Triplet-Triplet Annihilation Up-Conversion Luminescent Assisted Free-Radical Reactions of Polymers Using Visible Light

Due to low penetration ability of ultraviolet (UV) light, UV-induced free radical reactions of polymers are limited to the preparation of thin-layer materials such as coatings and inks. Although upconversion (UC) nanomaterials that can be excited by near-infrared (NIR) light and emit UV light which is used to achieve polymerization or curing of monomers or prepolymers, low quantum efficiency and high excitation threshold limit their applications. Here, triplet-triplet annihilation up-conversion luminescent (TTA-UCL) chromophores of platinum (II) octaethylporphyrin (PtOEP) and 9,10-diphenylanthracene (DPA) are used to realize TTA-UCL-assisted photoinitiated polymerization of butyl acrylate (BA) and ethoxylated trimethylolpropane triacrylate (ETPTA) as well as photo curing of polyurethane acrylates (PUA) using visible light at 520 nm. The effects of chromophores concentrations and incident light power density on double-bond conversion rate are investigated. The results show that a mediate TTA-UCL chromophore concentration of 0.02% is beneficial for polymerization of ETPTA-co-BA with thickness of 25 mm within 15 min. Satisfied adhesion of colored plastic substrates using PUA prepolymers can be achieved after irradiation for 30 s when chromophore concentration of 0.1% is used. TTA-UCL assisted photoinitiated reactions show great potential in engineering aspects including quick repair of leaking tubes and photocuring of adhesives underwater.