NIR-Sensitized Photopolymerization with Iodonium Salts Bearing Weak Coordinating Anions

Abstract

Photoinitiated Polymerization of TPGDA was initiated with a NIR LED emitting at 790 nm using a redox based photoinitiator system comprising a cyanine as photosensitizer and a diaryl iodonium salt. The latter bears different anions exhibiting low coordination behavior; that is [B(Ph)4]-, [B(PhF5)4]-, [B(Ph(CF3)2)4]-, [B(Ph-4-Cl)4]-, [(CF3SO2)2N]-, PF6-, and [PF3(C2F5)3]-. Photo-DSC was applied to determine photopolymerization activity. This correlated with the conductivity with many of these anions showing that reactivity mostly correlates with ion mobility. Nevertheless, iodonium salts bearing as anions either [PF3(C2F5)3]-, [B(Ph(CF3)2)4]- or [(CF3SO2)2N]- exhibit an excellent solubility being larger than several 100 g L-1. Furthermore, NIR sensitized cationic photopolymerization of aziridines was successfully demonstrated.