Relative Activity of Possible Initiating Species Produced from Photolysis of Tetraphenyl and Triphenylbutyl Borates As Measured by Fluorescence Probe Techniques

Fluorescence probe techniques (FPT) have been used to obtain curing profiles for the polymerization of a model monomer, triethylene glycol diacrylate (TEGDA). A number of new chromophore ammonium salt triphenylbutyl and tetraphenylborates differing only in the structure of the ammonium salt moiety have been used as photoinitiators. The borates were chosen for study so that a comparison of their initiation efficiency would reveal information about the relative activity of possible initiating species produced upon borate photodecomposition. The results support our previous postulate that an α-aminoalkyl radical formed immediately after unimolecular decomposition from the tetraphenylborates is the most effective initiating species and that α−aminoalkyl radicals significantly increase the photoinitiator efficiency of triphenylbutylborates as well. The importance of other radicals to the initiation step is also discussed.