Synthesis And Properties Of Photoinitiator Of Oxime Ester Containing Aromatic Amine Group

Oxime ester photoinitiator is a commonly used free radical photoinitiator.Commercial oxime ester initiator is mainly used in light curing of 365nm light source.In order to improve the absorption of oxime ester molecules in the near ultraviolet and visible regions and be applied to the LED light source,in this paper,eight novel oxime ester photoinitiators were designed and synthesized.In these photoinitiators,the aromatic amine groups are introduced into the oxime ester molecule and the alkynyl group is used as the conjugated linking group.The synthesis route,the spectral properties and the application of these compounds in photopolymerization were discussed.The eight oxime ester are 9-hexyl-6-(phenylethynyl)-9H-carbazole-3-carbaldehyde O-benzoyl oxime,10-hexyl-7-(phenylethynyl)-10H-phenothiazine-3-carb-aldehyde O-benzoyl oxime,9-hexyl-6-(phenylethynyl)-9H-carbazole-3-carbaldehyde O-acryloyl oxime,10-hexyl-7-(phenylethynyl)-10H-pheno-thiazine-3-carbaldehyde O-acryloyl oxime,6-((4-(diphenylamino)phenyl)ethynyl)-9-hexyl-9H-carbazole-3-carbaldehyde O-benzoyl oxime,7-((4-(diphenylamino)phen-yl)ethynyl)-10-hexyl-1 OH-phenothiazine-3-carbaldehyde-O-benzoyl oxime ester,10-hexyl-7-((9-hexyl-9H-carbazole-3-yl)ethynyl)-10H-phenothiazine-3-carbaldehyde O-benzoyl oxime,9-hexyl-6-((10-hexyl-10H-phenothiazin-3-yl)ethynyl)-9H-carbazole-3-carbaldehyde O-benzoyl oxime,respectively.The synthesized molecules were characterized by means of NMR,MS and IR.The structure of the synthesized oxime ester molecules was optimized by density functional theory.The spectral properties of the eight oxime ester molecules synthesized were tested.It was found that Ph-CZ-OXE,Ph-CZ-Acyl,TPA-CZ-OXE and PTZ-CZ-OXE in which carbazole as bridging groups have strong absorption in the near-visible region,and Ph-PTZ-OXE?Ph-PTZ-Acyl?TPA-PTZ-OXE and CZ-PTZ-OXE in which Phenothiazine as a bridging group have strong absorption between the 400 and 500nm.The LUMO and HOMO orbital energy levels were calculated by Gaussian 09,and the UV spectra of oxime esters were analyzed and explained by the calculation results.It was proved that the introduction of the aromatic amine groups caused the red visible absorption of the oxime ester molecules.The fluorescence spectra of the oxime ester molecules were tested.It was found that the Stokes shift of the oxime ester molecules with phenothiazine groups as the bridging groups could reach more than 200nm,and the intramolecular charge transfer were obvious.The photoinitability and mechanism of the eight oxime ester molecules were studied by investigating the photopolymerization properties of TPGDA under 405nm and 455nm LED irradiation.It was found that eight oxime ester molecules could reach the end point of solidification within 15s under 405nm light source.The oxime ester containing phenothiazine group also had a good effect in 455nm light source.The photoinduced mechanism of the oxime ester molecules was studied by absorbing the steady-state photolysis and fluorescence quenching.The mechanism of the photoinitiator of oxime ester was proposed.The photopolymerization of TPGDA was induced by the photoinitiator composed of oxime ester and iodonium salt at the excitation of 405 nm and 455 nm.TPA-PTZ-OXE/ION and CZ-PTZ-OXE/ION in the 405nm light source only 5s can reach the end of curing,under 455nm light source,it need 20 seconds to achieve double bond conversion rate of 80%or more.The photolysis behavior of the system of oxime ester and iodonium salt was studied by UV-visible and fluorescence spectra with the irradiation time.The interaction between the oxime ester and the iodonium salt was investigated and sensitization mechanism of ester to iodonium Salt was proposed.