NIR Sensitizer Operating under Long Wavelength (1064nm) for Free Radical Photopolymerization Processes.

Abstract

Free radical polymerization upon near-infrared (NIR) light is still the subject of intense research efforts and remains a huge challenge particularly for long wavelengths (>1000nm). In this study, a NIR sensitizer operating upon long wavelength (1064nm) is proposed for an efficient polymerization of acrylate monomers. A new three-component photoinitiating system is developed comprising the NIR sensitizer in combination with an Iodonium salt (Iod) and an amine. Remarkably, the NIR sensitizer (IR 1064) absorbing strongly in all the near infrared region (700-1200nm) offers the possibility to use a broad range of irradiation wavelengths, i.e., examples are provided at 785 and 1064nm. Such long wavelengths are characterized by many advantages such as a deeper penetration of light and therefore a better curing of the monomer but it is also much safer than UV light. Excellent performance is observed for the three-component IR 1064/Iod/Amine system under air: high conversion of acrylate functions associated with a fast polymerization time. The use of IR 1064 as NIR sensitizer with a broad NIR absorption is-to the best of current knowledge-never proposed in the literature. The photoinitiating performances are studied using real-time Fourier transform infrared spectroscopy.