Different NIR dye scaffolds for polymerization reactions under NIR light

In this article, near-infrared dyes of different structures have been investigated as new photoinitiators/photosensitizers for the free radical polymerization (FRP) of methacrylates upon Near InfraRed (NIR) light exposure using a laser diode @785 nm, @940 nm and @1064 nm. Interestingly, the use of squaraine, squarylium, boron-pyrromethene and porphyrin derivatives as efficient photoinitiators is clearly highlighted. These dyes are used in combination with an iodonium salt and a phosphine. Additionally, a thermal initiator can be added to the resin to take advantage of the photothermal effect, i.e., to the heat release during the polymerization process, so that polymerization kinetics could be greatly improved compared to the pure photochemical mode. These dyes can be proposed as alternatives to the well-established cyanine dyes, more commonly used for the photopolymerization of (meth)acrylates under NIR light.