The Camphorquinone/Amine and Camphorquinone/Amine/Phosphine Oxide Derivative Photoinitiating Systems: Overview, Mechanistic Approach, and Role of the Excitation Light Source

The camphorquinone (CQ)/amine and CQ/diphenyl (2,4,6‐trimethylbenzoyl)‐phosphine oxide (TPO)/amine photoinitiating systems (PISs) are largely used in the area of dental resins, but the role of the light source in connection with the excited state processes has not been deeply investigated so far. Here, a state‐of‐the‐art analysis on the photochemistry of these PISs is provided. Novel experiments using electron spin resonance spin trapping, cyclic voltammetry, photolysis as well as the recording of film polymerization profiles (by real time Fourier transform infrared (FTIR) measurements) of a trifunctional low molecular weight acrylate and a more viscous bisphenol A‐glycidyl methacrylate/triethyleneglycol dimethacrylate blend under well‐defined irradiation conditions (dental light‐emitting diode (LED) and monochromatic laser diode; this has not been done before) are carried out. Although a noticeable improvement under a polychromatic Xe lamp is clearly obtained in the literature when using CQ/TPO/amine compared to CQ/amine, the polymerization profiles of the representative (meth)acrylate monomers are only slightly better under a dental blue LED irradiation (band spectrum centred at 477 nm) and not affected under a laser diode at 473 nm. This work allows a complete and final description of the overall initiation mechanisms in these PISs. image