The kinetics and mechanism of the photopolymerization of dimethacrylates using three-component initiation systems consisting of camphorquinone (CQ), diphenyliodonium hexafluorophosphate (Ph2IPF6), and either N,N,3,5-tetramethylaniline (TMA) or N,N-dimethylbenzylamine or triethylamine were studied by photo-DSC and UV-visible spectroscopy. The effect of monomer structure on the curing kinetics and photobleaching were also investigated. Photo-DSC studies showed fivefold increases in polymerization rate when all three components were present and the kinetics followed the trend: CQ/amine/Ph2IPF6 ≤laquo; CQ/amine > CQ/Ph 2IPF6.. For both CQ/amine/Ph2IPF6 and CQ/amine systems, the CQ was rapidly photobleached during the photo-DSC timescale but for the systems without amine there was an induction stage before CQ photobleaching was evident. Studies of the effect of monomer type on the photobleaching rate show that the photobleaching behavior was independent of monomer structure. Three photoinitiation mechanisms have been proposed. The reaction mechanism of the CQ/amine/Ph2IPF6 system involves the reduction of the excited CQ molecule by the amine to form ketyl and aminoalkyl radicals, followed by the irreversible oxidation of the amine, and to a lesser extent, the ketyl radical by the iodonium salt, to form an initiating radical.
|Number of pages||12|
|Journal||Journal of Polymer Science, Part A: Polymer Chemistry|
|Publication status||Published - 1 Dec 2011|
- curing of polymers
- differential scanning calorimetry (DSC)
- kinetics (polym.)
- three-component photoinitiator system