“…The detailed synthetic procedures as well as the basis of analytical results and spectral evidences of the tetramethylammonium phenyltrialkylborates the readers can find in my previous paper [13]. Scheme 1Structures of the sensitizer and co-initiators…”
This article introduces tri-cationic hemicyanine dye employed as a visible-light photoinitiator of acrylic monomers polymerization. This dye, in combination with borate anions, was found to be a very effective photoinitiating system. The kinetics of trimethylolpropane triacrylate polymerization was studied by a microcalorimetric method. The photoredox pair concentration, the co-initiator structure as well as the light intensity strongly affected the progress of the polymerization, leading, for example, to an increase in the polymerization rate and quantum yield of the process. The efficiency of these photoinitiators was discussed on the basis of the free energy change for electron transfer from a borate anion to an excited hemicyanine dye cation. The ∆Gel values were estimated for photoredox pairs containing a series of phenyltrialkylborate anions and one styrylpyridinium dye cation. 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. The photoinitiating abilities of the selected novel photoredox pairs (BPB61, BPB7, BPB8, and BPB9) are comparable with the photoinitiating efficiency of commercially available photoinitiators.
“…The detailed synthetic procedures as well as the basis of analytical results and spectral evidences of the tetramethylammonium phenyltrialkylborates the readers can find in my previous paper [13]. Scheme 1Structures of the sensitizer and co-initiators…”
This article introduces tri-cationic hemicyanine dye employed as a visible-light photoinitiator of acrylic monomers polymerization. This dye, in combination with borate anions, was found to be a very effective photoinitiating system. The kinetics of trimethylolpropane triacrylate polymerization was studied by a microcalorimetric method. The photoredox pair concentration, the co-initiator structure as well as the light intensity strongly affected the progress of the polymerization, leading, for example, to an increase in the polymerization rate and quantum yield of the process. The efficiency of these photoinitiators was discussed on the basis of the free energy change for electron transfer from a borate anion to an excited hemicyanine dye cation. The ∆Gel values were estimated for photoredox pairs containing a series of phenyltrialkylborate anions and one styrylpyridinium dye cation. 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. The photoinitiating abilities of the selected novel photoredox pairs (BPB61, BPB7, BPB8, and BPB9) are comparable with the photoinitiating efficiency of commercially available photoinitiators.
“…The general method of the synthesis of tetramethylammonium phenyltriethylborate salt (B6) and dyes 1, 2, 3 and 4 together with their spectral characteristic are described elsewhere [26][27][28][29][30]. Solvents and monomers [trimethylolpropane triacrylate (TMPTA), 1,6-hexanediol diacrylate (HDODA), lauryl acrylate (LA)] were obtained commercially from Aldrich Chemical Co. and used as received.…”
Section: Experimental Materials and Methodsmentioning
Photoinitiating systems based on BF 2 derivatives and tetramethylammonium phenyltriethylborate salt were tested in photopolymerization reactions through the photo-DSC method. The good rates of TMPTA polymerization and final monomer conversion were obtained for tested system. The effect of the type of heterocycle on their properties was revealed. The excited state processes, investigated by nanosecond flash photolysis, lie on a fast excited state photoinitiated cleavage leading to reactive species. A triplet state is observed for investigated derivatives.
“…4-Aminobenzaldehydes were prepared following the procedures given by Gawinecki et al [11]. Dyes and borate salts were synthesized in our laboratory using procedures described in the literature [12][13][14][15][16]. The final products were identified by 1 H NMR spectroscopy.…”
A series of homodimeric styrylbenzimidazolium dyes were synthesized and applied as visible light initiators for the polymerization of acrylic monomer. In the photoinitiating system, hemicyanine dye cation acts as an electron acceptor whereas borate anion is an electron donor. The photochemistry of the series of bichromophoric hemicyanine borates: 1,3-bis{2-[4-(N-alkylamino)styryl]-1-methylbenzimida-zolium}propane, 1,5-bis{2-[4-(N-alkylamino)styryl]-1-methylbenzimidazolium}pentane, 1,10-bis{2-[4-(N-alkylamino)styryl]-1-methylbenzimidazolium}decane, was compared to the photochemistry of structurally related monochromophoric hemicyanine borates. The photoinitiating efficiency of the donor-acceptor pairs is discussed based on the free energy change for the photoinduced electron transfer from borate anion to dye cation.
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