P(VDF-TrFE-CTFE) of homogeneous chemical composition

Abstract

The invention relates to a P(VDF-TrFE-CTFE) polymer having a homogeneous chemical composition, a composition and a film derived therefrom, as well as uses. Figure for the abstract: Figure 1

Description

Title of the invention: Homogeneous chemical composition P(VDF-TrFE-CTFE) Technical field

[0001] The invention relates to the field of manufacturing P(VDF-TrFE-CTFE) polymers by a suspension polymerization process and to P(VDF-TrFE-CTFE) polymers as such, in particular those that can be obtained according to the process of the invention. Previous art

[0002] It is known from the prior art to manufacture P(VDF-TrFE-CTFE) by a suspension polymerization process.

[0003] For example, it is known from WO2016 / 055712 to initially inject all the monomers and then initiate polymerization while maintaining constant pressure in the reactor during polymerization. A P(VDF-TrFE-CTFE) with a VDF / TrFE / CTFE molar composition of 62.5 / 32.8 / 4.7 has been exemplified.

[0004] It is also known from WO2010 / 116105 to load an initial mixture of VDF and TrFE, devoid of CTFE and CFE, into an autoclave and inject a secondary mixture of VDF, TrFE, and CTFE or CFE, so as to maintain constant pressure in the reactor during polymerization. The example given relates to a P(VDF-TrFE-CFE) with a molar composition of VDF / TrFE / CFE 61.7 / 29.8 / 8.5. A similar process is described in WO2014 / 091130, which discloses P(VDF-TrFE-CTFE) having a CTFE molar proportion of 1.97% to 8.5% relative to the total number of moles of VDF, TrFE, and CTFE monomers. Such a process ensures better polymer homogeneity and reproducibility than a process in which all the monomers are added initially. The polymer obtained, although having a more homogeneous chemical composition, still exhibits a significant heterogeneity, which the inventors were able to evaluate using DSC measurements.

[0005] Furthermore, P(VDF-TrFE-CTFE) polymers are known for their ferroelectric-relaxant properties. "Relaxing ferroelectric" polymers are characterized by a paraelectric (PE) relaxor-ferroelectric (RFE) crystal transition over a wide temperature range. At this transition, a broad dielectric permittivity peak 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 lower temperatures. They are also characterized by a fairly fine hysteresis cycle of the "electric displacement" curve as a function of the "applied electric field".

[0006] There is currently a need to supply P(VDF-TrFE-CTFE) capacitors with an even thinner hysteresis loop, i.e., with an even lower remanent polarization value. These characteristics can be particularly useful for energy storage applications. There is also a need to supply P(VDF-TrFE-CTFE) capacitors with a higher dielectric constant, which is particularly useful for organic electronics applications. Objective of the invention

[0007] An objective of the invention is to provide P(VDF-TrFE-CTFE) having a more homogeneous chemical composition.

[0008] According to at least some embodiments, an objective is to propose P(VDF-TrFE-CTFE) having a thinner hysteresis loop compared to P(VDF-TrFE-CTFE) of the prior art of similar average chemical composition.

[0009] According to at least some embodiments, an objective is to propose P(VDF-TrFE-CTFE) having a higher dielectric constant than P(VDF-TrFE-CTFE) of the prior art of analogous average chemical composition. Summary of the invention

[0010] The invention relates to a polymer essentially composed of, or composed of, repeating units resulting from the polymerization of VDF, TrFE, and CTFE, denoted P(VDF-TrFE-CTFE). This polymer has a chemical composition

[0011] C [X;Y] homogeneous. The parameter X satisfies the inequality: 30.0 < X ​​< 100 (eq. 7). The parameter X represents the mole proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in the polymer. Preferably, X satisfies the inequality: 45.0 < X ​​< 90.0 (eq. 7a). More preferably, X satisfies the inequality: 50.0 < X ​​< 80.0 (eq. 7b).

[0012] The parameter Y satisfies the inequality 0.1 < Y ​​< 15.0 (eq. 8). The parameter Y represents the mole proportion, expressed as a percentage, in units resulting from the polymerization of CTFE relative to the total number of moles in units resulting from the polymerization of VDF, TrFE, and CTFE in the polymer. According to some preferred embodiments, particularly those utilizing the ferroelectric relaxing character of P(VDF-TrFE-CTFE), Y satisfies the following inequality: 4.0 < Y < 10.0 (eq. 8a). According to other embodiments, Y < 4.0 or Y > 10.0 may also be given.

[0013] The homogeneity of the chemical composition of the polymer is characterized by a scanning differential calorimetry thermogram of said polymer, measured in The second heating cycle uses heating and cooling ramps at 10°C / min, and we can identify: Tim, the initial temperature of the melting peak, or, if there are multiple melting peaks, the lowest initial temperature, and Tfm, the final temperature of the melting peak, or, if there are multiple melting peaks, the highest final temperature. The values ​​of Tim and Tfm satisfy the inequality: Tfm - Tim < 50°C (eq. 9).

[0014] The values ​​of Tim and Tfm preferentially satisfy the inequality: Tfm-Tim< 45°C (eq. 9a), more preferably the inequality: Tfm-Tim< 40°C (eq. 9b), even more preferably the inequality: Tfm-Tim < 35°C (eq. 9c), and most preferably: Tfm-Tim < 30°C (eq. 9d).

[0015] According to certain embodiments, the homogeneity of chemical composition is also characterized by the same differential scanning calorimetry thermogram of said polymer, on which one can identify: Tpm, the peak temperature of the melting peak, or, where applicable in the presence of several melting peaks, the peak temperature of the melting peak having the highest absolute value of heat flux. The values ​​of Tfm and Tpm satisfy: Tfm-Tpm < 15°C (eq. 10), preferably: Tfm-Tpm < 12°C (eq. 10a), and even more preferably: Tfm-Tpm < 10°C (eq. 10b).

[0016] According to some embodiments, the weight average molar mass Mw of the polymer is at least 550,000 g / mol, as measured by size exclusion chromatography with dimethylformamide, as eluent, with a set of 3 columns of increasing porosity, the stationary phase being a styrene-DVB gel.

[0017] The invention also relates to a composition comprising at least one polymer according to the invention and at least one liquid vehicle selected from: dimethylformamide; dimethylacetamide; dimethyl sulfoxide; ketones; furans; esters; carbonates; phosphates; or a mixture thereof.

[0018] The invention also relates to a polymer film according to the invention.

[0019] Finally, the invention relates to the use of the polymer according to the invention or of the film according to the invention for its ferroelectric or ferroelectric relaxer properties.

[0020] The invention also relates to the use of the polymer according to the invention or the film according to the invention for its high dielectric constant value.

[0021] The invention also relates to the use of the polymer according to the invention or the film according to the invention, for its high efficiency value / / , the efficiency / / being calculated according to the equation:

[0022] [Math.l] , where WrecUp is the recoverable energy density and Wioss is the lost energy density, observable on the first quadrant of a hysteresis loop. Detailed description of the invention Figures

[0023] [Fig. 1] illustrates the shape of a DSC thermogram during the second heating cycle, with heating and cooling ramps at 10°C / min, of a P(VDF-TrFE-CTFE) according to the invention (thermogram A) and of a P(VDF-TrFE-CTFE) according to the prior art (thermogram B). The x-axis represents the temperature reached during the second heating cycle and the y-axis the measured heat flux.

[0024] [Fig. 2] illustrates the shape of the "first quadrant," i.e., the upper right quadrant, of the hysteresis loop obtained during the polarization of a P(VDF-TrFE-CTFE) according to the invention (loop A) and a P(VDF-TrFE-CTFE) according to the prior art (loop B). The x-axis represents the applied electric field. The y-axis represents the polarization of the polymer. Process

[0025] The present invention relates to a process for manufacturing a P(VDF-TrFE-CTFE) polymer by suspension polymerization in a liquid, of vinylidene fluoride, VDF, trifluoroethylene, TrFE, and chlorotrifluoroethylene, CTFE, to obtain a P(VDF-TrFE-CTFE) of target composition Cp [Xp ;YP].

[0026] The process comprises: - the injection into a reactor of a composition Ci [Xi;Yi] in VDF, TrFE and CTFE monomers, to form a mixture of Mi monomers in the suspension liquid, - the initiation of the polymerization of the Mb monomer mixture and - the continuation of polymerization at a substantially constant pressure in the reactor, by injection into the reactor of VDF, TrFE and CTFE monomers of composition C2 [X2 ;Y2].

[0027] The inventors focused on selecting specific ranges of Yi and Y2 values ​​to obtain a P(VDF-TrFE-CTFE) with a more homogeneous chemical composition, in particular a better distribution of the repeating unit resulting from the polymerization of CTFE within the polymer chains, than that of polymers obtained according to prior art processes. "Homogeneity" in the context of the invention means that the different polymer chains have essentially the same proportion of VDF, TrFE, and CTFE. The homogeneity of chemical composition is easily assessed in the invention by examining the differential scanning calorimetry (DSC) thermogram of the polymer during the second heating.

[0028] The parameter Xi represents the mole proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition Ci. The parameter Yi represents the mole proportion, expressed as a percentage, of CTFE monomer relative to the total number of moles of VDF, TrFE, and CTFE monomers in composition Cp.

[0029] The parameter X2 represents the molar proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition C2. The parameter Y2 represents the molar proportion, expressed as a percentage, of CTFE monomer relative to the total number of moles of VDF, TrFE and CTFE monomers in composition C2.

[0030] The parameter Xp represents the target mole proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in the polymer. The parameter Yp represents the target mole proportion, expressed as a percentage, in units resulting from the polymerization of CTFE relative to the total number of moles in units resulting from the polymerization of VDF, TrFE, and CTFE in the polymer.

[0031] The AXi parameter is defined as follows:

[0032] [Math.2]

[0033] The parameter AX2 is defined as follows:

[0034] [Math.3] / ç _ y \ | — ) x 100

[0035] The AYi parameter is defined as follows:

[0036] [Math.4]

[0037] The parameter AY2 is defined as follows:

[0038] [Math.5]

[0039] The process according to the invention is characterized in that the parameters Yp, AYi and AY2 satisfy the following inequalities:

[0040] 0.1 < Yp < 15.0 (eq. 1)

[0041] -0.70 < AYi <-0.15 (eq. 2), and

[0042] -0.40 <AY2 <0.65 (eq. 3).

[0043] Selecting Yi to satisfy inequality eq. 2, in other words, fitting AYi for a target value Yp, makes it possible to obtain, from the initiation of polymerization, i.e., at a low conversion rate of the monomers in the Mb mixture, a P(VDF-TrFE-CTFE) with a molar proportion of CTFE equal to or close to the target proportion Yp. Selecting Y2 to satisfy inequality eq. 3, in other words, fitting AY2 for a target value Yp, makes it possible to maintain the molar proportion of CTFE relative to the VDF, TrFE, and CTFE monomers almost constant in the reactor, so that the polymer chains formed at any time during polymerization all have a molar proportion in units resulting from the polymerization of CTFE equal to or close to Yp. Thus, the polymer chains produced during polymerization all have a molar proportion in repeating units resulting from the polymerization of CTFE equal to or close to Yp.

[0044] According to certain embodiments, we have: 0.5 < Yp, or 1.0 < Yp, or 1.5 < Yp, 2.0 < Yp, or 2.5 < Yp, or 3.5 < Yp, or even 4.0 < Yp. In embodiments where P(VDF-TrFE-CTFE) is used for its ferroelectric relaxor properties, we advantageously have: 4.0 < Yp.

[0045] According to certain embodiments, we have: Yp < 14.0, or Yp < 13.0, or Yp < 12.0, or Yp < 11.0, or even Yp < 10.0. In embodiments where P(VDF-TrFE-CTFE) is used for its ferroelectric relaxor properties, we advantageously have: Yp < 10.0.

[0046] The method according to the invention can be implemented for Yp satisfying one of the following inequalities: Yp< 2.0, or 2.0 < Yp< 4.0, or 4.0 < Yp< 10.0 (eq. la), or 10.0 < Yp< 12.0, or 12.0 < Yp< 14.0.

[0047] According to particular embodiments, Yp can in particular satisfy one of the following inequalities: 4.0 < Yp < 5.5, or 5.5 < Yp < 7.0, or 7.0 < Yp < 8.5, or even 8.5 < Yp < 10.0.

[0048] Since the CTFE monomer is more reactive, particularly more reactive with itself than with the VDF and TrFE monomers, the proportion of CTFE in the composition Ci is such that the proportion Yi is strictly less than Yp. This is why AYi is always negative.

[0049] Preferably AYi satisfies the inequality: -0.60 < AYi < -0.20 (eq. 2a).

[0050] Preferably still, AYi satisfies the inequality: -0.57 < AYi < -0.25 (eq. 2b).

[0051] According to certain embodiments, in particular when we have: 50.0 < Xp < 80.0 (eq. 4b) and 4.0 < Yp < 10 (eq. la), AYi advantageously satisfies the inequality:

[0052] -0.55 < AYi < -0.30 (eq. 2c). In particular, we can have -0.55 < AYi < -0.45, or

[0053] -0.45 < AYj < -0.35.

[0054] Injecting VDF, TrFE, and CTFE monomers of composition C2 during continued polymerization at substantially constant pressure maintains a constant molar proportion of VDF, TrFE, and CTFE in the reactor. This injection, in particular, maintains a constant molar proportion of CTFE relative to the total number of moles of VDF, TrFE, and CTFE monomers in the reactor. Ideally, the parameter AY2 should be equal to 0. In practice, the parameter AY2 satisfies inequality eq. 3.

[0055] According to some preferred embodiments, the parameter AY2 satisfies the following inequality: -0.25 < AY2 < 0.50 (eq. 3a).

[0056] According to some more preferred embodiments, the parameter AY2 satisfies the following inequality: -0.12 < AY2 < 0.36 (eq. 3b). In particular, we can have:

[0057] -0.12 < AY2 < -0.09, or -0.09 < AY2 < 0,

[0058] or 0 <AY2 <0.09, or 0.09 <AY2 <0.18, or 0.18 <AY2 <0.36.

[0059] The same reasoning applies to AXi and AX2 as that developed for AY i and AY2, but due to the relatively analogous reactivity of the VDF and the TrFE to each other and to themselves, the adjustment of Xi and X2 has less impact than that of Yi and Y2.

[0060] The target molar proportion Xp generally satisfies the inequality:

[0061] 30.0 <Xp <100 (eq. 4).

[0062] In particular, we can have the parameter Xp satisfying one of the following inequalities: Xp < 100, or Xp < 95, or Xp < 90, or Xp < 85, or Xp < 80, or Xp < 75.

[0063] In particular, Xp may satisfy one of the following inequalities: 35.0 < Xp, or 45.0 < Xp, or 50.0 < Xp, or 55.0 < Xp, or 60.0 < Xp.

[0064] According to preferred embodiments, the parameter Xp satisfies the inequality:

[0065] 45.0 < Xp < 90.0 (eq. 4a).

[0066] According to more preferred embodiments, the parameter Xp satisfies the inequality: 50.0 < Xp < 80.0 (eq. 4b). In particular, we can have 50.0 < Xp < 60.0, or 60.0 < Xp < 70.0, or even 70.0 < Xp < 80.0.

[0067] The parameter AXi generally satisfies the inequality: -8.0 < AXi < 6.5 (eq. 5).

[0068] In particular, the parameter AXi may satisfy one of the following inequalities: -7.0 < AXb or -6.0 < AXb or -5.0 < AXb or -4.0 < AXb or -3.0 < AXb or -2.0 < AXi, -1.0 < AXb

[0069] In particular, the parameter AXi may satisfy one of the following inequalities: AXi < 1.0, or AXi < 2.0, or AXi < 3.0, or AXi < 3.5, or AXi < 4.0, or AXi < 5.0, or AXi < 6.0.

[0070] According to preferred embodiments, the parameter AXi satisfies the following inequality: -7.0 < AXi < 4.0 (eq. 5a). In particular, one can have:

[0071] -7.0 < AXi < -4.0, or -4.0 < AX! < -2.0, -2.0 < AX! < -1.0, or -1.0 < AXi < 1.0,

[0072] or 1.0 < AXi < 2.0, or 2.0 < AXi < 3.5, or 3.5 < AXi < 4.0.

[0073] According to certain embodiments, particularly when we have: 60.0 < Xp < 80.0 and 4.0 < Yp < 10 (eq. la), AXi advantageously satisfies the following inequality:

[0074] -2.0 <AXi <3.5 (eq. 5b).

[0075] According to certain embodiments, particularly when we have: 50.0 < Xp < 60.0 and 4.0 < Yp < 10 (eq. la), AXi advantageously satisfies the following inequality:

[0076] -6.5 < AXi < -2.0 (eq. 5b).

[0077] The parameter AX2 should ideally be equal to 0. In practice, the parameter AX2 generally satisfies the following inequality: -8.0 < AX2 < 8.0 (eq. 6).

[0078] According to preferred embodiments, AX2 satisfies the following inequality:

[0079] -4.0 < AX2 < 4.0 (eq. 6a). In particular, we can have: -4.0 < AX2 < 2.0,

[0080] or -2.0 < AX2 <2.0 (eq. 6b), or even 2.0 < AX2 < 4.0.

[0081] The polymerization involved is a suspension polymerization in a liquid, referred to in the present invention as the suspension liquid. It is carried out by suspending the monomers of VDF, TrFE, and CTFE in the suspension liquid. The suspension liquid is advantageously water or an aqueous solution.

[0082] The reaction can be initiated by adding a radical polymerization initiator, which may, in particular, be an organic peroxide such as a peroxydicarbonate. It is generally used in an amount of 0.1 to 10 g per kilogram of the total monomer charge. Preferably, the amount used is 0.5 to 5 g / kg. The amount used may be 0.5 to 1.5 g / kg, or 1.5 to 3 g / kg, or 3.0 to 5 g / kg. Generally, the initiation of the reaction itself is carried out by the combined action of adding the polymerization initiator and a temperature increase, which is accompanied by a pressure increase. The initiator may be added to the reactor after or before the monomer composition Ci has been injected into the reactor. According to some embodiments, the initiator is added to the reactor after the composition Ci of monomers has been injected into the reactor.According to some embodiments, the initiator is added to the reactor after a temperature rise in the reactor to a predetermined temperature, . in particular up to a predetermined temperature close to the temperature at which polymerization is initiated.

[0083] Furthermore, it may be advantageous to add a suspending agent to the reaction medium to facilitate the suspension of the monomers in the suspension liquid. In particular, a cellulose derivative, especially a cellulose ether such as methylcellulose, ethylhydroxyethylcellulose, or hydroxypropylmethylcellulose, may be used in an amount of 0.1 to 5 g per kilogram of the total weight of the monomers in the mixture Mb. Preferably, the amount used is 0.25 to 3.5 g / kg. The amount used may be 0.25 to 1.0 g / kg, or 1.0 to 3.0 g / kg, or 3.0 to 3.5 g / kg. The suspending agent may be added to the reactor after or before the monomer composition Ci has been injected into the reactor. According to advantageous embodiments, the suspending agent is added to the reactor after the composition Ci of VDF, TrFE and CTFE monomers has been injected into the reactor.

[0084] Finally, a chain length regulating agent can, according to certain embodiments, be added to the reaction medium. Ethyl acetate, diethyl carbonate, or an alcohol such as isopropanol, for example, can be used in an amount of 1 to 100 g per kilogram of the total monomer loading. Preferably, the amount used is 2 to 40 g / kg. The chain length regulating agent can be added to the reactor after or before the monomer composition Ci has been injected into the reactor. It can be added all at once or in fractions over several injections.

[0085] The reaction medium is preferably stirred to suspend the monomers in the suspension liquid and / or during the polymerization reaction.

[0086] Preferably, the polymerization is essentially carried out under temperature and pressure conditions for which the monomers in the reactor are in a supercritical state.

[0087] Polymerization can be carried out at a target polymerization pressure, in particular a target polymerization continuation pressure, of 50 to 130 bar, and preferably at a pressure of 70 to 110 bar. The initiation of polymerization and its continuation result in a pressure decrease in the reactor due to the consumption of some of the monomers. This pressure decrease is compensated by injecting VDF, TrFE, and CTFE monomers of composition C2 into the reactor, and optionally by injecting a suspension liquid into the reactor, in order to maintain a substantially constant pressure in the reactor. "Substantially constant" means a pressure can vary by plus or minus 30%, preferably by plus or minus 20%, preferably still by plus or minus 15%. According to certain embodiments, the pressure can vary by plus or minus 10% or plus or minus 5%.

[0088] According to some advantageous embodiments, the pressure in the reactor increases slightly as the polymerization reaction progresses in order to take into account the decrease in the volume available for the monomers due to the space occupied by the polymer obtained. For example, the pressure may increase by 1% or less, or 2% or less, or 4% or less, or 8% or less, or 10% or less, or 12% or less, or even 15% or less, between the beginning and the end of the polymerization continuation step at substantially constant pressure.

[0089] According to some non-preferred embodiments, the pressure decrease during polymerization is partially compensated by the injection of a suspension liquid, of the same or different nature as the suspension liquid used to suspend the VDF, TrFE, CTFE monomers of mixture Mi in the reactor. According to some embodiments, the suspension liquid injected to maintain a substantially constant pressure during polymerization is of the same nature as the suspension liquid used to suspend the VDF, TrFE, CTFE monomers of mixture Mi in the reactor.

[0090] According to some preferred embodiments, the pressure decrease during polymerization is compensated by injecting only VDF, TrFE and CTFE monomers of composition C2 into the reactor. In other words, preferably, the pressure is maintained substantially constant during polymerization without additional injection of suspension liquid.

[0091] Polymerization can, in particular, be carried out primarily at a reaction medium temperature higher than the critical temperature of the monomer mixture in the reactor. This temperature is generally less than or equal to 70°C. In some embodiments, this temperature is less than or equal to 60°C, or less than or equal to 55°C, or less than or equal to 52°C, or less than or equal to 50°C. This temperature is generally greater than or equal to 35°C. In some embodiments, this temperature is greater than or equal to 40°C, or greater than or equal to 45°C. In order to control the temperature of the reaction medium, the reactor is equipped with temperature control means (for example, with a double jacket through which a heat transfer fluid circulates).

[0092] According to certain preferred embodiments, the temperature is maintained substantially constant during the continuation of the polymerization at substantially constant pressure. By substantially constant, we mean a temperature that can vary by plus or minus 30%, preferably by plus or minus 20%, preferably still by plus or minus 15%, and even more preferably plus or minus 10% around a target polymerization temperature value, especially around a target polymerization continuation temperature value.

[0093] According to certain embodiments, the continuation of polymerization at substantially constant pressure is implemented using VDF, TrFE, CTFE monomers of composition C2 where the values ​​of the parameters X2 and Y2 remain constant. This is particularly the case when composition C2 is injected in the form of a pre-prepared gas mixture.

[0094] According to certain embodiments, the continuation of polymerization at substantially constant pressure is implemented using a composition C2 with a variable chemical composition [X2; Y2]. This is particularly the case when the composition C2 is injected as a stream of independent monomers. These embodiments make it possible to take into account the reduction in the volume available for the monomers due to the space occupied by the resulting polymer.

[0095] The decrease in the volume available for the monomers in the reactor during polymerization is generally neglected, so that in practice polymerization can be carried out at constant pressure and constant injected C2 composition, yielding a more homogeneous P(VDF-TrFE-CTFE) than those of the prior art. According to certain embodiments,

[0096] It is possible to consider using a variable volume reactor, so that the volume available for the monomers remains constant throughout the polymerization.

[0097] The polymerization continuation step at substantially constant pressure ends when the injection of C2 composition monomers ceases. In one scenario, this cessation can occur either when the reactor has reached its full capacity, with the polymer and water occupying the entire reactor volume. In a second scenario, this cessation can be implemented because a predetermined quantity of C2 composition monomers has been added during the polymerization continuation step at substantially constant pressure. In this case, it is advantageous to abruptly stop the polymerization reaction by adding a termination agent and / or by rapidly cooling the reaction medium in order to avoid chemical inhomogeneity of the P(VDF-TrFE-CTFE).

[0098] The reactor can then be emptied. The collected product can be filtered, washed and dried in a manner known per se.

[0099] An advantage of the process according to the invention is that it can be implemented at any mass proportion between the total mass quantity Q2 of VDF, TrFE and CTFE monomers injected during the continuation of polymerization at substantially constant pressure and the total mass quantity Qien monomers VDF, TrFE, and CTFE are initially injected to form the Mb mixture because, at any point during polymerization, the P(VDF-TrFE-CTFE) has a chemical composition equal to or close to the target composition Cp [Xp; Yp]. However, advantageously, the Q2 / Qi ratio is generally greater than or equal to 0.5. Preferably, the Q2 / Qi ratio is greater than or equal to 0.75. Even more preferably, the Q2 / Qi ratio is greater than or equal to 0.90. Extremely preferably, the Q2 / Qi ratio is greater than or equal to 1.0.

[0100] The process allows for the production of P(VDF-TrFE-CTFE) of any molar mass. The P(VDF-TrFE-CTFE) according to the invention, obtainable by a process of the invention, generally have a weight-average molar mass Mw greater than or equal to 50,000 g / mol and less than or equal to 5,000,000 g / mol. The weight-average molar mass can be adjusted by modifying certain process parameters, such as the temperature in the reactor, or by adding a chain-regulating agent. The molecular weight distribution can be estimated by SEC (size-exclusion chromatography) with dimethylformamide (DMF) as the eluent, using a set of three 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 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. According to some embodiments, the weight average molar mass Mw of the polymer is at least 550,000 g / mol, or at least 600,000 g / mol, or at least 700,000 g / mol, or at least 750,000 g / mol, or at least 800,000 g / mol, or at least 850,000 g / mol. In some embodiments, the weight-average molar mass Mw of the polymer is at most 4,000,000 g / mol, or at most 3,000,000 g / mol, or at most 2,000,000 g / mol, or at most 1,500,000 g / mol. In some embodiments, the weight-average molar mass Mw of the polymer is from 550,000 g / mol to 1,500,000 g / mol. Polymer

[0101] The invention also relates to a P(VDF-TrFE-CTFE) polymer, of homogeneous chemical composition, having composition C [X;Y], where the parameter X represents the molar proportion, expressed as a percentage, in units from the polymerization of VDF relative to the total number of moles in units from the polymerization of VDF and TrFE in the polymer and, where the parameter Y represents the molar proportion, expressed as a percentage, in units from the polymerization of CTFE relative to the total number of moles in units from the polymerization of VDF, TrFE and CTFE in the polymer.

[0102] Such a P(VDF-TrFE-CTFE) is advantageously obtained by a suspension polymerization process, in particular by a process according to the invention.

[0103] Ideally, the process according to the invention makes it possible to obtain a P(VDF-TrFE-CTFE) having exactly the desired chemical composition. In practice, the parameter X generally satisfies the following inequality: 0.75 Xp < X < 1.25 Xp and the parameter Y generally satisfies the following inequality: 0.75 Yp < Y < 1.25 Yp.

[0104] Preferably we have: 0.85 Xp < X < 1.15 Xp. Even more preferably we have: 0.90 Xp < X < 1.10 Xp. Most preferably we have: 0.95 Xp < X < 1.05 Xp.

[0105] Preferably we have: 0.85 Yp < Y < 1.15 Yp. Even more preferably we have: 0.90 Yp < Y < 1.10 Yp. Most preferably we have: 0.95 Yp < Y < 1.05 Yp.

[0106] According to advantageous embodiments, we have: 0.90 Xp < X < 1.10 Xp and 0.85 Yp < Y < 1.15 Yp.

[0107] According to even more advantageous embodiments, we have: 0.95 Xp < X < 1.05 Xp and 0.90 Yp < Y < 1.10 Yp.

[0108] According to some embodiments, we have: 27 < X < 100, and preferably 28.5 < X < 100. In particular, we can have 30 < X ​​< 100.

[0109] According to some advantageous embodiments, we have: 40.5 < X < 99, and preferably 42.75 < X < 94.5. In particular, we can have 45.0 < X ​​< 90.0.

[0110] According to even more advantageous embodiments, we have: 45.0 < X ​​< 88.0 and preferably 47.5 < X < 84.0. In particular, we can have: 50.0 < X ​​< 80.0, and especially: 50.0 < X ​​< 60.0, or 60.0 < X ​​< 70.0, or even 70.0 < X ​​< 80.0.

[0111] According to some embodiments, we have: 0.085 < Y < 17.25, and preferably 0.09 < Y < 16.5. In particular, we can have: 0.1 < Y ​​< 15.0.

[0112] According to some advantageous embodiments, we have: 3.4 < Y < 11.5, and preferably 3.6 < Y < 11.0. In particular, we can have: 4.0 < Y < 10.0, and especially: 4.0 < Y < 5.5, or 5.5 < Y < 7.0, or 7.0 < Y < 8.5, or 8.5 < Y < 10.0.

[0113] According to other embodiments, we can also have Y < 2.0, or 2.0 < Y < 4.0, or 10.0 < Y < 12.0, or 12.0 < Y < 14.0.

[0114] The value of parameter X, i.e., the VDF / (VDF+TrFE) molar ratio in the polymer, can be determined by proton NMR. The polymer is dissolved in a suitable deuterated solvent, and the NMR spectrum is recorded on an FT-NMR spectrometer equipped with a multinuclear probe. The hydrogen nucleus of the TrFE unit (CHF=CF₂) gives a distinct signal at approximately 5 ppm, while the two hydrogen atoms of the CH₂ group of the VDF units give a centered bulk at 3 ppm. Relative integration of the two signals gives the relative abundance of the two monomers, i.e., their molar ratio.

[0115] The amount of CTFE can be determined by measuring the mass content of chlorine by elemental analysis and / or by performing fluorine NMR. Combining this with the results of proton NMR makes it possible to calculate Y, i.e., the molar ratio CTFE / (VDF+TrFE+CTFE).

[0116] The P(VDF-TrFE-CTFE) obtained according to the process of the invention has, according to at least some embodiments, chain ends of the formulas -CF2H and / or -CF2CH3 in an amount of at most 100 mmol / kg of repeating units resulting from the polymerization of VDF in the polymer, as measured in the method described in PIANCA, M., et al. End groups in fluoropolymers. Journal of Fluorine Chemistry. 1999, vol.95, p.71-84. Preferably, the chain ends of the formulas -CF2H and / or -CF2CH3 are in an amount of at most 80 mmol / kg, or at most 60 mmol / kg, or at most 40 mmol / kg of repeating units resulting from the polymerization of VDF in the polymer.

[0117] The P(VDF-TrFE-CTFE) of the invention essentially consists of, or is composed of, repeating units resulting from the polymerization of VDF, TrFE, and CTFE. In some embodiments, it may include at least one additional repeating unit resulting from the polymerization of a monomer other than VDF, TrFE, and CTFE. This optional additional repeating unit is preferably in a minor proportion, i.e., it may represent less than 25%, less than 10%, less than 5%, less than 2%, or less than 1% molar relative to the number of moles of repeating units resulting from CTFE in the polymer. In other embodiments, the P(VDF-TrFE-CTFE) of the invention consists of repeating units resulting from the polymerization of VDF, TrFE, and CTFE.

[0118] The homogeneity of the composition is assessed by means of the differential scanning calorimetry thermogram of the polymer, measured during a second heating at 10°C / min, according to standard 11357-3:2018. On this thermogram, in accordance with the standard, the following temperatures can be identified:

[0119] Tp m, the peak temperature of the melting peak. This temperature corresponds to a maximum of the heat flux in absolute value. If there are several melting peaks, it corresponds to the peak temperature of the melting peak with the highest heat flux in absolute value;

[0120] Tf m, the final temperature of the melting peak. If there are several melting peaks, it corresponds to the highest final temperature;

[0121] Tim, the initial temperature of the melting peak. If there are several melting peaks, it corresponds to the lowest initial temperature.

[0122] The temperatures Tf m and T; m correspond to temperatures at which the melting endotherm detaches from the baseline.

[0123] The P(VDF-TrFE-CTFE) according to the invention has a homogeneity of chemical composition characterized in that on its DSC thermogram in second heating with heating and cooling temperature ramps at 10°C / min, we have: Tfm -Tim< 50°C (eq. 9), preferably: Tfm-Tim< 45°C (eq. 9a), more preferably: Tfm-Tim< 40°C (eq. 9b), even more preferably: Tfm-Tim < 35°C (eq. 9c), and most preferably: Tfm-Tim < 30°C (eq. 9d).

[0124] Complementarily, or alternatively, the P(VDF-TrFE-CTFE) according to the invention has a homogeneity of chemical composition characterized in that on its DSC thermogram in second heating with heating and cooling temperature ramps of 10°C / min, we have: Tfm-Tpm< 15°C (eq. 10), preferably such that Tfm-Tpm< 12°C (eq. 10a); and more preferably such that Tfm-Tpm<10°C (eq. 10b). Composition

[0125] The polymer according to the invention can be formulated within a composition. The composition comprises a single or alternatively a mixture of polymers according to the invention.

[0126] According to certain embodiments, the composition may comprise at least one polymer according to the invention and at least one liquid vehicle of said at least one polymer. This composition, commonly referred to as "ink," may be prepared by dissolving or suspending the polymer(s) according to the invention in the liquid vehicle. Preferably, the liquid vehicle is a solvent. Advantageously, this solvent is a polar aprotic solvent, in particular one that may be selected from: dimethylformamide; dimethylacetamide; dimethyl sulfoxide; ketones, in particular acetone, methylethyl ketone, methylisobutyl ketone, and cyclopentanone; furans, in particular tetrahydrofuran; esters, in particular methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and propylene glycol methyl ether; carbonates, in particular dimethyl carbonate; phosphates, in particular triethyl phosphate, or mixtures thereof.The total mass concentration of polymers in the liquid vehicle can be from 0.1 to 30%, preferably from 0.5 to 20%.

[0127] According to certain embodiments, the composition may comprise one or more other polymers than those of the invention, having in particular polar or reactive functions enabling improvement of the adhesion of the composition to a given substrate.

[0128] The composition may optionally include one or more additives, in particular selected from surface tension modifying agents, rheology modifying agents, heat capacity modifying agents, and other modifying agents. resistance to aging, adhesion modifying agents, pigments or dyes, flame retardants or crosslinking aid additives.

[0129] The composition may optionally include fillers, including nanofillers, such as barium strontium titanate (BST) nanowires. Movie

[0130] The polymer according to the invention has, according to certain embodiments at least, sufficient mechanical properties to allow it to be shaped into a film.

[0131] The film can be prepared using the polymer according to the invention or a composition comprising it, for example by applying an ink to a substrate or by hot melt extrusion or compression.

[0132] The substrate may be of any nature and in particular consist of one or more layers of glass or metal(s) or organic (in particular polymeric).

[0133] The film may optionally be stretched if necessary. Stretching (when performed) is preferably carried out with a stretch ratio of at least 10% to 700%. In particular, the film may have a stretch ratio of at least 150%, or at least 200%, or at least 250%, or at least 300%, or at least 350%, or at least 400%. The stretch ratio corresponds to the ratio of the surface area of ​​the film after stretching to the surface area of ​​the film before stretching.

[0134] The films can also, after optionally being stretched, be annealed, that is to say, heated to a temperature below Tfm, preferably below Tpm, and preferably below Tim, for several hours, then cooled. The annealing temperature is generally from 70°C to 140°C, and can, according to certain embodiments, be from 100°C to 120°C.

[0135] Stretching and annealing most often allow the crystallinity and dielectric stiffness to be increased.

[0136] The invention makes it possible to obtain films of desired thickness. In particular, the film can have a thickness from 1 micrometer to 100 micrometers. Among these thicknesses, the thinnest may be preferred to avoid generating excessively high voltages. Thus, films with a thickness of 1 to 50 micrometers and even 1 to 10 micrometers are particularly preferred.

[0137] Electrodes can be deposited on the film, in particular by metallization or by deposition of conductive material (silver, copper, conductive polymer, silver nanowires, carbon black, NTC, etc...).

[0138] According to some embodiments, the film prepared from the polymer according to the invention can be a layer of a multilayer device. Applications

[0139] Due to its electroactive properties, in particular ferroelectric or ferroelectric relaxer, the polymer according to the invention can be used in actuators, and in particular for haptics, microfluidics, or in loudspeakers.

[0140] Furthermore, due to a high dielectric constant and / or high efficiency as defined in the examples, the polymer according to the invention can also be used in an energy storage system, in particular a capacitor, an organic transistor, or an electrostatic clutch. Examples

[0141] Comparative example 1: Synthesis of a P(VDF-TrFE-CTFE) according to the prior art, with an initial mixture devoid of CTFE.

[0142] A first mixture Mi of monomers consisting of 130 g of TrFE and 210 g of VDF, i.e., of composition [Xi;Yi] = [67.5% mol; 0% mol], was injected at room temperature into a stirred reactor containing 2.69 kg of demineralized water. Methylhydroxypropyl cellulose was then used to facilitate the suspension of the monomer mixture Mi in the water.

[0143] The monomer suspension was then heated to a temperature of 46°C. Once this temperature was reached, 1 g of polymerization initiator (dipropyl peroxydicarbonate) was introduced into the reactor. The pressure in the reactor reached 90 bar before polymerization began. Polymerization initiation was detected by a decrease in reactor pressure caused by monomer consumption. From the moment polymerization began, a C2 composition of VDF, TrFE, CTFE with [X2; Y2] = [67.5 mol%; 14.5 mol%] was continuously injected to maintain a pressure of approximately 90 bar in the reactor.

[0144] The reaction was stopped after the introduction of 408 g of the secondary mixture by cooling the reactor. The polymer produced was washed with demineralized water.

[0145] The polymer obtained is a P(VDF-TrFE-CTFE) had a molar composition [X;Y] of [67.4%mol ;8.2%mol] the unit contents resulting from the polymerization of VDF, TrFE and CTFE being determined by NMR, and an average molar mass by weight of 776,000 g / mol determined by SEC with polystyrene standards.

[0146] Example 1 (invention): Synthesis of a P(VDF-TrFE-CTFE) according to the invention with an average composition similar to that of comparative example 1

[0147] A first monomer mixture Mi consisting of 359 g of VDF, 208 g of TrFE and 45 g of CTFE, i.e., of composition [Xi;Yi] = [68.0 mol%; 5.5 mol%], was introduced at room temperature into a stirred reactor containing 2.22 kg of demineralized water. Methylhydroxypropyl cellulose was then used to facilitate the suspension of the monomer mixture Mi in the water.

[0148] The monomer suspension was then heated to a temperature of 46°C. Once this temperature was reached, 3.7 g of polymerization initiator (dipropyl peroxydicarbonate) was introduced into the reactor. The pressure in the reactor reached 90 bar before polymerization began. Polymerization initiation can be detected by a decrease in reactor pressure due to monomer consumption. From the moment polymerization began, a C2 composition of VDF, TrFE, CTFE with [X2; Y2] = [67.5 mol%; 9.6 mol%] was continuously injected to maintain a pressure in the reactor essentially equal to 90 bar.

[0149] The reaction was stopped after the introduction of 523 g of the secondary mixture by cooling the reactor. The polymer produced was washed with demineralized water.

[0150] The polymer obtained is a P(VDF-TrFE-CTFE) had a molar composition [X;Y] of [69.9%mol;8.1%mol] the unit contents resulting from the polymerization of VDF, TrFE and CTFE being determined by NMR and an average molar mass by weight of 866,000 g / mol determined by SEC with polystyrene standards.

[0151] Examples 2-3 and comparative examples 2-3: Synthesis of other P(VDF-TrFE-CTFE) according to the invention and according to the prior art

[0152] Other syntheses were carried out under operating conditions similar to those of Example 1, modifying the compositions [X1; YJ and [X2; Y2] in order to obtain for Examples 2 and 3 P(VDF-TrFE-CTFE) of composition [X;Y] different from the polymer according to Example 1.

[0153] Other syntheses were carried out under operating conditions similar to those of comparative example 1, modifying the compositions [X1; YJ and [X2; Y2] in order to obtain for comparative examples 2 and 3 P(VDF-TrFE-CTFE) of composition [X;Y] different from the polymer according to example 1.

[0154] The set of values ​​[Xi; YJ, [X2; Y2] and [X; Y] for all examples and comparative examples has been compiled in Table 1 below.

[0155] The parameters AXi -, AYi -, AX2 -, AY2 • were also calculated.

[0156] The AXi parameter is defined as follows:

[0157] [Math.6] .--¾ -.¾ = | x W0 s X 7

[0158] The AX2- parameter is defined as follows:

[0159] [Math.7] ML, = ( ■“ JX 100

[0160] The AYi parameter is defined as follows:

[0161] [Math.8]

[0162] The parameter AY2' is defined as follows:

[0163] [Math.9] AK,

[0164] [Tables 1] Ex XX: x,; (% word) Y. (% word) â¥r AXr Camp. 1 67.4 8.2 67.5 0.0 in r< co 14.5 -1.88 0.77 O;09 0 10 Ext 68.4 8.3 68.0 5.5 CD >4' Vl 9.6 -0.34 0.16 -0.58 1.34 Camp. 2 78.6 2 2 72.0 0.0 72.3 7.9 -1.88 2.61 2.05 2.05 Ex.2 69.0 2.0 69.8 0.9 67.5 1.9 -0.5.3 -05 1.25 -2.16 Comp.3 66.6 5 2 65.5 0.0 65.5 9.3 -1.83 0.80 -1.65 -1.65 Ex 3 68.1 5.1 69.8 3.2 67.5 5.8 -6.38 0.13 1.28 -0.88 Characterizations

[0165] Differential scanning calorimetry (DSC) analyses were performed on a Mettler Toledo apparatus equipped with an internal cooler and operating under a nitrogen (N2) flow on the polymers of the examples and comparative examples.

[0166] The thermal measurement procedure consists of two successive thermal cycles, each cycle consisting of: - an isothermal period of 5 min at -50°C; - a temperature increase at 10°C / min up to 250°C; - an isothermal period of 5 minutes at 250°C; - a temperature cooling at 10°C / min down to -50°C, marking the End of a cycle.

[0167] The temperatures Tim, Tpm and Tfm were identified on the thermograms during the second heating. Table 2 summarizes the measurements taken as well as the differences Tfm-Tim and Tfm-Tpm, representative of the spread of the phase transition during melting.

[0168] [Tables2] Ex. rcj (6C) K; CC) 1«- IL. fC) QC Comp.1 & sort 60 1218 150.0 65.0 273 Ex.1 102.0 124.8 131.0 29.0 6.3 Comp 2 110.0 147.8 164.0 54.0 16.2 Ex 2 128, S 145.8 150.0 22.0 4.4 Camp. 3 10O 139.2 154.0 54.0 14.8 Ex.3 116.8 138.2 143.0 27.0 05 &

[0169] The polymers according to the invention have a phase transition in melting that is tight over a narrow temperature range, which is indicative of better homogeneity of the chemical composition of P(VDF-TrFE-CTFE), compared to polymers according to the prior art which have a phase transition in melting spread over a wide temperature range, which is indicative of significant heterogeneity of the chemical composition of P(VDF-TrFE-CTFE).

[0170] By way of illustration, [Fig.1] represents the second heating thermograms of a polymer according to the invention (thermogram A) and of a polymer according to the prior art (thermogram B).

[0171] To evaluate the electroactive properties of polymers, devices were fabricated as follows. A 10 nm thick chromium electrode followed by a 100 nm thick silver electrode was deposited onto a 15 x 15 mm glass substrate by chemical vapor deposition (CVD). A polymer film was deposited on the substrate using a Dr. Blade from a 7 wt% polymer solution in ethyl acetate. The film thickness after solvent evaporation was measured at 3 µm. Annealing was performed at 105 °C on a hot plate for 2 hours. A 100 nm thick silver electrode was then deposited over the film by CVD.

[0172] Permittivity measurements were performed using a broadband dielectric spectroscopy system and a Solartron 1260 A impedance analyzer, at various temperatures between -30°C and 70°C. Sample temperature control was performed using a Linkam LTS 350 temperature control system. Measurements were carried out with a 1 V AC voltage signal, with a signal frequency of 1 kHz.

[0173] Table 3 sets together the maximum relative permittivity measurements (emax, unitless), and the temperature at which these permittivities were measured (T, °C).

[0174] [Tables3] Ref T fC) Comp. 1 48.7 40.0 Ex.1 56:3 40.0 Ex. 3 72.5 50.0

[0175] Comparison of the dielectric measurements carried out on the polymer according to example 1 with the measurements carried out on the polymer according to comparative example 1 shows that the polymer of homogeneous chemical composition according to the invention has a maximum permittivity higher than that of the comparative polymer of the same chemical composition but heterogeneous (increase of the order of 15%), and that this permittivity is maximum for the same temperature.

[0176] Polarization hysteresis was also measured by recording several polarization hysteresis cycles with an aixACCT Systems TF Analyzer 2000E. The measurements were performed by applying a continuous triangular signal with a frequency of 10 Hz, at room temperature (25 °C), and with an applied electric field of 1700 kV / cm.

[0177] The maximum polarization (Pmax, pC.cm2) and remanent polarization (Pr, pC.cm2) measurements of the polarization hysteresis have been compiled in Table 4.

[0178] Table 4 also contains recoverable energy density values ​​(WreCuP, KJ / m3) and efficiency 0 / ,%) calculated as follows.

[0179] The recoverable energy density (WrecUp) is interpreted visually as the area above the hysteresis loop of the first quadrant, while the lost energy density (Wioss) is represented by the area inside the loop of the first quadrant.

[0180] The efficiency (z?) is calculated according to the equation:

[0181] [Math.10]

[0182] A graphic illustration of the regions corresponding to the recoverable and lost energy density is provided in [Fig.2] for a polymer according to the invention (hysteresis curve (A)) and for a prior art polymer of the same average chemical composition (hysteresis curve (B)).

[0183] [Tables4] Ex. -T PF Emcadlé (%) Compl 4.7 0 3 2200.0 63.0 Exd 5.0 0.7 2307.0 66.0 Ex2 7.6 4.9 1728.0 30.0 Ex.3 6.2 LS 2284.0 54.0

[0184] By comparing the results for the polymer according to Example 1 with the results for the polymer according to Comparative Example 1, it can be seen that better homogeneity of the chemical composition of the polymer, such as that obtained according to the invention, makes it possible to achieve a higher maximum polarization (+6%) and to form a thinned hysteresis characterized by a decrease in the remanent polarization of (-12.5%). The recoverable energy density is increased (+5%) as well as the efficiency (+5%).

[0185] This application also discloses the following objects of a process for manufacturing the process according to the invention:

[0186] Subject 1. Process for manufacturing a P(VDF-TrFE-CTFE) polymer by polymerization of vinylidene fluoride, VDF, trifluoroethylene, TrFE, and chlorotrifluoroethylene, CTFE, in suspension in a liquid, to obtain a P(VDF-TrFE-CTFE) of target composition Cp [Xp ;YP],

[0187] where Xp represents the target molar proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in the polymer and,

[0188] where Yp represents the target molar proportion, expressed as a percentage, in units resulting from the polymerization of CTFE relative to the total number of moles in units resulting from the polymerization of VDF, TrFE and CTFE in the polymer,

[0189] said process comprising: - the injection into a reactor of a composition Ci [Xi ;YJ in VDF, TrFE and CTFE monomers, to form a mixture of Mi monomers in the suspension liquid,

[0190] where Xi represents the molar proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition Ci and,

[0191] where Yi represents the molar proportion, expressed as a percentage, of CTFE monomer relative to the total number of moles of VDF, TrFE and CTFE monomers in the composition Ci; - the initiation of polymerization of the Mi monomer mixture; and, - the continuation of polymerization at a substantially constant pressure in the reactor, by injection into the reactor of VDF, TrFE and CTFE monomers of composition C2 [X2;Y2], and optionally by injection into the reactor of a suspension liquid, each of the parameters X2 and Y2 being independently constant or variable during the continuation of polymerization at substantially constant pressure,

[0192] where X2 represents the molar proportion, expressed as a percentage, of VDF monomer relative to the total number of moles of VDF and TrFE monomers in composition C2,

[0193] and where Y2 represents the molar proportion, expressed as a percentage, of CTFE monomer relative to the total number of moles of VDF, TrFE and CTFE monomers in composition C2;

[0194] said process being characterized in that Yp, AYi and AY2 satisfy the following inequalities:

[0195] 0.1 < Yp < 15.0 (eq. 1)

[0196] -0.70 < AYi <-0.15 (eq. 2), and

[0197] -0.40 <AY2 <0.65 (eq. 3);

[0198] in which the parameters AYi and AY2 are defined as follows:

[0199] [Math. 11] Ai; = and AK, =

[0200] Object 2. A method according to object 1, in which the parameter AY2 satisfies the following inequality:

[0201] -0.25 <AY2 <0.50 (eq. 3a).

[0202] Object 3. A method according to object 2, in which the parameter AY2 satisfies the following inequality:

[0203] -0.12 <AY2 <0.36 (eq. 3b).

[0204] Object 4. A method according to any one of objects 1 to 3, wherein the parameter AYi satisfies the following inequality:

[0205] -0.60 <AY! < -0.20 (eq. 2a);

[0206] and preferably the parameter AYi satisfies the following inequality:

[0207] -0.57 < AYi < -0.25 (eq. 2b).

[0208] Object 5. A method according to any one of objects 1 to 4, wherein the parameter Xp satisfies the following inequality: 30.0 < Xp < 100 (eq. 4), and wherein the parameter AXi satisfies the following inequality: -8.0 < AXi < 6.5 (eq. 5), the parameter AXi being defined as follows:

[0209] [Math. 12] ZX - AX = ! —---M x 100

[0210] Object 6. Method according to object 5, in which the parameter AXi satisfies the following inequality: -7.0 < AXi < 4.0 (eq. 5a).

[0211] Object 7. A method according to any one of objects 1 to 6, wherein the parameter Xp satisfies the following inequality: 30.0 < Xp < 100 (eq. 4), and wherein the parameter AX2 satisfies the following inequality: -8.0 < AX2 < 8.0 (eq. 6), wherein the parameter AX2 is defined as follows:

[0212] [Math. 13] ZX -.¥a\ \ X /

[0213] Object 8. A method according to object 7, in which the parameter AX2 satisfies the following inequality: -4.0 < AX2 < 4.0 (eq. 6a).

[0214] Object 9. A method according to any one of objects 1 to 8, wherein the parameter Yp satisfies the following inequality:

[0215] 4.0 < Yp < 10. (eq. la).

[0216] Object 10. A method according to any one of objects 1 to 9, in which the parameter Xp satisfies the following inequality: 45.0 < Xp < 90.0 (eq. 4a), and preferably the following inequality: 50.0 < Xp < 80.0 (eq. 4b).

[0217] Item 11. A process according to any one of items 1 to 10, wherein the suspension liquid is water or an aqueous solution.

[0218] Item 12. A process according to any one of items 1 to 11, wherein the polymerization is essentially carried out under temperature and pressure conditions for which the monomers in the reactor are in the supercritical state.

[0219] Item 13. A process according to any one of items 1 to 12, wherein the polymerization is essentially carried out at a pressure, in particular a polymerization continuation pressure, of 50 to 130 bars, and preferably of 70 to 110 bars.

[0220] Item 14. A process according to any one of items 1 to 13, wherein the continuation of polymerization is carried out without injection of suspension liquid in order to maintain a substantially constant pressure in the reactor.

[0221] Item 15. A method according to any one of items 1 to 14, wherein X2 and Y2 remain constant during the continuation of polymerization.

Claims

Demands

1. Polymer P(VDF-TrFE-CTFE), of homogeneous chemical composition, having composition [X;Y], where X represents the mole proportion, expressed as a percentage, in units resulting from the polymerization of VDF relative to the total number of moles in units resulting from the polymerization of VDF and TrFE in the polymer and, where Y represents the mole proportion, expressed as a percentage, in units resulting from the polymerization of CTFE relative to the total number of moles in units resulting from the polymerization of VDF, TrFE and CTFE in the polymer, the parameter X satisfying the inequality: 30 < X ​​< 100 (eq. 7), and the parameter Y satisfying the inequality 0.1 < Y ​​< 15.0 (eq.8), the homogeneity of chemical composition being characterized by a scanning differential calorimetry thermogram of said polymer, measured in second heating with heating and cooling ramps at 10°C / min, on which one can identify: Tim, the initial temperature of the melting peak, or where applicable in the presence of several melting peaks, the lowest initial temperature, Tfm, the final temperature of the melting peak, or where applicable in the presence of several melting peaks, the highest final temperature, the values ​​of Tim and Tfm satisfying the inequality: Tfm-Tim< 50°C (eq. 9); preferably: Tfm-Tim< 45°C (eq. 9a); more preferably: Tfm-Tim< 40°C (eq. 9b); even more preferred: Tfm-Tim < 35°C (eq. 9c), and most preferred: Tfm-Tim < 30°C (eq. 9d).

2. Polymer according to claim 1, wherein the homogeneity of chemical composition is characterized by said differential scanning calorimetry thermogram, on which one can identify: Tpm, the peak temperature of the melting peak, or where applicable in the presence of several melting peaks the peak temperature having the highest absolute value heat flux, the values ​​of Tfm and Tpm satisfying: Tfm-Tpm< 15°C (eq. 10); preferably: Tfm-Tpm< 12°C (eq. 10a); and more preferably: Tfm-Tpm< 10°C (eq. 10b).

3. Polymer according to any one of claims 1 and 2, wherein the parameter X satisfies the inequality: 45.0 < X ​​< 90.

0.

4. Polymer according to any one of claims 1 to 3, wherein the parameter Y satisfies the inequality: 4.0 < Y < 10.

5. Polymer according to any one of claims 1 to 4, wherein the weight average molar mass Mw of the polymer is at least 550,000 g / mol, as measured by size exclusion chromatography with dimethylformamide, as eluent, with a set of 3 columns of increasing porosity, the stationary phase being a styrene-DVB gel.

6. Composition comprising at least one polymer according to any one of claims 1 to 5 and at least one liquid vehicle selected from: dimethylformamide; dimethylacetamide; dimethyl sulfoxide; ketones; furans; esters; carbonates; phosphates; or mixtures thereof.

7.

8. Polymer film according to any one of claims 1 to 5. Use of the polymer according to any one of claims 1 to 5 or of the film according to claim 7 for its ferroelectric or ferroelectric relaxer properties.

9. Use of the polymer according to any one of claims 1 to 5 or of the film according to claim 7 for its high dielectric constant value.

10. Use of the polymer according to any one of claims 1 to 5 or of the film according to claim 7, for its high efficiency value / / , the efficiency r) being calculated according to the equation: [Math. 14] w , in which WreCuP is the recoverable energy density and Wiossest is the lost energy density, observable on the first quadrant of a hysteresis loop.

Images