Well-Defined Titanium Complex for Free-Radical and Cationic Photopolymerizations under Visible Light and Photoinduction of Ti-Based Nanoparticles

A quinoline-derived titanium complex (TiQ) is shown here to possess remarkable photosensitizing properties when treated with an iodonium salt (Iod) to initiate, under visible light irradiation, (i) the free-radical photopolymerization of acrylate monomer in aerated/laminate conditions, (ii) the cationic photopolymerization of epoxy monomer under air, and (iii) the in situ formation of Ti-based nanoparticles (NPs) inside coatings. The photochemical properties of the TiQ/Iod photoinitiating system have been probed by electron paramagnetic resonance, laser flash photolysis, and real-time Fourier transform infrared spectroscopy, which provide an insight into the possible radical/cationic pathways. The microstructural properties of the photosynthesized Ti-based NPs have been investigated by bright-field conventional transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy. The macroscopic mechanical properties of the resulting nanocomposite reveal that the generation of these Ti-based NPs in a polyacrylate/polyether blend matrix leads to an increase of mechanical resistance by toughening the matrix.