Fluoropolymer composition with improved adhesion

Abstract

The invention relates to a composition comprising at least one fluoropolymer and from 0.005% to 5.0% by weight of at least one APA additive, relative to the weight of the at least one fluoropolymer, characterised in that the at least one APA additive is a polymer comprising a repeat unit 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 method for manufacturing a fluoropolymer-based coating on a substrate, to such a coating on the substrate, to a device comprising such a polymer coating on the substrate, and to its uses.

Description

[0001] Description

[0002] Title: Composition of fluoropolymer(s) with improved adhesion

[0003] Technical field

[0004] The invention relates to the field of adhesion of a fluoropolymer to a surface, in particular to a metal surface or to a polymer surface. More particularly, the invention relates to a composition comprising a fluoropolymer and an additive intended to improve the adhesion of said fluoropolymer to a surface.

[0005] The invention also relates to a method for manufacturing a coating from the additive composition on a surface. The invention further relates to the composite comprising the coating adhering to the surface. The invention also relates to an electronic device comprising the composite. Finally, the invention relates to the use of said additive for improving the adhesion of a fluoropolymer to a surface.

[0006] Prior art

[0007] Fluoropolymers, for example those based on vinylidene fluoride CF2=CH2 (VDF), in particular PVDF and copolymers comprising VDF, are known to offer excellent mechanical stability properties, very high chemical inertness, as well as good resistance to aging. These qualities are exploited for very varied application fields. In particular, certain fluorinated polymers based on vinylidene fluoride (VDF), such as P(VDF-TrFE), P(VDF-TrFE-CTFE), P(VDF-TrFE-CFE), are used for their electroactive properties, particularly in electronic devices.

[0008] However, due to their high chemical inertness, fluoropolymers suffer from a problem of adhesion to substrates, particularly on metallic substrates, which can be particularly problematic for certain applications. However, if the fluoropolymer separates or delaminates from the surface of the substrate with which it is in direct contact, it can no longer fulfill its initial function (transformation of a physical quantity for a transducer, binder for an electrode, protective coating, thermal insulation, etc.).

[0009] For example, a transducer formed by an electroactive fluoropolymer placed between two electrodes will no longer function or will function poorly if the fluoropolymer separates or delaminates, even partially, from its electrodes. It is recalled that a polymer is said to be electroactive if it exhibits a response (deformation, temperature variation, etc.) when an electric field is applied and / or if a stress (mechanical, thermal, etc.) induces an electrical response within the material. Several solutions have been proposed in the prior art to improve the adhesion of fluoropolymers to substrates, particularly to metal substrates. Three main approaches can be cited:

[0010] A first approach is to add an adhesion-promoting monomer to the polymer chain of the fluoropolymer. This has been described, for example, in WO 2017 / 129881. This patent document describes, in particular, terpolymers consisting of repeating units derived from vinylidene fluoride (VDF), trifluoroethylene (TrFE) and an adhesion-promoting monomer chosen from a vinylphosphonic acid dialkyl ester, vinylphosphonic acid and (2-trifluoromethyl) acrylic acid. This approach has the disadvantage of having to modify the structure of the fluoropolymer chain, which can in certain cases have a negative impact on its useful properties, in particular its mechanical properties and / or, where appropriate, its electroactive properties.Furthermore, such polymers are not currently available on an industrial scale and require more or less significant modifications to the manufacturing processes of industrially produced fluoropolymers.

[0011] A second approach is to intercalate a primer layer between the fluoropolymer and the substrate. This was for example described in the publication: "Whang, WT, & 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". The compound 3-aminopropyltriethoxysilane (3-APS) was used as an adhesion primer for PVDF on an aluminum or silicon substrate. This approach has the disadvantage of having to add an additional step of applying a primer layer between the fluoropolymer and its substrate. This additional step can be tedious to implement and in any case represents a significant additional cost at the industrial level (manufacturing time) compared to a direct application of the fluoropolymer on its substrate.

[0012] A third approach, the one chosen to implement the present invention, is that of adding an additive to the fluoropolymer. This solution has the advantage of overcoming two of the aforementioned drawbacks: the chemical composition of the polymer chain of a fluoropolymer intended for a particular use does not need to be modified, and the method of manufacturing a fluoropolymer coating on a substrate involves modifications that are not very restrictive.

[0013] There is thus currently a need to provide compositions of additive fluorinated polymer(s) making it possible to improve the adhesion of said fluorinated polymer to a substrate while modifying as little as possible the useful properties of said fluorinated polymer and / or while modifying as little as possible the methods of manufacturing a coating of said polymer on the substrate. Objectives of the invention

[0014] An objective of the invention is to provide a composition comprising a fluoropolymer making it possible to improve the adhesion of the fluoropolymer to a substrate, while modifying the useful properties of said fluoropolymer as little as possible.

[0015] In certain embodiments where the fluoropolymer has electroactive properties, an objective of the invention is to essentially retain its electroactive properties.

[0016] Another objective of the invention is also to provide a method for manufacturing a coating of the fluoropolymer on a substrate which is simple to implement and allows good adhesion of the coating to the substrate.

[0017] In some embodiments, the coating manufacturing process is carried out under mild conditions.

[0018] According to certain embodiments, the method of manufacturing the coating is efficient, and can in particular be implemented sufficiently quickly.

[0019] Another objective of the invention is to provide a composite comprising a coating based on the fluoropolymer adhering to a substrate and / or a device incorporating this composite.

[0020] Another objective of the invention is also to provide an additive to be added to the fluoropolymer to improve its adhesion to a substrate.

[0021] Summary of the invention

[0022] The invention relates, according to a first aspect, to a composition comprising:

[0023] - at least one fluorinated polymer;

[0024] - from 0.005% to 5.0% by weight of at least one APA additive, relative to the weight of said at least one fluorinated polymer, characterized in that said at least one APA additive is a polymer comprising a repeating unit derived from methyl methacrylate, and at least one graftable functional group arranged at at least one end of its polymer chain.

[0025] The inventors of the present invention have noticed that such an APA polymer, added as an additive to the fluoropolymer, makes it possible to improve the adhesion of the fluoropolymer to a substrate in a significant manner, even at very low loading rates. Without being bound by theory, it seems that this remarkable improvement in adhesion is due to the double condition fulfilled by the additive: a good affinity for the fluoropolymer, and at least one graftable functional group placed at one end of the polymer chain, making it possible to graft this end to the substrate, in particular by heat treatment. It has also been demonstrated that the addition of APA polymer as an additive, in particular in small proportions, has little influence on the useful properties of said fluoropolymer, in particular in the case where the fluoropolymer is an electroactive polymer and the useful property is an electroactive property of the polymer.According to certain embodiments, said at least one graftable functional group disposed at at least one end of the polymer chain of said at least one APA additive is chosen from the groups: nitroxy, carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0026] According to certain embodiments, said at least one APA additive comprises at one end of its polymer chain a graftable functional group being a nitroxy.

[0027] According to certain embodiments, said at least one APA additive comprises at one end of its polymer chain at least one graftable functional group chosen from the groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0028] According to certain embodiments, said at least one APA additive comprises at one end of its polymer chain at least one graftable functional group being a nitroxy, and at another end of its polymer chain at least one graftable functional group chosen from the groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0029] According to certain embodiments, said at least one graftable functional group disposed at one end of the polymer chain of said at least one APA additive is a hydroxyl function.

[0030] According to certain embodiments, said at least one graftable functional group disposed at one end of the polymer chain of said at least one APA additive is a carboxyl function.

[0031] According to certain embodiments, the repeating unit derived from methyl methacrylate in the polymer chain of said at least one APA additive represents at least 40%, preferably at least 50%, and extremely preferably at least 70%, by weight relative to the total weight of the polymer chain of said at least one APA additive.

[0032] According to certain embodiments, the repeating unit derived from methyl methacrylate in the polymer chain of said at least one APA additive represents at least 90% by weight, relative to the total weight of the polymer chain of said at least one APA additive.

[0033] According to certain embodiments, the total weight of APA additive(s) represents 0.01% or more, and preferably 0.05% or more, relative to the total weight of fluoropolymer(s).

[0034] According to certain embodiments, the total weight of APA additive(s) represents 3.0% or less, and preferably 2.0% or less, relative to the total weight of fluorinated polymer(s). According to certain embodiments, the APA additive is capable of being obtained by nitroxide-controlled radical polymerization using an alkoxyamine. The alkoxyamine may in particular have the chemical formula: [Chem 1 ]

[0035] (I), in which:

[0036] - Ri is a cyclic or non-cyclic hydrocarbon group with or without heteroatom which may contain at least one metallic species;

[0037] - R2 is a cyclic or non-cyclic hydrocarbon group with or without heteroatom which may contain at least one metallic species;

[0038] - Ri and R2 may or may not be part of the same cyclic structure;

[0039] - Z is a monovalent hydrocarbon group, cyclic or not, with or without heteroatom.

[0040] According to certain embodiments, the group Z of the alkoxyamine of formula (I) is a group carrying one or more graftable functional groups, each graftable functional group being chosen from the groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0041] Advantageously, the alkoxyamine is chosen from:

[0042] - a compound of formula:

[0043] [Chem 2]

[0044] (H), and

[0045] - an adduct formed by the reaction of an equivalent of the compound of formula (II) with an acrylic, methacrylic, or vinylaromatic monomer carrying at least one graftable functional group.

[0046] According to certain embodiments, said at least one APA additive is a linear polymer.

[0047] According to certain embodiments, said at least one APA additive is a gradient or random type polymer. According to certain embodiments, said at least one APA additive does not comprise a repeating unit comprising a graftable functional group.

[0048] According to certain embodiments, said at least one APA additive is a linear polymer and / or one not comprising a repeating unit comprising a graftable functional group, and is essentially constituted, or constituted, of repeating units derived from methyl methacrylate and styrene, the mass proportion of repeating units derived from styrene representing from 0.5% to 15%, and preferably from 1.0% to 10%, relative to the total mass of the units derived from methyl methacrylate and styrene.

[0049] According to certain embodiments, said at least one APA additive is an AB-type or ABA-type block polymer, in which the block(s) A comprise, independently of one another, at least one repeating unit comprising said at least one graftable functional group and the block B comprises a repeating unit derived from methyl methacrylate. Advantageously, the block B of said at least one APA additive does not comprise a repeating unit comprising a graftable functional group.

[0050] According to certain embodiments, said at least one APA additive has a number average molar mass of 1000 g / mol to 100,000 g / mol, and preferably of 2000 g / mol to 50,000 g / mol.

[0051] According to certain embodiments, said at least one fluoropolymer comprises at least 40 mol% of repeating unit derived from vinylidene fluoride, relative to the total sum of moles of repeating units constituting said at least one fluoropolymer, and optionally at least one repeating unit derived from a monomer X, other than vinylidene fluoride, having the formula CXiX2=CX3X4, in which each group Xi, X2, X3 and X4 is independently chosen from H, Cl, F, Br, I and C1-C3 alkyl groups which are optionally partially or totally halogenated.

[0052] According to certain embodiments, said at least one fluoropolymer is a PVDF.

[0053] According to certain embodiments, said at least one fluoropolymer is a P(VDF-TrFE), P(VDF-TrFE-CTFE), or P(VDF-TrFE-CFE), or a mixture thereof.

[0054] According to certain embodiments, said at least one fluoropolymer is a P(VDF-TFE) or P(VDF-HFP).

[0055] According to certain embodiments, said 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.

[0056] According to certain embodiments, the composition according to the invention comprises a solvent or a mixture of miscible solvents, in which the fluoropolymer and the APA additive are in solution.The solvent or mixture of miscible solvents may in particular be chosen from: dimethylformamide; N-methyl-2-pyrrolidone; dimethylacetamide; dimethylsulfoxide; γ-butyrolactone; ketones, in particular acetone, methyl ethyl ketone (or butan-2-one), methyl isobutyl ketone, cyclopentanone, cyclohexanone, diisobutyl ketone; furans, in particular tetrahydrofuran; esters, in particular methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, and ethyl acetoacetate; carbonates, in particular dimethyl carbonate and propylene carbonate; and phosphates, including trimethylphosphate, triethylphosphate, and mixtures thereof.

[0057] According to certain embodiments, the composition according to the invention is essentially constituted, or constituted, of said at least one fluoropolymer, of said at least one APA additive, and optionally of said solvent or mixture of miscible solvents.

[0058] The invention relates, according to a second aspect, to a method for manufacturing a coating based on fluorinated polymer(s) on a substrate, comprising: i) deposition of a composition according to the invention; ii) where appropriate, removal of the solvent or mixture of solvents possibly present in said composition following deposition of said composition; and, iii) grafting onto the substrate at least a portion of said at least one APA additive present in said composition.

[0059] According to certain embodiments, said grafting onto the substrate of at least a portion of said at least one APA additive is carried out by at least one heating step at a temperature of 50°C to 220°C, and preferably ranging from 80°C to 200°C.

[0060] According to certain embodiments, said grafting onto the substrate of at least a portion of said at least one APA additive is carried out by at least one heating step at a temperature less than or equal to 160°C for a duration less than or equal to 20 minutes.

[0061] The invention relates, according to a third aspect, to a composite comprising a coating based on fluoropolymer(s) adhering to a substrate, said coating comprising at least one fluoropolymer and from 0.005% to 5.0% by weight of at least one APA additive, relative to the weight of said at least one fluoropolymer, said at least one APA additive being a polymer comprising a repeating unit derived from methyl methacrylate, and at least one graftable functional group arranged at at least one end of its polymer chain. According to certain embodiments, the composite is capable of being obtained by a method for manufacturing a coating based on fluoropolymer(s) on a substrate, described in the second aspect of the invention.

[0062] According to certain embodiments, said at least one APA additive is according to the characteristics of said at least one APA additive described in the first aspect of the invention. According to certain embodiments, said at least one fluoropolymer is according to the characteristics of said at least one fluoropolymer described in the first aspect of the invention.

[0063] According to certain embodiments of the second aspect or the third aspect of the invention, the substrate can be a surface of glass, silicon, quartz, polymer material, metal, nitride, or a mixed surface composed of several of these materials.

[0064] The invention relates, according to a fourth aspect, to a device comprising a composite according to the third aspect of the invention.

[0065] According to certain embodiments, said coating based on fluoropolymer(s) is an electroactive coating, or an insulating and / or protective layer, or an electrode binder.

[0066] According to certain embodiments, the device may be an optoelectronic device, a transistor, in particular a field effect transistor, a chip, a battery, a photovoltaic cell, a light-emitting diode, in particular an organic light-emitting diode, a sensor, an actuator, a transformer, a haptic device, a microelectromechanical system, or a detector.

[0067] The invention relates according to a fifth aspect to uses.

[0068] The invention relates in particular to the use of at least one APA polymer as an additive in a composition based on fluorinated polymer(s) to improve the adhesion of said composition to a substrate, said APA additive being a polymer comprising a repeating unit derived from methyl methacrylate, and at least one graftable functional group arranged at one end of its polymer chain.

[0069] According to certain embodiments, said at least one APA polymer represents from 0.005% to 5.0% by weight of the total weight of fluorinated polymer(s) in said composition based on fluorinated polymer(s).

[0070] According to certain embodiments, said at least one APA polymer represents 0.01% or more, and preferably 0.05% or more, by weight relative to the total weight of fluorinated polymer(s) in said composition based on fluorinated polymer(s).

[0071] According to certain embodiments, said at least one APA polymer represents 3.0% or less, and preferably 2.0% or less, relative to the total weight of fluoropolymer(s) in said composition based on fluoropolymer(s). According to certain embodiments, said at least one APA additive is according to the characteristics of said at least one APA additive described in the first aspect of the invention.

[0072] According to certain embodiments, said at least one fluoropolymer is according to the characteristics of said at least one fluoropolymer described in the first aspect of the invention. Brief description of the figures

[0073] [Fig 1] schematically represents the 180° peel test carried out in example 2 to evaluate the adhesion of a film to a substrate.

[0074] [Fig 2] represents the tensile force (ordinates expressed in Newton per 25 mm, N / 25 mm) measured during the peel test of example 2 from solutions of PF-1 and APA-1, as a function of the mass proportion of APA-1 compared to PF-1 in the tested solutions (abscissas expressed in mass percent, % wt).

[0075] [Fig 3] represents the remanent polarization (ordinates expressed in mC.nr 2 ) of PF-1 films with or without additives, depending on the mass proportion of APA-1 compared to PF-1 in the compositions tested (abscissa expressed in mass percentage, wt%).

[0076] [Fig 4] represents the variation of ADk (ordinates expressed in percent, %) as a function of the study temperature (abscissas expressed in degrees Celsius, °C) at 10kHz. Here the parameter “ADk” is defined according to the following formula: ADk = (Dkpur — Dkadd) / Dkpur *100, Where:

[0077] Dkpur = dielectric constant of the pure PF-2 film, taken at the temperature considered; Dkadd = dielectric constant of the PF-2 film with an additive of 0.5% by mass of APA-1 relative to PF-2, taken at the temperature considered

[0078] The ADk parameter therefore represents the variation in dielectric constant measured following the addition of APA-1.

[0079] [Fig. 5] represents the variation of “ATan 5” (ordinates expressed in percent, %) as a function of the study temperature (abscissas expressed in degrees Celsius, °C), at 10 kHz. Here the parameter “ATan 5” is defined according to the following formula:

[0080] Tan 5 P ur = value of the dielectric losses of the pure PF-2 film, taken at the temperature considered.

[0081] Tan SAPA = value of the dielectric losses of the PF-2 film added with 0.5% by weight of APA-1 relative to the weight of PF-2, taken at the temperature considered. The parameter ATan 5 therefore represents the variation in dielectric losses measured following the addition of APA-1.

[0082] Detailed description of the invention

[0083] Fluoropolymer (PF)

[0084] The PF polymer is a fluoropolymer, that is to say it comprises repeating units (or units, or structural units, or motifs) which are derived from (that is to say which are obtained by polymerization of) fluorinated monomers. The PF polymer may in particular be a polymer comprising a vinylidene fluoride (VDF) repeating unit.

[0085] The PF polymer may in particular be a polymer based on the repeating unit derived from VDF, i.e. comprising at least 50% by mole of repeating unit derived from VDF, relative to the total sum of moles of repeating units constituting the PF polymer.

[0086] In some embodiments, the PF polymer is a PVDF homopolymer, i.e., is made up of the repeating unit derived from VDF.

[0087] In certain embodiments, the PF polymer is a copolymer (in the broad sense), that is to say it comprises units derived from at least one other monomer X than VDF.

[0088] A single monomer X can be used, or several different monomers X, depending on the case.

[0089] In some embodiments, monomer X may be of formula CXiX2=CX3X4, wherein each group Xi, X2, X3 and X4 is independently selected from H, Cl, F, Br, I and C1-C3 (preferably C1-C2) alkyl groups, which are optionally partially or fully halogenated - wherein monomer X is different from VDF (i.e., if X1 and X2 are H, at least one of X3 and X4 is not F; and if X1 and X2 are F, at least one of X3 and X4 is not H).

[0090] In certain embodiments, each group X1, X2, X3 and X4 independently represents an H, F, Cl, I or Br atom, or a methyl group optionally comprising one or more substituents selected from F, Cl, I and Br.

[0091] In some embodiments, each group X1, X2, X3 and X4 independently represents an H, F, Cl, I or Br atom.

[0092] In some embodiments, only one of X1, X2, X3 and X4 represents a Cl or I or Br atom, and the others of the groups X1, X2, X3 and X4 independently represent: an H or F atom or a C1-C3 alkyl group optionally comprising one or more fluorine substituents; preferably, an H or F atom or a C1-C2 alkyl group optionally comprising one or more fluorine substituents; and more preferably, an H or F atom or a methyl group optionally comprising one or more fluorine substituents.

[0093] Examples of monomers X are: vinyl fluoride (VF), trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropene (HFP), trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene (in cis or preferably trans form), hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropenes and in particular 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene, perfluoroalkylvinylethers and in particular those of general formula Rf-O-CF=CF2, Rf being an alkyl group, preferably C1 to C4 (preferred examples being perfluoropropylvinylether or PPVE and perfluoromethylvinylether or PMVE).

[0094] In some embodiments, the monomer X comprises a chlorine or bromine atom. It may in particular be chosen from bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene. Chlorofluoroethylene may denote either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene (CFE) isomer is preferred. Chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene (in cis or trans form, preferably trans) or 2-chloro-3,3,3-trifluoropropene.

[0095] In certain preferred embodiments, the PF polymer comprises units derived from VDF and HFP, or is a P(VDF-HFP) polymer consisting of units derived from VDF and HFP. Such a PF polymer is particularly useful for the manufacture of planarization or passivation layers of electronic devices.

[0096] The molar proportion of repeating units derived from HFP is preferably from 2 to 50%, in particular from 5 to 40%, in moles relative to the total number of moles of repeating units derived from VDF and HFP.

[0097] The P(VDF-HFP) copolymer may in particular be as described in documents WO 01 / 32726 and US 6,586,547 to which express reference is made.

[0098] In certain preferred embodiments, the PF polymer comprises units derived from VDF and TFE, or is a P(VDF-TFE) polymer consisting of units derived from VDF and TFE. This polymer is generally used for its piezoelectric properties.

[0099] The molar proportion of repeating units derived from TFE is preferably from 8% to 30%, preferably from 15% to 28%, more preferably from 18% to 25%, and extremely preferably from 20% to 22%, relative to the total number of moles of the units derived from VDF and TFE.

[0100] In some embodiments, the PF polymer comprises units derived from VDF and: CFE, or CTFE, or TrFE.

[0101] In certain preferred embodiments, the PF polymer comprises units derived from VDF and TrFE. Such a PF polymer is generally useful for the fabrication of electroactive layers.

[0102] According to certain advantageous embodiments, the PF polymer may in particular be a P(VDF-TrFE) polymer, i.e. consisting of units derived from VDF and TrFE. These polymers are generally used for their piezoelectric, pyroelectric and ferroelectric properties, for example in sensors, energy harvesting devices, actuators, loudspeakers or ferroelectric memories.

[0103] The molar proportion of repeating units derived from TrFE is preferably from 15% to 50%, preferably from 17% to 35%, and more preferably from 18% to 32.5%, relative to the total number of moles of units derived from VDF and TrFE. Such polymers are ferroelectrics. The term "ferroelectric" is understood to mean an electroactive polymer characterized by a hysteresis cycle of the electric displacement-applied electric field curve. Its coercive field at 25°C is typically lower in absolute value than 60 V / pm and higher than 40 V / pm. Its remanent polarization at 25°C is quite high, and can typically reach a value higher than 50 mC / m 2 The Curie temperature corresponds to a ferroelectric -> paraelectric (FE -> PE) crystal structure transition, called the Curie transition.

[0104] The molar proportion of repeating units derived from TrFE may in particular be from 15% to 18%, or from 18% to 22.5%, or from 22.5% to 27.5%. According to particular embodiments, the molar proportion of repeating units derived from TrFE is from 18.0% to 22.5%, relative to the total number of moles of the units derived from VDF and TrFE.

[0105] The molar proportion of repeat units derived from TrFE can also be from 27.5% to 32.5%, or from 32.5% to 37.5%, or from 37.5% to 42.5%, or from 42.5% to 47.5%, or from 47.5% to 50%, relative to the total number of moles of the motifs derived from VDF and TrFE.

[0106] According to certain advantageous embodiments, the polymer PF may comprise units derived from VDF, TrFE and another monomer X as defined above, different from VDF and TrFE, or else be a polymer P(VDF-TrFE-X) consisting of units derived from VDF, TrFE and another monomer X as defined above, different from VDF and TrFE. In this case, preferably, the other monomer X is chosen from TFE, HFP, trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene (in cis or preferably trans form), bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene.

[0107] CTFE or CFE are particularly preferred. Indeed, P(VDF-TrFE-CTFE) and P(VDF-TrFE-CFE) terpolymers are known to have a high dielectric constant (“high-k”) as well as for their electrostrictive and electrocaloric properties and are used for example as “High-k” dielectric in organic thin film transistors (OTFT), actuators and electrocaloric devices.

[0108] The molar proportion of units derived from TrFE is preferably from 10% to 60%, more preferably from 15% to 55% and more preferably from 20% to 50%, relative to the total number of moles of units derived from VDF and TrFE. The molar proportion of units derived from another monomer X, in addition to VDF and TrFE (the monomer X being in particular CTFE or CFE), relative to the number of moles of units constituting the polymer PF, is preferably from 0.05% to 15%, and more preferably from 2% to 12%. According to certain embodiments, X is CTFE or CFE, the molar proportion of X relative to the number of moles of units constituting the polymer PF, being from 4% to 10%. P(VDF-TrFE-CFE) and P(VDF-TrFE-CTFE) having the above-mentioned proportions of TrFE and CFE or CTFE are relaxor ferroelectrics.The term "relaxing ferroelectric" refers to an electroactive polymer characterized by a relaxor-ferroelectric (RFE) paraelectric (PE) crystalline transition over a wide temperature range. At this transition, a broad peak in dielectric permittivity is observed, the temperature of this maximum depending on the frequency of the applied electric field: the lower the frequency of the electric field, the more the dielectric permittivity maximum is shifted towards low temperatures. At the (RFE)->(PE) transition temperatures or slightly higher, the application of an electric field makes it possible to generate and align the nanopolar regions, inducing an entropy variation, and thus a significant electrocaloric effect over a wide temperature range.Relaxant ferroelectric polymers are characterized at 25°C, and at a frequency of about 1 Hz by a hysteresis cycle of the "electric displacement" curve as a function of the "applied electric field" much finer than the hysteresis cycle of a ferroelectric polymer. They typically have a coercive field less than or equal in absolute value to 45 V / pm and a remanent polarization less than or equal to 40 mC / m. 2 In the embodiments where X is CTFE or CFE, the molar proportion of units derived from CTFE or CFE may in particular be from 0.05% to 0.5%, or from 0.5% to 2%, or from 2% to 3%, or from 3% to 4%, or from 10% to 12%, or from 12% to 15%, relative to the number of moles of the units constituting the PF polymer.

[0109] The molar composition of units in fluoropolymers can be determined by various means such as infrared spectroscopy or RAMAN spectroscopy. Classical methods of elemental analysis in carbon, fluorine and chlorine or bromine or iodine, such as X-ray fluorescence spectroscopy, allow the mass composition of polymers to be calculated unambiguously, from which the molar composition is deduced.

[0110] Multi-nucleus NMR techniques, including proton (1 H) and fluorine (19 F), can also be used by analyzing a solution of the polymer in a suitable deuterated solvent. The NMR spectrum is recorded on an FT-NMR spectrometer equipped with a multi-nuclear probe. The specific signals given by the different monomers are then identified in the spectra produced according to one or the other nucleus. Thus, for example, the unit derived from TrFE gives a specific signal in proton NMR characteristic of the CFH group (at approximately 5 - 7 ppm, when the solvent is pyridine for example). The same is true for the CH2 groups of VDF (massive between 2 - 4 ppm, when the solvent is pyridine for example). The relative integration of the two signals gives the relative abundance of the two monomers, i.e. the VDF / TrFE molar ratio. Similarly, the CF3 group, for example, gives characteristic and well-isolated signals in fluorine NMR.The combination of the relative integrations of the different signals obtained in proton NMR and fluorine NMR leads to a system of equations whose resolution leads to obtaining the molar concentrations of the units resulting from the different monomers.

[0111] Finally, it is possible to combine elemental analysis, for example for heteroatoms such as chlorine, bromine or iodine, and NMR analysis. Thus, the content of CTFE-derived units in a P(VDF-TrFE-CTFE) terpolymer, for example, can be determined by measuring the chlorine content by elemental analysis.

[0112] The person skilled in the art thus has a range of methods or combinations of methods enabling him to determine unambiguously and with the necessary precision the composition of fluorinated polymers.

[0113] The PF polymer is preferably random. The PF polymer is preferably linear.

[0114] PF polymer can be produced using any known process, such as emulsion polymerization, suspension polymerization and solution polymerization.

[0115] When the fluoropolymer comprises units derived from VDF and / or TrFE as well as another monomer X as described above, it is preferable to use the method described in document WO 2010 / 116105. This method makes it possible to obtain polymers of high molecular weight and suitable structuring.

[0116] In brief, the preferred method includes the following steps:

[0117] - loading an initial mixture containing only VDF and / or TrFE (without the other monomer X) into a stirred autoclave containing water;

[0118] - heating the autoclave to a predetermined temperature, close to the polymerization temperature;

[0119] - injecting a radical polymerization initiator mixed with water into the autoclave, in order to reach a pressure in the autoclave which is preferably at least 80 bars, so as to form a suspension of the VDF and / or TrFE monomers in water;

[0120] - the injection of a second mixture of VDF and / or TrFE and X into the autoclave;

[0121] - as soon as the polymerization reaction starts, the continuous injection of said second mixture into the autoclave reactor, in order to maintain the pressure at an essentially constant level, preferably at least 80 bars.

[0122] The radical polymerization initiator may be, in particular, an organic peroxide of the peroxydicarbonate type. It is generally used in an amount of 0.1 to 10 g per kilogram of the total monomer loading. Preferably, the amount used is 0.5 to 5 g / kg.

[0123] The initial mixture advantageously comprises only VDF and / or TrFE in a proportion equal to that of the desired final polymer.

[0124] The second mixture advantageously has a composition which is adjusted so that the total composition of 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.

[0125] The weight ratio between the second mixture and the initial mixture is preferably from 0.5 to 2, more preferably from 0.8 to 1.6.

[0126] Implementing this process with an initial mixture and a second mixture makes the process independent of the reaction start-up phase, which is often unpredictable. The polymers thus obtained are in the form of a powder, without a crust or skin.

[0127] The pressure in the autoclave reactor is preferably 80 to 110 bars, and the temperature is maintained at a level preferably of 40°C to 60°C.

[0128] The second mixture can be injected continuously into the autoclave. It can be compressed before being injected into the autoclave, for example by using one or two successive compressors, generally at a pressure higher than the pressure in the autoclave.

[0129] After synthesis, the polymer can be washed and dried.

[0130] The weight average molar mass Mw of the PF polymer is preferably at least 100,000 g. mol' 1 , preferably at least 200,000 g. mol' 1 and more preferably at least 300,000 g. mol' 1 or at least 400,000 g. mol' 1. It can be adjusted by changing some process parameters, such as the temperature in the reactor, or by adding a transfer agent. The molecular weight distribution can be estimated by SEC (size exclusion chromatography) with dimethylformamide (DMF) as eluent, with a set of 3 columns of increasing porosity. The stationary phase is a styrene-DVB gel. The detection method is based on a measurement of the refractive index, and the calibration is carried out with polystyrene standards. The sample is dissolved at 0.5 g / L in DMF and filtered through a 0.45 µm nylon filter.

[0131] Adhesion Promoting Polymer Additive (APA)

[0132] APA polymer is a suitable polymer intended to improve the adhesion of fluoropolymer to a substrate by being added as an additive. This polymer includes units derived from the polymerization of methyl methacrylate (MMA) in order to allow good affinity between the PF fluoropolymer chains and the polymer chains of the APA additive.

[0133] Indeed, poly(methyl methacrylate) is known to have a good affinity with fluorinated polymers, in particular with poly(vinylidene fluoride) with which it is even miscible in all proportions (Flory-Huggins parameter x between PVDF and PMMA negative).

[0134] Advantageously, the Flory-Huggins parameter x between the fluoropolymer PF, in particular PVDF, and the APA additive is less than or equal to 0.5 and preferably less than or equal to 0. In the case where the APA polymer is a block polymer, it is one of the blocks, and according to certain embodiments all the blocks, which has / have a Flory-Huggins parameter x with the fluoropolymer PF, in particular PVDF, strictly less than 0.5, and preferably strictly less than 0.

[0135] The proportion of units derived from methyl methacrylate is generally at least 40% by weight, relative to the total weight of polymer of the APA additive.

[0136] According to advantageous embodiments, the proportion of units derived from methyl methacrylate may be at least 50%, and preferably at least 70%, by weight relative to the total weight of APA polymer. The proportion of units derived from methyl methacrylate may in particular 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 APA polymer.

[0137] According to particular embodiments, the proportion of units derived from methyl methacrylate may be at least 90% by weight, relative to the total weight of APA polymer. The proportion of units derived from methyl methacrylate may in particular 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 APA polymer.

[0138] The APA additive comprises at least one functional group intended to improve adhesion with a substrate, in particular by grafting to the surface of this substrate, referred to in the invention as a graftable functional group.

[0139] Said at least one graftable functional group is arranged at at least one end of the polymer chain of the APA additive.

[0140] Grafting consists of the formation of a strong interaction between the substrate and the APA additive, in particular by the formation of covalent bonds.

[0141] The APA additive is preferably a linear polymer and has two ends.

[0142] The APA additive can be either a random or gradient copolymer, or a block copolymer.

[0143] The term "statistical copolymer" means a copolymer resulting from the polymerization of at least two monomers in which the distribution of the monomer units along the chain follows a statistical law, for example of the Bernoullian type (Markov zero order) or Markovian of the first or second order.

[0144] The term "gradient copolymer" is understood to mean a copolymer resulting from the polymerization of at least two monomers generally obtained by living or pseudo-living polymerization, such as the NMP polymerization presented below. Thanks to these polymerization modes, the polymer chains grow simultaneously and therefore incorporate the same ratios of comonomers at each instant. The distribution of the comonomers in the polymer chains therefore depends on the evolution, during the synthesis, of the relative concentrations of the comonomers.

[0145] The term "block copolymer" means a copolymer resulting from the polymerization of at least two monomers, comprising one or more uninterrupted sequences of each of the distinct polymer species, the polymer sequences being chemically different from one or more of the other(s) and being linked together by a chemical bond (covalent, ionic, hydrogen bond, or coordination).

[0146] In some embodiments, "group disposed at one end of the polymer chain" may mean that a group is located at the end of the polymer chain.

[0147] The graftable functional group may be arranged at one end, or at two ends, or at several ends, or at all ends of the polymer chain. In the preferred case where the polymer is linear, the graftable functional group may be arranged at one end or at both ends of the polymer chain.

[0148] Preferably, the polymer chain does not comprise any graftable functional group(s) apart from said at least one graftable functional group arranged at one of the ends, or at two of the ends, or at several of the ends, or at all of the ends of the polymer chain. In the preferred case where the polymer is linear, said at least one graftable functional group may be arranged at only one end of the polymer chain, the polymer chain not comprising any other graftable functional group apart from said at least one graftable functional group arranged at only one end of the polymer chain. In the preferred case where the polymer is linear, said at least one graftable functional group may be arranged at both ends of the polymer chain, the polymer chain not comprising any other graftable functional group apart from said at least one graftable functional group at both ends of the polymer chain.

[0149] Said at least one graftable functional group disposed at said at least one end of the polymer chain of the APA additive may be introduced by a polymerization initiator (as exemplified in the present application) and / or by a chain limiting agent or by a capping agent.

[0150] A set of graftable functional groups arranged at said at least one end of the polymer chain of the APA additive may be introduced using a repeating unit having said at least one graftable functional group in a small block “A” in the case of a block polymer. The block polymer may in particular be of the AB or ABA type, the block “A” comprising a repeating unit comprising at least one graftable functional group and the block “B” having a good affinity for the fluoropolymer PF. The at least one graftable functional group arranged at at least one end of the polymer chain of the APA additive may advantageously be chosen from: nitroxy, carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0151] According to certain embodiments, the at least one graftable functional group disposed at one end of the polymer chain of the APA additive may be a nitroxy.

[0152] According to certain embodiments, the at least one graftable functional group disposed at one end of the polymer chain of the APA additive may be selected from: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0153] According to preferred embodiments, the at least one graftable functional group disposed at one end of the polymer chain of the APA additive may be chosen from: hydroxyl, carboxyl, and phosphonic acid.

[0154] According to particular embodiments, the at least one graftable functional group arranged at one end of the polymer chain of the APA additive is chosen from: hydroxyl and carboxyl.

[0155] According to certain embodiments, the APA additive comprises at one end of its chain at least one graftable functional group, in particular a single graftable functional group, being a hydroxyl.

[0156] According to certain embodiments, the APA additive comprises at one end of its chain at least one graftable functional group, in particular a single graftable functional group, being a carboxyl.

[0157] According to certain embodiments, the APA additive comprises at the same end of its chain a graftable functional group being a hydroxyl and a graftable functional group being a carboxyl.

[0158] According to certain embodiments, the APA additive comprises at one end of its chain a nitroxy and does not comprise any other graftable functional group.

[0159] According to certain embodiments, the APA additive comprises at one end of its chain a nitroxy and comprises at another end of its chain at least one graftable functional group chosen from: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

[0160] According to certain embodiments, the APA additive comprises at one end of its chain a nitroxy and comprises at another end of its chain at least one graftable functional group chosen from: hydroxyl, carboxyl, and phosphonic acid.

[0161] According to certain embodiments, the APA additive comprises at one end of its chain a nitroxy and comprises at another end of its chain at least one graftable functional group chosen from: hydroxyl and carboxyl. According to certain embodiments, the APA additive comprises at one end of its chain a nitroxy and comprises at another end of its chain a single graftable functional group, being a hydroxyl.

[0162] According to certain embodiments, the APA additive comprises at one end of its chain a nitroxy and comprises at another end of its chain a single graftable functional group, being a carboxyl.

[0163] According to certain embodiments, the APA additive comprises at one end of its chain a nitroxy and comprises at another end of its chain a graftable functional group being a hydroxyl and a graftable functional group being a carboxyl.

[0164] According to certain embodiments, the APA additive may comprise at least one other repeating unit different from that resulting from the polymerization of methyl methacrylate.

[0165] According to certain embodiments, the APA additive may in particular comprise at least one repeating unit comprising said at least one graftable functional group. These embodiments relate in particular to cases where the APA polymer is a block polymer, in particular an AB or ABA type block polymer, where the block(s) A each comprise, independently of one another, said at least one repeating unit comprising said at least one graftable functional group and the block “B” has a good affinity for the fluoropolymer PF. Advantageously, said at least one repeating unit comprising at least one graftable functional group does not comprise a crosslinkable function. In particular, it does not comprise a group of oxirane, aziridine or thiirane type, or a carbon-carbon double bond, or a carbon-carbon triple bond.

[0166] In these embodiments, block B advantageously has a Flory-Huggins parameter x with the fluorinated polymer PF less than or equal to 0.5 and preferably less than or equal to 0. Block B preferably comprises at least 70% by mass of repeating unit derived from methyl methacrylate relative to the total mass of block B. The proportion of units derived from methyl methacrylate in block B may in particular 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 particular embodiments, the proportion of units derived from methyl methacrylate in block B may 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 comprise a repeating unit comprising a graftable functional group.

[0167] In these embodiments, the A block(s) represent in total less than 50% by weight of the total weight of the APA block polymer. The A block(s) may represent less than 40% by weight, or less than 30% by weight, or less than 25% by weight, or less than 20% by weight, or less than 15% by weight, or less than 10% by weight, of the total weight of the APA block polymer. In certain embodiments, said at least one repeating unit comprising said at least one graftable functional group may represent less than 20% by weight, or less than 15% by weight, or less than 10% by weight, or less than 5% by weight, of the total weight of the APA block polymer.

[0168] Advantageously, the block(s) A have, independently of one another, less affinity with the fluoropolymer PF than the block B. The proportion of units derived from methyl methacrylate in each block A may represent less than 25%, or less than 20%, or less than 15%, or less than 10%, or less than 5% by weight relative to the total weight of said block A. The block(s) A may, independently of one another, not contain any repeating unit derived from methyl methacrylate. According to certain embodiments, the block(s) A have, independently of one another, a Flory-Huggins parameter x with the fluoropolymer PF strictly greater than 0.5.

[0169] According to certain embodiments, a repeating unit comprising said at least one graftable functional group may in particular be chosen from acrylic, methacrylic, non-(meth)acrylic vinyl monomers. It may in particular be chosen 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-methacryloxypropyl trimethoxysilane, 3-methacryloxypropylmethyl dimethoxysilane, methacryloxymethyl trimethoxysilane, 3-methacryloxypropyl tris(2-methoxyethoxy) silane, phosphorus-containing methacrylates such as alkylene glycol phosphate methacrylates,non-meth(acrylic) silylated vinyl monomers, such as vinyl trimethoxysilane, vinyl diimethoxymethylsilane, vinyl triethoxysilane, vinyl tripropoxysilane, vinyl triisopropoxysilane, vinyl tris(methoxyethoxy)silane, vinyl tributoxysilane, vinyl triacetoxysilane, vinyl trichlorosilane, vinyl methyldichlorosilane, vinyltris(2-methoxyethoxy)silane, and silylated styrenic monomers.,

[0170] According to certain embodiments, a repeating unit comprising said at least one graftable functional group may in particular be chosen from acrylic acid or its salts, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate, methacrylic acid or its salts, and hydroxyalkyl methacrylates such as 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate.

[0171] When the APA additive is a random or gradient polymer, said at least one other repeating unit different from that derived from methyl methacrylate preferably does not comprise a graftable functional group. According to certain embodiments, said at least one other repeating unit than that derived from methyl methacrylate does not comprise a graftable functional group.

[0172] Such a repeating unit may in particular be chosen from vinylaromatic monomers such as styrene or substituted styrenes, in particular alpha-methylstyrene, tert-butylstyrene, ortho-, meta-, or para-methylstyrene, ortho-, meta- or para-ethylstyrene, o-methyl-p-isopropylstyrene, alkyl, cycloalkyl or aryl acrylates such as methyl, ethyl, propyl, butyl, ethylhexyl or phenyl acrylate, etheralkyl acrylates such as 2-methoxyethyl acrylate, alkoxy- or aryloxy-polyalkylene glycol acrylates such as methoxypolyethylene glycol acrylates, ethoxypolyethylene glycol acrylates, methoxypolypropylene glycol, methoxy-polyethylene glycol-polypropylene glycol acrylates, fluorinated acrylates, isobornyl acrylate, 4-tert-butyl cyclohexyl acrylate, alkyl, cycloalkyl, alkenyl or aryl methacrylates such as methyl, ethyl, propyl, butyl methacrylate,lauryl, cyclohexyl, allyl, phenyl or naphthyl, etheralkyl methacrylates such as 2-ethoxyethyl methacrylate, alkoxy- or aryloxy-polyalkylene glycol methacrylates such as methoxypolyethylene glycol methacrylates, ethoxypolyethylene glycol methacrylates, methoxypolypropylene glycol methacrylates, methoxy-polyethylene glycol-polypropylene glycol methacrylates, and fluorinated methacrylates such as 2,2,2-trifluoroethyl methacrylate.,

[0173] Advantageously, said at least one repeating unit other than that derived from methyl methacrylate not comprising a graftable functional group also does not comprise a crosslinkable function. In particular, it does not comprise a group of oxirane, aziridine or thiirane type, or a carbon-carbon double bond, or a carbon-carbon triple bond. For example, said at least one repeating unit other than that derived from methyl methacrylate not comprising a functional group is advantageously not a unit derived from glycidyl methacrylate.

[0174] According to certain embodiments, said at least one other repeating unit than that derived from methyl methacrylate not comprising a graftable functional group represents 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 APA polymer.

[0175] According to certain embodiments, the APA additive is a polymer, essentially consisting of, or consisting of, a repeating unit derived from methyl methacrylate, optionally of at least one repeating unit different from methyl methacrylate and not comprising a graftable functional group, and also optionally of at least one repeating unit different from methyl methacrylate comprising a graftable functional group. According to particular embodiments, the APA additive is a block polymer, in particular of the ABA or AB type, in which:

[0176] - the block(s) A each comprise, independently of one another, said at least one repeat unit comprising said at least one graftable functional group;

[0177] - the proportion of units derived from methyl methacrylate in each block A represents less than 25%, or less than 20%, or less than 15%, or less than 10%, or less than 5% by weight relative to the total weight of said block A;

[0178] - block B does not include any repeating unit comprising a graftable functional group;

[0179] - the proportion of units derived from methyl methacrylate in block B represents 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 in block B; and,

[0180] - the A block(s) represent in total less than 50% by weight of the total weight of the APA block polymer.

[0181] According to particular embodiments, the APA additive is a random or gradient polymer, essentially consisting of, or consisting of, a repeating unit derived from methyl methacrylate and at least one different repeating unit of methyl methacrylate and not comprising a graftable functional group.

[0182] The APA additive may, for example, be a statistical or gradient polymer, consisting of repeating units derived from methyl methacrylate and styrene, the mass proportion of repeating units derived from styrene representing from 0.5% to 15%, and preferably from 1.0% to 10%, relative to the total mass of repeating units derived from methyl methacrylate and styrene.

[0183] Advantageously, the APA additive has a number average molar mass of 1000 g / mol to 100,000 g / mol, and preferably of 2000 g / mol to 50,000 g / mol. The molecular weight distribution can be estimated by SEC with polystyrene standards.

[0184] The APA additive can be implemented by any polymerization technique known to those skilled in the art. It is generally manufactured by radical polymerization and preferably by controlled radical polymerization. Among the controlled radical polymerization techniques, we can cite: NMP ("Nitroxide Mediated Polymerization"), RAFT ("Reversible Addition and Fragmentation Transfer"), ATRP ("Atom Transfer Radical Polymerization"), INIFERTER ("Initiator-Transfer-Termination"), and RITP ("Reverse Iodine

[0185] Transfer Polymerization").

[0186] According to advantageous embodiments, the APA additive can be manufactured by NMP, i.e. by nitroxide-controlled radical polymerization, using an alkoxyamine carrying at least one graftable functional group. This synthesis technique is well known to those skilled in the art and is for example described in EP1468029 and EP1526138. Block polymers comprising MMA as a repeating unit are commercially available under the name Nanostrength® (Arkema).

[0187] Alkoxyamine

[0188] Alkoxyamines have the chemical formula:

[0189] [Chem 3] in which:

[0190] - Ri is a cyclic or non-cyclic hydrocarbon group with or without heteroatom which may contain at least one metallic species;

[0191] - R2 is a cyclic or non-cyclic hydrocarbon group with or without heteroatom which may contain at least one metallic species;

[0192] - Ri and R2 may or may not be part of the same cyclic structure;

[0193] - Z is a monovalent hydrocarbon group, cyclic or not, with or without heteroatom.

[0194] According to advantageous embodiments, Z comprises a graftable functional group.

[0195] Preferably, the alkoxyamines are those whose nitroxide (also called controlling fragment) is chosen from the following:

[0196] - nitroxides of formula: (with R=H, alkyl fragment, SO2-Ph, SC Me, Na, K), (with e, ),

[0197]

[0198] - (2,2,6,6-tetramethylpiperidin-1-yl)oxy or (2,2,6,6-tetramethylpiperidin-1 - yl)oxyl

[0199] - N-tert-butyl-1-phenyl-2-methylpropyl nitroxide,

[0200] - N-(2-hydroxymethylpropyl)-1-phenyl-2-methylpropyl nitroxide,

[0201] - N-tert-butyl-1-dibenzylphosphono-2,2-dimethyl-propyl nitroxide

[0202] -N-tert-butyl-1-di(2,2,2-trifluoroethyl)phosphono-2,2-dimethylpropyl-nitroxide,

[0203] - N-tertiobutyl[(1-diethylphosphono)-2-methylpropyl]nitroxide,

[0204] - N-(1-methylethyl)-1-cyclohexyl-1-(diethylphosphono)nitroxide,

[0205] - N-(1-phenylbenzyl)-[(1-diethylphosphono)-1-methylethyl]nitroxide,

[0206] - N-phenyl-1-diethylphosphono-2,2-dimethylpropylnitroxide,

[0207] - N-phenyl-1-diethylphosphono-1-methylethylnitroxide,

[0208] - N-(1-phenyl2-methylpropyl)-1-diethylphosphonomethylethylnitroxide,

[0209] - and N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide. The latter nitroxide is the preferred nitroxide for the polymerization of acrylic or methacrylic repeating unit(s). A commercially available alkoxyamine comprising this nitroxide is N-(2-methylpropyl)-N-(1 - diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxyprop-2-yl)hydroxylamine having the following structural formula (II):

[0210] [Chem 4]

[0211] This compound is marketed by the company ARKEMA under the name Blocbuilder®.

[0212] Derivatives of the abovementioned alkoxyamines, in particular derivatives of the alkoxyamine of formula (I), can be obtained by the reaction of an equivalent of alkoxyamine with an acrylic, methacrylic, or vinylaromatic monomer carrying said at least one graftable functional group. These monomers may in particular be chosen from: silylated styrenes, acrylic acid and its salts, hydroxyalkyl acrylates, in particular C2-C10 hydroxyalkyl acrylates and for example 2-hydroxyethyl acrylate, phosphorus-containing acrylates such as alkylene glycol phosphate acrylates, silylated acrylates, methacrylic acid and its salts, hydroxyalkyl methacrylates, in particular C2-C10 hydroxyalkyl methacrylates and for example 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, and methacrylates such as 3-methacryloylpropyltrimethylsilane.

[0213] Composition

[0214] The composition comprises at least one, i.e. one or more, fluoropolymer PF and at least one, i.e. one or more, APA additive.

[0215] The composition may in particular comprise a single type of fluoropolymer and a single type of APA additive.

[0216] The mass proportion of APA additive(s) relative to the fluoropolymer(s) PF in the composition is from 0.005% to 5%, it being understood that if the composition comprises several APA additives, respectively several fluoropolymers, the mass proportion is expressed by considering the total weight of APA additives and respectively by considering the total weight of fluoropolymers.

[0217] For the sake of brevity and clarity, in the remainder of the section devoted to the composition, the determinants "a" and "the" have been used before "APA additive" and "PF fluoropolymer". They mean by default, and unless otherwise stated, "at least one" and "said at least one" APA additive and "at least one" and "said at least one" PF fluoropolymer. They include, according to particular embodiments, cases where the composition comprises only one type of fluoropolymer and / or one type of APA additive.

[0218] The mass proportion of APA additive relative to the PF polymer in the composition may in particular be from 0.005% to 0.01%, or from 0.01% to 0.05%, or from 0.05% to 0.1%, or from 0.1% to 0.3%, or from 0.3% to 0.5%, or from 0.5% to 0.7%, or from 0.7% to 0.9%, or from 0.9% to 1.0%, or from 1.0% to 2.0%, or from 2.0% to 3.0%, or from 3.0% to 4.0%, or from 4.0% to 5.0%. Ranges of 0.01 to 3.0%, and from 0.05 to 2.0% of APA polymer additive constitute examples of preferred ranges. Advantageously, the mass proportion of APA additive relative to the PF polymer in the composition is 0.01% or more, and preferably 0.05% or more, so as to significantly improve the adhesion of the PF fluorinated polymer.

[0219] Advantageously, the mass proportion of APA additive relative to the PF polymer in the composition is kept as low as possible so as to have the least possible impact on the useful properties of the PF fluorinated polymer. It may in particular be 3.0% or less, and preferably 2.0% or less.

[0220] The PF polymer and the APA additive can be dissolved in a solvent or a mixture of solvents.

[0221] By "solution" is meant a homogeneous dispersion of the constituents in the solvent, at the molecular level. The term solution is used here in contrast to a suspension of polymer particles in a liquid vehicle, and in contrast to a polymer emulsion or latex.

[0222] Preferably, the solvent is chosen from: dimethylformamide; N-methyl-2-pyrrolidone; dimethylacetamide; dimethylsulfoxide; γ-butyrolactone; ketones, in particular acetone, methyl ethyl ketone (or butan-2-one), methyl isobutyl ketone, cyclopentanone, cyclohexanone, diisobutyl ketone; furans, in particular tetrahydrofuran; esters, in particular methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol methyl ether acetate, glyceryl triacetate, diethylene glycol monobutyl ether acetate, and ethyl acetoacetate; carbonates, in particular dimethylcarbonate and propylene carbonate; and phosphates, in particular trimethylphosphate and triethylphosphate. Mixtures of these compounds can also be used.

[0223] In some embodiments, the solvent may be N-methyl-2-pyrrolidone.

[0224] In some embodiments, the solvent may be selected from the list consisting of: 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, trimethylphosphate, triethylphosphate. Mixtures of these compounds may also be used.

[0225] The composition, in solution form, preferably comprises from 0.1 to 60%, preferably from 0.5 to 30% by weight, more preferably from 1 to 20% by weight, and extremely preferably from 3 to 15% by weight of non-volatile dry matter.

[0226] The composition may optionally comprise one or more additives other than the APA additive, in particular chosen from surface tension modifying agents, rheology modifying agents, ageing resistance modifying agents, pigments or dyes, fillers (including nanofillers). The other additive(s) generally represent less than 10%, preferably less than 5%, and even more preferably less than 1% by weight relative to the weight of PF polymer.

[0227] According to certain embodiments, the composition is essentially composed of, or consisting of, at least one fluoropolymer and at least one APA additive. The composition may optionally comprise one or more additives other than the APA additive.

[0228] According to some embodiments, the composition consists essentially of, or consists of, at least one fluoropolymer, at least one APA additive and one or more miscible solvents. The composition may optionally comprise one or more additives other than the APA additive.

[0229] Preparation of a composition in the form of a solution

[0230] The solution composition can be prepared by dissolving the PF polymer, dissolving the APA additive, and mixing. The dissolution of the PF and APA polymers can be simultaneous or not as described below.

[0231] The temperature applied during this preparation is preferably from 0 to 60°C, more preferably from 10 to 50°C, more preferably from 15 to 40°C, and ideally from 20 to 30°C. In certain embodiments, the preparation is carried out at room temperature. Advantageously, the preparation is carried out with moderate stirring.

[0232] In some variants, the PF polymer is dissolved in the solvent on one side, and the APA polymer is dissolved in the same solvent on the other side, and then the two solutions are mixed. The solvent used can be formed by a single compound or by a mixture of compounds miscible with each other.

[0233] In other variants, one of the PF and APA polymers is dissolved in the solvent, and then the other of the PF and APA polymers is added to the solution and dissolved in turn. The solvent used can be formed by a single compound or by a mixture of compounds miscible with each other.

[0234] In still other variants, the solvent of the composition is a mixture of a first solvent and a second solvent of different compositions which are miscible with each other. The PF polymer is dissolved in the first solvent to form a first solution, the APA polymer is dissolved in the second solvent to form a second solution, and then the first solution and the second solution are mixed to form the composition in solution form. The first solvent and the second solvent may each be formed by a single compound or by a mixture of compounds which are miscible with each other. For example, the first solvent and the second solvent may each be formed by mixtures of the same compounds, in different proportions between the first solvent and the second solvent.

[0235] When additives other than the APA polymer additive are to be added to form the solution composition, they may be added before, during or after the PF polymer and polymer additive are dissolved.

[0236] The miscibility of solvent compounds with each other, or of solvents with each other, is checked by obtaining a transparent and homogeneous solution after mixing, at the preparation temperature which is used (and preferably at room temperature).

[0237] The solutions of fluoropolymer(s) with APA polymer additives can generally be stored if necessary for a period ranging from several days to several weeks or several months, since the APA polymer does not a priori degrade the fluoropolymer chains, as demonstrated in Example 5.

[0238] Process for manufacturing a coating on a substrate

[0239] The substrate on which the composition can be deposited may be an electrical conductor, an electrical insulator or a semiconductor. The substrate may in particular be a surface of glass, or silicon, or quartz, or polymer material (in particular polyethylene terephthalate, polyethylene naphthalate, PEDOT-PSS), or metal, or a mixed surface composed of several different materials.

[0240] According to certain preferred variants, the substrate is or comprises a metallic surface M, comprising gold, silver, chromium, aluminum, copper, lithium, zinc, nickel, cobalt, manganese, and their alloys. According to certain preferred variants, the substrate is or comprises an oxidized surface, with functions of the -M-OH type, M representing a metallic atom which may in particular be gold, silver, chromium, aluminum, copper, lithium, zinc, nickel, cobalt, manganese, and their alloys.

[0241] According to certain preferred variants, the substrate is or comprises a surface comprising silanol -SiOH functions, and in particular a glass or silicon surface.

[0242] The application of the composition to form a coating may include spreading by discrete or continuous means. The deposition may be carried out in particular by spin-coating, by spray coating, by bar coating, by slotted head coating, by dip coating, by roll-to-roll printing, by screen printing, by flexographic printing, by lithographic printing or by inkjet printing, by electrospinning, or by extrusion.

[0243] According to particular embodiments, the deposition of a composition not comprising a solvent can be carried out by extrusion.

[0244] According to particular embodiments, the deposition of a composition in the form of a solution can be carried out by coating, in particular with a bar or a film puller ("bar coating") or by screen printing.

[0245] When the composition is applied in solution form, the solvent must be evaporated after deposition. Evaporation may be carried out at room temperature (23°C) and / or by heating to a temperature preferably ranging from 50 to 150°C. The layer may be subjected to ventilation to facilitate evaporation. The evaporation time may be, for example, from 1 minute to 24 hours, preferably from 2 minutes to 5 hours, and more preferably from 3 minutes to 2 hours. The evaporation time may in particular be less than 1 hour. The evaporation time may in particular be 30 minutes or less, or 20 minutes or less, or 15 minutes or less, or 10 minutes or less.

[0246] The coating formed may have a thickness of 1 μm to a thickness of the order of a millimeter. Such thicknesses may be obtained by a single deposition according to one of the aforementioned methods or by a deposition of successive layers produced by iteration of at least one of the aforementioned methods.

[0247] According to certain embodiments, the coating has a thickness of 1 μm to 100 μm. The coating may in particular have a thickness of 1 μm to 10 μm, or of 10 μm to 50 μm, or of 50 μm to 100 μm. The coating may in particular be in the form of a film of substantially constant thickness.

[0248] According to certain embodiments, the coating has a thickness of 100 μm to 1000 μm. The coating may in particular have a thickness of 100 μm to 250 μm, or of 250 μm to 500 μm, or of 500 μm to 1000 μm. The coating may in particular be in the form of a layer of substantially constant thickness.

[0249] According to certain embodiments, the coating has a thickness strictly greater than 1000 μm, for example 1 to 2 mm.

[0250] One or more annealing steps may be carried out after the formation of the coating comprising the fluoropolymer(s) and the APA additive(s) on the substrate. Annealing makes it possible in particular to obtain the grafting, if necessary the increase in grafting, of the APA additive on the substrate and / or to increase the crystallization of the fluoropolymer. The annealing step(s) may in particular be carried out, independently of each other, at a temperature of 80°C to 220°C. The temperature of each annealing may in particular be from 80°C to 100°C, or from 100°C to 120°C, or from 120°C to 150°C, or from 150°C to 160°C, or from 160°C to 170°C, or from 170°C to 180°C, or from 180°C to 190°C, or from 190°C to 200°C, or from 200°C to 220°C. The duration of each annealing may be for example from 1 minute to 2 hours, and preferably from 2 minutes to 30 minutes, it being understood that, generally speaking, the higher the temperature of an annealing, the more the duration of this annealing can be reduced.The duration of each annealing may be 30 minutes or less, or 20 minutes or less, or 10 minutes or less. The duration of each annealing may be 1 minute or more, 2 minutes or more, or 3 minutes or more.

[0251] The annealing may in particular be carried out in a single step by subjecting the deposited layer to a temperature of 80 to 220°C, preferably 90 to 200°C, more preferably 100°C to 180°C, more preferably 110°C to 160°C, and in particular 120 to 150°C. The duration of this single annealing may be, for example, 1 minute to 2 hours, and preferably 2 minutes to 30 minutes. The duration of this single annealing may be 30 minutes or less, or 20 minutes or less, or 10 minutes or less. The duration of this single annealing may be 1 minute or more, 2 minutes or more, or 3 minutes or more. In some embodiments, a single anneal is performed at a temperature of 150°C or less for a period of 30 minutes or less, for a period of 20 minutes or less, or for a period of 10 minutes or less.

[0252] The annealing may also be carried out in several stages, for example two stages, a first annealing may be carried out at a high temperature, from more than 150°C to 200°C. A second annealing may be carried out at a lower temperature, from 100°C to 150°C. In this embodiment, the duration of each annealing may be for example from 30 seconds to 1.5 hours, preferably from 45 seconds to 1 hour, and more preferably from 1 minute to 30 minutes. The duration of the first annealing may be for example from 30 seconds to 30 minutes, and preferably from 1 minute to 15 minutes. The duration of the first annealing may be 15 minutes or less, or 10 minutes or less, or 5 minutes or less. The duration of the second annealing may be for example from 1 minute to 1.5 hours, and preferably from 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.

[0253] Thus, the grafting can be carried out in one or more steps, by heating during the evaporation of the solvent (in the case where the composition is applied in the form of a solution) and / or during at least one annealing step. The grafting can in particular be carried out by one or more heating steps at a temperature of 50°C to 220°C, and preferably of 80°C to 200°C. For each heating, the temperature ranges may be chosen 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, the grafting may be carried out in one or more steps, by heating to a temperature less than or equal to 200°C, and preferably less than or equal to 160°C, and more preferably less than or equal to 120°C.

[0254] The grafting may last in total from 1 minute to 6 hours, and 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 grafting may in particular last 45 minutes or less, 30 minutes or less, 20 minutes or less, 15 minutes or less, or 10 minutes or less.

[0255] According to certain embodiments, the grafting can be carried out by one or more heating steps at a temperature less than or equal to 200°C, and preferably less than or equal to 160°C, and preferably still 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 preferably still 10 minutes or less.

[0256] According to particular embodiments, the grafting can be carried out by one or more heating steps at a temperature less than or equal to 160°C for a total duration less than or equal to 20 minutes.

[0257] According to particular embodiments, the grafting can be carried out by a single heating step at a temperature less than or equal to 160°C for a duration less than or equal to 20 minutes.

[0258] According to particular embodiments, the grafting can be carried out by one or more heating steps at a temperature less than or equal to 120°C for a total duration less than or equal to 15 minutes.

[0259] According to particular embodiments, the grafting can be carried out by a single heating step at a temperature less than or equal to 120°C for a duration less than or equal to 15 minutes.

[0260] In embodiments where the fluoropolymer is a ferroelectric polymer, for example P(VDF-TrFE), the coating grafted onto the substrate can then be polarized according to methods known per se: by contact polarization by applying a direct or alternating voltage or by non-contact polarization using the Corona effect.

[0261] Coating adhering to its substrate

[0262] The invention also relates to a composite comprising a coating based on fluoropolymer(s) adhering to a substrate.

[0263] The coating has as its composition compositions derived from the compositions according to the invention after their application and their grafting onto a substrate.

[0264] At least a portion of said at least one APA additive present in the composition to be applied is grafted to the surface of the substrate and ensures good adhesion of the coating to the substrate. In the embodiments where the composition according to the invention to be applied is in solution form, i.e. comprises one or more solvents, the composition of the coating corresponds to the same composition essentially free of, or free of, the solvent(s).

[0265] The composite is advantageously obtained by the manufacturing process according to the invention of a coating on a substrate.

[0266] Device

[0267] The invention also relates to a device comprising such a composite. The polymer coating may be electroactive, be an insulating and / or protective layer, or even be an electrode binder.

[0268] The device may in particular be an optoelectronic device, a transistor, in particular a field effect transistor, a chip, a battery, a photovoltaic cell, a light-emitting diode, in particular an organic light-emitting diode, a sensor, an actuator, a transformer, a haptic device, a microelectromechanical system and a detector.

[0269] Use

[0270] The invention relates to the use of APA polymer(s) as additive(s) in a composition based on fluorinated polymer(s) to improve the adhesion of the fluorinated polymer(s) to a substrate, the APA polymer(s) comprising a repeating unit derived from methyl methacrylate, and at least one graftable functional group arranged at one end of its polymer chain.

[0271] The examples below show in particular that the use of an APA polymer, even in very small proportions, can increase the adhesion of a fluoropolymer to any type of substrate, in particular metals (aluminium, silver) and a polymer material (PEDOT:PSS). The use of the APA polymer can make it possible to obtain an adhesion between a coating based on fluoropolymer(s) and its substrate greater than or equal to 1.0 N Z25 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 according to a 180° peel test carried out at a speed of 0.5 mm / s on a 25 mm wide strip of coating.The use of the APA polymer can make it possible to increase adhesion between a coating based on fluoropolymer(s) and its substrate by more than 25%, or more than 50%, or more than 100%, or more than 250%, or more than 500%. The examples below show that the APA polymer can in particular be used as an additive in a ferroelectric fluoropolymer composition to improve adhesion without significantly altering its electroactive properties. The APA polymer added in the above-mentioned proportions reduces the remanent polarization as measured according to Example 4 of the additivated fluoropolymer by less than 12%, preferably less than 10%, more preferably less than 8%, more preferably less than 6%, more preferably less than 4% and extremely preferably less than 3% compared to the non-additivated fluoropolymer.

[0272] The examples below show that the APA polymer can in particular be used as an additive in a relaxor ferroelectric fluoropolymer composition to improve adhesion while improving or without significantly altering its electroactive properties. The APA polymer added in the above-mentioned proportions makes it possible in particular to increase the dielectric constant at a frequency greater than or equal to 1 KHz compared to the non-additive fluoropolymer 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 be from 25% to 45%. The APA polymer added in the above-mentioned proportions makes it possible in particular not to significantly vary the dielectric losses at a frequency greater than or equal to 1 KHz compared to the non-additive fluoropolymer at all temperatures between 23°C and 110°C.

[0273] The APA polymer and the fluoropolymer(s) may be as described above in the body of the description.

[0274] The composition based on fluoropolymer(s) may, before adding the APA polymer, consist essentially of, or consist of at least one fluoropolymer. This composition may optionally include one or more additives other than the APA additive.

[0275] The composition based on fluoropolymer(s) may, before adding the APA polymer, be essentially composed of, or composed of, at least one fluoropolymer and one or more miscible solvents. This composition may optionally comprise one or more additives other than the APA additive. According to advantageous embodiments, the weight of APA polymer may represent from 0.005% to 5.0% by weight of the total weight of fluoropolymer(s). The weight of APA polymer may preferably represent 0.01% or more, and more preferably 0.05% or more, relative to the total weight of fluoropolymer(s). The weight of APA polymer may preferably represent 3.0% or less, and more preferably 2.0% or less, relative to the total weight of fluoropolymer(s).

[0276] Examples

[0277] Example 1 - Synthesis of an adhesion promoting additive (APA-1) A hydroxy-functionalized alkoxyamine was prepared from the alkoxyamine BlocBuilder®MA, marketed by Arkema. This alkoxyamine has the chemical formula:

[0278] [Chem 5]

[0279] In a 1 L nitrogen-purged flask, 226.17 g of BlocBuilder®MA (1 equivalent), 68.9 g of 2-hydroxyethyl acrylate (1 equivalent), and 548 g of isopropanol were introduced. The reaction mixture was heated at reflux (80 °C) for 4 h and then the isopropanol was evaporated under vacuum. This gave 297 g of hydroxyl-functionalized alkoxyamine in the form of a very viscous yellow oil.

[0280] A synthesis of a P(M MA-S) gradient copolymer was carried out by nitroxide-controlled polymerization using the synthesized hydroxyl-functionalized alkoxyamine. Toluene, styrene (S) and methyl methacrylate (MMA) monomers, and hydroxyl-functionalized alkoxyamine were introduced into a stainless steel reactor equipped with a mechanical stirrer and a jacket. The mass ratio between styrene (S) and methyl methacrylate (MMA) monomers was 5 / 95, respectively. The mass loading of toluene was set at 30% relative to the reaction medium. The reaction mixture was stirred and degassed by bubbling nitrogen at room temperature for 30 minutes. The temperature of the reaction medium was then raised to 115°C. Time t=0 was triggered at room temperature (23°C).The temperature was maintained at 115°C throughout the polymerization until a monomer conversion of around 70% was reached. Samples were taken at regular intervals to determine the polymerization kinetics by gravimetry (dry extract measurement). When a conversion of 70% was reached, 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 such a quantity as to produce a copolymer solution of around 25% by mass. This copolymer solution was then introduced dropwise into a beaker containing a non-solvent (heptane), so as to precipitate the copolymer. The mass ratio between solvent and non-solvent (methyl ethyl ketone / heptane) was around 1 / 10. The precipitated copolymer was recovered as a white powder after filtration and drying.The copolymer thus synthesized and purified is called “APA-1” in the following examples. It was used as an adhesion promoting additive.

[0281] Example 2 - Evaluation of adhesion properties for an additive fluoropolymer film on an aluminum substrate

[0282] A P(VDF-TrFE) copolymer, consisting of repeating units derived from vinylidene fluoride (VDF) and trifluoroethylene (TrFE), having a VDF:TrFE molar ratio of 80.0:20.0 (Piezotech®FC20, marketed by Arkema), was used as the fluoropolymer. This polymer is referred to as “PF-1” in the following examples.

[0283] Solutions of PF-1 supplemented with APA-1 were implemented as follows: The fluoropolymer was dissolved in methyl ethyl ketone (MEK) to obtain a 10% mass solution (by weight of PF-1 relative to the weight of MEK).

[0284] The APA-1 copolymer was also dissolved in MEK at 10% by weight (weight of PF-1 relative to weight of MEK).

[0285] The two solutions thus prepared were mixed so as to obtain solutions of variable concentrations of APA-1, containing from 0% to 0.20% (low value in additive 0.01%) by mass of APA-1 relative to the mass of fluoropolymer PF-1.

[0286] Films of PF-1 fluorinated polymer with various proportions of APA-1 and a film of non-additive PF-1 fluorinated polymer were prepared on 1235 aluminum substrates (15 μm thick sheet). The aluminum substrates were previously cleaned with a cloth soaked in ethanol. On a first half of these substrates, a solution of egg lecithin, used as an anti-adhesive, dissolved at a level of 1% by mass in cyclohexane, was dispensed by bar-coating, then the film was dried at room temperature. The PF-1 solutions, with or without additives, were then dispensed over the entire substrate by bar-coating so as to obtain films having a thickness of 15 μm once dried. The wet films were left to dry at room temperature (23°C) for fifteen minutes, then were placed in an oven for twenty minutes at 140°C. The substrates thus prepared were cut into 25 mm wide strips.

[0287] The samples produced were tested on an Instrom® 5565 type tensile testing machine, equipped with a 100 N force sensor, via a 180° peel test carried out at a speed of 0.5 mm / s, according to the diagram shown in Figure 1. With reference to this figure, the film 3 of PF-1, with or without additives, deposited on the aluminum substrate 1 and the egg lecithin anti-adhesive 2, undergoes a 180° peel test by applying a tensile force 4.

[0288] The results of the adhesion tests thus carried out for the different solutions produced are reported on the graph in Figure 2, which represents the tensile force (N / 25mm) measured as a function of the mass proportion of APA-1 compared to PF-1 in the tested solutions (%). It is noted that the APA-1 additive makes it possible to considerably increase the initial adhesion properties of the unadditified PF-1 film (control). A tensile force of 0.05 to 0.1 N / 25 mm makes it possible to peel the unadditified PF-1 film. The use of only 0.01% by weight of APA-1 compared to PF-1 makes it possible to multiply the adhesion force by 20 to 40, since the measured adhesion force is 2 N / 25 mm.

[0289] Example 3 - Evaluation of electroactive properties for an additive PF-1 film

[0290] Solutions of PF-1 additive with APA-1 were implemented as in example 2. Solutions of variable concentrations of APA-1, containing from 0% to 5% (low value in additive 0.5%) by mass of APA-1 relative to the mass of fluoropolymer PF-1, were prepared.

[0291] Glass substrates were used for the production of electroactive films. These substrates were first coated over their entire surface with an egg lecithin solution (serving as an anti-adhesive) using a cloth soaked in said 1% lecithin solution in cyclohexane. Then the desired PF-1 solution, with or without additives, was dispensed by bar-coating onto the glass substrate so as to obtain a final dry film with a thickness of 15 μm. The freshly coated films were left to dry at room temperature (23°C) for fifteen minutes, then were placed in an oven for 20 minutes at 140°C.

[0292] The electroactive properties of the obtained films were evaluated as follows: each film was placed between two gold electrodes on the sample holder, then compressed to a height of 2.5 kN / crrr 2 under a hydraulic press to ensure good contact between the film and the electrodes. An alternating voltage was then applied to the electrode terminals to obtain an electric field depending on the thickness (15 pm) of the film, ranging from 25 V / pm to 150 V / pm in steps of 5 V / pm. The remanent polarization (Pr) of the film considered was then extracted from the hysteresis curve obtained at 150 V / pm.

[0293] The results obtained for the different films produced are shown in the graph in Figure 3, which represents the remanent polarization (mC.rrr 2) as a function of the mass proportion (% wt) of APA-1 compared to PF-1, in films based on PF-1 with or without additives. These results show a decrease in Pr of only 2.1% for each % of APA-1 introduced into the PF-1 film, whereas adhesion is excellent even from very low mass proportions of APA-1, (of the order of 0.1%, see example 2; Figure 2).

[0294] Example 4 - Evaluation of adhesion properties for an additive fluoropolymer film on electrodes obtained by screen printing (PEDOT-PSS or Silver)

[0295] An untreated 50 μm thick PET (polyethylene terephthalate) substrate supplied by ADDEV Materials was used for screen printing tests. A 1% egg lecithin solution (serving as a release layer) in cyclohexane was first dispensed onto half of the surface of the PET substrate and then dried at room temperature.

[0296] Screen printing inks (silver or conductive polymer blend; see Table 1 below) were then dispensed onto the other remaining half of the PET substrate by bar-coating, so as to obtain a continuous dry film of material a few microns or even fifteen microns thick at the end of the process. The wet film of freshly dispensed ink was then placed in an oven at 140°C for 10 minutes. Once returned to room temperature, a solution of PF-1 copolymer (see example 2) at 10% by mass in MEK, with or without additives of APA-1 at a level of 0.2% by mass depending on the type of sample produced, was dispensed by bar-coating so as to obtain a final dry film with a thickness of approximately 15 μm. The wet film of freshly dispensed ink was left to dry at room temperature (23°C) for fifteen minutes, then the resulting stack of materials was placed in an oven at 140°C for 20 minutes.The substrates thus prepared were cut into samples of 25 mm on each side, thus all comprising a part where the PF-1 film, with or without additives, rests directly on the non-stick film (lecithin) and a part where it rests directly on the screen printing ink studied (PEDOT-PSS or silver).

[0297] The operating conditions of the adhesion tests carried out below were identical to those described in Example 2.

[0298] The different results obtained are grouped in Table 1.

[0299] [Table 1]

[0300] Several points are notable in view of the results in Table 1:

[0301] On PEDOT-PSS type ink (conductive polymer), the PF-1 film with APA-1 additive adheres perfectly, since it is the PEDOT-PSS / PET interface that yields during the adhesion test, whereas it is the PEDOT-PSS / PF-1 interface that yields when the APA-1 additive is not present.

[0302] On the different "silver" type inks, it was found that the non-additive PF-1 film which adheres the most to the material is that dispensed on the Loctite ECI-1011 reference (presented in Table 1 on line 3). Consequently, the tensile force values ​​of the reference films (non-additive with APA-1) are necessarily all less than or equal to 1.4 N / 25 mm, and it is always an adhesive rupture at the interface between the PF-1 film and the material. The films where the APA-1 additive is present all have tensile force values ​​strictly greater than 1.4 N / 25 mm. The rupture is in certain cases of the cohesive type, that is to say that it is the additive PF-1 film which breaks before it can be peeled off.

[0303] Example 5 - Stability of Additive Fluoropolymer Solutions A terpolymer of P(VDF-TrFE-CTFE), consisting of repeating units derived from vinylidene fluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE) having a VDF:TrFE:CTFE molar ratio of 60.9:30.6:8.5 was used as the fluoropolymer. This polymer is referred to as “PF-2” in the following examples.

[0304] Here we compared the evolution over time of two different solutions:

[0305] - a solution of 10% by mass of PF-2 in cyclopentanone, and containing 1% by mass of APA-1 compound, relative to the mass of PF-2;

[0306] - a solution of 10% by mass of PF-2 in cyclopentanone, and containing 1% by mass of (3-aminopropyl)triethoxysilane compound relative to the mass of PF-2. The (3-aminopropyl)triethoxysilane compound is an additive known from the prior art as an adhesion promoter for PVDF and its derivatives.

[0307] Twenty-four hours after mixing the additives with the PF-2 stock solution, a very marked yellow-orange coloration was observed for the solution comprising (3-aminopropyl)triethoxysilane, indicating degradation of the PF-2 skeleton by the (3-aminopropyl)triethoxysilane additive, while the absence of coloration was noted for the solution comprising the APA-1 additive, indicating excellent stability of the corresponding solution.

[0308] It was also noted that the onset of coloration in the case of the additive (3-aminopropyltriethoxysilane) was clearly visible to the naked eye after only a few minutes following mixing with the PF-2 solution, thus indicating very rapid degradation.

[0309] Finally, it was noted that the solution with APA-1 remained colorless even after several weeks at room temperature, and even for an APA-1 concentration of 5.0% by mass relative to the mass of PF-2. An identical result was obtained when cyclopentanone was replaced by aliphatic ketone solvents such as MEK.

[0310] An identical evolution could be observed regardless of the fluorinated polymer used, for example for a vinylidene fluoride homopolymer or PF-1.

[0311] Example 6 - Adhesion properties of the PF-2 fluoropolymer with additives

[0312] Two stock solutions at 10% by mass in PF-2, respectively in APA-1, in cyclopentanone, were prepared.

[0313] A first ink (concentrated in APA-1) was produced by mixing the two mother solutions in such a way as to obtain a proportion of 5% by mass of APA-1 relative to the mass of PF-2. A second ink (diluted in APA-1) was prepared by simple dilution of a part of this first solution to obtain a final concentration of 0.5% by mass of APA-1, relative to the mass of PF-2.

[0314] Stainless steel substrates (type 314) were cut with a guillotine to a size of approximately 10cm x 6cm, then each sample was taped via a Kapton® adhesive border to a glass support independently of each other. The steel substrates were briefly cleaned with a cloth soaked in absolute ethanol.

[0315] A first substrate (sample no. 1) was coated by bar-coating with the non-additive PF-2 solution in order to obtain a wet film with a theoretical thickness of 1000 pm.

[0316] A second substrate (sample no. 2) was coated with the PF-2 copolymer solution with 0.5% by weight of APA-1 to obtain a wet film with a theoretical thickness of 1000 μm.

[0317] A third substrate (sample no. 3) was coated with the PF-2 copolymer solution with 0.5% by weight of APA-1 to obtain a wet film with a theoretical thickness of 1000 μm.

[0318] The substrates were then placed under a ventilated grid until the solvent had completely evaporated. The thickness of the dry films was approximately 30 μm

[0319] Samples 1 and 2 were annealed in a ventilated oven at 110°C for 9 minutes.

[0320] Sample 3 was annealed using a first anneal at 200°C for 9 minutes and a second anneal at 110°C for also 9 minutes.

[0321] A crosshatch adhesion test (ASTM D3359 - method B) was then performed once the samples had returned to room temperature.

[0322] The polymer films on their substrate were cut a first time with a special knife with 7 blades, 5 of which in the middle were spaced narrowly (~1 mm), then a second time with the same instrument at an angle of 90° relative to the first cut. This resulted in a grid of 25 squares with a side of 1 mm on which the film's adhesion performance could subsequently be judged. An adhesive tape with controlled adhesion power, typically 6-7 N / cm, was then applied to the grid and then torn off at 180°.

[0323] The adhesion results, observed after removal of the adhesive tape, expressed in "crosshatch rank" are summarized in Table 2 below. The crosshatch classification ranges from 0B to 5B, with intermediate ranks 1B, 2B, 3B and 4B. Rank 5B means that after the adhesive tape has been peeled off, the sides of the cut grid edges are smooth, and no matrix squares have been detached. Conversely, rank 4B means that detachments of small pieces of the film at the intersections of the cuts, with less than 5% of the entire grid affected, are observable. Rank 3B means that the film has broken up on the sides of the cuts or at the intersections of the grid, with an affected area of ​​between 5 and 15% of the grid. Rank 2B means that the film has broken up along the sides of the cuts or at the grid intersections into long ribbons or entire grid squares, with an affected area between 15 and 35% of the grid.Grade 1B means that the film has broken down along the sides of the cuts or at the grid intersections in long ribbons or entire grid squares, with an affected area of ​​between 35 and 65% of the grid. Grade 0B corresponds to any deterioration of the film that cannot be classified above.

[0324] [Table 2]

[0325] Reference sample No. 1 PF-2 has a rank of "0B". In fact, the film completely detached from the steel substrate without too much difficulty when peeled off via the adhesive tape.

[0326] Samples #2 and #3 of additive PF-2 show a “5B” rank. Indeed, the films remained intact after removal of the adhesive tape.

[0327] Example 7 - Evaluation of dielectric properties for an additive PF-2 film

[0328] Two stock solutions at 10% by mass in PF-2, respectively in APA-1, in cyclopentanone were prepared.

[0329] A first ink was produced by mixing the two mother solutions in such a way as to obtain a proportion of 5% by mass of APA-1 compared to the mass of PF-2.

[0330] A second ink was prepared by simply diluting a portion of this first solution to obtain a final concentration of 0.5% by mass of APA-1, relative to the mass of PF-2.

[0331] Films were then prepared. Each ink was bar-coated onto a glass substrate previously coated with egg lecithin, to obtain a final dry thickness of approximately 30 μm (knife at 1000 μm). The glass substrate was then placed directly in an oven at a temperature of 110°C for 9 minutes for solvent evaporation and copolymer crystallization. After processing, the films were simply peeled from their respective substrates. Two films were thus produced under identical process conditions: a film where the terpolymer P(VDF-ter-TrFE-ter-CTFE) is pure (serving as a reference), and a film where the APA-1 additive is added at a rate of 0.5% by mass relative to the mass of PF-2.

[0332] Dielectric measurements were performed on these films. The measurements were carried out on an ALPHA-AN impedance spectrometer from Novocontrol. The measuring cell was thermalized to the desired temperature by Peltier effect. Each film was introduced into the cell and subjected to a low sinusoidal voltage of frequency 10kHz for each temperature point defined between 20°C and 110°C in steps of 5°C. The dielectric permittivity (noted Dk) and the corresponding dielectric losses (Tan 5) of the material were thus 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 film between the two electrodes.

[0333] The graph in Figure 4 shows that the dielectric constant of the APA-1 additive film is greater than that of the pure material (ADk <0).

[0334] The graph in Figure 5 shows that the dielectric losses are generally slightly higher after the addition of APA-1, but that they still remain limited to less than 15% compared to the initial value (without additive). It should be noted that for certain temperatures the dielectric losses are lower than those of the non-additive material (values ​​where ATan 5 >0).

Claims

Claims 1. Composition comprising: - at least one fluorinated polymer and, - from 0.005% to 5.0% by weight of at least one APA additive, relative to the weight of said at least one fluoropolymer; said composition being characterized in that said at least one APA additive is a polymer comprising a repeating unit derived from methyl methacrylate, and at least one graftable functional group arranged at at least one end of its polymer chain; said at least one graftable functional group being capable of being grafted to the surface of a substrate.

2. Composition according to claim 1, in which said at least one APA additive comprises at one end of its polymer chain a graftable functional group being a nitroxy.

3. Composition according to any one of claims 1 and 2, in which said at least one APA additive comprises at one end of its polymer chain at least one graftable functional group chosen from the groups: carboxyl, hydroxyl, mercapto, silyl, alkoxysilyl, alkylsilyl, sulfonic acid, phosphate, phosphonic acid and phosphinic acid.

4. Composition according to any one of claims 1 to 3, in which said at least one graftable functional group arranged at one end of the polymer chain of said at least one APA additive is a hydroxyl function.

5. Composition according to any one of claims 1 to 4, in which said at least one graftable functional group arranged at one end of the polymer chain of said at least one APA additive is a carboxyl function.

6. Composition according to any one of claims 1 to 5, in which the repeating unit derived from methyl methacrylate in the polymer chain of said at least one APA additive represents at least 40%, preferably at least 50%, and extremely preferably at least 70%, by weight relative to the total weight of the polymer chain of said at least one APA additive.

7. Composition according to any one of claims 1 to 6, in which the total weight of APA additive(s) represents 0.01% or more, and preferably 0.05% or more, relative to the total weight of fluorinated polymer(s).

8. Composition according to any one of claims 1 to 7, in which the total weight of APA additive(s) represents 3.0% or less, and preferably 2.0% or less, relative to the total weight of fluorinated polymer(s).

9. Composition according to any one of claims 1 to 8, in which the APA additive is capable of being obtained by a nitroxide-controlled radical polymerization using an alkoxyamine.

10. Composition according to claim 9, in which the alkoxyamine is chosen from: - a compound of formula: [Chem 7] (H) , and - an adduct formed by the reaction of an equivalent of the compound of formula (II) with an acrylic, methacrylic, or vinylaromatic monomer carrying at least one graftable functional group.

11. Composition according to any one of claims 1 to 10, in which said at least one APA additive is a gradient or statistical type polymer, and does not comprise a repeating unit comprising a graftable functional group.

12. Composition according to claim 11, in which said at least one APA additive is essentially constituted, or constituted, of repeating units derived from methyl methacrylate and styrene, the mass proportion of repeating units derived from styrene representing from 0.5% to 15%, and preferably from 1.0% to 10%, relative to the total mass of repeating units derived from methyl methacrylate and styrene.

13. Composition according to any one of claims 1 to 10, in which said at least one APA additive is a polymer with AB-type or ABA-type blocks, in which the A block(s) comprise, independently of one another, at least one repeating unit comprising said at least one graftable functional group and block B comprises a repeating unit derived from methyl methacrylate.

14. Composition according to claim 13, in which block B of said at least one APA additive does not comprise a repeating unit comprising a graftable functional group.

15. Composition according to any one of claims 1 to 14, in which said at least one fluoropolymer comprises at least 40 mol% of repeating unit derived from vinylidene fluoride, relative to the total sum of moles of repeating units constituting said at least one fluoropolymer, and optionally at least one repeating unit derived from a monomer X, other than vinylidene fluoride, having the formula CXiX2=CX3X4, in which each group Xi, X2, X3 and X4 is independently chosen from H, Cl, F, Br, I and C1-C3 alkyl groups which are optionally partially or totally halogenated.

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

17. Method for manufacturing a coating based on fluorinated polymer(s) on a substrate, comprising: iv) depositing a composition according to any one of claims 1 to 16; v) where appropriate, removing the solvent or mixture of solvents possibly present in said composition following the deposit of said composition; and, vi) grafting onto the substrate at least a portion of said at least one APA additive present in said composition.

18. Composite comprising a coating based on fluoropolymer(s) adhering to a substrate, said coating comprising at least one fluoropolymer and from 0.005% to 5.0% by weight of at least one APA additive, relative to the weight of said at least one fluoropolymer, said at least one APA additive being a polymer comprising a repeating unit derived from methyl methacrylate, and at least one graftable functional group arranged at at least one end of its polymer chain.

19. Device comprising a composite according to claim 18.

20. Use of at least one APA polymer as an additive in a composition based on fluorinated polymer(s) to improve the adhesion of said composition to a substrate, said APA additive being a polymer comprising a repeating unit derived from methyl methacrylate, and at least one graftable functional group arranged at one end of its polymer chain.

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