A series of photoinitiators, quaternary ammonium tetraphenylborate salts (QA Salts-BPh4) with various chromophores, have been synthesized and characterized by elemental analysis (EA), H-1 NMR and IR. The photochemistry and photophysics of QA Salts-BPh4 have been investigated by UV spectroscopy. The formation of triethylenediamine (TEDA) and phenyl free radical in the photolysis of QA Salts-BPh4 was ascertained by mass spectrometric method. Their reactivity in the thermal curing of epoxide resin such as EPON827 and radical polymerization of acrylate monomers such as trimethylolpropane triacrylate (TMPTA) was studied. It is found that the relative initiator efficiency of QA Salts-BPh4 is related to the structure of chromophore. (c) 2005 Elsevier Ltd. All rights reserved.