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 PDPA‐azo were fully characterized with comprehensive spectroscopic methods including NMR, FTIR, UV–vis, TGA, and so on. PDPA‐azo showed photo‐isomerization 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.