Synthesis,characterization, and photoresponsive studies on lignin functionalized with (E)‐2‐(4‐(naphthalen‐1‐yldiazenyl)phenyl)acetic acid

A chromophoric system (E)‐2‐(4‐(naphthalen‐1‐yldiazenyl)phenyl)acetic acid incorporated onto a nature friendly biopolymeric core material, lignin (technical lignin, lignin sulphonic acid M.W. 52,400), and the photo responsive behavior of the product was investigated. The product was characterized by UV–visible, fluorescence, Fourier transform infrared, and nuclear magnetic resonance spectroscopic methods. The results of the studies show that the incorporation of the chromophoric system on to the lignin core enhanced the light absorption and light stabilization properties of the chromophoric system. The trans‐cis photoisomerization and the reverse cis‐trans thermal conversions were also assisted by the lignin core. The remarkable stability on irradiation shows that this is a novel photoresponsive system with excellent light fastening properties which would find application in coating materials, dyes, paints, inks, and many more. Copyright © 2012 John Wiley & Sons, Ltd.