One-Component Cleavage Photoinitiators Initiated by Near-Infrared II Region Light for Photopolymerization

Advanced optical clear adhesives (OCAs) with ultraviolet (UV)-blocking abilities are in demand for the organic light-emitting diode panel design of foldable smartphones. However, conventional UV or visible-light curing methods are ineffective due to the incorporation of UV-resistant additives and the high transparency requirements in the visible region. Near-infrared (NIR) light, particularly in the second near-infrared region (NIR-II), offers a promising solution to this challenge. In this study, a series of heptamethine cyanine derivatives, denoted as CySPhs, was designed and developed as a novel class of NIR-II light-initiated one-component cleavage photoinitiators. CySPhs can be efficiently activated into radicals upon exposure to NIR-II light (1064 nm), eliminating the need for additional coinitiators in a single-component system. This direct and efficient initiation facilitates monomer photopolymerization. Additionally, a series of experiments, encompassing polymerization kinetics, EPR, NMR, and LC-MS, was conducted to substantiate the initiation mechanism. Notably, this successful polymerization process was applied to various monomers, underscoring the advantages of CySPhs as NIR-II photoinitiators in the fabrication of OCAs.