Unusually highly efficient,singlet state,visible light photoinitiators based on styrylbenzimidazolium phenyltributylborate photoredox pairs for vinyl monomers free radical polymerization |
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Authors: | Marek Pietrzak Beata Jędrzejewska Jerzy Pączkowski |
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Institution: | University of Technology and Life Sciences, Faculty of Chemical Technology and Engineering, Seminaryjna 3, 85‐326 Bydgoszcz, Poland |
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Abstract: | In this article, hemicyanine dye–borate complexes, for example, 1,3‐dimethyl‐2‐4‐(N,N‐dialkylamino)styryl]benzimidazolium phenyl‐tri‐n‐butylborates, were employed as the novel, very effective photoinitiators operating in the visible light region. The influence of the sensitizers and electron donor structure on the photopolymerization kinetics of multiacrylate monomer was investigated by photo‐DSC. The maximum photopolymerization quantum yield measured for 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol triacrylate (TMPTA) was about 67 for sample of thickness of about 1 mm under 100 mW/cm2 laser irradiation. It was found that the polymerization rate and the final conversion degree were depended on the dye structure. Moreover, the photoinitiating systems described gave a double bond conversion higher than the photoinitiator possessing as chromophore RBAX (Rose Bengal derivative), the common triplet state initiator. Additionally, the rate of photopolymerization depends on ΔGel of electron transfer between borate anion and styrylbenzimidazolium cation. This latter value was estimated for a series of styrylbenzimidazolium borate salts. The relationship between the rate of polymerization and the free energy of activation for electron transfer reaction gives the dependence predicted by the classical theory of electron transfer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4119–4129, 2009 |
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Keywords: | dye photoinitiators dyes/pigments electron transfer kinetics (polym ) Marcus theory radical polymerization |
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