Synthesis and Characterization of Photoprocessable Lignin-Based Azo Polymer

Lignin-based azo polymer-bearing pseudo-stilbene-type azo chromophores have been synthesized by a post-azo coupling reaction between the modified alkali lignin and diazonium salts of 4-aminobenzoic acid in DMF with high yield. The polymer synthesized was characterized by using spectroscopic methods. Significant dichroism and surface relief patterns could be photoinscribed on the prepared azo polymer films by using appropriate laser beams. Self-assembly of the lignin-based polymer in selective solvents (THF/H2O) can give uniform colloidal spheres, which can be elongated along the polarization direction of the irradiation light. This novel synthesized lignin-based azo polymer could potentially be used for applications such as reversible optical data storage, photoswitching, sensors, and other photo-driven devices, which provide a simple strategy for value-added utilization of lignin biomass resources.