Development of boron-containing photoinitiating systems for sustainable photopolymerization – Photo-B

The aim of the present proposal is to rationally design new boron-centered photo-initiating systems for a sustainable photopolymerization. In collaboration with an industrial partner, the polymerization of monomers, including those issued from renewable sources, will be achieved using visible light without resorting to expensive inert conditions. Existing radical photopolymerization processes are widespread in industry (e.g. for coatings, varnishes, paints, inks, etc.), but they rely on high intensity UV light sources and suffer from oxygen inhibition. Not only is this highly energy consuming, it also means that one cannot photopolymerize materials sensitive to UV light, such as pigments or inorganic oxides. Besides the lamp itself uses highly toxic mercury to function. The possibility to use industrially safer, low-energy irradiation systems based on visible light emitting diodes (LEDs) would constitute a significant breakthrough, as it would cut energy costs and avoid the use of expensive photochemical equipment. Near UV or visible light have a greater penetration depth and can pass through a wider range of materials than UV light, making it possible to have larger, less expensive reactors. For polymerization of pigmented media, this would also allow color printing without pigment degradation. Dry thin ink films as well as thick coatings and cure through volumes could be obtained, that are not accessible using existing technologies. However, because visible light cannot be absorbed by most of the commercial photoinitiating systems (PIS), there is an urgent need to introduce new photoinitiators (PIs) or photoinitiating systems with absorption profiles in the visible region. Building on previous collaborative efforts by the coordinator (P1) and partner 3, this proposal will seek to (i) introduce NHC-boranes which can be sensitive to LED light but remain compatible with polymerization in air; (ii) extend their use to visible light induced emulsion polymerization; (iii) expand the scope of photopolymerizable monomers to bio-sourced feedstocks.