Synthesis, characterization and visible light activated fluorescence of azo caged aggregation-induced emission polymers.

Tetraphenylethylene (TPE) based aggregation-induced emission (AIE) polymers containing different degrees of functionalization of photobleachable azo chromophores were developed and their photophysical properties were explored. The synthesized epoxy monomer derived from TPE core reacted with aniline to give the precursor polymer, which confirmed typical AIE characteristics. Then through a post-polymerization azo-coupling scheme, various contents of 2-phenylazo-4, 5-dicyanoimidazole groups were readily introduced into the TPE based epoxy precusor polymer. Experimental results suggested that only a small amount of such imidazole-type azo component could totally cage the intense AIE fluorescence of the whole polymer due to the fluorescence resonance energy transfer process. By exposure to visible light (450 nm), azo units could be photo bleached notably, thus resulting in dramatic recovery of the blue fluorescence. Depending on this, visible light induced fluorescent patterns were easily fabricated and erased, indicating that the prepared azo caged AIE Polymers could be promising candidates for anti-counterfeiting and optical information storage. Visible light activated fluorescence of imidazole-type azo caged aggregation-induced emission polymers was reported. The effect of azo contents on fluorescence intensity was studied, which revealed that only a small amount of imidazole-type azo groups could totally cage the strong AIE fluorescence of the polymers. Irradiated with visible light, azo chromophores could be photo bleached, leading to remarkable recovery of the blue fluorescence. Fluorescent patterns have been easily fabricated. Image 1 • Only a small amount of imidazole-type azo chromophores could totally cage the strong AIE fluorescence of the polymers. • Imidazole-type azo chromophores could be photo bleached with visible light. • Visible light induced fluorescent patterns have been easily fabricated and erased. [ABSTRACT FROM AUTHOR]