Ketone group containing polymers photochemistry

The ketone group is a useful model because it can be excited selectively in the presence of other groups commonly contained in polymer chains, such as the phenyl rings in polystyrene, and so the locus of excitation is well defined. Furthermore, there is a great deal known about the photochemistry of aromatic and aliphatic ketones, and one can draw on this body of information in interpreting the results. A further advantage of the ketone chromophore is that it exhibits a number of photochemical processes from the same excited state. Thus one has a probe of die effects of the polymer matrix on these processes by determination of the quantum yields. The competing processes include (1) fluorescence (Eq. 26), (2) phosphorescence (Eq. 27), (3) the Norrish type-I reaction (Eq. 28), (4) the Norrish type-II reaction (Eq. 29), (5) photoreduction (Eq. 30), (6) the... 

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