Newly synthesized polybenzoxazole derivative with an adjacent hydroxyphenyl ring for optical sensing

A photoluminescent polymer with a 2-(2'-hydroxyphenyl)benzoxazole unit in the molecular main chain was synthesized through the deprotection reaction of a precursor polymer. The amorphous, conjugated polymer emitted green light, both in solution and as a solid, with a fluorescence emission maximum at 518 nm from an excited keto tautomer because of excited-state intramolecular proton transfer. The polymer showed different fluorescence emission spectra in solvents with different polarities because of intramolecular hydrogen-bond interruption. The intramolecular hydrogen-bond-induced emission change was successfully used as a sensitive sensing signal for metal cations as expected, the polymer acting as a fluorescence-based chemosensor. (c) 2005 Wiley Periodicals, Inc.