Azobenzene functionalized poly(diphenylacetylene): Polymer synthesis and tunable fluorescent emission

Abstract

We prepared an azobenzene-functionalized poly(diphenyl-substituted acetylene) (named as PDPA-azo) through the post-polymerization modification route by using the activated ester strategy. The structures of the derived PDPAazo were fully characterized with comprehensive spectroscopic methods including NMR, FTIR, UV-vis, TGA, and so on. PDPA-azo showed photoisomerization behavior due to the azobenzene moiety in the side chain. Since the short spacer between polymer main-chain and side-chain, PDPA-azo could not form liquid-crystal phase despite the presence of azobenzene mesogen in the polymer structure. It was noted that the modification of the precursor polymer PDPA-PFP with primary amine-functionalized azobenzene converted the fluorescence behavior from aggregation-induced emission enhancement to aggregation-caused quenching. The control experimental results suggested that the changes in fluorescent behaviors after irradiating under 365 and 254 nm UV lamps could be correlated to the photo-induced isomerization of the azobenzene group. As a result, the fluorescence properties of PDPA-azo can be adjusted by different external stimuli.