Abstract
Applicability of a series of coumarin derivatives as fluorescent probes for monitoring progress of cationic photopolymerization processes by Fluorescence Probe Technique (FPT) has been studied using triethylene glycol divinyl ether as a model monomer and diphenyliodonium hexafluorophospate as a cationic photoinitiator. The following coumarins were evaluated: Coumarin 1, Coumarin 6H, Coumarin 102, Coumarin 120, Coumarin 151, Coumarin 343 and Coumarin 466. It has been found that despite the presence of an amino group in their structure, at low concentrations of the order of 0.1%, the Coumarins 1, 102, 343 and 466 can be used as the fluorescent probes for the cationic photopolymerization, while Coumarin 343 exhibits the best performance. At high concentrations, the aminocoumarins slow down the photopolymerization rate and extend induction period. All of the aminocoumarins are applicable as long-wavelength sensitizers for diphenyliodonium photoinitiators, enabling photopolymerization at the irradiation wavelengths, where the photoinitiator does not absorb. At short wavelengths, where both photoinitiator and probe absorb light, and at the probe concentrations below 0.1%, Coumarin 343 and Coumarin 1 accelerate the cationic photopolymerization by supplying an additional route for the photoinitiator cleavage beside its direct cleavage upon light absorption. The direct initiation and sensitization mechanisms are proposed.
Published Version
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