The initiation reaction in the molecular iodine‐induced polymerization of vinyl alkyl ethers

The first stage in the molecular iodine‐initiated polymerization of some vinyl alkyl ethers has been investigated at ambient temperature in several solvents. An equilibrium is established between monomer and iodine, prior to polymerization, which has the stoichiometry I2 + MX. The equilibrium constants in n‐hexane, cyclohexane, and chloroform have been investigated and the heat of formation of X determined. The results indicate that X is a diiodide and not a charge‐transfer complex. In solvents of higher dielectric constant, the equilibrium is perturbed by polymerization. Conventional spectrophotometry and stopped‐flow techniques have been employed to determine the rate of equilibration. In all of the solvents examined, a first‐order dependence on [monomer] and a second‐order dependence on [iodine] was observed. A mechanism is proposed.