Substituted cyclopropenium salts as photoinitiators for cationic polymerization of glycidyl phenyl ether

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 sl ow 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 irradiat ion at 300 nm. The polymerization afforded polyGPE with M-w of 4100-8100. T he initiating species was identified as a proton produced from photolysis o f the triarylcyclopropenium cation.