at least one photoinitiator which promotes free radical polymerization by generating reactive specie by way of {HEAD ~ unimolecular homolysis} resulting from {TAIL ~ photoexcitation}, said photoinitiator having the formula ##STR27## wherein A1 and A2 are the same or different and each is a benzenoid or nonbenzenoid aromatic radical 
resulting from
at least one photoinitiator which promotes free radical polymerization by generating reactive specie by way of { HEAD ~ unimolecular homolysis } resulting from { TAIL ~ photoexcitation } , said photoinitiator having the formula # # STR27 # # wherein A1 and A2 are the same or different and each is a benzenoid or nonbenzenoid aromatic radical
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