Fluorescence On/Off Switching in Polymers Bearing Diarylethene and Fluorene in Their Side Chains

Abstract

A diarylethene–fluorene dyad connected by an ester bond ( DE-FL ) and random and alternative copolymers with diarylethene and fluorene moieties in their side chains ( poly(DE1 x - co -FL1 y ) and poly(DE1- alt -FL2) ) were synthesized, and their fluorescence on/off switching properties were investigated. All compounds exhibited reversible photochromism and fluorescence on/off switching in a solution upon alternating irradiation with ultraviolet and visible light. Although the fluorescence intensity of DE-FL linearly decreased with increasing photocyclization conversion of the diarylethene, the fluorescence intensity of poly(DE1 x - co -FL1 y ) at the same molar fraction of diarylethene/fluorene significantly decreased with photocyclization conversion. Moreover, the fluorescence intensity of the polymers in the photostationary state was much lower than that of DE-FL . These results indicate that the fluorescence on/off switching properties of the polymers were improved by introducing diarylethene and fluorene moieties into their side chains. Moreover, it was revealed that the monomer sequences and the molar fractions of the diarylethene and fluorene moieties affected the fluorescence on/off switching properties of the copolymers.