Eosin-triethanolamine system

We, as well as Chesneau and Fouassier, find that the photospeed increases linearly with light intensity. From this observation one can conclude that chain termination reaction is not the usual interaction between two macroradicals. We have measured the initial rate of photopolymerization using thin foil calorimetry and find a linear relationship between the rate of photopolymerization at low conversions (less than 15%) and the absorbed light intensity. Using the same monomer but with a different photoinitiator (to be discussed in detail later) we observe an order of one half with respect to light intensity both by thin foil calorimetry and by measuring the polymer spike. Therefore we conclude that the linear dependence observed for the Eosin-triethanolamine system is real and not an artifact of the technique employed to determine the photospeed. 

We have also used the Eosin-triethanolamine system to design a two-photon system based on visible laser-induced photopolymerization followed by UV-induced crosslinking as a means of building a three-dimensional network structure aimed at three-dimensional imaging. The key to our design, shown in Scheme 4 below, is incorporation of an acrylate monomer... 

Parallel sets of polymerization experiments were carried out using the monomer mixture described above with an Eosin-triethanolamine initiator system irradiated (514 nm) for short periods of time. The resulting prepolymer (or partly polymerized) solution was then exposed to UV radiation, as above, and the extent of crosslinking was measured. Since the polymerization at 514 nm was not carried out to completion, bleaching of the dye was incomplete at the concentration of the initiator used. Film formation was observed, but only after 3 minutes of irradiation. The lower levels of crosslinking can be attributed to partial masking of the oxime absorption by the residual initiator. Like experiments with a He-Cd laser (325 nm) produced gel along the laser path. 

Electron transfer to the xanthenes, particularly reduction with amines, has been used for a number of years to initiate acrylate polymerization. A typical system is that reported to form volume holograms—lithium or zinc acrylate, triethanolamine and Eosin, Erythrosin, or Rose Bengal [290], Similar mixtures are used to form printing plates photoreducible dye, phenylac-ridine, and acrylate monomer [292], A recent patent application discloses aryl iodonium salts, Rose Bengal, and oxidizable triazines such as 2-methyl-4,6-bis(trichloromethyl)-s-triazine to polymerize acrylates [292],... 

In the particular case of the carboxylates of the eosin family, a careful examination of electron transfer paths was made by K. Tokumaru and cowor-kers [158, 159, 160]. They found that eosin Y (EY ) was able to sensitize hydrogen evolution from water under visible light irradiation in a system made of an amine donor, methyl viologen (MV2+) mediator and redox catalyst such as colloidal platinum. In a water-ethanol solution of EY, in the presence of MV2+ and triethanolamine (TEOA), a maximum quantum yield of 0.3 was measured for the MV + radical cation formation. Kinetic measurements of the EY triplet quenching constant by MV2+ (kq = 3.109 M 1 s 1) and TEOA... 

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