certain embodiments of fluoropolymers having electroactive properties, the object of the present invention is to substantially maintain their electroactive properties.

[0013] Another object of the present invention is to provide a method for manufacturing a fluoropolymer coating on a substrate, which is easy to implement and enables the coating to adhere well to the substrate.

[0014] According to some implementation schemes, the method for manufacturing the coating is carried out under mild conditions.

[0015] According to some implementations, the method for manufacturing the coating is efficient and, in particular, can be performed quickly enough.

[0016] Another object of the present invention is to provide a composite material comprising a coating based on the fluoropolymer adhered to a substrate and / or a device incorporating such a composite material.

[0017] Another object of the present invention is to provide an additive to be added to fluoropolymers to improve their adhesion to substrates.

[0018] According to a first aspect, the present invention relates to a composition comprising:

[0019] -At least one fluoropolymer;

[0020] - Relative to the weight of the at least one fluoropolymer, 0.005% to 5.0% by weight of at least one additive APA,

[0021] The feature is that the at least one additive APA is a polymer comprising repeating units generated from methyl methacrylate and at least one graftable functional group disposed at at least one end of its polymer chain.

[0022] The inventors of this invention have noted that the addition of this polymeric APA as an additive to the fluoropolymer advantageously improves the adhesion of the fluoropolymer to a substrate, even at very low loading levels. Without being bound by theory, it appears that this significant improvement in adhesion is due to the additive satisfying a dual condition: good affinity for the fluoropolymer, and at least one graftable functional group disposed at one end of the polymer chain, allowing that end to be grafted onto the substrate, particularly by heat treatment. It can also be demonstrated that the addition of polymeric APA as an additive, particularly in low proportions, has little effect on the useful properties of the fluoropolymer, especially when the fluoropolymer is an electroactive polymer and the useful property is the electroactive nature of the polymer.

[0023] According to certain embodiments, the at least one graftable functional group disposed at at least one end of the polymer chain of the at least one additive APA is selected from the following groups: nitroxy, carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and hypophosphonic acid.

[0024] According to certain embodiments, the at least one additive APA contains a graftable functional group at one end of its polymer chain, the graftable functional group being a nitro group.

[0025] According to certain embodiments, the at least one additive APA contains at one end of its polymer chain at at least one graftable functional group selected from the following groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid, and hypophosphonic acid.

[0026] According to certain embodiments, the at least one additive APA contains at least one graftable functional group at one end of its polymer chain, the graftable functional group being a nitro group, and at the other end of its polymer chain contains at least one graftable functional group selected from the following groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid, and hypophosphonic acid.

[0027] According to certain embodiments, the at least one graftable functional group disposed at one end of the polymer chain of the at least one additive APA is a hydroxyl functional group.

[0028] According to certain embodiments, the at least one graftable functional group disposed at one end of the polymer chain of the at least one additive APA is a carboxyl functional group.

[0029] According to certain embodiments, the repeating units generated by methyl methacrylate in the polymer chain of the at least one additive APA account for at least 40% of the total weight of the polymer chain of the at least one additive APA, preferably at least 50%, and most preferably at least 70%.

[0030] According to certain embodiments, the repeating units generated by methyl methacrylate in the polymer chain of the at least one additive APA account for at least 90% by weight of the total weight of the polymer chain of the at least one additive APA.

[0031] According to certain embodiments, the total weight of additive APA accounts for 0.01% or more, and preferably 0.05% or more, relative to the total weight of the fluoropolymer.

[0032] According to certain embodiments, the total weight of additive APA accounts for 3.0% or less, and preferably 2.0% or less, relative to the total weight of the fluoropolymer.

[0033] According to certain embodiments, additive APA can be obtained by free radical polymerization of alkoxyamines controlled by nitride oxides. Alkoxyamines may specifically have the following chemical formula:

[0034] [Chemical Formula 1]

[0035] (I),

[0036] in:

[0037] -R1 is a cyclic or acyclic hydrocarbon group with or without heteroatoms, and may contain at least one metallic entity;

[0038] -R2 is a cyclic or acyclic hydrocarbon group with or without heteroatoms, and may contain at least one metallic entity;

[0039] -R1 and R2 may or may not form part of the same ring structure;

[0040] -Z is a cyclic or acyclic monovalent hydrocarbon group with or without heteroatoms.

[0041] According to certain embodiments, the Z group of the alkoxyamine of formula (I) is a group having one or more graftable functional groups, each graftable functional group being selected from the following groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and hypophosphonic acid.

[0042] Advantageously, alkoxyamines are selected from:

[0043] -A compound of the following formula:

[0044] [Chemical Formula 2]

[0045] (II), and

[0046] - An adduct formed by reacting 1 equivalent of a compound of formula (II) with an acrylic, methacrylic, or vinyl aromatic monomer having at least one graftable functional group.

[0047] According to certain embodiments, the at least one additive APA is a linear polymer.

[0048] According to certain embodiments, the at least one additive APA is a gradient or random polymer.

[0049] According to certain embodiments, the at least one additive APA does not contain repeating units containing graftable functional groups.

[0050] According to certain embodiments, the at least one additive APA is a linear polymer and / or does not contain repeating units with graftable functional groups, and is substantially composed of or consisting of repeating units produced from methyl methacrylate and styrene, wherein the weight percentage of repeating units produced from styrene is 0.5% to 15%, preferably 1.0% to 10%, relative to the total weight of the units produced from methyl methacrylate and styrene.

[0051] According to certain embodiments, the at least one additive APA is an AB-type or ABA-type block polymer, wherein block A independently comprises at least one repeating unit containing the at least one graftable functional group, and block B comprises a repeating unit generated from methyl methacrylate. Advantageously, block B of the at least one additive APA does not contain a repeating unit containing a graftable functional group.

[0052] According to certain embodiments, the number-average molar mass of the at least one additive APA is from 1,000 g / mol to 100,000 g / mol, preferably from 2,000 g / mol to 50,000 g / mol.

[0053] According to certain embodiments, the at least one fluoropolymer comprises at least 40 mol% of repeating units generated from vinylidene fluoride, relative to the total molar amount of repeating units constituting the at least one fluoropolymer, and optionally at least one repeating unit generated from a monomer X other than vinylidene fluoride, the monomer having the formula CX1X2=CX3X4, wherein each X1, X2, X3 and X4 group is independently selected from H, Cl, F, Br, I and optionally partially or fully halogenated C1-C3 alkyl groups.

[0054] According to certain embodiments, the at least one fluoropolymer is PVDF.

[0055] According to certain embodiments, the at least one fluoropolymer is P(VDF-TrFE), P(VDF-TrFE-CTFE), or P(VDF-TrFE-CFE), or a mixture thereof.

[0056] According to certain embodiments, the at least one fluoropolymer is P(VDF-TFE) or P(VDF-HFP).

[0057] According to certain embodiments, the at least one fluoropolymer has a weight-average molar mass greater than or equal to 100,000 g / mol, and more preferably greater than or equal to 200,000 g / mol.

[0058] According to certain embodiments, the compositions according to the invention comprise a mixture of solvents or miscible solvents, wherein the fluoropolymer and the additive APA are in solution. The solvents or mixtures of miscible solvents may be particularly selected from: dimethylformamide; N-methyl-2-pyrrolidone; dimethylacetamide; dimethyl sulfoxide; γ-butyrolactone; ketones, particularly acetone, methyl ethyl ketone (or but-2-one), methyl isobutyl ketone, cyclopentanone, cyclohexanone, or diisobutyl ketone; furans, particularly tetrahydrofuran; esters, particularly methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, and ethyl acetoacetate; carbonates, particularly dimethyl carbonate and propylene carbonate; and phosphate esters, particularly trimethyl phosphate or triethyl phosphate; and mixtures thereof.

[0059] According to certain embodiments, the composition according to the invention is substantially composed of, or is composed of, at least one fluoropolymer, at least one additive APA, and optionally a mixture of the solvent or miscible solvent.

[0060] According to a second aspect, the present invention relates to a method for manufacturing a fluoropolymer-based coating on a substrate, the method comprising:

[0061] i) Deposition of the composition according to the invention;

[0062] ii) If appropriate, after deposition of the composition, remove any solvent or solvent mixture that may be present in the composition; and

[0063] iii) Grafting at least a portion of the at least one additive APA present in the composition onto the substrate.

[0064] According to certain embodiments, the grafting of at least a portion of the at least one additive APA onto the substrate is carried out through at least one heating stage at a temperature of 50 °C to 220 °C, and preferably 80 °C to 200 °C.

[0065] According to certain embodiments, the grafting of at least a portion of the at least one additive APA onto the substrate is performed by heating at a temperature of less than or equal to 160 °C for a period of less than or equal to 20 minutes in at least one stage.

[0066] According to a third aspect, the present invention relates to a composite material comprising a fluoropolymer-based coating adhered to a substrate, the coating comprising at least one fluoropolymer and at least one additive APA in an amount of 0.005% to 5.0% by weight relative to the at least one fluoropolymer, the at least one additive APA being a polymer comprising repeating units generated from methyl methacrylate and at least one graftable functional group disposed at at least one end of its polymer chain.

[0067] According to certain embodiments, the composite material can be obtained by a method for producing a fluoropolymer-based coating on a substrate as described in the second aspect of the invention.

[0068] According to certain embodiments, the at least one additive APA conforms to the characteristics of the at least one additive APA described in the first aspect of the present invention.

[0069] According to certain embodiments, the at least one fluoropolymer conforms to the characteristics of the at least one fluoropolymer described in the first aspect of the present invention.

[0070] According to certain embodiments of the second or third aspect of the present invention, the substrate may be glass, silicon, quartz, polymer material, metal or nitride surface, or a mixed surface composed of several of these materials.

[0071] According to a fourth aspect, the present invention relates to an apparatus comprising a composite material according to a third aspect of the present invention.

[0072] According to some embodiments, the fluoropolymer-based coating is an electroactive coating, or an insulating and / or protective layer, or an electrode adhesive.

[0073] According to certain implementations, the device may be an optoelectronic device, a transistor (especially a field-effect transistor), a chip, a battery, a photovoltaic cell, a light-emitting diode (especially an organic light-emitting diode), a sensor, an actuator, a transformer, a tactile device, an electromechanical microsystem, or a detector.

[0074] According to the fifth aspect, the present invention relates to uses.

[0075] The present invention particularly relates to the use of at least one polymer APA as an additive in fluoropolymer-based compositions to improve the adhesion of said compositions to a substrate, said additive APA being a polymer comprising repeating units generated from methyl methacrylate and at least one graftable functional group disposed at one end of its polymer chain.

[0076] According to certain embodiments, the at least one polymer APA accounts for 0.005% to 5.0% by weight of the total weight of the fluoropolymer in the fluoropolymer-based composition.

[0077] According to certain embodiments, the at least one polymer APA accounts for 0.01% or more by weight, preferably 0.05% or more by weight, relative to the total weight of the fluoropolymers in the fluoropolymer-based composition.

[0078] According to certain embodiments, the at least one polymer APA accounts for 3.0% or less, preferably 2.0% or less, relative to the total weight of the fluoropolymers in the fluoropolymer-based composition.

[0079] According to certain embodiments, the at least one additive APA conforms to the characteristics of the at least one additive APA described in the first aspect of the present invention.

[0080] According to certain embodiments, the at least one fluoropolymer conforms to the characteristics of the at least one fluoropolymer described in the first aspect of the present invention. Attached Figure Description

[0081] [ Figure 1 The illustration shows a 180° peel test performed in Example 2 to evaluate the adhesion of the film to the substrate.

[0082] [ Figure 2 [] represents the tensile force measured during the peel test of Example 2, starting with solutions of FP-1 and APA-1 (vertical axis is expressed as Newton / 25 mm, N / 25 mm), as a function of the weight ratio of APA-1 to FP-1 in the test solution (horizontal axis is expressed as weight percentage, weight %).

[0083] [ Figure 3 The vertical axis represents the remanent polarization of the FP-1 film with or without the addition (denoted as mC). -2 The value is expressed as the weight ratio of APA-1 to FP-1 in the tested composition (the horizontal axis represents the weight percentage, weight %).

[0084] [ Figure 4The graph represents the change in ΔDk (vertical axis, percentage) as a function of the temperature under study (horizontal axis: degrees Celsius, °C) at 10 kHz. Here, the parameter “ΔDk” is defined according to the following formula:

[0085] ΔDk=(Dk) 纯 –Dk 添加 ) / Dk 纯 100,

[0086] in:

[0087] Dk 纯 = Dielectric constant of pure FP-2 film at the considered temperature;

[0088] Dk 添加 = Dielectric constant of an FP-2 film with added additives of 0.5 wt% APA-1 relative to FP-2, obtained at the temperature under consideration.

[0089] Therefore, the parameter ΔDk represents the change in dielectric constant measured after adding APA-1.

[0090] [ Figure 5 [] represents the change in "Δtan δ" (vertical axis represents percentage, %) as a function of temperature (horizontal axis represents degrees Celsius, °C) at 10 kHz. Here, the parameter "δ tan δ" is defined according to the following formula:

[0091] Δ tan δ=(tan δ 纯 –tan δ APA ) / tan δ 纯 100

[0092] in:

[0093] tan δ 纯 = Dielectric loss of pure FP-2 film at the temperature under consideration;

[0094] tan δ APA = Dielectric loss value of FP-2 film with 0.5% by weight of APA-1 relative to the weight of FP-2, obtained at the temperature under consideration.

[0095] Therefore, the parameter Δ tan δ represents the change in dielectric loss measured after adding APA-1. Detailed Implementation Plan

[0096] Fluoropolymers (FP)

[0097] Polymer FP is a fluoropolymer, meaning it contains repeating units (or units, or structural units) produced by fluorinated monomers (i.e., obtained through polymerization).

[0098] Polymer FP can be a polymer containing repeating units of vinylidene fluoride (VDF).

[0099] The polymer FP can be a polymer based on repeating units generated by VDF, that is, containing at least 50 mol% repeating units generated by VDF relative to the total molar sum of the repeating units constituting the polymer FP.

[0100] In some implementations, the polymer FP is a PVDF homopolymer, that is, it consists of repeating units produced by VDF.

[0101] In some embodiments, polymer FP is a copolymer (in a broad sense), that is, it contains units generated from at least one monomer X other than VDF.

[0102] A single monomer X or several different monomers X can be used, depending on the situation.

[0103] In some embodiments, monomer X may have the formula CX1X2=CX3X4, wherein each X1, X2, X3 and X4 group is independently selected from H, Cl, F, Br, I and C1-C3 (preferably C1-C2) alkyl, which is optionally partially or completely halogenated - the monomer X is different from VDF (that is, if X1 and X2 represent H, then at least one of X3 and X4 does not represent F, and if X1 and X2 represent F, then at least one of X3 and X4 does not represent H).

[0104] In some embodiments, each X1, X2, X3, and X4 group independently represents an H, F, Cl, I, or Br atom or optionally contains one or more methyl groups selected from F, Cl, I, and Br substituents.

[0105] In some embodiments, each X1, X2, X3, and X4 group independently represents an H, F, Cl, I, or Br atom.

[0106] In some embodiments, only one of X1, X2, X3, and X4 represents a Cl, I, or Br atom, and the other groups in the X1, X2, X3, and X4 groups independently represent: H or F atoms or C1-C3 alkyl groups optionally containing one or more fluorine substituents; preferably, H or F atoms or C1-C2 alkyl groups optionally containing one or more fluorine substituents; and more preferably, H or F atoms or methyl groups optionally containing one or more fluorine substituents.

[0107] Examples of monomer X are as follows: vinyl fluoride (VF), trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), trifluoropropylene, especially 3,3,3-trifluoropropylene, tetrafluoropropylene, especially 2,3,3,3-tetrafluoropropylene or 1,3,3,3-tetrafluoropropylene (cis or preferably trans), hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropylene, especially 1,1,3,3,3-pentafluoropropylene or 1,2,3,3,3-pentafluoropropylene, perfluoroalkyl vinyl ethers, especially those of general formula R f Those with -O-CF=CF2, R f It is an alkyl group, preferably a C1 to C4 alkyl group (preferred examples are perfluoropropyl vinyl ether or PPVE, and perfluoromethyl vinyl ether or PMVE).

[0108] In some embodiments, monomer X comprises a chlorine or bromine atom. It may be particularly selected from bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, and chlorotrifluoropropylene. Chlorofluoroethylene may represent 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene isomer (CFE) is preferred. Chlorotrifluoropropylene is preferably 1-chloro-3,3,3-trifluoropropylene (cis or trans, preferably trans) or 2-chloro-3,3,3-trifluoropropylene.

[0109] In some preferred embodiments, the polymer FP comprises units generated from VDF and HFP, or is a P(VDF-HFP) polymer composed of units also generated from VDF and HFP. Such polymer FPs are particularly useful for fabricating planarization or passivation layers for electronic devices.

[0110] The molar proportion of repeating units generated by HFP is preferably 2% to 50%, particularly 5% to 40%, relative to the total molar proportion of repeating units generated by VDF and HFP.

[0111] The P(VDF-HFP) copolymer can be specifically cited as described in documents WO 01 / 32726 and US 6 586 547.

[0112] In some preferred embodiments, the polymer FP comprises units generated from VDF and TFE, or is also a P(VDF-TFE) polymer composed of units generated from VDF and TFE. This polymer is typically used due to its piezoelectric properties.

[0113] The molar proportion of repeating units generated by TFE is preferably 8% to 30%, more preferably 15% to 28%, more preferably 18% to 25%, and extremely preferably 20% to 22%, relative to the total molar proportion of units generated by VDF and TFE.

[0114] In some embodiments, the polymer FP comprises units generated from VDF and the following: CFE, or CTFE, or TrFE.

[0115] In some preferred embodiments, the polymer FP comprises units generated from VDF and TrFE. This polymer FP is typically used to fabricate electroactive layers.

[0116] According to certain advantageous embodiments, polymer FP can be, in particular, polymer P (VDF-TrFE), that is, composed of units generated from VDF and TrFE. These polymers are commonly used in, for example, sensors, energy recovery devices, actuators, loudspeakers, or ferroelectric memories due to their piezoelectric, thermoelectric, and ferroelectric properties.

[0117] The molar proportion of repeating units generated by TrFE is preferably 15% to 50%, more preferably 17% to 35%, and more preferably 18% to 32.5%, relative to the total molar number of units generated by VDF and TrFE. This polymer is ferroelectric. The term "ferroelectric" should be understood to mean an electroactive polymer characterized by a hysteresis loop in the electric displacement-applied electric field curve. Its absolute value of the coercive field at 25 °C is typically less than 60 V / μm and greater than 40 V / μm. Its remanent polarization at 25 °C is quite high and can typically reach values ​​greater than 50 mC / m². The Curie temperature corresponds to the ferroelectric -> paraelectric (FE -> PE) crystal structure transformation, known as the Curie transformation.

[0118] The molar percentage of repeating units generated by TrFE can particularly have values ​​of 15% to 18%, or 18% to 22.5%, or 22.5% to 27.5%. According to a specific embodiment, the molar percentage of repeating units generated by TrFE is 18.0% to 22.5% relative to the total number of moles generated by VDF and TrFE.

[0119] The molar percentage of repeating units generated by TrFE may also be 27.5% to 32.5%, or 32.5% to 37.5%, or 37.5% to 42.5%, or 42.5% to 47.5%, or 47.5% to 50%, relative to the total number of moles of units generated by VDF and TrFE.

[0120] According to certain advantageous embodiments, polymer FP may comprise units derived from VDF, TrFE, and another monomer X, as defined above, which is different from VDF and TrFE; or it may be polymer P (VDF-TrFE-X) composed of units derived from VDF, TrFE, and another monomer X, as defined above, which is different from VDF and TrFE. In this case, preferably, the other monomer X is selected from TFE, HFP, trifluoropropylene, especially 3,3,3-trifluoropropylene, tetrafluoropropylene, especially 2,3,3,3-tetrafluoropropylene or 1,3,3,3-tetrafluoropropylene (cis or preferably trans), bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene, and chlorotrifluoropropylene.

[0121] CTFE or CFE is particularly preferred. This is because P(VDF-TrFE-CTFE) and P(VDF-TrFE-CFE) terpolymers are known to have high dielectric constants (“high k”), and their electrostrictive and electrothermal properties are also known, and they are used, for example, as “high k” dielectrics in organic thin-film transistors (OTFTs), actuators and electrothermal devices.

[0122] The molar proportion of units produced by TrFE is preferably 10% to 60%, more preferably 15% to 55%, and even more preferably 20% to 50%, relative to the total number of moles of units produced by VDF and TrFE.

[0123] In addition to VDF and TrFE, the molar proportion of units generated from another monomer X (in particular CTFE or CFE) relative to the molar number of units constituting polymer FP is preferably 0.05% to 15%, more preferably 2% to 12%.

[0124] According to certain embodiments, X is CTFE or CFE, and the molar ratio of X to the molar number of units constituting polymer FP is 4% to 10%. P(VDF-TrFE-CFE) and P(VDF-TrFE-CTFE) polymers having the above-mentioned ratios of TrFE and CFE or CTFE are relaxor ferroelectrics. The term "relaxor ferroelectric" is understood to mean an electroactive polymer characterized by relaxor ferroelectricity (RFE) over a wide temperature range. The paraelectric (PE) crystal transition occurs. At the level of this transition, a broad peak in the dielectric constant is observed, the temperature of which the maximum value depends on the frequency of the applied electric field: the lower the frequency of the electric field, the greater the shift of the maximum dielectric constant to lower temperatures. (RFE) At or slightly above the temperature of the (PE) transition, the application of an electric field allows for the generation and alignment of nanopole regions, causing a change in entropy and thus a significant electrothermal effect over a wide temperature range. Relaxor ferroelectric polymers at 25 °C and a frequency of about 1 Hz are characterized by a hysteresis loop as a function of the "applied electric field" curve, which is much finer than that of ferroelectric polymers. They typically have a coercive field of less than or equal to 45 V / μm and a remanent polarization of less than or equal to 40 mC / m².

[0125] In embodiments where X is CTFE or CFE, the molar percentage of units generated by CTFE or CFE may be particularly 0.05% to 0.5%, or 0.5% to 2%, or 2% to 3%, or 3% to 4%, or 10% to 12%, or 12% to 15%, relative to the number of moles of units constituting polymer FP.

[0126] The molar composition of units in fluoropolymers can be determined by various methods, such as infrared spectroscopy or Raman spectroscopy. Conventional methods for elemental analysis of carbon, fluorine, and chlorine or bromine or iodine, such as X-ray fluorescence spectroscopy, allow for the precise calculation of the polymer's weight composition, from which the molar composition can be derived.

[0127] Multinuclear NMR technology, especially proton NMR, can also be used. 1 H) and fluorine ( 19 FT-NMR techniques are performed by analyzing polymer solutions in suitable deuterated solvents. NMR spectra are recorded on an FT-NMR spectrometer equipped with multinuclear probes. The specific signals given by various monomers in the spectra produced by one or more nuclei are then located. Thus, for example, units produced by TrFE give a specific signal characteristic of the CFH group in proton NMR (e.g., at approximately 5-7 ppm when the solvent is pyridine). The same is true for the CH2 group of VDF (e.g., a broad unresolved peak between 2-4 ppm when the solvent is pyridine). The relative integral of the two signals gives the relative abundance of the two monomers, i.e., the VDF / TrFE molar ratio.

[0128] In the same manner, for example, the CF3 group gives characteristic and well-separated signals in fluorine NMR. The combination of relative integrals of the various signals obtained in proton NMR and fluorine NMR produces a set of equations, the analysis of which leads to the determination of the molar concentrations of units produced by various monomers.

[0129] Finally, elemental analysis (e.g., for heteroatoms such as chlorine, bromine, or iodine) can be combined with NMR analysis. Thus, for example, in a P(VDF-TrFE-CTFE) terpolymer, the content of units generated by CTFE can be determined by elemental analysis to measure the chlorine content.

[0130] Therefore, those skilled in the art can use a variety of methods or combinations of methods to enable them to determine the composition of fluoropolymers precisely and with the necessary accuracy.

[0131] Polymer FP is preferably random. Polymer FP is preferably linear.

[0132] Polymer FP can be produced using any known method, such as emulsion polymerization, suspension polymerization, and solution polymerization.

[0133] When the fluoropolymer comprises units generated from VDF and / or TrFE and another monomer X as described above, the method described in document WO 2010 / 116105 is preferred. This method allows for the acquisition of polymers with high molecular weight and suitable structure.

[0134] In short, the preferred method includes the following stages:

[0135] - The initial mixture containing only VDF and / or TrFE (without the other monomer X) is loaded into a stirred autoclave containing water;

[0136] - Heat the autoclave to a predetermined temperature close to the polymerization temperature;

[0137] - A free radical polymerization initiator mixed with water is injected into an autoclave to achieve a pressure preferably at least 80 bar in the autoclave, thereby forming a suspension of VDF and / or TrFE monomers in water;

[0138] - Inject a second mixture of VDF and / or TrFE and X into the autoclave;

[0139] - Once the polymerization reaction begins, the second mixture is continuously injected into the autoclave reactor in order to maintain the pressure at a substantially constant level, preferably at least 80 bar.

[0140] The free radical polymerization initiator can be an organic peroxide of the dicarbonate type. It is typically used in an amount of 0.1 to 10 g per kilogram of total monomer charge. Preferably, the amount used is 0.5 to 5 g / kg.

[0141] The initial mixture advantageously contains only VDF and / or TrFE in proportions equal to the desired final polymer.

[0142] The second mixture advantageously has a regulated composition such that the total composition of the monomers introduced into the autoclave (including the initial mixture and the second mixture) is equal to or approximately equal to the composition of the desired final polymer.

[0143] The weight ratio of the second mixture to the initial mixture is preferably 0.5 to 2, more preferably 0.8 to 1.6.

[0144] Implementing this method using the initial mixture and the second mixture allows the process to proceed independently of the initiation phase of the reaction, which is typically unpredictable. The resulting polymer is in powder form, without a shell or skin.

[0145] The pressure in the autoclave reactor is preferably 80 to 110 bar, and the temperature is preferably maintained at 40 °C to 60 °C.

[0146] The second mixture can be continuously injected into the autoclave. It can be compressed before being injected into the autoclave, for example, using a compressor or two compressors in succession, typically to a pressure greater than that in the autoclave.

[0147] After synthesis, the polymer can be washed and dried.

[0148] The weight-average molar mass (Mw) of polymer FP is preferably at least 100,000 g·mol⁻¹. -1 Preferably at least 200,000 g / mol -1 More preferably at least 300,000 g·mol -1 Or at least 400,000 g·mol -1 It can be adjusted by changing certain parameters of the method (e.g., temperature in the reactor) or by adding a transfer agent. Molecular weight distribution can be estimated by SEC (size exclusion chromatography) using dimethylformamide (DMF) as the eluent, with a set of three columns exhibiting increased porosity. The stationary phase is a styrene-DVB gel. The detection process is based on refractive index measurements and calibrated using polystyrene standards. The sample is dissolved in DMF at 0.5 g / L and filtered through a 0.45 μm nylon filter.

[0149] Adhesion-promoting polymer additives (APA)

[0150] Polymer APA is a suitable polymer designed to improve the adhesion of fluoropolymers to substrates by being added as an additive. This polymer comprises units produced by the polymerization of methyl methacrylate (MMA) to achieve good affinity between the fluoropolymer FP chain and the polymer chain of the additive APA.

[0151] Specifically, poly(methyl methacrylate) is known to have good affinity with fluoropolymers, especially poly(vinylidene fluoride), and poly(methyl methacrylate) is even miscible with poly(vinylidene fluoride) in all proportions (negative Flory-Huggins parameter χ between PVDF and PMMA).

[0152] Advantageously, the Flory-Huggins parameter χ between the fluoropolymer FP (especially PVDF) and the additive APA is less than or equal to 0.5, preferably less than or equal to 0. In the case where the polymer APA is a block polymer, it is one of the blocks, and according to some embodiments, all the blocks, having a Flory-Huggins parameter χ that is strictly less than 0.5, preferably strictly less than 0, compared to that of the fluoropolymer FP, especially PVDF.

[0153] The proportion of units produced by methyl methacrylate relative to the total weight of the polymer with additive APA is typically at least 40% by weight.

[0154] According to an advantageous embodiment, the proportion of units generated from methyl methacrylate can be at least 50%, preferably at least 70%, of the total weight of the polymer APA. The proportion of units generated from methyl methacrylate relative to the total weight of the polymer APA can particularly be at least 55%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90%, by weight.

[0155] According to a particular embodiment, the proportion of units produced from methyl methacrylate relative to the total weight of the polymer APA can be at least 90% by weight. Specifically, the proportion of units produced from methyl methacrylate relative to the total weight of the polymer APA can be at least 91%, or at least 92%, or at least 93%, or at least 94%, or at least 95% by weight.

[0156] The additive APA contains at least one functional group designed to improve adhesion to the substrate (particularly by grafting onto the surface of the substrate), referred to in this invention as a graftable functional group.

[0157] The at least one graftable functional group is arranged at at least one end of the polymer chain of the additive APA.

[0158] Grafting involves forming strong interactions between the substrate and the additive APA, particularly through the formation of covalent bonds.

[0159] The additive APA is preferably a linear polymer with two ends.

[0160] The additive APA can be a random or gradient copolymer, or a block copolymer.

[0161] The term “random copolymer” should be understood to mean a copolymer produced by the polymerization of at least two monomers, wherein the distribution of monomer units along the chain follows a random law, such as Bernoulli (zero-order Markov) or first- or second-order Markov type.

[0162] The term "gradient copolymer" should be understood to mean a copolymer produced by the polymerization of at least two monomers, which is typically obtained through the following:

[0163] Living or pseudo-living polymerization, such as NMP polymerization given below. With these polymerization methods, the polymer chains grow simultaneously, thus incorporating the same proportion of comonomers at each moment. Therefore, the distribution of comonomers in the polymer chains depends on the change in the relative concentration of comonomers during synthesis.

[0164] The term "block copolymer" should be understood as a copolymer produced by the polymerization of at least two monomers, comprising one or more monomers.

[0165] Each distinct polymer entity is an uninterrupted sequence of polymeric entities that are chemically distinct from one another and are linked together by chemical (covalent, ionic, hydrogen, or coordination) bonds.

[0166] According to certain implementations, the term "group disposed at one end of a polymer chain" may mean that the group is located at the end of the polymer chain.

[0167] The graftable functional group can be located at one end, two ends, several ends, or all ends of the polymer chain. In the preferred case where the polymer is a straight chain, the graftable functional group can be located at one or two ends of the polymer chain.

[0168] Preferably, the polymer chain contains no graftable functional groups other than the at least one graftable functional group disposed at one, two, several, or all ends of the polymer chain. In a preferred embodiment where the polymer is linear, the at least one graftable functional group may be disposed at a single end of the polymer chain, and the polymer chain contains no other graftable functional groups other than the at least one graftable functional group disposed at a single end of the polymer chain. In a preferred embodiment where the polymer is linear, the at least one graftable functional group may be disposed at both ends of the polymer chain, and the polymer chain contains no other graftable functional groups other than the at least one graftable functional group at both ends of the polymer chain.

[0169] The at least one graftable functional group disposed at at least one end of the polymer chain of the additive APA can be introduced by a polymerization initiator (as illustrated in this patent application) and / or a chain restrictor or end-capping agent.

[0170] In the case of block polymers, a set of graftable functional groups can be introduced at at least one end of the polymer chain of additive APA using repeating units having at least one graftable functional group in small-sized blocks "A". The block polymer can be, in particular, of the AB or ABA type, where block "A" comprises repeating units containing at least one graftable functional group and block "B" has good affinity for the fluoropolymer FP.

[0171] At least one graftable functional group disposed at at least one end of the polymer chain of the additive APA may advantageously be selected from: nitro group, carboxyl group, hydroxyl group, mercapto group, silyl group, alkoxysilyl group, alkylsilyl group, sulfonic acid group, phosphate group, phosphonic acid group and hypophosphonic acid group.

[0172] According to certain embodiments, at least one graftable functional group disposed at one end of the polymer chain of the additive APA may be a nitro group.

[0173] According to certain embodiments, at least one graftable functional group disposed at one end of the polymer chain of the additive APA may be selected from: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid, and hypophosphonic acid.

[0174] According to a preferred embodiment, at least one graftable functional group disposed at one end of the polymer chain of the additive APA may be selected from: hydroxyl, carboxyl and phosphonic acid.

[0175] According to a specific implementation scheme, at least one graftable functional group disposed at one end of the polymer chain of the additive APA is selected from hydroxyl and carboxyl groups.

[0176] According to certain embodiments, the additive APA contains at least one graftable functional group at one end of its chain, particularly a single graftable functional group, which is a hydroxyl group.

[0177] According to certain embodiments, the additive APA contains at least one graftable functional group at one end of its chain, particularly a single graftable functional group, which is a carboxyl group.

[0178] According to certain implementations, the additive APA contains a graftable functional group as a hydroxyl group and a graftable functional group as a carboxyl group at the same end of its chain.

[0179] According to certain implementations, the additive APA contains a nitro group at one end of its chain and does not contain other graftable functional groups.

[0180] According to certain embodiments, the additive APA contains a nitro group at one end of its chain and at the other end of its chain at at least one graftable functional group selected from the following: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and hypophosphonic acid.

[0181] According to certain embodiments, the additive APA contains a nitro group at one end of its chain and at the other end of its chain at at least one graftable functional group selected from the following: hydroxyl, carboxyl and phosphonic acid.

[0182] According to certain embodiments, the additive APA contains a nitro group at one end of its chain and at the other end of its chain at at least one graftable functional group selected from the following: hydroxyl and carboxyl groups.

[0183] According to certain embodiments, the additive APA contains a nitro group at one end of its chain and a single graftable functional group, which is a hydroxyl group, at the other end of its chain.

[0184] According to certain embodiments, the additive APA contains a nitro group at one end of its chain and a single graftable functional group, which is a carboxyl group, at the other end of its chain.

[0185] According to certain embodiments, the additive APA contains a nitro group at one end of its chain and a graftable functional group as a hydroxyl group and a graftable functional group as a carboxyl group at the other end of its chain.

[0186] According to certain embodiments, the additive APA may contain at least one other repeating unit that is different from the repeating unit produced by the polymerization of methyl methacrylate.

[0187] According to certain embodiments, the additive APA may specifically comprise at least one repeating unit containing the at least one graftable functional group. These embodiments particularly relate to the case where the polymer APA is a block polymer, especially an AB or ABA type block polymer, wherein each block A independently comprises the at least one repeating unit containing the at least one graftable functional group, and block B has a good affinity for the fluoropolymer FP. Advantageously, the at least one repeating unit containing the at least one graftable functional group does not contain a crosslinkable functional group. In particular, it does not contain ethylene oxide, aziridine, or thiapropyl ring type groups, or carbon-carbon double bonds, or carbon-carbon triple bonds.

[0188] In these embodiments, block B advantageously has a Flory-Huggins parameter χ of less than or equal to 0.5, preferably less than or equal to 0, with respect to the fluoropolymer FP. Block B preferably comprises at least 70% by weight of repeating units derived from methyl methacrylate, relative to the total weight of block B. The proportion of units derived from methyl methacrylate in block B can particularly be at least 55%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90% by weight, relative to the total weight of block B. According to a particular embodiment, the proportion of units derived from methyl methacrylate in block B can be at least 91%, or at least 92%, or at least 93%, or at least 94%, or at least 95% by weight, relative to the total weight of block B. Block B preferably does not contain repeating units containing graftable functional groups.

[0189] In these embodiments, block A comprises less than 50% by weight of the total weight of the block polymer APA. Block A may comprise less than 40%, or less than 30%, or less than 25%, or less than 20%, or less than 15%, or less than 10% by weight of the total weight of the block polymer APA. In some embodiments, the at least one repeating unit comprising the at least one graftable functional group may comprise less than 20%, or less than 15%, or less than 10%, or less than 5% by weight of the total weight of the block polymer APA.

[0190] Advantageously, block A independently has a lower affinity for the fluoropolymer FP than block B. The proportion of units derived from methyl methacrylate in each block A may be less than 25%, less than 20%, less than 15%, less than 10%, or less than 5% by weight of the total weight of said block A. Block A may independently contain no repeating units derived from methyl methacrylate. According to some embodiments, block A independently has a Flory-Huggins parameter χ with the fluoropolymer FP that is strictly greater than 0.5.

[0191] According to certain embodiments, the repeating unit containing the at least one graftable functional group may be particularly selected from acrylic, methacrylic, or non-(meth)acrylic vinyl monomers. It may be particularly selected from: acrylic acid or its salts, hydroxyalkyl acrylates, such as 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate, silylated acrylates, phosphorus-containing acrylates, such as alkylene glycol phosphate acrylates, methacrylic acid or its salts, hydroxyalkyl methacrylates, such as 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate, silylated methacrylates, such as (3-methacryloyloxypropyl)trimethoxysilane, (3-methacryloyloxypropyl)methyldimethoxysilane, methacryloyloxymethyltrimethoxysilane, or (3-methacryloyloxypropyl)trimethoxysilane. Propyl)tris(2-methoxyethoxy)silane, phosphorus-containing methacrylates, such as alkylene glycol phosphate methacrylates, non-methyl (acrylic) silylated vinyl monomers, such as vinyltrimethoxysilane, vinyldimethoxymethylsilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltri(methoxyethoxy)silane, vinyltributoxysilane, vinyltriacetoxysilane, vinyltrichlorosilane, vinylmethyldichlorosilane, vinyltri(2-methoxyethoxy)silane, and silylated styrene monomers.

[0192] According to certain embodiments, the repeating unit containing the at least one graftable functional group may be particularly selected from acrylic acid or a salt thereof, hydroxyalkyl acrylates (e.g., 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate), methacrylic acid or a salt thereof, and hydroxyalkyl methacrylates (e.g., 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate).

[0193] When the additive APA is a random or gradient polymer, the at least one repeating unit other than the repeating unit produced by methyl methacrylate preferably does not contain graftable functional groups.

[0194] According to certain embodiments, the at least one other repeating unit, unlike the repeating unit produced by methyl methacrylate, does not contain graftable functional groups.

[0195] Such repeating units may be specifically selected from vinyl aromatic monomers, such as styrene or substituted styrene, particularly α-methylstyrene, tert-butylstyrene, o-, m-, or p-methylstyrene, o-, m-, or p-ethylstyrene or o-methyl-p-isopropylstyrene, alkyl acrylates, cycloalkyl acrylates, or aryl acrylates, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, ethylhexyl acrylate, or phenyl acrylate, alkyl ether acrylates, such as 2-methoxyethyl acrylate, alkoxy- or aryloxy polyalkylene glycol acrylates, such as methoxy polyethylene glycol acrylate, ethoxy polyethylene glycol acrylate, methoxy polypropylene glycol acrylate, or methoxy polyethylene glycol-polypropylene glycol acrylate, fluorinated acrylates, and isobornyl acrylate. 4-(tert-butyl)cyclohexyl acrylate, alkyl methacrylates, cycloalkyl methacrylates, alkenyl methacrylates, or aryl methacrylates, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, allyl methacrylate, phenyl methacrylate, or naphthyl methacrylate, alkyl methacrylates, such as 2-ethoxyethyl methacrylate, alkoxy- or aryloxy polyalkylene glycol methacrylates, such as methoxy polyethylene glycol methacrylate, ethoxy polyethylene glycol methacrylate, methoxy polypropylene glycol methacrylate, or methoxy polyethylene glycol-polypropylene glycol methacrylate, and fluorinated methacrylates, such as 2,2,2-trifluoroethyl methacrylate.

[0196] Advantageously, the at least one other repeating unit, unlike the repeating unit produced from methyl methacrylate that does not contain graftable functional groups, also does not contain crosslinkable functional groups. In particular, it does not contain ethylene oxide, aziridine, or thiapropyl ring type groups, or carbon-carbon double bonds, or carbon-carbon triple bonds. For example, the at least one other repeating unit, unlike the repeating unit produced from methyl methacrylate that does not contain functional groups, is advantageously not a unit produced from glycidyl methacrylate.

[0197] According to certain embodiments, the at least one other repeating unit, which is different from the repeating unit produced by methyl methacrylate and does not contain a repeating unit that can be grafted with functional groups, accounts for less than 50%, or less than 40%, or less than 30%, or less than 25%, or less than 20%, or less than 15% by weight relative to the total weight of the polymer APA.

[0198] According to certain embodiments, the additive APA is a polymer that is substantially composed of or consists of: repeating units generated from methyl methacrylate, optionally at least one repeating unit different from methyl methacrylate and not containing graftable functional groups, and optionally at least one repeating unit different from methyl methacrylate containing graftable functional groups.

[0199] According to a specific embodiment, the additive APA is a block polymer, particularly an ABA or AB type block polymer, wherein:

[0200] - Each of the blocks A independently contains at least one repeating unit containing at least one graftable functional group;

[0201] - Each block A accounts for less than 25%, or less than 20%, or less than 15%, or less than 10%, or less than 5% by weight of the units produced from methyl methacrylate, relative to the total weight of said block A.

[0202] - Block B does not contain any repeating units containing graftable functional groups;

[0203] - The proportion of units derived from methyl methacrylate in block B is at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90% by weight, relative to the total weight of block B; and

[0204] - Block A accounts for less than 50% of the total weight of the block polymer APA.

[0205] According to a specific embodiment, the additive APA is a random or gradient polymer consisting essentially of: repeating units derived from methyl methacrylate and at least one repeating unit different from methyl methacrylate and not containing graftable functional groups.

[0206] The additive APA can be, for example, a random or gradient polymer composed of repeating units derived from methyl methacrylate and styrene, wherein the weight percentage of the repeating units derived from styrene is 0.5% to 15% of the total weight of the repeating units derived from methyl methacrylate and styrene, preferably 1.0% to 10%.

[0207] Advantageously, the number-average molar mass of the additive APA is from 1,000 g / mol to 100,000 g / mol, preferably from 2,000 g / mol to 50,000 g / mol. The molecular weight distribution can be estimated by SEC using polystyrene standards.

[0208] Additive APA can be used using any polymerization technique known to those skilled in the art. It is typically manufactured through the following methods:

[0209] Free radical polymerization, preferably controlled radical polymerization. Within controlled radical polymerization techniques, NMP (nitrogen oxide-mediated polymerization) and RAFT (Rapid Reduction Polymerization) can be mentioned.

[0210] (Reversible addition and fracture transfer), ATRP

[0211] (Atom transfer radical polymerization), INIFERTER

[0212] (Initiator-Transfer-Termination) and RITP (Reverse Iodine)

[0213] (Transfer aggregation).

[0214] According to an advantageous embodiment, the additive APA can be manufactured via NMP, i.e., by oxynitride-mediated radical polymerization using an alkoxyamine with at least one graftable functional group. This synthetic technique is well known to those skilled in the art and is described, for example, in EP 1 468 029 and EP 1 526 138. Block polymers containing MMA as repeating units are commercially available under the name Nanostrength® (Arkema).

[0215] Alkoxyamines

[0216] Alkoxyamines have the following chemical formula:

[0217] [Chemical Formula 3]

[0218] (I)

[0219] in:

[0220] -R1 is a cyclic or acyclic hydrocarbon group with or without heteroatoms, and may contain at least one metallic entity;

[0221] -R2 is a cyclic or acyclic hydrocarbon group with or without heteroatoms, and may contain at least one metallic entity;

[0222] -R1 and R2 may or may not form part of the same ring structure;

[0223] -Z is a cyclic or acyclic monovalent hydrocarbon group, with or without heteroatoms.

[0224] According to a favorable implementation scheme, Z contains graftable functional groups.

[0225] Preferably, the alkoxyamine is selected from those whose nitrogen oxide (also known as the control agent fragment):

[0226] -Nitrogen oxides of the following formula:

[0227] , ,

[0228] (Where R=H, alkyl fragment, SO2-Ph, SO2Me, Na, K),

[0229] , , , ,

[0230] (where R = Me, Et),

[0231] (where R = Me, Et),

[0232] , ,

[0233] (where R = H, Me),

[0234] , , , ,

[0235] , , ,

[0236] (where R = Me, Et),

[0237] (where R = Me, Et),

[0238] , , , , (where R = Me, Et),

[0239]

[0240] (where R = Me, Et),

[0241] ,

[0242] (where R = Me, Et),

[0243] (where R = H, CF3, NMe2),

[0244] (where R = Me, Et),

[0245] ,

[0246] , ,

[0247] (where R = Me, Et),

[0248] , , ,

[0249] , , ,

[0250] ,

[0251] (where R = H, CH3, nC4H9, CH2-Ph),

[0252] ,

[0253] (where R = H, CH3, Ph),

[0254] , , ,

[0255] (where R = H or alkyl),

[0256] , , ,

[0257] , , , , , ,

[0258] , , , , ,

[0259] (where R = OH or OTMS),

[0260] , , ,

[0261] , , ,

[0262] , , ,

[0263] , , ,

[0264] , , ,

[0265] (where R = H or Me), , , ,

[0266] , , , ,

[0267] , , ,

[0268] ,

[0269] (where R = Eth, IPr, or CHex),

[0270] , ,

[0271] , , ,

[0272] ,

[0273] (where R = H, NO2),

[0274] (where R = H, Et),

[0275] ,

[0276] , , ,

[0277] , ;

[0278] -(2,2,6,6-Tetramethylpiperidin-1-yl)oxy or (2,2,6,6-Tetramethylpiperidin-1-yl)oxy

[0279] -N-tert-butyl-1-phenyl-2-methylpropyl nitride,

[0280] -N-(2-hydroxymethylpropyl)-1-phenyl-2-methylpropyl nitride,

[0281] -N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl oxynitride

[0282] -N-tert-butyl-1-bis(2,2,2-trifluoroethyl)phosphono-2,2-dimethylpropyl oxynitride

[0283] -N-tert-butyl-1-diethylphosphono-2-methylpropyl nitride

[0284] -N-(1-methylethyl)-1-cyclohexyl-1-(diethylphosphono)nitrogen oxide,

[0285] -N-(1-Phenylenyl)-1-Diethylphosphono-1-methylethyl oxyoxide,

[0286] -N-phenyl-1-diethylphosphono-2,2-dimethylpropyl oxynitride

[0287] -N-phenyl-1-diethylphosphono-1-methylethyl nitrogen oxide,

[0288] -N-(1-Phenyl-2-methylpropyl)-1-diethylphosphonomethylethyl oxynitride,

[0289] - and N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl oxynitride.

[0290] The latter nitrogen oxide is a preferred nitrogen oxide for the polymerization of repeating units of acrylic or methacrylic acids. A commercially available alkoxyamine containing this nitrogen oxide is N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxypropyl-2-yl)hydroxylamine, which has the following formula (II) as its expanded form:

[0291] [Chemical Formula 4]

[0292] (II)

[0293] This compound is sold by Arkema under the name Blocbuilder®.

[0294] The above-mentioned alkoxyamine derivatives, particularly those of formula (I), can be obtained by reacting an equivalent of the alkoxyamine with an acrylic, methacrylic, or vinyl aromatic monomer having at least one graftable functional group. These monomers are particularly selected from: silylated styrene, acrylic acid and its salts, hydroxyalkyl acrylates, especially C2-C acrylic acid. 10 Hydroxyalkyl esters and, for example, 2-hydroxyethyl acrylate, phosphorus-containing acrylates such as alkylene glycol phosphate acrylates, silanized acrylates, methacrylic acid and its salts, hydroxyalkyl methacrylates, especially C2-C methacrylic acid. 10 Hydroxyalkyl esters and, for example, 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, and methacrylates such as (3-methacryloylpropyl)trimethylsilane.

[0295] Composition

[0296] The composition contains at least one (i.e., one or more) fluoropolymer FP and at least one (i.e., one or more) additive APA.

[0297] The composition may specifically contain a single type of fluoropolymer and a single type of additive APA.

[0298] The weight ratio of additive APA to fluoropolymer FP in the composition is 0.005% to 5%. It should be understood that if the composition contains multiple additives APA and multiple fluoropolymers, the weight ratios are expressed by taking into account the total weight of additive APA and the total weight of fluoropolymers, respectively.

[0299] For the sake of brevity and clarity, in the sections concerning the composition, the qualifiers "an," "a," and "the" are used before "additive APA" and "fluoropolymer FP." Unless otherwise stated, they implicitly refer to "at least one" and "the at least one" additive APA and "at least one" and "the at least one" fluoropolymer FP. According to a particular embodiment, they include cases where the composition contains only a single type of fluoropolymer and / or a single type of additive APA.

[0300] The weight percentage of additive APA relative to polymer FP in the composition can be particularly 0.005% to 0.01%, or 0.01% to 0.05%, or 0.05% to 0.1%, or 0.1% to 0.3%, or 0.3% to 0.5%, or 0.5% to 0.7%, or 0.7% to 0.9%, or 0.9% to 1.0%, or 1.0% to 2.0%, or 2.0% to 3.0%, or 3.0% to 4.0%, or 4.0% to 5.0%. Ranges of 0.01% to 3.0% and 0.05% to 2.0% of polymer additive APA constitute examples of preferred ranges.

[0301] Advantageously, the additive APA is present in a weight ratio of 0.01% or more, and preferably 0.05% or more, of the polymer FP in the composition, in order to significantly improve the adhesion of the fluoropolymer FP.

[0302] Advantageously, the weight proportion of additive APA relative to the polymer FP in the composition is kept as low as possible so as to have the least possible impact on the useful properties of the fluoropolymer FP. It can particularly be 3.0% or less, preferably 2.0% or less.

[0303] Polymer FP and additive APA can be dissolved in solvents or solvent mixtures.

[0304] The term "solution" should be understood as a homogeneous dispersion of components at the molecular level in a solvent. As used herein, "solution" is contrasted with a suspension of polymer particles in a liquid carrier and with a polymer emulsion or latex.

[0305] Preferably, the solvent is selected from: dimethylformamide; N-methyl-2-pyrrolidone; dimethylacetamide; dimethyl sulfoxide; γ-butyrolactone; ketones, especially acetone, methyl ethyl ketone (or but-2-one), methyl isobutyl ketone, cyclopentanone, cyclohexanone, or diisobutyl ketone; furans, especially tetrahydrofuran; esters, especially methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, and ethyl acetoacetate; carbonates, especially dimethyl carbonate and propylene carbonate; and phosphates, especially trimethyl phosphate and triethyl phosphate. Mixtures of these compounds may also be used.

[0306] According to some implementation schemes, the solvent may be N-methyl-2-pyrrolidone.

[0307] According to certain embodiments, the solvent may be selected from the list of the following compositions: dimethylformamide, N-methyl-2-pyrrolidone, dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, diisobutyl ketone, tetrahydrofuran, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, ethyl acetoacetate, dimethyl carbonate, propylene carbonate, trimethyl phosphate, and triethyl phosphate. Mixtures of these compounds may also be used.

[0308] The composition in solution form preferably contains 0.1% to 60% by weight, more preferably 0.5% to 30% by weight, more preferably 1% to 20% by weight, and extremely preferably 3% to 15% by weight of non-volatile solids.

[0309] The composition may optionally contain one or more additives other than additive APA, particularly selected from surface tension modifiers, rheology modifiers, aging resistance modifiers, pigments or dyes, or fillers (including nanofillers). These other additives generally constitute less than 10% by weight, preferably less than 5%, and more preferably less than 1% relative to the polymer FP.

[0310] According to certain embodiments, the composition consists essentially of or comprises at least one fluoropolymer and at least one additive APA. The composition may optionally contain one or more other additives different from the additive APA.

[0311] According to certain embodiments, the composition comprises essentially, or comprises, at least one fluoropolymer, at least one additive APA, and one or more miscible solvents. The composition may optionally contain one or more other additives different from the additive APA.

[0312] Preparation of compositions in solution form

[0313] The composition in solution can be prepared by dissolving polymer FP, by dissolving additive APA, and by mixing. As described below, the dissolution of polymer FP and APA may or may not be simultaneous.

[0314] The temperature applied during this preparation is preferably from 0 °C to 60 °C, more preferably from 10 °C to 50 °C, even more preferably from 15 °C to 40 °C, and ideally from 20 °C to 30 °C. In some embodiments, the preparation is carried out at ambient temperature. Advantageously, the preparation is carried out with gentle stirring.

[0315] In some alternative forms, polymer FP is dissolved in a solvent on one hand, and polymer APA is dissolved in the same solvent on the other hand, and then the two solutions are mixed. The solvent used can be formed from a single compound or from a mixture of miscible compounds.

[0316] In other alternative forms, one of polymers FP and APA is dissolved in a solvent, and then the other of polymers FP and APA is added to the solution and dissolved sequentially. The solvent used can be formed from a single compound or from a mixture of miscible compounds.

[0317] In other alternative forms, the solvent of the composition is a mixture of a first solvent and a second solvent of different miscible compositions. Polymer FP is dissolved in the first solvent to form a first solution, polymer APA is dissolved in the second solvent to form a second solution, and then the first and second solutions are mixed to form the composition in solution form. The first and second solvents can each be formed from a single compound or from a mixture of miscible compounds. For example, the first and second solvents can each be formed from a mixture of the same compounds, wherein the proportions of the first and second solvents are different.

[0318] When additives different from polymer additive APA must be added to form a composition in solution, they can be added before, during, or after the dissolution of polymer FP and polymer additive APA.

[0319] The miscibility of solvent compounds or solvents is confirmed by the clear and homogeneous solution obtained after mixing at the preparation temperature used (and preferably at ambient temperature).

[0320] If needed, fluoropolymer solutions with added polymer APA can typically be stored for days to weeks or months because polymer APA does not a priori degrade the fluoropolymer chains, as shown in Example 5.

[0321] Method for preparing coatings on substrates

[0322] The substrate on which the composition can be deposited can be an electrical conductor, an electrical insulator, or a semiconductor. The substrate can in particular be a glass, or silicon, or quartz, or a polymer material (especially polyethylene terephthalate, polyethylene naphthalate, PEDOT-PSS), or a metal surface, or a mixed surface composed of several different materials.

[0323] According to certain preferred alternatives, the substrate is or comprises a metallic M surface, including gold, silver, chromium, aluminum, copper, lithium, zinc, nickel, cobalt, manganese, and alloys thereof. According to certain preferred alternatives, the substrate is or comprises an oxide surface having functional groups of the -M-OH type, where M represents a metal atom, which may be, in particular, gold, silver, chromium, aluminum, copper, lithium, zinc, nickel, cobalt, manganese, and alloys thereof.

[0324] According to certain preferred alternatives, the substrate is or includes a surface containing silanol-SiOH functional groups, particularly a glass or silicon surface.

[0325] Applying the composition to form a coating may include spreading in a discrete or continuous manner. Deposition may be carried out, in particular, by spin coating, by spraying, by coating with a bar or film coater (bar coating), by slot coating, by dip coating, by roll-to-roll printing, by screen printing, by flexographic printing, by offset printing, by inkjet printing, by electrospinning, or by extrusion.

[0326] According to a particular embodiment, the deposition of a solvent-free composition can be carried out by extrusion.

[0327] According to a particular embodiment, the deposition of the composition in solution form can be carried out by coating, particularly with a bar or film coater (bar coating) or by screen printing.

[0328] When the composition is applied in solution form, the solvent must evaporate after deposition. Evaporation can be carried out at ambient temperature (23 °C) and / or by heating to a temperature preferably in the range of 50 °C to 150 °C. The layer can be ventilated to promote evaporation. The evaporation duration can be, for example, from 1 minute to 24 hours, preferably from 2 minutes to 5 hours, more preferably from 3 minutes to 2 hours. The evaporation duration can be particularly less than 1 hour. The evaporation duration can be particularly 30 minutes or less, or 20 minutes or less, or 15 minutes or less, or 10 minutes or less.

[0329] The resulting coating can have a thickness on the order of 1 μm to millimeters. This thickness can be obtained by a single deposition according to one of the methods described above or by iterative layer deposition using at least one of the methods described above.

[0330] According to some embodiments, the coating thickness is from 1 μm to 100 μm. Specifically, the coating thickness can be from 1 µm to 10 µm, or from 10 µm to 50 µm, or from 50 µm to 100 µm. The coating can particularly be provided in the form of a film of substantially constant thickness.

[0331] According to some embodiments, the coating thickness is from 100 μm to 1000 μm. The coating thickness can particularly be from 100 µm to 250 µm, or from 250 µm to 500 µm, or from 500 µm to 1000 µm. The coating can particularly be provided in the form of a layer of substantially constant thickness.

[0332] According to some implementations, the coating thickness is strictly greater than 1000 µm, for example, 1 to 2 mm.

[0333] After forming a coating comprising a fluoropolymer and an additive APA on a substrate, one or more annealing stages may be performed. Annealing specifically allows for the grafting of the additive APA to the substrate (if appropriate, an increase in grafting) and / or increases in the crystallization of the fluoropolymer. Annealing stages may be performed independently of each other at temperatures ranging from 80 °C to 220 °C. The temperature for each annealing may be specifically 80 °C to 100 °C, or 100 °C to 120 °C, or 120 °C to 150 °C, or 150 °C to 160 °C, or 160 °C to 170 °C, or 170 °C to 180 °C, or 180 °C to 190 °C, or 190 °C to 200 °C, or 200 °C to 220 °C. The duration of each annealing cycle can range from, for example, 1 minute to 2 hours, and is preferably from 2 minutes to 30 minutes. It should be understood that, generally, the higher the annealing temperature, the more the annealing duration can be reduced. The duration of each annealing cycle can be 30 minutes or less, or 20 minutes or less, or 10 minutes or less. The duration of each annealing cycle can be 1 minute or more, 2 minutes or more, or 3 minutes or more.

[0334] Annealing can be performed in a single stage by subjecting the deposited layer to temperatures of 80 °C to 220 °C, preferably 90 °C to 200 °C, more preferably 100 °C to 180 °C, even more preferably 110 °C to 160 °C, and particularly 120 °C to 150 °C. The duration of this single annealing can be, for example, from 1 minute to 2 hours, preferably from 2 minutes to 30 minutes. The duration of this single annealing can be 30 minutes or less, or 20 minutes or less, or 10 minutes or less. The duration of this single annealing can be 1 minute or longer, 2 minutes or longer, or 3 minutes or longer. According to some embodiments, single annealing is performed at a temperature of 150 °C or lower for a duration of 30 minutes or less, 20 minutes or less, or 10 minutes or less.

[0335] Annealing can also be performed in several stages, such as two stages. The first annealing can be performed at a high temperature of greater than 150 °C to 200 °C. The second annealing can be performed at a lower temperature of 100 °C to 150 °C. In this embodiment, the duration of each annealing can be, for example, 30 seconds to 1.5 hours, preferably 45 seconds to 1 hour, more preferably 1 minute to 30 minutes. The duration of the first annealing can be, for example, 30 seconds to 30 minutes, preferably 1 minute to 15 minutes. The duration of the first annealing can be 15 minutes or less, or 10 minutes or less, or 5 minutes or less. The duration of the second annealing can be, for example, 1 minute to 1.5 hours, preferably 2 minutes to 30 minutes. The duration of the second annealing can be 20 minutes or less, or 15 minutes or less, or 10 minutes or less.

[0336] Therefore, grafting can be carried out in one or more stages, by heating during solvent evaporation (when the composition is applied in solution form) and / or during at least one annealing stage. Grafting can be carried out, in particular, by one or more heating stages at temperatures from 50 °C to 220 °C, preferably from 80 °C to 200 °C. For each heating, the temperature range can be selected from the following ranges: 50 °C to 80 °C, or 80 °C to 100 °C, or 100 °C to 120 °C, or 120 °C to 150 °C, or 150 °C to 160 °C, or 160 °C to 170 °C, or 170 °C to 180 °C, or 180 °C to 190 °C, or 190 °C to 200 °C, or 200 °C to 220 °C. According to certain embodiments, grafting can be carried out in one or more stages by heating to a temperature of less than or equal to 200°C, preferably less than or equal to 160°C, more preferably less than or equal to 120°C.

[0337] The graft can last from 1 minute to 6 hours, preferably less than 5 hours, more preferably less than 4 hours, more preferably less than 3 hours, more preferably less than 2 hours, and more preferably less than 1 hour. The graft can particularly last for 45 minutes or less, 30 minutes or less, 20 minutes or less, 15 minutes or less, or 10 minutes or less.

[0338] According to certain implementations, grafting can be performed by one or more heating stages at a temperature of less than or equal to 200 °C, and preferably less than or equal to 160 °C, and even more preferably less than or equal to 120 °C, for a total duration of 45 minutes or less, preferably 30 minutes or less, preferably 20 minutes or less, preferably 15 minutes or less, and even more preferably 10 minutes or less.

[0339] According to a particular implementation, grafting can be performed in one or more heating stages at a temperature of less than or equal to 160 °C for a total duration of less than or equal to 20 minutes.

[0340] According to a specific implementation scheme, grafting can be carried out in a single heating stage at a temperature of less than or equal to 160 °C for a duration of less than or equal to 20 minutes.

[0341] According to a particular implementation, grafting can be performed in one or more heating stages at a temperature of less than or equal to 120 °C for a total duration of less than or equal to 15 minutes.

[0342] According to a specific implementation scheme, grafting can be performed in a single heating stage at a temperature of less than or equal to 120 °C for a duration of less than or equal to 15 minutes.

[0343] In embodiments where the fluoropolymer is a ferroelectric polymer (e.g., P(VDF-TrFE)), the coating grafted onto the substrate can then be polarized using methods known per se: contact polarization by applying a DC or AC voltage or non-contact polarization by using a corona effect.

[0344] The coating adheres to its substrate

[0345] The present invention also relates to a composite material comprising a fluoropolymer-based coating adhered to a substrate.

[0346] The coating has a composition derived from the composition according to the invention after it is applied and grafted onto the substrate.

[0347] It is found that at least a portion of the at least one additive APA present in the composition to be applied is grafted onto the surface of the substrate, thereby enabling good adhesion between the coating and the substrate to be ensured.

[0348] In embodiments where the composition according to the invention to be applied is in solution form (i.e., containing one or more solvents), the composition of the coating corresponds to the same composition that is substantially free of or contains no solvent.

[0349] Composite materials are advantageously obtained by means of a method according to the invention of forming a coating on a substrate.

[0350] Device

[0351] The present invention also relates to devices comprising such a composite material. The polymer coating may be electroactive, may be an insulating and / or protective layer, or may be an electrode adhesive.

[0352] The device can be, in particular, an optoelectronic device, a transistor, especially a field-effect transistor, a chip, a battery, a photovoltaic cell, a light-emitting diode, especially an organic light-emitting diode, a sensor, an actuator, a transformer, a tactile device, an electromechanical microsystem, and a detector.

[0353] use

[0354] The present invention relates to the use of polymer APA as an additive in fluoropolymer-based compositions to improve the adhesion of fluoropolymers to substrates, wherein the polymer APA comprises repeating units generated from methyl methacrylate and at least one graftable functional group disposed at one end of its polymer chain.

[0355] The examples below specifically demonstrate that even using polymeric APAs in very small proportions can increase the adhesion of fluoropolymers to any type of substrate, particularly metals (aluminum, silver) and polymeric materials (PEDOT:PSS). Using polymeric APAs can result in adhesion between fluoropolymer-based coatings and their substrates greater than or equal to 1.0 N / 25 mm, or greater than or equal to 1.5 N / 25 mm, or greater than or equal to 2 N / 25 mm, or greater than or equal to 3 N / 25 mm, or greater than or equal to 4 N / 25 mm, or greater than or equal to 5 N / 25 mm, or greater than or equal to 6 N / 25 mm, or greater than or equal to 7 N / 25 mm, or greater than or equal to 8 N / 25 mm, or greater than or equal to 9 N / 25 mm, as measured by a 180° peel test performed at a rate of 0.5 mm / s on a 25 mm wide coating strip. The use of polymer APA can increase the adhesion between fluoropolymer-based coatings and their substrates by more than 25%, or more than 50%, or more than 100%, or more than 250%, or more than 500%.

[0356] The following examples demonstrate that polymeric APAs are particularly suitable as additives in ferroelectric fluoropolymer compositions to improve adhesion without substantially impairing their electroactive properties. Compared to the unadded fluoropolymer, the addition of polymeric APAs in the above proportions reduces the residual polarization of the added fluoropolymer, as measured according to Example 4, by less than 12%, preferably less than 10%, more preferably less than 8%, more preferably less than 6%, more preferably less than 4%, and most preferably less than 3%.

[0357] The following examples demonstrate that polymeric APA can be used particularly as an additive in relaxor ferroelectric fluoropolymer compositions to improve adhesion while improving or not significantly impairing their electroactive properties. Compared to unadded fluoropolymers, polymeric APA added in the above proportions can particularly increase the dielectric constant at frequencies greater than or equal to 1 kHz at all temperatures between 23 °C and 110 °C. For temperatures ranging from 20 °C to 60 °C, this increase can range from 5% to 20%. For temperatures ranging from 60 °C to 110 °C, this increase can range from 25% to 45%. Compared to unadded fluoropolymers, polymeric APA added in the above proportions makes it particularly possible to avoid significant changes in dielectric loss at frequencies greater than or equal to 1 kHz at all temperatures between 23 °C and 110 °C.

[0358] Polymer APA and fluoropolymers can be as described above in the main text of the specification.

[0359] Prior to the addition of polymer APA, the fluoropolymer-based composition may consist substantially of at least one fluoropolymer or be composed of at least one fluoropolymer. The composition may optionally contain one or more other additives different from the additive APA.

[0360] Prior to the addition of polymer APA, the fluoropolymer-based composition may consist substantially of at least one fluoropolymer and one or more miscible solvents, or the same thereof. The composition may optionally contain one or more other additives different from the additive APA.

[0361] According to an advantageous embodiment, the weight of the polymer APA can be from 0.005% to 5.0% by weight of the total weight of the fluoropolymer. The weight of the polymer APA is preferably 0.01% or more, and more preferably 0.05% or more, relative to the total weight of the fluoropolymer. The weight of the polymer APA is preferably 3.0% or less, and more preferably 2.0% or less, relative to the total weight of the fluoropolymer.

[0362] Example

[0363] Example 1 - Synthesis of Adhesion Promoting Additive (APA-1)

[0364] Hydroxyl-functionalized alkoxyamines were prepared from alkoxyamine BlocBuilder® MA (sold by Arkema). The alkoxyamine has the following chemical formula:

[0365] [Chemical Formula 5]

[0366] (II)

[0367] 226.17 g of BlocBuilder® was introduced into a 1 L round-bottom flask purged with nitrogen, along with 68.9 g of MA (1 equivalent), 2-hydroxyethyl acrylate (1 equivalent), and 548 g of isopropanol. The reaction mixture was heated under reflux (80 °C) for 4 h, followed by vacuum evaporation of the isopropanol. This yielded 297 g of a very viscous, yellow oil containing hydroxylated alkoxyamines.

[0368] The gradient copolymer P(MMA-S) was synthesized using a synthesized hydroxyl-functionalized alkoxyamine via oxynitride-mediated polymerization. Toluene, along with styrene (S) and methyl methacrylate (MMA) monomers and the hydroxyl-functionalized alkoxyamine, was introduced into a stainless steel reactor equipped with a mechanical stirrer and a jacket. The weight ratio of styrene (S) to methyl methacrylate (MMA) monomers was 5 / 95. The toluene charge was set at 30% by weight relative to the reaction medium. The reaction mixture was stirred and degassed with bubbling nitrogen at ambient temperature for 30 minutes. The temperature of the reaction medium was then brought to 115°C. The trigger time t=0 was set at ambient temperature (23°C). The temperature was maintained at 115°C throughout the polymerization until approximately 70% monomer conversion was achieved. Samples were removed at regular intervals to determine polymerization kinetics by gravimetric analysis (measurement of solids content). When 70% conversion was achieved, the reaction medium was cooled to 60°C, and the solvent and residual monomers were evaporated under vacuum. After evaporation, methyl ethyl ketone (MEK) was added to the reaction medium in an amount sufficient to produce a copolymer solution of approximately 25% by weight. This copolymer solution was then introduced dropwise into a beaker containing a non-solvent (heptane) to precipitate the copolymer. The weight ratio of solvent to non-solvent (methyl ethyl ketone / heptane) was approximately 1 / 10. The precipitated copolymer was recovered as a white powder after filtration and drying.

[0369] The copolymer thus synthesized and purified is designated as "APA-1" in a later section of the examples. It is used as an adhesion-promoting additive.

[0370] Example 2 - Evaluation of the adhesion properties of the added fluoropolymer film on an aluminum substrate

[0371] The P(VDF-TrFE) copolymer is used as a fluoropolymer consisting of repeating units derived from vinylidene fluoride (VDF) and trifluoroethylene (TrFE) with a VDF:TrFE molar ratio of 80.0:20.0 (Piezotech® FC20, sold by Arkema). This polymer is referred to as "FP-1" in a later section of the examples.

[0372] The FP-1 solution with added APA-1 is prepared as follows: the fluoropolymer is dissolved in methyl ethyl ketone (MEK) to obtain a 10% by weight solution (based on the weight of FP-1 relative to the weight of MEK).

[0373] The copolymer APA-1 was also dissolved in MEK at a level of 10% by weight (based on the weight of FP-1 relative to the weight of MEK).

[0374] The two solutions prepared in this way are mixed to obtain APA-1 solutions of different concentrations, which contain 0% to 0.20% APA-1 by weight relative to the weight of the fluoropolymer FP-1 (the lowest value of the additive is 0.01%).

[0375] Films with and without added APA-1 fluoropolymer FP-1 were prepared on aluminum 1235 substrates (15 μm thick sheets). The aluminum substrates were pre-cleaned with rags soaked in ethanol. A lecithin solution dissolved in cyclohexane as a release agent at a level of 1% by weight was applied to the first half of these substrates via rod coating, and the films were then dried at ambient temperature. The solutions with or without added FP-1 were then applied to the entire substrate via rod coating to obtain films with a thickness of 15 μm after drying. The wet films were dried at ambient temperature (23 °C) for 15 minutes and then placed in an oven at 140 °C for 20 minutes. The prepared substrates were then cut into strips with a width of 25 mm.

[0376] The prepared samples were tested on an Instrom® 5565 tensile testing apparatus equipped with a 100 N force sensor, according to... Figure 1 The illustrated scheme is tested by a 180° peel test at a rate of 0.5 mm / s. Referring to the figure, the FP-1 film 3, with or without lecithin release agent, deposited on the aluminum substrate 1 and lecithin release agent 2, is subjected to a 180° peel test by applying a tensile force 4.

[0377] The results of adhesion tests on the resulting different solutions are plotted in... Figure 2 The graph shows the tensile force (N / 25 mm) as a function of the weight percentage (%) of APA-1 relative to FP-1 in the test solution. It was found that the additive APA-1 significantly enhanced the initial adhesion properties of the unadded FP-1 film (control). Tensile forces of 0.05 to 0.1 N / 25 mm allowed for the peeling of the additive-free FP-1 film. Using only 0.01% by weight of APA-1 relative to FP-1 multiplied the adhesive strength by 20 to 40, as the measured adhesive strength was 2 N / 25 mm.

[0378] Example 3 - Evaluation of the electroactive properties of the added FP-1 membrane

[0379] The FP-1 solution with added APA-1 was prepared as in Example 2. Solutions with different concentrations of APA-1 were prepared, containing 0% to 5% (the lowest value for the additive is 0.5%) of APA-1 by weight relative to the weight of the fluoropolymer FP-1.

[0380] Electroactive films were produced using glass substrates. First, the entire surface of these substrates was coated with an egg lecithin solution (used as a release agent) using a cloth soaked in a 1% lecithin solution in cyclohexane. Then, the desired amount of FP-1 solution, with or without FP-1, was dispensed onto the glass substrates using a rod coating process to obtain a final dry film with a thickness of 15 μm. The newly coated film was dried at ambient temperature (23 °C) for 15 minutes, followed by an oven drying at 140 °C for 20 minutes.

[0381] The electroactive properties of the obtained membranes were evaluated as follows: each membrane was placed between two gold electrodes on a sample holder and then compressed to 2.5 kN / cm² under a hydraulic press. -2 The level was adjusted to ensure good contact between the membrane and the electrode. An AC voltage was then applied to the electrode terminals to obtain an electric field along the membrane thickness (15 μm), ranging from 25 V / μm to 150 V / μm in 5 V / μm increments. The residual polarization (RP) of the membrane under consideration was then extracted from the hysteresis curve obtained at 150 V / μm.

[0382] The results obtained for the different membranes produced are plotted on... Figure 3 On the curve, it represents the remanent polarization (mC.m -2 ) is a function of the weight ratio (weight%) of APA-1 relative to FP-1-based membranes with or without added FP-1.

[0383] These results indicate that for every 1% of APA-1 introduced into the FP-1 membrane, the RP decreases by only 2.1%, even from a very low weight proportion of APA-1 (approximately 0.1%, see Example 2); Figure 2 It also has excellent adhesion.

[0384] Example 4 - Evaluation of the adhesion properties of the added fluoropolymer film on the electrode obtained by screen printing (PEDOT-PSS or silver)

[0385] Screen printing tests were conducted on untreated 50 μm thick PET (polyethylene terephthalate) substrates provided by ADDEV Materials. First, a 1% solution of lecithin in cyclohexane (as a non-stick layer) was dispensed onto one half of the PET substrate surface and then dried at ambient temperature.

[0386] The screen-printed ink (a conductive blend of silver or polymer; see Table 1 below) was then dispensed onto the remaining half of the PET substrate by bar coating to obtain a continuous dry film of material with a thickness of several micrometers, and in fact even about 15 micrometers, at the end of the process. The wet film of the newly dispensed ink was then placed in an oven at 140 °C for 10 minutes. Once back to ambient temperature, a 10 wt% solution of copolymer FP-1 (see Example 2) in MEK was dispensed by bar coating, with or without APA-1 at a level of 0.2 wt%, depending on the type of sample produced, to obtain a final dry film with a thickness of about 15 μm. The wet film of the freshly dispensed ink was dried at ambient temperature (23 °C) for 15 minutes, and the resulting material stack was then placed in an oven at 140 °C for 20 minutes. The substrate thus prepared was cut into samples with a side length of 25 mm, so that all samples included a portion of the FP-1 film, with or without the FP-1 film, directly on the non-stick film (phospholipid) and another portion directly on the screen printing ink (PEDOT-PSS or silver) under study.

[0387] The operating conditions for the adhesion tests performed below are the same as those described in Example 2.

[0388] The different combinations of results obtained are shown in Table 1.

[0389] [Table 1]

[0390] Based on the results in Table 1, the following points are noteworthy:

[0391] Regarding PEDOT-PSS (conductive polymer) type inks, FP-1 films with added APA-1 adhered perfectly because the PEDOT-PSS / PET interface failed during the adhesion test, whereas the PEDOT-PSS / FP-1 interface failed when the additive APA-1 was absent.

[0392] Regarding various "silver" type inks, it has been found that the unadded FP-1 film adheres best to the material in the case of the control Loctite ECI-1011 (presented in row 3 of Table 1). Therefore, the tensile strength values ​​of the control films (without APA-1) are all necessarily less than or equal to 1.4 N / 25 mm, and always involve adhesive failure at the interface between the FP-1 film and the material. Films with added APA-1 all exhibit tensile strength values ​​strictly greater than 1.4 N / 25 mm. In some cases, the failure is cohesive, meaning that the added FP-1 film breaks before it can be peeled off.

[0393] Example 5 – Stability of the Added Fluoropolymer Solution

[0394] A P(VDF-TrFE-CTFE) terpolymer was used as the fluoropolymer, which consisted of repeating units derived from vinylidene fluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE) with a VDF:TrFE:CTFE molar ratio of 60.9:30.6:8.5. This polymer is referred to as "FP-2" in the following sections of the examples.

[0395] In this case, the changes of two different solutions over time were compared:

[0396] - A 10% solution of FP-2 in cyclopentanone, and containing 1% by weight of compound APA-1 relative to FP-2;

[0397] A 10% by weight solution of FP-2 in cyclopentanone, and containing 1% by weight of compound (3-aminopropyl)triethoxysilane relative to the weight of FP-2. Compound (3-aminopropyl)triethoxysilane is an additive known in the art as an adhesion promoter for PVDF and its derivatives.

[0398] Twenty-four hours after the additive was mixed with the FP-2 mother liquor, a very distinct orange-yellow coloration was observed in the solution containing (3-aminopropyl)triethoxysilane, indicating that the FP-2 backbone was degraded by the additive (3-aminopropyl)triethoxysilane. It was noted that the solution containing the additive APA-1 did not show any coloration, indicating the excellent stability of the corresponding solution.

[0399] It was also noted that, in the case of the additive (3-aminopropyl)triethoxysilane, the onset of coloring was clearly visible to the naked eye only a few minutes after mixing with the FP-2 solution, indicating that the degradation was very rapid.

[0400] Finally, it is noteworthy that the solution containing APA-1 remained colorless even after several weeks at ambient temperature, even though the concentration of APA-1 relative to the weight of FP-2 was 5.0% (by weight). The same results were obtained when cyclopentanone was replaced with an aliphatic ketone-type solvent such as MEK.

[0401] Regardless of the type of fluoropolymer used, such as for vinylidene fluoride homopolymer or FP-1, the same changes can be observed.

[0402] Example 6 – Adhesion properties of fluoropolymer FP-2 with additives

[0403] Two mother liquors containing 10% by weight of FP-2 and APA-1 in cyclopentanone were prepared.

[0404] The first ink (concentrated in APA-1) is produced by mixing the two mother liquors to obtain a ratio of 5% by weight of APA-1 relative to FP-2. The second ink (diluted in APA-1) is prepared by simply diluting a portion of this first solution to obtain a final concentration of 0.5% by weight of APA-1 relative to FP-2.

[0405] Cut out stainless steel substrates (type 314) to approximately 10 cm × 6 cm using a cutter, then individually glue each sample to the glass support via the perimeter of Kapton® adhesive. Simply clean the steel substrates with a swab soaked in anhydrous ethanol.

[0406] The first substrate (sample 1) was coated with the unadded FP-2 solution using a bar coating method to obtain a wet film with a theoretical thickness of 1000 μm.

[0407] The second substrate (sample 2) was coated with a copolymer FP-2 solution containing 0.5% by weight of APA-1 to obtain a wet film with a theoretical thickness of 1000 μm.

[0408] The third substrate (sample 3) was coated with a copolymer FP-2 solution containing 0.5% by weight of APA-1 to obtain a wet film with a theoretical thickness of 1000 μm.

[0409] The substrate was then placed under a ventilated oven until the solvent had completely evaporated. The dry film thickness was approximately 30 μm.

[0410] Samples 1 and 2 were annealed in a ventilated oven at 110 °C for 9 minutes.

[0411] Sample 3 was annealed by first annealing at 200 °C for 9 minutes and then by second annealing at 110 °C for 9 minutes.

[0412] Once the sample has returned to ambient temperature, a cross-hatching adhesion test (ASTM D3359 - Method B) is then performed.

[0413] The polymer film on its substrate is first cut using a special blade with seven blades, five of which are spaced at a restricted interval (~1 mm) in the middle. A second cut is then made using the same apparatus at a 90° angle relative to the first cut. This yields a grid of 25 squares with sides of 1 mm, on which the film's adhesion properties can then be assessed. Adhesive tape with controlled adhesive strength (typically 6-7 N / cm) is then applied to the grid and peeled off at 180°.

[0414] The adhesion results observed after tape removal, expressed as "grid grade," are summarized in Table 2 below. The grid classification ranges from 0B to 5B, with intermediate ratings of 1B, 2B, 3B, and 4B. A rating of 5B indicates that after tape removal, the sides of the cut grid edges are smooth, and no matrix squares are separated. Conversely, a rating of 4B means that small pieces of film separation can be observed at the intersections of the cuts, with less than 5% of the entire grid affected. A rating of 3B means that the film peels off along the sides of the cuts or at the intersections of the grids, with the affected area ranging from 5% to 15% of the grid. A rating of 2B indicates that the film peels off in large strips or entire squares of the grid along the sides of the cuts or at the intersections of the grids, with the affected area between 15% and 35% of the grid. A rating of 1B indicates that the film peels off in large strips or entire squares of the grid along the sides of the cuts or at the intersections of the grids, with the affected area between 35% and 65% of the grid. A rating of 0B corresponds to any degradation of the film that cannot be classified above.

[0415] [Table 2]

[0416]

[0417] Sample 1, compared to FP-2, showed a "0B" rating. This is because the film separated completely from the steel substrate without much trouble during the tape peeling process.

[0418] Samples 2 and 3, which had FP-2 added, exhibited a "5B" rating. This is because the film remained intact after the tape was removed.

[0419] Example 7 - Evaluation of the dielectric properties of the added FP-2 film

[0420] Two mother liquors containing 10% by weight of FP-2 and APA-1 in cyclopentanone were prepared.

[0421] The first ink is produced by mixing the two mother liquors to obtain a weight ratio of 5% APA-1 relative to FP-2.

[0422] The second ink is prepared by simply diluting a portion of the first solution to obtain a final concentration of 0.5% (by weight) of APA-1 relative to FP-2.

[0423] The films were then prepared. Each ink was applied to a glass substrate pre-coated with lecithin by bar coating to achieve a final dried thickness of approximately 30 μm (blade at 1000 μm). The glass substrate was then placed directly in an oven at 110 °C for 9 minutes to evaporate the solvent and allow the copolymer to crystallize. After processing, the films were simply peeled off from their respective substrates. Thus, two films were produced under the same processing conditions: one film in which the P(VDF-ter-TrFE-ter-CTFE) terpolymer was pure (as a control) and the other film in which the APA-1 additive was added at a level of 0.5% relative to the weight of FP-2.

[0424] Dielectric measurements were performed on these films. The measurements were conducted on an Alpha-A impedance spectrometer from Novocontrol. The measurement chamber was heated to the desired temperature via the Peltier effect. Each film was introduced into the chamber and subjected to a low sinusoidal voltage at a frequency of 10 kHz in 5 °C steps for each temperature point defined between 20 °C and 110 °C. Thus, the dielectric constant (denoted as Dk) and the corresponding dielectric loss (Tanδ) of the material were extracted at each temperature point at a frequency of 10 kHz from the measurement of the phase shift of the current at the terminals of the capacitor formed by the films between the two electrodes.

[0425] Figure 4 The images show that the dielectric constant of the film with added APA-1 is greater than that of the pure material (ΔDk<0).

[0426] Figure 5 The images show that the dielectric loss is slightly higher overall after the addition of APA-1, but they remain the same, limited to less than 15% relative to the initial value (without additive). It should be noted that for some temperatures, the dielectric loss is lower than that of the material without the additive (values ​​when Δ tan δ > 0).

Claims

1. A composition comprising: - at least one fluoropolymer and - 0.005% to 5.0% by weight of at least one additive APA relative to the weight of the at least one fluoropolymer; The composition is characterized in that the at least one additive APA is a polymer comprising repeating units generated from methyl methacrylate and at least one graftable functional group disposed at at least one end of its polymer chain. The at least one graftable functional group can be grafted onto the surface of the substrate.

2. The composition according to claim 1, wherein the at least one additive APA contains a graftable functional group at one end of its polymer chain, the graftable functional group being a nitro group.

3. The composition according to any one of claims 1 and 2, wherein the at least one additive APA comprises at one end of its polymer chain at at least one graftable functional group selected from the group consisting of: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and hypophosphonic acid.

4. The composition according to any one of claims 1 to 3, wherein, The at least one graftable functional group disposed at one end of the polymer chain of the at least one additive APA is a hydroxyl functional group.

5. The composition according to any one of claims 1 to 4, wherein, The at least one graftable functional group disposed at one end of the polymer chain of the at least one additive APA is a carboxyl functional group.

6. The composition according to any one of claims 1 to 5, wherein, Relative to the total weight of the polymer chain of the at least one additive APA, the repeating units generated by methyl methacrylate in the polymer chain of the at least one additive APA account for at least 40% by weight, preferably at least 50% by weight, and most preferably at least 70% by weight.

7. The composition according to any one of claims 1 to 6, wherein, The total weight of additive APA is 0.01% or more, and preferably 0.05% or more, relative to the total weight of the fluoropolymer.

8. The composition according to any one of claims 1 to 7, wherein, The total weight of additive APA is 3.0% or less, and preferably 2.0% or less, relative to the total weight of the fluoropolymer.

9. The composition according to any one of claims 1 to 8, wherein the additive APA can be obtained by using alkoxyamines via free radical polymerization controlled by nitrides.

10. The composition according to claim 9, wherein the alkoxyamine is selected from: -Compounds of the following formula: [Chemical Formula 7] (II) and - An adduct formed by reacting 1 equivalent of a compound of formula (II) with an acrylic, methacrylic, or vinyl aromatic monomer having at least one graftable functional group.

11. The composition according to any one of claims 1 to 10, wherein the at least one additive APA is a gradient or random polymer and does not contain repeating units containing graftable functional groups.

12. The composition according to claim 11, wherein the at least one additive APA is substantially composed of or composed of the following: The repeating units produced from methyl methacrylate and styrene, relative to the total weight of the repeating units produced from methyl methacrylate and styrene, account for a weight percentage of repeating units produced from styrene ranging from 0.5% to 15%, and preferably from 1.0% to 10%.

13. The composition according to any one of claims 1 to 10, wherein the at least one additive APA is an AB-type or ABA-type block polymer, wherein block A independently comprises at least one repeating unit containing the at least one graftable functional group, and block B comprises a repeating unit generated from methyl methacrylate.

14. The composition of claim 13, wherein the block B of the at least one additive APA does not contain repeating units containing graftable functional groups.

15. The composition according to any one of claims 1 to 14, wherein, Relative to the total molar amount of repeating units constituting the at least one fluoropolymer, the at least one fluoropolymer comprises at least 40 mol% repeating units generated from vinylidene fluoride, and optionally at least one repeating unit generated from a monomer X having the formula CX1X2=CX3X4, which is different from vinylidene fluoride, wherein each X1, X2, X3 and X4 group is independently selected from H, Cl, F, Br, I and optionally partially or fully halogenated C1-C3 alkyl groups.

16. The composition according to any one of claims 1 to 15, wherein, The at least one fluoropolymer is P(VDF-TrFE), P(VDF-TrFE-CTFE), or P(VDF-TrFE-CFE), or a mixture thereof.

17. A method for manufacturing a fluoropolymer-based coating on a substrate, the method comprising: iv) Deposition of the composition according to any one of claims 1 to 16; v) If appropriate, after deposition of the composition, remove any solvent or solvent mixture that may be present in the composition; and vi) Grafting at least a portion of the at least one additive APA present in the composition onto the substrate.

18. A composite material comprising a fluoropolymer-based coating adhered to a substrate, the coating comprising at least one fluoropolymer and at least one additive APA in an amount of 0.005% to 5.0% by weight relative to the at least one fluoropolymer, the at least one additive APA being a polymer comprising repeating units generated from methyl methacrylate and at least one graftable functional group disposed at at least one end of its polymer chain.

19. An apparatus comprising the composite material according to claim 18.

20. Use of at least one polymer APA as an additive in a fluoropolymer-based composition to improve the adhesion of said composition to a substrate, said additive APA being a polymer comprising a repeating unit generated from methyl methacrylate and at least one graftable functional group disposed at one end of its polymer chain.

Images