| Enzymatic synthesis of a water-soluble, conducting polyanline (PANI) using a template-guided approach was studied in this paper. Horseradish peroxidase (HRP) is used to polymerize aniline in the presence of a new polyanionic template, poly(vinylsulfonic acid, sodium salt) (PVS). The effects of reaction conditions on the polymerization were worked out. Meanwhile, the products were compared with those synthesized using different templates. And what is more, the method for the synthesis of polyaniline with the immobilized horseradish peroxidase enzyme was investigated.In the study of polymerization of aniline catalyzed by free HRP, effects of different buffer solution, concentration of initiator (H2O2), and the molar ratio of aniline to PVS (based on the monomer repeat unit) on the polymerization were investigated. The products were characterized by UV-vis-near-IR and FTIR spectroscopy, thermogravimetric analysis, and four-point probe conductivity measurement. The results showed that PVS could be used as a new template in the synthesis of PANI. The reaction should be carried out in a 4.0~5.0 pH buffer aqueous solution at room temperature (25 °C). The concentration of initiator (H2O2) was 10nM~20nM, and the molar ratio of PVS to aniline was 1-1.5. The conductivity of PVS/PANI complex was 4.78 X10'1 S/cm, which was obviously higher than any other complex already having been reported.In the study of polymerization of aniline catalyzed by immobilized HRP, the enzyme HRP was immobilized on chitonsan powder and the surface of calcium alginate (CA) microspheres respectively by a simple glutaraldehyde bridge method. The alginate-chitosan-alginate (ACA) microcapsules were also used to immobilize HRP. The results showed that the HRP immobilized on chitosan powder and CA microspheres was an effective catalyst for the polymerization of aniline. It was defeated while using the HRP immobilized by ACA microcapsules as catalyst. The HRP immobilized on chitosan powder was stable and remained active after being stored in pH6.0 buffer solution at room temperature for about 72hr. When the immobilized HRP was used in the reaction, the proper pH of buffer solution and concentration of initiator (H2O2) were similar to that ofpolyaniline obtained with free HRP. The amount of catalyst used should be controlled around 0.lg/mL. The microspheres with HRP immobilized on the surface were functional microspheres, which were easier to recover than the chitosan powder. Functional microspheres are remarkable and need to be further investigated.This paper provides necessary experimental and theoretical foundation for further studies of enzyme-catalyzed polymerization of aniline. |
