Relative activity of possible initiating species produced from photolysis of tetraphenyl and triphenylbutyl borates as measured by fluorescence probetechniques

Fluorescence probe techniques (FPT) have been used to obtain curing profile s for the polymerization of a model monomer, triethylene glycol diacrylate (TEGDA). A number of new chromophore ammonium salt triphenylbutyl and tetra phenylborates differing only in the structure of the ammonium salt moiety h ave been used as photoinitiators. The berates 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 berate photodecomposition. The results support our previous postulate that an alph a-aminoalkyl radical formed immediately after unimolecular decomposition fr om the tetraphenylborates is the most effective initiating species and that alpha-aminoalkyl radicals significantly increase the photoinitiator effici ency of triphenylbutylborates as well. The importance of other radicals to the initiation step is also discussed.