Solubility properties of poly(1,1‐difluoroethylene) in dipolar aprotic solvents

A screening study of the solubility of poly(1,1‐difluoroethylene) (PVF 2 , M̄ w = 2 × 10 5 ) at room temperature in a wide variety of dipolar aprotic species has facilitated the discovery of a series of new solvents ( N ‐methyloxazolidone, cyclic‐substituted ureas) and rationalization of the data in a two‐dimensional solubility map involving their dipole moment, μ, and their hydrogenx‐bond‐accepting (HBA) power β (Taft solvatochromic parameter). This map may be used as a predictive tool for the research of new functional classes of solvents, such as N ‐substituted mixed amideester of phosphoric acid or N ‐substituted sulfurous diamides. The variations of the intrinsic viscosity of the polymer with solvent polarity may be quantitatively analyzed using a linear multiparametric correlation which emphasizes the two opposite contributions of cavitation effects (Hildebrand solubility parameter δ) and of polymer–solvent interactions (β) on the coil expansion: [η] (dL.g −1 ) = 0.792 ‐ 1.2 × 10 −3δ2 (J.cm −3 ) + 1.59 β. Finally, 1,3‐dimethyl‐2‐oxo‐hexahydropyrimidine ( N,N′ ‐dimethylpropylene urea) leads to the highest value of the refractive index increment ( dn/dc = −0.065 mL.g −1 at λ = 632 nm), and thus appears as the best solvent for light‐scattering measurements.