Electrocaloric polymers, inks and films containing them, and their uses

Abstract

The present invention relates to a polymer containing VDF-based units that exhibits an electrocaloric effect under the influence of a fluctuating electric field. The polymer contains 0.1 to 10.0 mol % double bonds, which are substantially non-conjugated. The present invention also relates to corresponding compositions and films, as well as various uses.

Description

[Technical Field]

[0001] This invention relates to the field of electrocalorific materials.

[0002] More specifically, the present invention relates to an electroactive polymer that exhibits a significant electrocaloric effect, i.e., a significant variation in adiabatic temperature, when the polymer is exposed to a fluctuating electric field.

[0003] The present invention also relates to inks and films based on electroactive polymers.

[0004] This invention ultimately relates to various possible uses of polymers, particularly in the form of films. [Background technology]

[0005] The electrocaloric effect is a property of a bipolar dielectric material that spontaneously emerges when exposed to a fluctuating electric field, due to temperature fluctuations. The physical origin of this phenomenon relates to changes in dipole order and, therefore, to fluctuations in dipole entropy induced by the application of an electric field. The application of an electric field Ec orders and orienteds the dipoles of these materials, resulting in a decrease in their dipole entropy and an increase in their temperature under adiabatic conditions. Conversely, a decrease or suppression of the electric field results in an increase in their dipole entropy and a decrease in their temperature under adiabatic conditions. Therefore, under given experimental conditions, the electrocaloric material exhibits a variation in adiabatic temperature ΔT in response to the applied electric field Ec under adiabatic conditions. EC It is characterized by the following: Alternatively, the electrocalorific material has a change in isothermal entropy ΔS with respect to the applied electric field Ec under isothermal conditions. EC It is characterized by the following.

[0006] The electrocaloric effect is currently the subject of much research on thermoelectric or magnetocaloric effects for the development of new cooling systems that are more environmentally friendly and energy-efficient than systems that operate on gas compression [see SHI, Junye, HAN, Donglin, LI, Zichao et al., Electrocaloric cooling materials and devices for zero-global-warming-potential, high-efficiency refrigeration. Joule, 2019]. Ferroelectric materials and relaxor ferroelectrics are the materials of greatest interest for these applications because they are likely to have high electrocaloric performance due to the strong coupling between the applied electric field and their dipole structure. In particular, this coupling is close to or slightly above a ferroelectric → paraelectric (FE → PE) or relaxor ferroelectric → paraelectric (RFE → PE) phase transition due to the strong reversible fluctuations in the polarization of these materials, especially under an electric field, and their high dielectric constant. In other words, near the phase transition FE→PE or RFE→PE, relatively weak fluctuations in the electric field cause significant fluctuations in entropy and temperature. The good flexibility and ease of processing of these materials in the form of thin films with large surface areas are other parameters that make them particularly suitable for use in solid-state refrigeration systems.

[0007] Among ferroelectric and relaxa-ferroelectric polymer materials, fluoropolymers based on VDF and TrFE are the most researched. They currently exhibit the highest performance quality.

[0008] The electrocaloric properties of P(VDF-TrFE) type ferroelectric copolymers are at their maximum value near the ferroelectric-to-paraelectric (FE→PE) transition. The FE→PE transition of this type of polymer is narrow; that is, it occurs over a small temperature range, relatively high, typically strictly above 60°C. This hinders their use in cooling systems that must operate near ambient temperature and / or over a wide temperature range.

[0009] The use of relaxa ferroelectric polymers makes it possible to overcome at least some of the above drawbacks. This is because irradiated P(VDF-TrFE), P(VDF-TrFE-CTFE), or P(VDF-TrFE-TrFE-CTFE) type relaxa ferroelectric polymers have an expanded (RFE→PE) phase transition compared to the FE→PE phase transition of ferroelectric polymers, i.e., this occurs over a wider temperature range. Furthermore, the RFE→PE transition is generally located at a lower temperature than the FE→PE transition temperature of ferroelectric polymers. Therefore, this makes it possible to envision the use of relaxa ferroelectric polymers in cooling systems with a wide range of temperatures, particularly those that must operate near and / or over a wide range of ambient temperatures.

[0010] The electrothermal performance quality of a material can be theoretically (indirectly) estimated from its dielectric properties using equations derived from Maxwell's relation, as follows.

[0011]

number

[0012] For example, Neese et al. found that a P(VDF-TrFE) type ferroelectric copolymer, composed of 55 mol% VDF and 45 mol% TrFE, having a Curie temperature (FE→PE transition) of approximately 70°C, exhibits an adiabatic temperature change (ΔT) from 12°C to approximately 80°C in response to a high electric field of 209 V / μm. ECIt could be estimated by the "indirect" method that it can bring about EC ([See reference: NEESE, Bret, CHU, Baojin, LU, Sheng-Guo, et al., Large electrocaloric effect in ferroelectric polymers near room temperature. Science, 2008, Vol. 321, No. 5890, pp. 821 - 823]).

[0013] However, the reliability of the indirect method for estimating ΔT EC is currently being questioned for certain materials, especially fluoropolymers [See LU, S.G., ROZIC, B., ZHANG, Q.M., et al., Comparison of directly and indirectly measured electrocaloric effect in relaxor ferroelectric polymers. Applied Physics Letters, 2010, Vol. 97, No. 20, p. 202901].

[0014] Another measurement method known as "direct" can compare the performance qualities of materials with each other and has thus been developed, at least in part, to overcome the above-mentioned drawbacks of the indirect method [See LU, S.G., ROZIC, B., ZHANG, Q.M., et al., Comparison of directly and indirectly measured electrocaloric effect in relaxor ferroelectric polymers. Applied Physics Letters, 2010, Vol. 97, No. 20, p. 202901].

[0015] For example, Li et al. were able to directly measure that a P(VDF-TrFE-CFE) relaxor polymer with a composition of 59.2 / 33.6 / 7.2 mol% can exhibit a significant electrocaloric effect over an extended temperature range of about 40 °C. In this way, the variation ΔT of the adiabatic temperature up to 7.6 °C EC could be measured at 30 °C under an electric field of 100 V / μm [see LI, Xinyu, QIAN, Xiao-shi, LU, S.G. et al., Tunable temperature dependence of electrocaloric effect in ferroelectric relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene termpolymer). Applied Physics Letters, 2011, Vol. 99, No. 5, p. 052907].

[0016] In order to enable the development of an effective cooling device, there is currently a need to provide VDF-based fluoropolymers with improved electrocaloric properties, i.e., a larger variation ΔT of the adiabatic temperature EC at a given alternating electric field. The electric field used to obtain a high variation of the adiabatic temperature should be as low as possible in order to limit energy consumption and the use of expensive and dangerous control electronics.

[0017] From this perspective, Zhang, G. et al. proposed adding nanometer fillers such as barium strontium titanate (BST) nanowires to P(VDF-TrFE-CFE) with a composition of 62.3 / 29.7 / 7.8 mol%. The P(VDF-TrFE-CFE) formulation provided with such a filler has a ΔT with a maximum value exceeding at least 7.5 °C over a measurement temperature range of 0 to 60 °C under an electric field with an amplitude equal to 75 V / μm EC making it possible to measure. In contrast, for P(VDF-TrFE-CFE) without a filler, the ΔT is 3.5 to 4.5 °C over a measurement temperature range of 0 to 60 °C under an electric field with an amplitude equal to 75 V / μm ECThe following was measured [ZHANG, G. et al., Ferroelectric Polymer Nanocomposites with Complementary Nanostructured Fillers for Electrocaloric Cooling with High Power Density and Great Efficiency. ACS Applied Energy Materials, 2018, 1(3), pp.1344~1354].

[0018] Nevertheless, the introduction of nanometer-sized fillers into polymer matrices presents several drawbacks. First, it complicates the molding of the material because it requires very good dispersion of these fillers. In addition, handling nanoparticles in polymer manufacturing methods is complicated due to the potential risks to human health of free nanoparticles. Finally, the presence of fillers tends to mechanically weaken the material and reduce its dielectric strength.

[0019] WO2019075061 assumes, without providing examples, that the polymer of formula (I) will have favorable electrocaloric properties.

[0020] [ka] In the formulas, in each example of a unit, n and m are integers independently chosen between 1 and 1000, p is an integer greater than n + m, R1, R2, R3, and R4 are independently chosen from -H, -F, -Cl, -Br, -I, -NH2, -NHZ, -NZ2, -BH2, -BHZ, -BZ2, OZ, -SeZ, -TeZ, -SO2Z, -OCOZ, -NHCOZ, -COOZ, -CONH2, -CONHZ, -CONZ2, -CH2F, and -CHF2, and Z is independently chosen from a hydrogen atom, alkyl group, aryl group, or aralkyl group in each example of a unit.

[0021] A method for producing polymer (I) is disclosed, which involves contacting the initial polymer (II) with an alkaline hydroxide (strong base pKa>14) such as LiOH, NaOH, KOH, or CsOH to bring about dehalogenation, and polymer (II) has the following formula.

[0022] [ka] In the formula, n, m, p, R1, R2, R3, and R4 are as defined for the polymer in Formula 1.

[0023] The sole example of WO2019075061 demonstrates the production of a polymer containing a double bond, which is produced from the dehydrofluorination of PVDF in dimethylacetamide with a saturated solution of sodium hydroxide in isopropanol.

[0024] The electrocaloric properties of the manufactured polymer were not measured. The type of double bond in the manufactured polymer was also not determined.

[0025] Nevertheless, in light of US Patent No. 4904739 concerning a similar method for the dehydrofluorination of PVDF, the resulting polymer appears to contain a high proportion of conjugated double bonds.

[0026] Furthermore, it is known to those skilled in the art that fluoropolymers containing conjugated double bonds, obtained by dehydrofluoridation as a result of the action of a strong base, are not very stable with heat, turn yellow, decompose easily, and yield polymers that are easily crosslinked during the action of a strong base.

[0027] Furthermore, this method has the drawback of using dimethylacetamide as a solvent, which is harmful (by contact / inhalation) and potentially CMR (Chronic Mitigation Reactive).

[0028] Therefore, in order to develop an effective cooling device, we are currently working to improve the electrocaloric characteristics under predetermined fluctuating electric fields and environmental (temperature) conditions, i.e., to improve the adiabatic temperature fluctuation ΔT. EC There is a need to provide VDF-based fluoropolymers that exhibit the following properties. The electric field used to obtain high variations in adiabatic temperature should, in preference, be as low as possible to limit energy consumption and restrict the use of expensive and dangerous (high-voltage) control electronics. [Prior art documents] [Patent Documents]

[0029] [Patent Document 1] International Publication No. 2019 / 075061 [Patent Document 2] U.S. Patent No. 4904739 [Non-patent literature]

[0030] [Non-Patent Document 1] SHI, Junye, HAN, Donglin, LI, Zichao et al., Electrocaloric cooling materials and devices for zero-global-warming-potential, high-efficiency refrigeration.Joule,2019 [Non-Patent Document 2] NEESE, Bret, CHU, Baojin, LU, Sheng-Guo et al., Large electrocaloric effect in ferroelectric polymers near room temperature.Science, 2008, vol. 321, No. 5890, pp. 821~823 [Non-Patent Document 3] LU, SG, ROZIC, B., ZHANG, QM et al., Comparison of directly and indirectly measured electrocaloric effect in relaxor ferroelectric polymers. Applied Physics Letters, 2010, vol. 97, No. 20, p. 202901 [Non-Patent Document 4] LI, Xinyu, QIAN, Xiao-shi, LU, SG et al., Tunable temperature dependence of electrocaloric effect in ferroelectric relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene termpolymer). Applied Physics Letters, 2011, vol. 99, No. 5, p. 052907 [Non-Patent Document 5] ZHANG, G. et al., Ferroelectric Polymer Nanocomposites with Complementary Nanostructured Fillers for Electrocaloric Cooling with High Power Density and Great Efficiency. ACS Applied Energy Materials, 2018, 1(3), pp.1344~1354 [Overview of the project] [Problems that the invention aims to solve]

[0031] This invention proposes to provide improved fluoropolymers compared to those of the prior art, which exhibit a significant electrocaloric effect when exposed to a fluctuating electric field, as well as compositions and films derived therefrom, and related uses.

[0032] Furthermore, the objective is to propose an improved fluoropolymer that exhibits high dielectric strength to withstand numerous electric field cycles without breakdown, at least according to one embodiment.

[0033] The objective is, further, to propose improved fluoropolymers that exhibit good thermal and / or chemical stability, in order to enable the sustained and reliable use of the polymer in the apparatus, at least according to one embodiment. [Means for solving the problem]

[0034] The present invention relates to a polymer that exhibits an electrocaloric effect under the influence of a fluctuating electric field, - Units of -(CF2-CH2)- (III) in concentrations of 30 mol% to 90 mol%, - At least one unit of formula (CX1X2-CX3X4)- (IV) in concentrations of 1 mol% to 59.9 mol%, - At least one unit of formula -(CY1Y2-CY3Z)- (V) in a quantity of 0 mol% to (20-N) mol%, - Nmol% of ethylene units (multiple units allowed) selected from a list consisting of -(CY3=CF)-, -(CY3=CX1)-, -(CY3=CX2)-, -(CY1=CY3)-, -(CY2=CY3)-, and combinations thereof. [In the formula, X1 and X2 independently represent alkyl groups containing 1 to 3 carbon atoms, which may be -H, -F, or partially or completely fluorinated. X3 and X4 independently represent alkyl groups containing 1 to 3 carbon atoms, which may be -F or partially or completely fluorinated, except that both X1 and X2 are -H, and both X3 and X4 are -F. Y1 and Y2 independently represent alkyl groups containing -H, -F, -Cl, or 1 to 3 carbon atoms which may be partially or completely fluorinated. Y3 represents an alkyl group containing -F, -Cl, or 1 to 3 carbon atoms which may be partially or completely fluorinated. Z represents a halogen atom other than -F. N is a number in the range of 0.1 to 10.0. Includes.

[0035] The polymer according to the present invention essentially does not exhibit conjugated carbon-carbon double bonds.

[0036] The inventors of the present invention have, quite surprisingly, found that under the same conditions of electric field fluctuations and at one identical measurement temperature, such polymers exhibit better electrocaloric properties than polymers having substantially the same composition but without double bonds and / or polymers having substantially the same composition but with conjugated double bonds. These findings are based on measurements of adiabatic temperature fluctuations performed on test bench 1, as shown in Figure 1, for the polymers according to the present invention. These measurements were compared with measurements performed on polymers having substantially the same composition but without carbon-carbon double bonds and / or polymers having substantially the same composition but with conjugated carbon-carbon double bonds, under the same conditions of electric field fluctuations and at one identical measurement temperature.

[0037] Furthermore, the inventors observed that at least some of these polymers, and indeed even most of them, are chemically and thermally stable and possess good dielectric strength.

[0038] According to some embodiments, X1 can represent -H or F, and X2, X3, and X4 can all represent -F.

[0039] According to some embodiments, Z represents -Cl.

[0040] According to some embodiments, Y3 represents -F, and both Y1 and Y2 represent -H or F.

[0041] According to some embodiments, the polymer according to the present invention contains at least 1 mol%, preferably at least 2 mol%, more preferably at least 3 mol%, of units of formula (V), and very preferably at least 4 mol%.

[0042] According to some specific embodiments, a polymer in which X1 is -H, all three X2, X3, and X4 are -F, Y3 is -F, both Y1 and Y2 are -H, and Z is -Cl has an N value selected from 0.1 to 2, preferably 0.1 to 1.5, and even more preferably 0.1 to 1.

[0043] According to some specific embodiments, a polymer in which X1 represents -H, all three X2, X3, and X4 represent -F, all three Y1, Y2, and Y3 represent -F, and Z represents -Cl has an N value selected from 0.1 to 10.0, preferably 1.0 to 8.0, more preferably 2.0 to 7.5, and most preferably 2.2 to 7.0.

[0044] The polymer according to the present invention is, advantageously, a relaxa ferroelectric polymer.

[0045] In some embodiments, the polymer is 20 mC / m 2 The following residual polarization and / or 25V.μm -1 The following coercivity fields are used, and both remanent polarization and coercivity measurements are performed in a field with a temperature of 25°C, a frequency of 1 Hz, and a voltage of 150 V / μm.

[0046] According to some embodiments, the polymer has a weight-average molecular weight of 200,000 g / mol or more, preferably 300,000 g / mol or more, and preferably 400,000 g / mol or more.

[0047] According to some embodiments, the polymer has a melting enthalpy of 10 J / g or more, preferably 15 J / g or more, and the melting enthalpy is measured in accordance with standard ISO 11357-2:2013 during a second heating using a temperature gradient of 10°C / min.

[0048] A high weight-average molecular weight makes it possible to achieve a high degree of crystallinity in particular for polymers. Polymers having a high weight-average molecular weight and / or high degree of crystallinity have better dielectric strength and particularly advantageous mechanical properties, making it possible to produce films that are sufficiently mechanically strong.

[0049] According to some embodiments, the polymer has a relative permittivity of 15 or more, preferably 20 or more, more preferably 40 or more, and very preferably 55 or more over a temperature range of at least 5°C, preferably at least 10°C, preferably at least 20°C, and very preferably at least 30°C, and the relative permittivity is measured at 1 kHz.

[0050] According to some embodiments, the polymer has a maximum dielectric constant at a temperature of 60°C or lower, preferably 50°C or lower, and more preferably 40°C or lower, and the dielectric constant is measured at 1 kHz.

[0051] The polymer according to the present invention can be obtained by a method comprising the following: a) Providing an initial polymer containing the following in terms of total moles of polymer: - Units for formula (CF2-CH2)- (III) in concentrations of 40 mol% to 90 mol%, - At least one unit of formula (CX1X2-CX3X4)- (IV) in a concentration of 9.9 mol% to 59.9 mol%, - At least one unit of formula (CY1Y2-CY3Z)- (V) in amounts of 0.1 mol% to 20 mol%, [In the formula, X1, X2, X3, X4, Y1, Y2, Y3, and Z are as defined above.] b) Dehalogenation of the initial polymer (wherein dehalogenation essentially consists of the elimination of -Z and adjacent hydrogen atoms, at least partially).

[0052] According to some embodiments, the obtained polymer has an adiabatic temperature variation at at least 0.5°C greater, preferably at least 1°C greater, and more preferably at least 1.5°C greater, with respect to the adiabatic temperature variation of the initial polymer at at least one measurement temperature, and the measurement of the adiabatic temperature variation is performed by a fluctuating electric field having an amplitude equal to 86 V / μm.

[0053] According to some embodiments, the polymer has a maximum relative permittivity that is at least 5% greater, preferably at least 10% greater, and more preferably at least 25% greater than the maximum dielectric constant of the initial polymer, and the relative permittivity is measured at 1 kHz.

[0054] According to some embodiments, the dehalogenation step in the method is carried out with a reaction rate of at least 0.1, and preferably with a reaction rate of at least 0.2.

[0055] The present invention also relates to a composition comprising one or more polymers and one or more liquid vehicles according to the present invention.

[0056] The present invention also relates to a film comprising a polymer according to the present invention. This film has a thickness of 0.1 micrometers or more. Preferably, it can have a thickness in the range of 1 micrometer to 100 micrometers. More preferably, it can have a thickness in the range of 1 micrometer to 50 micrometers, and in particular, a thickness in the range of 1 micrometer to 10 micrometers. If the film is too thin, the latter is too mechanically weak. If the film is too thick, an excessively high voltage must be applied to obtain a predetermined electric field.

[0057] Finally, this invention relates to possible uses of polymers, particularly the use of polymers in film form.

[0058] The polymer according to the present invention can be used in heat transfer systems, particularly cooling systems.

[0059] The polymers according to the present invention can also be used in energy storage systems, particularly capacitors, organic transistors, actuators, or electrostatic clutches. [Modes for carrying out the invention]

[0060] <Fluoropolymers containing essentially non-conjugated double bonds> The polymer according to the present invention comprises, or more preferably essentially, the following: - Units for formula (CF2-CH2)- (III) in concentrations of 30 mol% to 90 mol%, - At least one unit of formula (CX1X2-CX3X4)- (IV) in concentrations of 1 mol% to 59.9 mol%, - At least one unit of formula -(CY1Y2-CY3Z)- (V) in a quantity of 0 mol% to (20-N) mol%, - Nmol% of ethylene units (multiple units allowed) selected from a list consisting of -(CY3=CF)-, -(CY3=CX1)-, -(CY3=CX2)-, -(CY1=CY3)-, -(CY2=CY3)-, and combinations thereof. [In the formula, X1 and X2 independently represent alkyl groups containing 1 to 3 carbon atoms, which may be -H, -F, or partially or completely fluorinated. X3 and X4 independently represent alkyl groups containing 1 to 3 carbon atoms, which may be -F or partially or completely fluorinated, except that both X1 and X2 are -H, and both X3 and X4 are -F. Y1 and Y2 independently represent alkyl groups containing -H, -F, -Cl, or 1 to 3 carbon atoms which may be partially or completely fluorinated. Y3 represents an alkyl group containing -F, -Cl, or 1 to 3 carbon atoms which may be partially or completely fluorinated. Z represents a halogen atom other than -F. N is a number in the range of 0.1 to 10.0.

[0061] The molar composition of units in fluoropolymers can be determined by various methods such as infrared spectroscopy or Raman spectroscopy. Conventional methods of elemental analysis of elements such as carbon, fluorine, and chlorine or bromine or iodine, such as X-ray fluorescence spectroscopy, allow for the clear calculation of the polymer's composition by weight, and the molar composition can be estimated from the polymer's weight. Furthermore, analysis of a polymer solution in a suitable deuterated solvent allows for the determination of the composition using multinuclear NMR techniques, particularly proton ( 1 H) and fluorine ( 19 F) NMR techniques may be used. The NMR spectrum is recorded using an FT-NMR spectrometer equipped with a multinuclear probe. Then, specific signals given by various monomers are positioned within the spectrum generated according to each nucleus. For example, units produced by the polymerization of VDF give a signal specific to the -CH2- group (a wide range of undegraded peaks centered around 3 ppm) in proton NMR. Similarly, units produced from TrFE give a specific signal characteristic of the -CFH- group (approximately 5 ppm) in proton NMR. In fluorine NMR, the signals from the -CF2- and -CFCL- units of CFE and CTFE are mixed with the signals of the -CF2- units of VDF and TrFE from -90 to -132 ppm. The -CHF- unit of TrFE gives a characteristic signal from -194 to -220 ppm. By combining the proton NMR spectrum and the fluorine NMR spectrum, it becomes possible to clearly estimate the molar composition of the polymer. The presence of conjugated and unconjugated double bonds in fluoropolymers can be evaluated by different spectroscopic methods, particularly Raman spectroscopy. (1720 cm²) -1 The valence vibration band corresponds to the presence of a single type of C=C double bond resulting from the -CF=CH- bond. Conjugated double bonds are in the 1500-1700 cm⁻¹ range. -1 It is observed in the valence vibration band, which is broader and has lower wavenumbers. The presence of a double bond can be quantified by proton NMR, as a signal appears in the 6.0–6.7 ppm range.

[0062] The inventors have demonstrated that the presence of 0.1% to N% of units having carbon-carbon double bonds (these double bonds are non-conjugated in the polymer structure) makes it possible to obtain polymers with high specific insulation constants and / or large electrocaloric effects.

[0063] In addition, these polymers are stable over time under normal conditions of use and implementation, according to at least some embodiments. That is, under normal conditions of use, and especially in the applications provided in this patent application, they do not decompose or decompose only slightly, they do not yellow or yellow only slightly, they do not crosslink or crosslink only slightly, and their viscosity in solution or in a melt does not change or changes only slightly.

[0064] The polymer contains 30 mol% to 90 mol% of units derived from vinylidene difluoride, relative to the total number of moles of units in the polymer composition.

[0065] According to some embodiments, the polymer may contain units derived from vinylidene difluoride in amounts of 30 mol% to 35 mol%, 35 mol% to 40 mol%, 40 mol% to 45 mol%, 45 mol% to 50 mol%, 50 mol% to 60 mol%, 60 mol% to 70 mol%, 70 mol% to 80 mol%, 80 mol% to 85 mol%, or 85 mol% to 90 mol%.

[0066] The polymer contains units of formula (IV) in amounts of 1 mol% to 59.9 mol% relative to the total number of moles of units in the polymer composition. According to some embodiments, the polymer may contain units of formula (IV) in amounts of 5 mol% to 10 mol%, 10 mol% to 15 mol%, 15 mol% to 20 mol%, 20 mol% to 30 mol%, 40 mol% to 50 mol%, 50 mol% to 55 mol%, or 55 mol% to 59.9 mol%.

[0067] The polymer may contain a single unit of formula (IV), or conversely, several different units of formula (IV).

[0068] According to some embodiments, the unit(s) of formula (IV) is derived from monomer units(s) selected from the list consisting of trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), trifluoropropene, particularly 3,3,3-trifluoropropene, tetrafluoropropene, particularly 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene, hexafluoroisobutylene, perfluorobutylethylene, and pentafluoropropene, particularly 1,1,3,3,3-pentafluoropropene or 1,2,3,3,3-pentafluoropropene.

[0069] According to some alternative forms, units of formula (IV) derived from several different fluoromonomers may be present in the polymer.

[0070] According to some embodiments, X1 can be -H or -F, and X2, X3, and X4 all represent -F. In other words, according to these embodiments, the polymer according to the present invention may therefore be a copolymer comprising units derived from trifluoroethylene (TrFE) and / or tetrafluoroethylene (TFE).

[0071] According to some embodiments, Z can represent -Cl, -Br, or -I. Advantageously, Z can represent -Cl.

[0072] The polymer contains units of formula (V) ranging from 0 mol% to (20-N) mol% relative to the total number of moles of the polymer's composition units, where N is a number in the range of 0.1 to 10.0.

[0073] According to some embodiments, the polymer may contain at least 1 mol%, preferably at least 2 mol%, more preferably at least 3 mol%, and very preferably at least 4 mol% of the units of formula (V). The presence of units of formula (V), in addition to the units of formulas (III) and (IV), generally makes it possible to obtain a relaxor ferroelectric polymer, the advantages of which are detailed below. In particular, the polymer may contain 4 mol% to 15 mol% of the units of formula (V).

[0074] The polymer may consist of a single unit of formula (V), or conversely, several different units of formula (V).

[0075] According to some embodiments, the unit(s) of formula (V) can be derived from monomer units(s) selected from the list consisting of 1,1-chlorofluoroethylene (1,1-CFE), 1,2-chlorofluoroethylene (1,2-CFE), chlorotrifluoroethylene (CTFE), 2-chloro-3,3,3-trifluoropropene (1233xf), 1-chloro-3,3,3-trifluoropropene (1233zd), 1,2-dichloro-1,2-difluoroethylene, 1,1-dichloro-1,1-difluoroethylene, and 1,1,2-trichloro-2-fluoroethylene.

[0076] Advantageously, Y3 can exhibit -F, and both Y1 and Y2 can exhibit -H or -F. In other words, according to these embodiments, the polymer may contain units derived from 1,1-CFE and / or CTFE.

[0077] In particular, according to some embodiments, the polymer includes units derived from vinylidene fluoride (VDF), TrFE, and CFE; or units derived from VDF, TrFE, and CTFE; or units derived from VDF, TrFE, CFE, and CTFE; or units derived from VDF, TFE, and CFE; or units derived from VDF, TFE, and CTFE; and all of these polymers further include essentially non-conjugated carbon-carbon double bonds. Furthermore, the polymers in the above list may include units derived from one or more additional monomers, such as, for example, units derived from HFP.

[0078] The polymer contains N mol% of ethylene units (or more) selected from a list consisting of -(CY3=CF)-, -(CY3=CX1)-, -(CY3=CX2)-, -(CY1=CY3)-, -(CY2=CY3)-, and combinations thereof. "N" is a number between 0.1 and 10 corresponding to the mole percent of the ethylene units relative to the total number of moles of units in the polymer composition. N can be a number in particular in the range of 0.1 to 0.2, or 0.2 to 0.3, or 0.3 to 0.5, or 0.5 to 1.0, or 1.0 to 2.0, or 2.0 to 3.0, or 3.0 to 4.0, or 4.0 to 5.0, or 5.0 to 6.0, or 6.0 to 7.0, or 7.0 to 8.0, or 8.0 to 9.0, or 9.0 to 10.0. The number "N" represents the dielectric constant and / or ΔT at the expected operating temperature for the polymer. EC You can make a choice that maximizes that value.

[0079] In embodiments in which the polymer includes units derived from vinylidene fluoride (VDF), TrFE, and CFE, particularly when the polymer is derived from P(VDF-TrFE-CFE) as the initial polymer, N is preferably selected from 0.1 to 2, more preferably from 0.1 to 1.5, and most preferably from 0.1 to 1. The number of N can be selected particularly from 0.1 to 0.5.

[0080] In embodiments in which the polymer includes units derived from VDF, TrFE, and CTFE, particularly when the polymer is derived from P(VDF-TrFE-CTFE) as the initial polymer, N is preferably selected from 0.1 to 10.0, preferably from 1.0 to 8.0, more preferably from 2.0 to 7.5, and most preferably from 2.2 to 7.0. The number of N can be particularly selected from 3.0 to 6.5.

[0081] The aforementioned polymer does not inherently exhibit conjugated carbon-carbon double bonds. The term "conjugated carbon-carbon double bond" is understood to mean any alternation of π-σ-π type single bonds and double bonds.

[0082] Therefore, the polymer generally exhibits a proportion of conjugated carbon-carbon double bonds of 10% or less, or 9% or less, or 8% or less, or 7% or less, or 6% or less, or 5% or less, or 4% or less, or 3% or less, or 2% or less, relative to the total number of carbon-carbon double bonds. Advantageously, the polymer exhibits a proportion of conjugated carbon-carbon double bonds of 1% or less, or 0.1% or less, relative to the total number of carbon-carbon double bonds, and ideally tends toward 0.

[0083] The polymer may be random and linear in shape.

[0084] The polymer according to the present invention exhibits an electrocaloric effect under the influence of a fluctuating electric field.

[0085] Advantageously, the polymer exhibits an adiabatic temperature variation ΔT of at least 1°C at at least one measurement temperature. EC The measurement of adiabatic temperature fluctuations is performed using an electric field with a predetermined amplitude ΔE. The measured temperature corresponds to the temperature to which the sample is exposed before it is subjected to the electric field fluctuation ΔE that causes the electrocaloric effect.

[0086] Preferably, the polymer undergoes an adiabatic temperature variation ΔT of at least 1.5°C, or at least 2°C, or at least 2.5°C, or at least 3°C, or at least 3.5°C, or at least 4.0°C, or at least 4.5°C, or at least 5°C, or at least 6°C, or at least 7°C, or at least 8°C, or at least 9°C, or at least 10°C in a predetermined fluctuating field at a predetermined measurement temperature. EC This indicates.

[0087] The electric field used to demonstrate the electrocaloric effect must be variable. This is because fluctuations in the electric field are what cause the electrocaloric effect.

[0088] Generally, the larger the amplitude of the electric field, the greater the electrocaloric effect. However, the maximum amplitude of the electric field must be appropriate so as not to reach the polymer breakdown voltage. Furthermore, generating high voltages requires certain electrical appliances with high energy consumption, which is not always desirable. According to some embodiments, the electric field used to demonstrate a significant electrocaloric effect for the uses described below may have a maximum amplitude of 500 V / μm or less, or 400 V / μm or less, or 300 V / μm or less, or 200 V / μm or less, or 150 V / μm or less, or 140 V / μm or less, or 130 V / μm or less, or 120 V / μm or less, or 110 V / μm or less, or 100 V / μm or less, or 90 V / μm or less.

[0089] According to some embodiments, the electric field can have an amplitude of 30 V / μm or more, or 40 V / μm or more, or 50 V / μm or more.

[0090] According to some embodiments, the polymer has a dielectric strength of 200 V / μm or more, preferably 300 V / μm or more, more preferably 400 V / μm or more, and very preferably 500 V / μm or more. Dielectric strength can be measured according to the standard ASTM D3755-97.

[0091] A square wave electric field with a maximum value equal to ΔE and a minimum value equal to 0 can typically be used.

[0092] ΔT EC To measure properly, the electric field frequency must be low enough to allow heat to diffuse through the polymer. Frequencies in the range of 1 mHz to 100 Hz, preferably in the range of 0.1 Hz to 10 Hz, can be used.

[0093] The measurement temperature can be between the glass transition temperature and the melting point of the polymer. The term "glass transition temperature" is understood to refer to the temperature at which at least partially amorphous polymers change from a rubbery state to a glassy state, or vice versa, as measured by differential scanning calorimetry (DSC) according to standard ISO 11357-2:2013, during a second heating at a heating rate of 10°C / min. The term "melting point" is understood to refer to the temperature at which at least partially crystalline polymers become a viscous liquid state, as measured by differential scanning calorimetry (DSC) according to standard ISO 11357-3:2018, during a second heating at a heating rate of 10°C / min.

[0094] Therefore, the measurement temperature can be particularly -20°C to 150°C, preferably 0°C to 100°C, more preferably 15°C to 60°C, and most preferably 20°C to 40°C.

[0095] Polymers can be ferroelectric. P(VDF-TrFE) type "ordinary ferroelectric" polymers, often simply labeled "ferroelectric," are characterized by a broad hysteresis loop in their electric displacement-applied field curve. For these materials, this loop is pronounced at high coercivity values, typically greater than 45 V / μm at 25°C, and typically 50 mC / m at 25°C. 2These materials are characterized by high residual polarization, which is greater than that of other materials. These materials exhibit maximum electrocaloric properties at temperatures close to the Curie temperature. At this temperature, a ferroelectric-to-paraelectric (FE→PE) crystal structure transition called the Curie transition occurs, corresponding to the abrupt depolarization of macroscopic ferroelectric domains. This transition is first-order narrow, characterized by a narrow dielectric constant maximum whose location is independent of the applied electric field frequency. The Curie temperature can be adjusted depending on the polymer composition, with higher proportions of vinylidene fluoride resulting in a higher Curie temperature. This temperature typically varies from 60 to 150°C for mol% of vinylidene fluoride in 55 mol% to 82 mol% P(VDF-TrFE) copolymers. While ferroelectric polymers possess advantageous electrocaloric properties, these properties are limited to temperatures too high for use in refrigeration equipment suitable for many applications. Furthermore, the narrowness of the electrocaloric performance peak due to the narrow Curie transition limits their applications.

[0096] Advantageously, this polymer can be relaxa-ferroelectric. Relaxa-ferroelectric polymers are characterized by a relaxa-ferroelectric (RFE) → paraelectric (PE) crystal transition over a wide temperature range. At this transition level, a broad peak in dielectric constant is observed, the temperature at which this maximum value is greatest depends on the frequency of the applied electric field, with the lower the electric field frequency, the lower the temperature at which the maximum dielectric constant shifts. At the temperature of the (RFE) → (PE) transition or slightly above, the application of an electric field makes it possible to generate and align nanopolar regions, inducing entropy fluctuations and resulting in a large electrocaloric effect over a wide temperature range.

[0097] Relaxa ferroelectric polymers are characterized by hysteresis loops of "electrical displacement" corresponding to the "applied electric field" curve, which are far finer than the hysteresis loops of ferroelectric polymers at 25°C and a frequency of approximately 1 Hz. They typically exhibit coercivity of 45 V / μm or less and 40 mC / m 2 It has the following residual polarization. According to some preferred embodiments, the polymer according to the present invention has a coercive field of 25 V / μm or less and 20 mC / m 2The following residual polarizations may be present. Relaxa ferroelectric polymers are generally obtained by introducing defects into the crystal structure of ferroelectric polymers, resulting in smaller polar domain sizes. This can be done, for example, by irradiating conventional ferroelectric polymers. However, it is preferable to obtain relaxa ferroelectricity by the presence of units arising from specific monomers such as CFE or CTFE.

[0098] By comparing with conventional ferroelectric polymers, the maximum dielectric constant and / or ΔT can be increased. EC The phase transition corresponding to the maximum value is obtained at lower temperatures, particularly 0–100°C, and in some cases 20–60°C. Thus, relaxa ferroelectric polymers have advantageous electrocaloric properties over a wide temperature range, especially at temperatures close to ambient temperature. Therefore, they are particularly advantageous for the manufacture of electrocaloric devices.

[0099] According to several embodiments, the polymer can have a weight-average molecular weight of 200,000 g / mol or more, preferably 300,000 g / mol or more, and preferably 400,000 g / mol or more. This makes it possible to impart appropriate mechanical properties to the film produced from the polymer according to the present invention. The molecular weight distribution can be estimated by size exclusion chromatography (SEC) using dimethylformamide (DMF) as the eluent and a set of three columns with increasing porosity. The stationary phase is styrene-DVB gel. The detection method is based on the measurement of the refractive index, and calibration is performed with a polystyrene standard. The sample is dissolved in 0.5 g / l DMF and filtered through a 0.45 μm nylon filter.

[0100] According to some embodiments, the polymer has a melting enthalpy of 10 J / g or more, preferably 15 J / g or more, and the melting enthalpy is measured according to standard ISO 11357-2:2013 during a second heating using a temperature gradient of 10°C / min. Generally, the higher the melting enthalpy, or similarly the higher the degree of crystallinity, the stronger the electrocaloric effect in the polymer.

[0101] The dielectric constant is a physical property that describes the response of a given medium to a given electric field. It can be measured at 1 kHz at a given measurement temperature. The method for measuring the dielectric constant is described in detail in the section focusing on examples.

[0102] The polymer according to the present invention can have a dielectric constant of 15 or more, preferably 20 or more, more preferably 40 or more, and very preferably 55 or more over a temperature range of at least 5°C, preferably at least 10°C, preferably at least 20°C, and very preferably at least 30°C.

[0103] According to some embodiments, the maximum dielectric constant of the polymer is obtained at a measurement temperature of 60°C or lower, preferably 50°C or lower, and more preferably 40°C or lower.

[0104] <Manufacturing method> The polymer according to the present invention can be obtained by a method comprising the following: a) Providing an initial polymer consisting of the following in total moles of polymer, preferably essentially derived from the following, and more preferably consisting of the following: - Units for formula (CF2-CH2)- (III) in concentrations of 40 mol% to 90 mol%, - At least one unit of formula (CX1X2-CX3X4)- (IV) in a concentration of 9.9 mol% to 59.9 mol%, - At least one unit of formula (CY1Y2-CY3Z)- (V) in amounts of 0.1 mol% to 20 mol%, [In the formula, X1, X2, X3, X4, Y1, Y2, Y3, and Z are as defined for the polymer according to the present invention.] b) Dehalogenation of the initial polymer (wherein dehalogenation essentially consists of the elimination of -Z and adjacent hydrogen atoms, at least partially).

[0105] The resulting polymer essentially exhibits a non-conjugated carbon-carbon double bond. More specifically, the polymer contains Nmol% of ethylene units(s) selected from a list consisting of -(CY3=CF)-, -(CY3=CX1)-, -(CY3=CX2)-, -(CY1=CY3)-, -(CY2=CY3)- and combinations thereof, and optionally, isolated -(CF2)- units that do not form part of a -(CF2)-(CH2)- unit and / or isolated -(CX3X4)- units that do not form part of a unit(s) of formula (IV) and / or isolated -(CY1Y2)- units that do not form part of a unit(s) of formula (V).

[0106] This polymer exhibits an adiabatic temperature ΔT that is at least 0.5°C greater, preferably at least 1°C greater, and more preferably at least 1.5°C greater, at at least one measured temperature, compared to the variation in the adiabatic temperature of the initial polymer. EC The variation in adiabatic temperature is measured using a fluctuating electric field with a maximum amplitude equal to 86 V / μm.

[0107] The initial polymer can be obtained according to methods known from the prior art. In particular, the initial polymer can be prepared by radical polymerization according to solution polymerization, suspension polymerization, emulsion polymerization, or microemulsion polymerization.

[0108] Copolymerization reactions generally proceed in the presence of radical initiators. These can be, for example, tert-alkyl peroxyesters such as tert-butyl peroxypiberate (or TBPPI) or tert-amyl peroxypiberate, peroxy dicarbonates such as bis(4-(tert-butyl)cyclohexyl) peroxydicarbonate, sodium persulfate, ammonium persulfate or potassium persulfate, benzoyl peroxide and its derivatives, tert-alkyl hydroperoxides such as tert-butyl hydroperoxide, tert-alkyl peroxides such as tert-butyl peroxide, or tert-alkyl peroxyalkanes such as 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane. Alternatively, or in addition to these, azo initiators or redox systems can be used as radical initiators. This polymer can also be obtained by reducing a P(VDF-CTFE) type copolymer to a P(VDF-TrFE-CTFE) type copolymer (WANG, Zhiming, ZHANG, Zhicheng and CHUNG, TC Mike. High dielectric VDF / TrFE / CTFE terpolymers prepared by hydrogenation of VDF / CTFE copolymers: synthesis and characterization. Macromolecules, 2006, vol. 39, no. 13, pp. 4268-4271).

[0109] The initial polymer can be selected according to its known electrocaloric properties. An initial polymer having good electrocaloric properties at temperatures close to the operating temperature of the polymer according to the present invention can be advantageously selected.

[0110] Alternatively, or in addition to the above, the initial polymer can be selected according to the temperature at which its dielectric constant is maximized. An initial polymer having a maximum dielectric constant at a temperature close to the operating temperature of the polymer according to the present invention is advantageously selected.

[0111] Dehalogenation of the initial polymer makes it possible to obtain a carbon-carbon double bond. Formally, this mainly consists of the elimination of the -Z atom and the hydrogen atom on the carbon adjacent to the carbon from which the -Z atom is eliminated. In the case of a halogen atom from which -Cl is eliminated, dehalogenation, called dehydrochlorination, is carried out by mixing a specific base at a specific concentration, under specific temperature conditions, for a specific time, in order to promote the elimination of halogen -Z and prevent the elimination of -F.

[0112] The base must be strong enough to eliminate -Z without eliminating -F. The base may have a pKa in the range of 8 to 12, preferably 9 to 11. It is advantageous that the base is a non-aromatic and non-nucleophilic tertiary amine, such as triethylamine. The base, for example triethylamine, may correspond to 0.01 to 2 molar equivalents relative to the number of moles of the unit of formula (V). According to some embodiments, it is preferable to adjust the proportion of the base, for example triethylamine, so that the unit of formula (V) is retained in the polymer at the end of the dehalogenation step. The base may correspond to 0.1 to 1 molar equivalent, or 0.15 to 0.5 molar equivalents, relative to the number of moles of the unit of formula (V).

[0113] Furthermore, the concentration of the base, the temperature conditions for dehalogenation, and therefore the duration of dehalogenation can be adapted by those skilled in the art to regulate the progress of the dehalogenation reaction and / or to limit the formation of conjugated carbon-carbon double bonds.

[0114] According to some embodiments, dehydrohalogenation is carried out with a reaction rate of at least 0.1, and preferably with a reaction rate of at least 0.2.

[0115] In some embodiments, after the step of reacting the initial polymer with the base, a step of removing any excess base may be performed.

[0116] According to some embodiments, dehalogenation is carried out to obtain a proportion of carbon-carbon double bonds of 10% or less, or 9% or less, or 8% or less, or 7% or less, or 6% or less, or 5% or less, or 4% or less, or 3% or less, or 2% or less, relative to the total number of carbon-carbon double bonds. Advantageously, dehalogenation is carried out such that the proportion of conjugated carbon-carbon double bonds tends to approach 1% or less, or 0.1% or less, or 0, relative to the total number of carbon-carbon double bonds.

[0117] According to some embodiments, the dehalogenation step can be carried out for a period of 1 to 10 hours, preferably 2 to 8 hours, at a temperature in the range of 20 to 80°C, preferably 30 to 60°C.

[0118] The products resulting from dehalogenation can be purified and / or incorporated into compositions containing the products, such as inks, or molded to form objects, such as films.

[0119] <Composition> The polymers according to the present invention can be incorporated into a composition. The composition may include a single polymer according to the present invention or a mixture of polymers according to the present invention.

[0120] According to some embodiments, the composition may include at least one polymer according to the present invention and at least one liquid vehicle for the at least one polymer. This composition, commonly referred to as “ink,” can be prepared by dissolving or suspending the polymer(s) according to the present invention in a liquid vehicle. Preferably, the liquid vehicle is a solvent. Advantageously, the solvent may be a polar aprotic solvent, particularly dimethylformamide, dimethylacetamide, dimethyl sulfoxide, ketones, particularly acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclopentanone, furan, particularly tetrahydrofuran, esters, particularly methyl acetate, ethyl acetate, propyl acetate, butyl acetate and propylene glycol methyl ether acetate, carbonates, particularly dimethyl carbonate, phosphoric acid, particularly triethyl phosphate, or mixtures thereof. The total weight concentration of the polymer in the liquid vehicle may be particularly 0.1% to 30%, preferably 0.5% to 20%.

[0121] According to some embodiments, the composition may include one or more polymers other than the polymer of the present invention that can exhibit advantageous electrocaloric effects. For example, the composition may include one or more ferroelectric polymers or relaxa ferroelectric polymers that do not have carbon-carbon double bonds. The composition may particularly include an initial polymer.

[0122] According to some embodiments, the composition may include one or more polymers other than the polymer of the present invention, particularly having polar or reactive functional groups, which enable improved adhesion of the composition to a given substrate.

[0123] The composition may optionally contain one or more additives, particularly one or more additives selected from surface tension modifiers, rheology modifiers, heat capacity modifiers, aging resistance modifiers, adhesion modifiers, pigments or dyes, flame retardants or crosslinking aids.

[0124] The composition may optionally contain fillers, particularly nanofillers such as barium strontium titanate (BST) nanowires.

[0125] <film> According to at least some embodiments, the polymer according to the present invention has sufficient mechanical properties to be formed into a film.

[0126] The film can be prepared using the polymer according to the present invention or a composition containing the same, for example, by coating an ink onto a substrate, or by hot-melt compression or extrusion.

[0127] The substrate can have any properties, and in particular consists of one or more layers of glass, metal, or organic (especially polymer).

[0128] The film can be stretched as needed. Stretching (if performed) is preferably carried out in a ratio of at least 10% to 700%. The film may have stretch ratios of at least 150%, at least 200%, at least 250%, at least 300%, 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.

[0129] This film can also be optionally stretched and then annealed, i.e., heated for several hours in the range of 70°C to 140°C, preferably in the range of 100°C to 120°C, and then cooled.

[0130] Both stretching and annealing generally allow for increased crystallinity and dielectric strength.

[0131] This invention makes it possible to obtain films with a thickness of 0.1 micrometers or more. For optimal utilization of the electrocaloric effect, a thickness of 1 to 100 micrometers is advantageous. Among these thicknesses, the minimum thickness may be preferable because it should not generate excessively high voltages. Therefore, films with a thickness of 1 to 50 μm, and even more so, 1 to 10 μm, are particularly preferred.

[0132] Electrodes can be deposited on a film, particularly by metallization or by the deposition of conductive materials (such as silver, copper, conductive polymers, silver nanowires, carbon black, or CNTs).

[0133] According to some embodiments, a film prepared from the polymer according to the present invention may be a layer of a multilayer film, the other layers may include the polymer according to the present invention, the same composition or a different composition, another polymer or a non-polymer material.

[0134] <Application> Due to their electrocaloric properties, the polymers according to the present invention can be used in heat transfer systems. A heat transfer system includes the polymers according to the present invention, particularly in the form of films. The films are capable of thermal contact with loads to be cooled and / or loads to be heated and / or heat transfer fluids. The system also includes a voltage source intended to be applied to a plate.

[0135] A heat transfer system can either remove heat or supply heat to another device, such as an electrical or electronic component.

[0136] Due to its pyroelectric properties, the polymer according to the present invention can be used in thermal energy recovery systems.

[0137] Due to its high dielectric constant, the polymer according to the present invention can also be used in energy storage systems, particularly capacitors, organic transistors, or electrostatic clutches.

[0138] Due to its electroactive properties, particularly its ferroelectric or relaxor ferroelectric properties, the polymer according to the present invention can also be used in actuators (for tactile, microfluidic, loudspeaker, etc.). [Brief explanation of the drawing]

[0139] [Figure 1] Figure 1 shows test bench 1, which is used to measure the electrocaloric performance quality of a polymer as a function of temperature. [Figure 2] Figure 2 shows a typical temperature fluctuation of plate 2 in test bench 1 while a square wave electric field with height ΔE is applied. ΔE corresponds to the maximum amplitude of the applied electric field and is expressed in volts / meter (V / m). The temperature fluctuation peak ΔT, which is comparable to an adiabatic temperature fluctuation, is expressed in Kelvin (K). The x-axis shown corresponds to time expressed in seconds (s). [Figure 3] Figure 3 shows the liquid 1H NMR spectrograms measured using the Bruker Advance DPX 400MHz electrical equipment for Comparative Example 1 and Examples 1-5. The x-axis corresponds to the chemical shift δH, expressed in ppm. [Figure 4] Figure 4 shows standardized Raman spectrograms of the unmodified (Comparative Example 1) and modified (Examples 1-5) P(VDF-TrFE-CTFE) terpolymers for the vibration band corresponding to 775-950 cm-1 -CF2-. The x-axis corresponds to the wavenumber expressed in cm-1, and the y-axis corresponds to the relative intensity. [Figure 5] Figure 5 shows standardized Raman spectrograms of the unmodified (Comparative Example 2) and modified (Comparative Examples 3 and Examples 6-7) P(VDF-TrFE-CFE) terpolymers for the vibration band between 775 and 950 cm⁻¹ -CF₂-. The x-axis corresponds to the wavenumber expressed in cm⁻¹, and the y-axis corresponds to the relative intensity. [Figure 6A]Figure 6A shows the variation in adiabatic temperature ΔTEC measured on a test bench like the one in Figure 1 at a measurement temperature of 25°C, as a function of the maximum amplitude (expressed as MV / m) of the applied electric field, for unmodified P(VDF-TrFE-CTFE) following Comparative Example 1 (lower curve) and modified P(VDF-TrFE-CTFE) following Example 4 (upper curve). [Figure 6B] Figure 6B shows the adiabatic temperature fluctuation ΔTEC (expressed in K) measured on a test bench like the one in Figure 1, under a measurement temperature gradient (expressed in °C) of 10 °C / min and an electric field with a maximum amplitude ΔE = 86 MV.m-1, for unmodified P(VDF-TrFE-CTFE) following Comparative Example 1 (lower curve) and modified P(VDF-TrFE-CTFE) following Example 4 (upper curve). [Figure 7A] Figure 7A shows the variation in adiabatic temperature ΔTEC measured on a test bench like the one in Figure 1 at a measurement temperature of 25°C, as a function of the maximum amplitude (expressed as MV / m) of the applied electric field, for unmodified P(VDF-TrFE-CFE) following Comparative Example 3 (lower curve) and modified P(VDF-TrFE-CFE) following Example 8 (upper curve). [Figure 7B] and [Figure 7C] Figure 7C shows the adiabatic temperature fluctuation ΔTEC (expressed in K) measured on a test bench like the one in Figure 1, under an electric field with a measurement temperature gradient (expressed in °C) of 10 °C / min and a maximum amplitude of ΔE = 60 MV.m-1 and ΔE = 75 MV.m-1, respectively, for unmodified P(VDF-TrFE-CFE) following Comparative Example 2 (lower curve) and modified P(VDF-TrFE-CFE) following Example 8 (upper curve). [Figure 8] Figure 8 shows the relative permittivity as a function of temperature for films of polymers annealed at 110°C for 1 hour according to Examples 1-5 and Comparative Example 1. The x-axis corresponds to temperature in °C, and the y-axis corresponds to relative permittivity. [Figure 9] Figure 9 shows the polarization as a function of the electric field at 25°C for films of polymers annealed at 110°C for 1 hour according to Examples 1-5 and Comparative Example 1. The x-axis corresponds to the electric field expressed in MV / m, and the y-axis corresponds to the polarization expressed in μC / cm². [Figure 10] Figure 10 shows the relative permittivity as a function of temperature of the polymer films annealed at 110°C for 1 hour according to Example 7 and Comparative Examples 2 and 3. The x-axis corresponds to temperature in °C, and the y-axis corresponds to relative permittivity. [Figure 11] Figure 11 shows the polarization as a function of the electric field at 25°C for films of polymers annealed at 110°C for 1 hour according to Example 8 and Comparative Example 2. The x-axis corresponds to the electric field expressed in MV / m, and the y-axis corresponds to the polarization expressed in μC / cm². [Figure 12] Figure 12 shows superimposed infrared spectrograms of the polymers according to Example 3 after storage at 110°C for 1 hour, 5 hours, and 3 days. The x-axis corresponds to the wavenumber expressed in cm⁻¹, and the y-axis corresponds to the normalized absorbance. [Examples]

[0140] <Determining Polymer Properties> <Measurement of electroactive performance quality and electrocaloric performance quality of polymer films> Referring to Figure 1, the polymer film 21 was prepared by blade coating, starting from a 100 mg / ml solution in a solvent in which it was soluble. For the polymers tested in the following examples, the solvent used was cyclopentanone.

[0141] This solution is prepared at ambient temperature (25°C) with magnetic stirring for 24 hours. A 14 μm film 21 is deposited on the substrate 22. The substrate 22 is made of PET, is 50 μm thick, and has been pre-metallized (Cr at 10 nm, Ag at 100 nm). After drying at 90°C for 2 hours, the upper electrode 23 is evaporated. Then, annealing is performed under vacuum at 105°C for 12 hours. A plate 2 containing the polymer film to be characterized is obtained.

[0142] Obtain low-field dielectric data using the "Solartron SI 1260" device sold by Solartron Analytical, which has an interface of "Solartron 1296 dielectric interface" and is equipped with the "TP94 Linkam" chamber sold by Linkam Scientific for temperature control. The measurements are carried out at 1 kHz at different temperatures.

[0143] Generate a polarization curve (electric displacement (D) as a function of electric field (E)) using the "aixACCT TF Analyzer 2000" device sold by aixACCT Systems, which is equipped with the "Treck 20 / 20C-HS" high-voltage amplifier sold by Treck.

[0144] Measure the electrothermal performance quality as a function of temperature and applied electric field from the test bench 1 shown in Figure 1. The test bench includes a plate 2 placed on a thermocouple 3, which is itself placed on a heat sink 4, and the heat sink 4 is itself placed on a heating means 5. The thermocouple 3 measures the temperature of the surface of the plate 2 and the fluctuations in the temperature of the plate 2. The heat sink 4 under the thermocouple 3 ensures the best possible thermal contact between the heating means 5, the thermocouple 3, and the film 21. The heating means 5 enables the system to be controlled to the measured temperature using a thermostat. A temperature gradient of 10 °C / min can be applied.

[0145] Apply a square-wave electric field with a minimum value equal to 0, a maximum value equal to +ΔE, and a period equal to approximately 90 seconds, which causes a very rapid change in temperature. The peak ΔT of this change can be measured and corresponds to what is shown by the change in adiabatic temperature in the present invention.

[0146] <Formation of essentially non-conjugated C-C double bonds by chemical modification of <P(VDF-TrFE-CTFE) polymer> 5 g of a P(VDF-TrFE-CTFE) terpolymer with a weight-average molar mass between 400000 and 600000 g / mol and a molar composition of 62 / 30 / 8 was dissolved in 100 ml of dimethyl sulfoxide (DMSO) in a 250 ml round-bottom flask. After dissolution, triethylamine (TEA) was added while stirring magnetically. After the reaction, the polymer was purified by precipitation from water, dried under vacuum, dissolved in acetone, and precipitated from a 60 / 40 ethanol / water mixture by weight. The product was dried under vacuum at 40 °C for 12 hours.

[0147] For various examples, the reaction parameters (amount of TEA, duration, and temperature) are shown in Table 1. The equivalent number of TEA is calculated relative to the number of -Cl atoms in the terpolymer. The content of double bonds DB expressed in mole percent is integrated from the signals according to the following relationship for the liquid 1 1H NMR spectrum (see Figure 3).

[0148]

Number

[0149]

Table 1

[0150] In the Raman spectrum of the sample (see Figure 4), the appearance of a single signal at 1720 cm -1 corresponding to the appearance of a single type of C=C double bond due to the bond (-CF=CH-, non-conjugated) is observed.

[0151] <Formation of C-C Double Bonds by Chemical Modification of P(VDF-TrFE-CFE) Polymers> 5 g of P(VDF-TrFE-CFE) terpolymer with an estimated weight-average molar mass between 400,000 and 600,000 g / mol and a molar composition of 66 / 27 / 7 is dissolved in 100 ml of DMSO in a 250 ml round-bottom flask. After dissolution, triethylamine (TEA) is added while magnetically stirring. After the reaction, the polymer is purified by precipitation in water, dried under vacuum, dissolved in acetone, and precipitated in a 60 / 40 ethanol / water mixture. The product is vacuum-dried at 40°C for 12 hours.

[0152] Table 2 shows different reaction parameters (amount of TEA, duration, and temperature). The number of TEA equivalents is calculated for the number of -Cl atoms in the terpolymer. The number of double bonds is liquid. 1 The calculation is performed as already explained from the 1H NMR spectrum.

[0153] [Table 2]

[0154] On the Raman spectrum of the sample (see Figure 5), 1750–1500 cm⁻¹ -1 Observe the appearance of multiple signals during this period. 1552cm -1 The vibrational frequency increased dramatically for the polymer with the highest degree of modification (Comparative Example 3), indicating the presence of conjugated double bonds. The presence of conjugated double bonds was confirmed by the brown discoloration of the most modified product (initially white or slightly yellow).

[0155] <Electrocaloric properties of the sample> Referring to Figure 6, we note the remarkable improvement in the electrocaloric properties of the polymer containing a non-conjugated double bond according to the present invention (Example 4) compared to a polymer with a similar structure that does not contain a double bond (Comparative Example 1), particularly the significant improvement in the variation of the adiabatic temperature under a predetermined measurement temperature and a predetermined maximum amplitude electric field. At a temperature of approximately 35°C, the ΔT was approximately 2.6K. EC The maximum value of (MAX) was determined. ΔT EC This is at least 0.85*ΔT over intervals of several tens of degrees Celsius, from approximately 28°C to 50°C. EC Equivalent to (MAX).

[0156] Referring to Figures 7A, 7B, and 7C, it is noted that the electrocaloric properties of the polymer containing a non-conjugated double bond according to the present invention (Example 7), particularly the variation in adiabatic temperature under a predetermined measurement temperature and a predetermined maximum amplitude electric field, are better than the variation in adiabatic temperature of a polymer with a similar structure containing a conjugated double bond (Comparative Example 1). In particular, referring to Figures 7B and 7C, ΔT EC The values ​​remained largely unchanged over the measurement temperature interval, meaning that a variation of less than 20% was observed for measurement temperatures in the range of 25°C to 50°C.

[0157] <Dielectric properties> Referring to Figures 8 and 10, it is noted that the polymers having non-conjugated double bonds according to the present invention have a higher dielectric constant (Examples 1-5, 6-7) than polymers with similar structures that do not contain double bonds (Comparative Examples 1, 2) or contain conjugated double bonds (Comparative Example 3).

[0158] Furthermore, the maximum dielectric constant relative to the polymer from Example 4 is observed in comparison to the polymers from Examples 1-3 and 5.

[0159] <Polarization> Referring to Figures 9 and 11, the polymers having non-conjugated double bonds according to the present invention (Examples 1-4, 6-7) are relaxa ferroelectric polymers.

[0160] Furthermore, note that an increase in the proportion of double bonds leads to an increase in remanent polarization and coercive field.

[0161] <Melting> The melting point and enthalpy of melting were measured in accordance with standard ISO 11357-3:2018 during the second heating with a heating gradient of 10°C / min.

[0162] [Table 3]

[0163] <Thermal stability> Referring to Figure 12, the 1700 cm² of the polymer according to Example 3 corresponds to the carbon-carbon double bond. -1 The valence vibration band remains present even after 3 days of storage at 110°C, demonstrating the polymer's good thermal stability.

Claims

1. The use of a polymer for electrocaloric effects under the influence of a fluctuating electric field, wherein the polymer is - Formula for 30 mol% to 90 mol% - (CF ２ -CH ２ ) - Unit of (III), - Formula for 1 mol% to 59.9 mol% - (CX １ X ２ - CX ３ X ４ ) - at least one unit of (IV), - 0 mol% to (20 - N) mol% of the formula -(CY １ Y ２ -CY ３ Z)-(V) of at least 1 unit, - Nmol% of - (CY ３ =CF)-,-(CY ３ = CX １ )-,-(CY ３ = CX ２ )-,-(CY １ =CY ３ )-,-(CY ２ =CY ３ ) - and ethylene units selected from a list consisting of combinations thereof [In the formula, X １ and X ２ This independently represents an alkyl group containing -H, -F, or 1 to 3 carbon atoms which may be partially or completely fluorinated, X ３ and X ４ This independently represents an alkyl group containing 1 to 3 carbon atoms, which may be -F or partially or completely fluorinated, provided that X １ and X ２ Both are -H, and X ３ and X ４ Except that both are -F, Y １ and Y ２ This independently represents an alkyl group containing -H, -F, -Cl, or 1 to 3 carbon atoms which may be partially or completely fluorinated. Y ３ This represents an alkyl group containing -F, -Cl, or one to three carbon atoms which may be partially or completely fluorinated. Z represents a halogen atom other than -F. N is a number in the range of 0.1 to 10.

0. Includes, The polymer essentially does not exhibit conjugated carbon-carbon double bonds, and the proportion of conjugated carbon-carbon double bonds is 10% or less of the total number of carbon-carbon double bonds. use.

2. X １ If X indicates -H or -F, ２ , X ３ and X ４ The use according to claim 1, wherein all three indicate -F.

3. The use according to claim 1 or 2, wherein Z represents -Cl.

4. Y ３ ga -F, Y １ and Y ２ The use according to any one of claims 1 to 3, wherein both of these indicate -H or -F.

5. The use according to any one of claims 1 to 4, wherein the polymer contains at least 1 mol% of the unit of formula (V).

6. The use according to any one of claims 1 to 5, wherein the polymer is relaxa ferroelectric.

7. The aforementioned polymer is 20 mC / m ２ The following residual polarization and / or 25 V. μm －１ The use according to any one of claims 1 to 6, wherein the following coercivity is provided, and the measurements of remanent polarization and coercivity are both performed at 25°C, a frequency of 1 Hz, and an electric field of 150 V / μm.

8. The use according to any one of claims 1 to 7, having a weight-average molecular weight of 200,000 g / mol or more.

9. The use according to any one of claims 1 to 8, wherein the enthalpy of fusion is 10 J / g or more, and the enthalpy of fusion is measured in a second heating with a temperature gradient of 10°C / min in accordance with the standard ISO 11357-2:2013.

10. The use according to any one of claims 1 to 9, wherein the relative permittivity is 15 or more over a temperature range of at least 5°C, and the relative permittivity is measured at 1 kHz.

11. The use according to any one of claims 1 to 10, wherein the dielectric constant has a maximum value at a temperature of 60°C or less, and the relative dielectric constant is measured at 1 kHz.

12. The use according to any one of claims 1 to 11, wherein the polymer can be obtained by a method comprising the following: a) Providing an initial polymer containing the following in total moles of polymer: - Formula for 40 mol% to 90 mol% - (CF ２ -CH ２ ) - Unit of (III), - Formula for 9.9 mol% to 59.9 mol% - (CX １ X ２ - CX ３ X ４ ) - at least one unit of (IV), - Formula for 0.1 mol% to 20 mol% - (CY １ Y ２ -CY ３ Z) - at least one unit of (V), [In the formula, X １ , X ２ , X ３ , X ４ , Y １ , Y ２ , Y ３ And Z is as defined in claim 1. b) Dehalogenation of the initial polymer (wherein the dehalogenation consists essentially of the elimination of -Z and adjacent hydrogen atoms, at least partially).

13. The use according to claim 10, wherein at least one measurement temperature, the adiabatic temperature variation is at least 0.5°C greater than the variation in the adiabatic temperature of the initial polymer, and the measurement of the adiabatic temperature variation is performed in a fluctuating electric field having a maximum amplitude equal to 86 V / μm.

14. The use according to claim 12 or 13, wherein the relative permittivity has a maximum value that is at least 5% greater than the maximum value of the dielectric constant of the initial polymer, and the relative permittivity is measured at 1 kHz.

15. The use according to any one of claims 12 to 14, wherein the dehalogenation reaction is carried out with a reaction progress of at least 0.

1.

16. The use according to any one of claims 1 to 15, wherein the polymer is in the form of a film containing the polymer.

17. The use according to claim 16, wherein the film has a thickness of 0.1 micrometers or more.

18. X １ This indicates -H, X ２ , X ３ and X ４ All three of them show -F, Y ３ ga -F, Y １ and Y ２ Both indicate -H, and Z indicates -Cl. The use according to claim 1 or any one of claims 5 to 15, wherein N is selected from 0.1 to 2.

19. X １ This indicates -H, X ２ , X ３ and X ４ All three of them show -F, Y １ , Y ２ and Y ３ All three indicate -F, and Z indicates -Cl. The use according to claim 1 or any one of claims 5 to 15, wherein N is selected from 0.1 to 10.

0.

20. Use of the polymer in a heat transfer system according to any one of claims 1 to 15 or any one of claims 18 and 19.

21. Use of the polymer in an energy storage system, an organic transistor, an actuator, or an electrostatic clutch, as described in any one of claims 1 to 15 or any one of claims 19 and 20.

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