Study On Biocatalytic Synthesis Of Water-Solubility Conducting Polyaniline

In this paper biocatalysis synthesis of water-souble conductingpolyaniline (PANI) by use of a template-guided approach was studied.Three different polymerization methods were established, including：①polymerization of aniline (ANI) in Sodium Dodecyl Sulfate (SDS)micellar solution catalyzed by Horseradish peroxidase（HRP）at differentpH value;②the synthesis of PANI in Dodecylbenzenesulfonic acid(DBSA) micellar solution catalyzed by hemoglobin (Hb) and③thepreparation of PANI in DBSA/cyclohexane/water reverse micelles byuse of Hb as catalyst. The optimal conditions for the synthesis werediscussed and the influence of these conditions on the product wereanalyzed.In the first system, the influence of pH value, H2O2concentrationand SDS concentration on the polymerization of aniline had beenexplored. It was found that water soluble conducting PANI could beproduced at pH1.0-2.0. The results were confirmed by UV-Vis spectraand conductivity determination. Results also suggested that theoptimum pH value for this reaction was2.0and the optimum SDScencentration and H2O2concentration were both about20mmol L-1.Results indicated that HRP lost its activity quickly at pH value below2.0in the presence of SDS. However HRP could still catalyze the productionof conducting polyaniline in SDS micellar solution when it wasdenatured. It was deduced that the catalytic ability of HRP on thepolymerization of aniline came mainly from the iron porphyrin of HRP.In the second system the effect of pH, ratio of concentration ofDBSA and aniline, and concentration of H2O2on the production ofconducting PANI were examined. Multiple factors design weredeveloped to determine the favorable conditions for the biocatalyticsynthesis of PANI. It was found that the yield of PANI can reach as high as126.9%by using Hb as catalyst under favorable reaction condition.UV–vis absorption, FTIR and XRD spectra indicated that the product wasDBSA doped conducting PANI. The morphology and particle size werestudied by FESEM, TEM and Nano zetasize respectively. Results showedthat the PANI/DBSA complex were nanoparticles with sphericalmorphology. The stability of the product was examined by TGA andzeta-potential methods. It was found that all of these samples showedgood stability. It was concluded from FTIR spectrum and TGA curve thatour polymer had a higher doping level and better thermal stability thanthat of the product synthesized by chemical method.In DBSA/cyclohexane/water reverse micelles the influence ofwater content (W0) on the stability and yield of the product weremainly studied. The ratio of concentration of DBSA and aniline, andconcentration of H2O2on the production of conducting PANI werealso examined. Single factor, two factors and the orthogonalexperiments design were developed to determine the favorableconditions for this syntem.Through all these experiments we discoveredthat the concentration of DBSA was the most influential factor on theyield. The yield would reduce with the increasing of DBSA concentration.UV–vis absorption, FTIR and XRD,TGA, FESEMand TEM spectra showedthat nanometer level, fibrous, DBSA doped PANI was obtained. W0value was the most influential factor on the size of the product. The sizeincreased with the increasing of W0value. Hence, the size of theproduct can be controlled by altering the W0value. By contrast withthe FTIR spectra and TGA curve of the product synthesized by chemicalmethod, It was conclude that the product synthesized by biocatalysismethod had a higher doping level and better thermal stability. PANIpolymerized in reverse micelles by chemical method had beenreported. But there is no report on biocatalysis polymerization of ANI inthe reverse micelles.So in this part a new approach to synthesize PANI was developed.