Iodine transfer emulsion polymerizations of vinylidene fluoride

Vinylidene fluoride emulsion polymerizations operated in semi-batch mode are reported. In order to control the polymer molar masses and to yield low dispersity material iodine transfer polymerizations were performed. Due to reversible deactivation of the radicals via iodine transfer the probability of chain termination and transfer to polymer events is strongly reduced. Mono- and difunctional perfluorinated alkyl compounds, namely C6F13I, C4F9I, and C4F8I2, were used as chain transfer agents (CTAs). The impact of the structure and concentration of these CTAs on molar mass and particle size distributions was investigated. The difunctional CTA is associated with the highest transfer activity and strongly affects the particle sizes. The experimental results are accompanied by Monte Carlo simulations to elucidate the initialization process and to derive chain transfer constants. The chain transfer constants for the pre-equilibrium and the main equilibrium are 7.1 and 0.094, respectively.