Synthesis of poly(2,5-dimethoxyanilie) (PDMA) catalyzed by nano reengineered horseradish peroxidase (HRP) with dendritic macromolecules, was studied as a function of reaction media. UV–vis, gel permeation chromatography and conductivity measurements were used to explain how the reaction media compositions influence the physical properties of PDMA. Nanostructured PDMA was also synthesized by oxidative polymerization in a novel and green bi-catalyst system involving HRP and ferric chloride. FTIR and UV–vis analysis confirmed the formation of emeraldine salt state of PDMA. The thermal stability of reengineered HRP granted further studies on the polymerization using bi-catalyst system at temperature of 50°C. The scanning electron microscopy images showed the changes in the morphology of synthesized PDMA from nanoporous structures to rod-like shapes by increasing the reaction temperature.