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Several 3-ketocoumarins with alkoxy or dialkylaniino substituents in the 7 position, which are efficient sensitizers for crosslinkable polymers, were evaluated as photoinitiators. Proper combinations of certain derivatives of these ketocoumarins with activators such as amines, acetic acid derivatives, and alkoxypyridinium salts gave quantum yields for initiated radical polymerization much higher than that obtained from the Michler's ketonehenzophenone combinations. For each class of activators the dependence of the efficiency of polymerization on the redox properties of the ketocoumarins is explained in terms of charge transfer or electron transfer from the activator to the excited ketocoumarin (acetic acid and amine activators, respectively) or electron transfer in the opposite direction (pyridinium salt activators).

-A nurober of selected aspects of the reciprocal interactions of polymers with excited solutes or polymer-hound chromophores are given. The role of free volume, glass-transition temperature (Tg), microscopic viscosity, and polarity or environments to which excited molecules are exposed is emphasized in order to illustrate possible manners in which the photophysical, photochemical, and subsequent chemistries can be influenced.Many of these factors can affect several monomolecular and bimolecular processes encountered in the sensitization of photocrosslinkable polymers: the photophysics of the sensitizer, energy transfer to the reactive sites on the polymer, and the formation of crosslinks. In fact, the triplet yields of aroylnaphthothiazole derivatives, a widely used class of sensitizers, are considerably higher in the more viscous polymeric matrices. These ~-in the polymer approach, however, a value of only ca. 0.7. As a resuitca search for more efficient triplet sensitizers led to a new class of compounds: 5-and 7-substituted 3-ketocoumarins.As a model for study of the bimolecular processes in polymers, we chose exciplex and excimer probes. The following conclusions were drawn: 1. Several exciplex and excimer emissions in polymeric media are considerably shifted to shorter wavelengths as compared with the maxima measured in fluid media, indicating that interactions are impaired in polymeric matrices. 2.Emissions from the polymer matrix above the glass-transition temperature are similar in wavelength and temperature dependence thereof to those observed in fluid solutions. 3.