Enzymatic Synthesis of Photoactive Poly(4-phenylazophenol)

Abstract

Enzymatic synthesis, employing horseradish peroxidase (HRP), has been used to prepare a novel photoactive azopolymer, poly(4-phenylazophenol), from 4-phenylazophenol. FTIR, FT-Raman, and NMR (1H, 13C) spectroscopy show that the coupling reaction occurs primarily at the ortho positions with some coupling at the meta positions of the phenol ring of the monomer as well. This results in the formation of a branched polyphenylene backbone with pendant azo functionalities on every repeat unit of the macromolecules. This enzymatically synthesized azophenol polymer has an extremely high dye content (nearly 100%) and is soluble in most polar organic solvents, and good optical quality thin films are easily formed. Polymer solutions show reversible trans to cis photoisomerization of the azobenzene groups with long relaxation time. The poly(azophenol) film exhibits photoinduced absorption dichroism and large photoinduced birefringence with unusual relaxation behavior. The resulting azobenzene loaded polymer behaves as a new type of glassy “macromolecular dye”.