Study On The Mechanism Of Synthesis Of Chiral Polyaniline Induced By Biological Moleculars

The mechanism on the synthesis of chiral polyaniline induced by biological moleculars was studied in this research. Three aspects were included mainly:(1) In dodecyl benzene sulfonic acid(DBSA) micelle system, chiral polyaniline was successfully synthesized by using a variety of single-configuration monosaccharides as chiral inducing agents, and ammonium persulfate(APS) as the oxidant.(2) The effects of a variety of carbohydrates on the producing of chiral polyaniline were investigated., Furthermore the mechanism on the synthesis of chiral polyaniline induced by carbohydrates has been concluded and proved through various experiments.(3) The mechanism on the synthesis of chiral polyaniline induced by protein was presented through the clever experimental design using hemoglobin(HB) as the example.Firstly, single configuration form of glucose, arabinose, galactose and mannose was utilized in the synthesis of chiral polyaniline as chiral induction agents respectively. Experimental results showed that the four kinds of single configuration monosaccharides all can successfully induce the production of chiral polyaniline which was confirmed by the typical characteristic absorption peaks of chiral polyaniline in the corresponding circular dichroism spectra. In addition, the absorption peaks of chiral polyaniline in circular dichroism spectra induced by different configurations monosaccharides exhibited mirror images, indicating that the opposite helical conformations of chiral polyaniline have been achieved. Furthermore, Fourier transform infrared spectroscopy(FTIR) also showed that monosaccharide was successfully doped into the chiral polyaniline. Interestingly, a carboxyl group was detected by FTIR, suggesting that monosaccharide is possibly oxidized by ammonium persulfate in an acidic environment. In addition, the circular dichroism spectra of dedoped and redoped chiral polyaniline showed that the chiral polyaniline induced by monosaccharide had a relatively stable helical structure. With the help of field emission scanning electron microscopy(FESEM), the morphology of chiral polyaniline was observed. It was found that the polyaniline obtained in the presence of monosaccharides presented similar nanoscale particles with coral-like in shape. The chiral polyaniline was also characterized by UV-visible absorption spectrum(UV-vis), thermal gravimetric analysis(TGA), X-ray diffraction analysis(XRD). Results showed that the product exhibited relatively high thermal stability, good conducting properties and crystal structure.Secondly, in the study of the mechanism on carbohydrate-induced synthesis of chiral polyaniline, the monose containing aldehyde group was found to have a better induction effect on the producing of chiral polyaniline. At the same time, the intensity of the typical CD absorption band of chiral polyaniline induced by the monose containing aldehyde group was higher than that induced by monose containing a keto group.This phenomenon may be ascribed to the production of carboxyl structure from monose with aldehyde group oxidized to by APS in an acidic reaction environment. The detection of p H during the reaction process proved the presence of carboxyl group which was also confirmed by infrared spectrum. However it was found that the inducing effect of maltose was not as good as the monose with aldehyde group which was supposed to be ascribed to the presence of glycosidic bonds. We also found that RNA and DNA which contained carbohydrate structure, can be used in the synthesis of chiral polyaniline, suggesting that the specific double helix structure of DNA is not the necessary condition to induce the production of chiral polyaniline. Results showed that the starch can also be preferably used in the synthesis of chiral polyaniline which was assumed be due to the large numbers of hydroxyl group existed in starch. A mechanism on carbohydrate-induced synthesis of chiral polyaniline was then put forward based on the above experiments.Finally, the mechanism on the synthesis of chiral polyaniline induced by protein was explored. A variety of experiments were conducted by using hemoglobin(HB) after treatmented as the inducer. Results indicated that the protein part among hemoglobin was responsible for the synthesis of chiral polyaniline while heme portion inside hemoglobin can only catalyze the generation of conducting polyaniline. In addition, the reason for the protein as a chiral inducing agent was found to be attributed to its amino acids exist in protein which was proved by the experiment using the inactivated and immobilized hemoglobin as the inducer. Further exploration showed that the primary structure of protein was important to chiral polyaniline, while the advanced structure of proteins was not a necessary condition which would be a blocker in chiral induction to some extent. The determination of SEM presented that whether the advanced structure of proteins can be fully expanded and form a homogeneous combination with the aniline monomer in reaction system will influence the regular morphology of chiral polyaniline.