Diketopyrrolopyrrole dyes: Structure/reactivity/efficiency relationship in photoinitiating systems upon visible lights

Several diketopyrrolopyrrole derivative based dyes (DPP), combined with an iodonium salt or an amine (and optionally an additive), are studied as photoinitiating systems for the cationic polymerization CP of epoxides or the free radical polymerization FRP of acrylates under different irradiation sources i.e. a very soft halogen lamp as well as laser diodes at 473 nm (blue light) and 532 nm (green light). The diketopyrrolopyrrole-furan derivative (FuDPP) is very efficient in CP. The structure/reactivity/efficiency relationships in this series of DPP derivatives are investigated. A comparison with a well known reference for visible light photoinitiating system (i.e. camphorquinone based photoinitiating system) is also provided showing the better efficiency of the new proposed structures. The photochemical mechanisms are studied by steady state photolysis, fluorescence, cyclic voltammetry, laser flash photolysis and electron spin resonance spin-trapping techniques.