Photoinitiation behavior of phenothiazines containing two oxime ester functionalities (OXEs) in free radical photopolymerization and 3D printing application

International audienceTwelve type I photoinitiators (PIs) containing two oxime esters functionalities on the terminal moiety were synthesized. These OXEs have high light absorptivities in the visible range, and some of them showed better photoinitiation abilities than the commercial photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), under the irradiation of a 405 nm LED. Photoinitiation mechanisms of these OXEs are proposed through theoretical calculations, the detection of CO2, and the ESR investigation of the free radical generation. 3D Objects could be manufactured successfully by using the most reactive OXEs as photoinitiators with a stereolithographic 3D printer. In addition, these reactive OXEs also displayed a thermal initiation behavior, meaning that these OXEs can served as thermal or photochemical initiators