IntroductionThe photoprocesses of aromatic chromophores introduced in polymers differ, in many aspects, from those of low-molecular-weight analogues '). In solution, they may be regarded as covalently-bonded chromophore aggregates and possess unique photophysical as well as photochemical properties, e. g., intramolecular excitation energy migration and photosensitizati~n~*~). . Chromophores introduced in the side chains of helical polypeptides, in particular, are arranged at regular intervals and can be further oriented rigidly by side-chainhide-chain and/or side-chain/main-chain interactions. In fact, induced circular dichroism (CD) is often observed when aromatic chromophores are bound to the side chains of helical polypeptides4-'). Sisido et al.,for example, prepared poly(L-1-and L-2-naphthylalanines) and observed strong CD signals indicative of exciton coupling in the 'B, band of the naphthalene chromophore in trimethyl phosphate solution and attributed them to rigid orientation of the naphthalene chromophores along the helical polypeptide chain4x5). Ueno et al. ' ), on the other hand, examined induced CD in the 'B, band of poly(y-1-naphthylmethyl Lglutamate) and its dependence on the solvent composition in the mixed solvents of dichloromethane and hexafluoroisopropyl alcohol, but found no concrete evidence for exciton coupling. The flexible ester linkage, as well as the long spacer chain between the chromophore and the main chain, apparently causes looser chromophore orientation and thus weaker interaction among the chromophores. c=o NH
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