A new series of triarylcyclopropenium tetrakis(pentafluorophenyl)gallates (I) were synthesized by anion exchange. These salts are photoacid generators from which we have measured the rates of acid release using the indicator Quinaldine Red (QR). Electron-donating substituents on the aromatic ring slow the rate of photoacid release. Cationic photopolymerization of glycidyl phenyl ether (GPE) was also examined. With 1 wt % triphenylcyclopropenium (TPCP) gallate, 90% of conversion of GPE was achieved within 20 min irradiation at 300 nm. The polymerization afforded polyGPE with M-w of 4100-8100. The initiating species was identified as a proton produced from photolysis of the triarylcyclopropenium cation.