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.