Study on Pyrrole Chalcone Derivatives Used for Blue LED Free Radical Photopolymerization: Controllable Initiating Activity Achieved Through Photoisomerization Property

In this study, three novel pyrrole chalcones (E-HP-1, E-HP-2, E-HP-3) with D-pi-A structures were designed and characterized as Norrish II photoinitiators. The photoisomerization properties and photochemistry activity with common amine coinitiator TEOA of pyrrole chalcones were evaluated by spectroscopic methods and theoretical calculations. E-HP-1/TEOA and E-HP-3/TEOA exhibited the excellent initiating ability for blue LED free radical photopolymerization of acrylates via photopolymerization kinetics. Notably, the photo-equilibrium of E-HP-3 composed of both E-HP-3 and Z-HP-3 was proved to be inactive during the photopolymerization, resulting in high storage stability to sunlight. Combined with Z-HP-3 in the equilibrium completely converting back to E-HP -3 upon the LED@465 irradiation, photoactivity of initiating system Z-HP-3/E-HP-3/TEOA could be controlled by the excitation of LED@465 nm, which has potential practical applications in the area of photopolymerization.