Homogeneous Phase Polymerization of Vinylidene Fluoride in Supercritical CO₂: Surfactant Free Synthesis and Kinetics

Vinylidene fluoride (VDF) polymerizations were carried out in homogeneous phase with supercritical carbon dioxide (scCO₂) at 120 °C and 1500 bar. To control molecular weight perfluorohexyl iodide was used. Molecular weight analysis by size-exclusion chromatography indicates that polymers of low polydispersities ranging from 1.5 to 1.2 at the highest iodide concentration of 0.25 mol · L⁻¹ were obtained. In addition, polymer molecular weight increases linearly with reaction time, indicating that living conditions were established. The "livingness" is based on the labile C-I bond. The weakness of the C-I bond is associated with a fast decomposition of the original hexyl iodide, thus, contributing to initiation and to a significant increase in the initiation rate in the initial phase of the polymerization.