Vinylidene fluoride and trifluoroethylene containing polymers latexes

An aqueous latex comprising particles of a polymer (F), wherein polymer (F) comprises:

• recurring units derived from vinylidene fluoride (VDF) in an amount of at least 60% moles and of at most 81% moles, with respect to the total moles of recurring units;
• recurring units trifluoroethylene (TrFE) in an amount of at least 18% moles and of at most 39% moles, with respect to the total moles of recurring units, and
• optionally recurring units derived from at least one additional monomer different from VDF and TrFE in an amount of 0 to 5% moles,
• said polymer (F) possessing thermodynamic ordered structure in the ferroelectric phase, such that the relation between:
• (i) the parameter Xc (%) defined as follows:
• Xc
• ⁢
• (
• %
• )
• =
• Δ
• ⁢
• H
• c
• (
• Δ
• ⁢
• H
• m
• +
• Δ
• ⁢
• H
• c
• )
• ×
• 100
• wherein ΔHc is the enthalpy associated to the Curie transition between ferroelectric and paraelectric phase, as determined in J/g by DSC technique on second heating scan, at a ramp rate of 10° C., and ΔHm, is the enthalpy of melting, as determined in J/g according to ASTM D3418;
• and
• (ii) the content of recurring units different from VDF expressed in % moles, with respect to the total moles of recurring units, designated as CM (% moles), satisfies the following inequality:
• Xc (%)≥a·CM (% moles)+b wherein a=−1.10 and b=75.00;
• and
• wherein the polymer (F) is obtained via polymerization in the presence of a fluorinated surfactant (C), wherein surfactant (C) complies with formula (I):
• wherein X1, X2, X3, equal or different from each other are independently selected from H, F, and C1-6 (per)fluoroalkyl groups, optionally comprising one or more catenary or non-catenary oxygen atoms;
• L represents a bond or a divalent group;
• RF is a divalent fluorinated C1-3 bridging group;
• and Y is an anionic functionality.