The invention relates to a method of polymerizing at least one monomer comprising a vinylidene fluoride monomer, the method comprising putting in contact the at least one monomer with a polymerization initiator -and an oxidizing agent, the polymerization initiator having the formula (I):

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wherein R.sub.f is a fluoroalkyl group comprising from 1 to 3 carbon atoms; and M.sup.x+ is chosen from a monovalent cation, or a divalent cation, or a trivalent cation, or a tetravalent cation.

A method for producing an aqueous dispersion of a fluorine-containing elastomer, including polymerizing a fluorine-containing monomer in the presence of a compound (1) having an aromatic ring, a hydrophilic group, and an unsaturated double bond, and an aqueous medium, to produce an aqueous dispersion of a fluorine-containing elastomer containing -CH.sub.2- in a main chain.

A method for producing an aqueous dispersion of a fluorine-containing elastomer, including polymerizing a fluorine-containing monomer in the presence of a compound (1) having an aromatic ring, a hydrophilic group, and an unsaturated double bond, and an aqueous medium, to produce an aqueous dispersion of a fluorine-containing elastomer containing -CH.sub.2- in a main chain.

Provided is a binder for a battery, including a fluorine-containing copolymer, wherein the fluorine-containing copolymer comprises a repeating unit (a) based on vinylidene fluoride and at least one repeating unit (b) selected from the group consisting of a repeating unit (bl) represented by a specific structural formula (bl) and a repeating unit (b2) represented by a structural formula (b2), and the fluorine-containing copolymer has a molar ratio of the repeating unit (a) to the repeating unit (b), (a)/(b), of 95/5 to 5/95.

Provided is a binder for a battery, including a fluorine-containing copolymer, wherein the fluorine-containing copolymer comprises a repeating unit (a) based on vinylidene fluoride and at least one repeating unit (b) selected from the group consisting of a repeating unit (bl) represented by a specific structural formula (bl) and a repeating unit (b2) represented by a structural formula (b2), and the fluorine-containing copolymer has a molar ratio of the repeating unit (a) to the repeating unit (b), (a)/(b), of 95/5 to 5/95.

The invention relates to a composition comprising at least one electroactive fluorinated terpolymer, and at least one second polymer compatible with the electroactive fluorinated terpolymer and having a glass transition temperature lower than that of the electroactive fluorinated terpolymer. The invention also relates to a method for producing said composition, and to a device such as an actuator comprising a substrate and a film of the above-mentioned composition.

The invention relates to a composition comprising at least one electroactive fluorinated terpolymer, and at least one second polymer compatible with the electroactive fluorinated terpolymer and having a glass transition temperature lower than that of the electroactive fluorinated terpolymer. The invention also relates to a method for producing said composition, and to a device such as an actuator comprising a substrate and a film of the above-mentioned composition.

An electrocaloric element for a heat transfer system includes an electrocaloric material of a copolymer of (i) vinylidene fluoride, and (ii) an addition polymerization monomer that is larger than vinylidene fluoride and includes a substituent more electronegative than chlorine. Electrodes are disposed on opposite surfaces of the electrocaloric material, and an electric power source is configured to provide voltage to the electrodes. The system also includes a first thermal flow path between the electrocaloric material and a heat sink, and a second thermal flow path between the electrocaloric material and a heat source.

An electrocaloric element for a heat transfer system includes an electrocaloric material of a copolymer of (i) vinylidene fluoride, and (ii) an addition polymerization monomer that is larger than vinylidene fluoride and includes a substituent more electronegative than chlorine. Electrodes are disposed on opposite surfaces of the electrocaloric material, and an electric power source is configured to provide voltage to the electrodes. The system also includes a first thermal flow path between the electrocaloric material and a heat sink, and a second thermal flow path between the electrocaloric material and a heat source.

VDF-co-(TFE or TrFE) polymers having a molecular weight of at least about 1,000,000 g/mol and a melt temperature less than about 240° C. The VDF copolymer contains at least about 50 mol % VDF monomer and may include an amount of at least one other monomer. The VDF copolymer may be used to form a membrane that has a node and fibril structure. The membrane has a percent porosity of at least 25%. A VDF-co-(TFE or TrFE) polymer membrane may be formed by lubricating the VDF copolymer, subjecting the lubricated polymer to pressure at a temperature below the melting point of the VDF copolymer to form a preform material, and expanding the preform material at a temperature below the melting temperature of the VDF copolymer. Dense VDF copolymer articles, filled VDF copolymer membranes, and VDF copolymer fibers are also provided.