Photobleaching and Regeneration of Camphorquinone in Light-Cured Thiol-Methacrylate Networks.

CLAUDIA I. VALLO; SILVANA V. ASMUSSEN

Villa Carlos Paz

Encuentro; XIII Encuentro Latinoamericano de Fotoquímica y Fotobiología (XIII ELAFOT); 2017

The mostcommonly used visible photoinitiator in resin formulations is camphorquinone(CQ), a blue light sensitive free radical photoinitiator. CQ displays anintense dark yellow color due to the presence of a conjugated diketonechromophore that absorbs at 470 nm. During irradiation of CQ and reduction ofone of the carbonyl groups, the conjugation is destroyed, causing a blue shiftof the remaining ketone?s absorption and loss of the yellow color [1]. This workdescribes a mechanism to explain the yellowing of initially photobleachedthiol-ene networks formulated with Camphorquinone (CQ) as photoactivator. The specimen of pentaerythritoltetra(3-mercaptopropionate) (PETMP)- 2,2-bis[4-(2-methacryloxyethoxy) phenyl]propane(BisEMA) resin containing 1 wt% CQ was 10 mm diameter an 3 mm thick.