Mechanistic and kinetic studies on the photoinitiated polymerization of tetrahydrofuran

Polymerization of tetrahydrofuran (THF) (bulk) promoted by a free radical source, 2,2‐dimethoxy‐2‐phenyl acetophenone (DMPA), in the presence of 4,4′‐di‐(methylphenyl)iodonium hexafluorophosphate was studied in detail. Rate dependence of the polymerizing system on both DMPA and the iodonium salt was studied dilatometrically. Rate saturation for the iodonium salt was attributed to the formation of iodobenzene, which may react with propagating cations to form an iodonium salt. DMPA was shown to be an efficient transfer agent in the cationic polymerization of THF. A transfer constant for DMPA was estimated to be 2.8 and, whilst the precise details of the overall mechanism cannot be deduced from the present results, it may result in functionalized polytetrahydrofuran chains having photochemically active end groups.