Study Of Preparation Of Polyaniline And Polyailine-gold Nanoparticle Composite

Polyaniline (PANI), among electricity conducting polymers, is widely studied due to its easy synthesis, high environmental stability, chemical stability, controllable electrical conductivity, unique electro-chemistry property, and reversible doping/dedoping mechanism. However, polyaniline, synthesized by usual chemical method, is extremely difficult to process due to its poor solubility and fusibility in common dissolvent, which becomes the major barrier to promotion of practical utility of PANI. As the emulsion polymerization process has several distinct advantages such as easy controllability, no heat dissipation and adhesion problem, the resultant PANI molecule has both high weight and narrow distribution, and can be used directly without further separations in many instances.Because of the good environmental stability, tunability of electricity conductivity, and unique electro-chemistry property of PANI, plus the unique optical, charge storaging and catalytic properties of metal nanoparticle, composites composed of these two substances are of more and more research interest over the recent years. Among these composites, nanoparticle composites PANI-Au, especially PANI-AuNPs, still show an special charge transfer and an ability to spontaneously form thiol monolayers on gold surfaces, and therefore has great potential applications in microelectronic devices and chemical sensors.Firstly, the kinetics and morphology of polyaniline film prepared by using ammonium persulfate (APS) as oxidant, and dodecylbenzoyl sulfonic acid (DBSA) as both emulsifier and dopant were studied. The kinetics of the formation of polyaniline film was determined by quartz crystal microbalance (QCM), and the morphology of film was characterized by scanning electron microscopy (SEM). The reaction exhibited half-order with respect to APS and first-order to aniline. The activation energy is 41.15kJ/mol, and the growth rate of PANI film increased with the rise of temperature and decreased with the increase of DBSA. The in situ UV–visible spectra of the emulsion polymerization were measured. The absorption of the PANI with time was also studied and compared to the growth of the PANI film using the QCM technique. The results indicated that the kinetics of PANI prepared by emulsion polymerization is according with the kinetics of PANI film formation.Secondly, HAuCl4 was used as oxidant and aniline (An) was used as reductant to prepare polyaniline-gold nanoparticles (PANI-AuNPs) composite. The formation of the film and the kinetics of the reaction were studied by quartz crystal microbalance (QCM). and the morphology of the film was characterized by SEM. The results indicated that the reaction exhibited half-order with respect to HauCl4 and 1.5 order to aniline. The reaction rate increased with the rise of temperature and decreased with the increase of HCl. The activation energy is 40.32kJ/mol. Gold particles with average diameter of about 400nm were decorated into or on the polyaniline film. The in situ UV–visible spectra of the chemical synthesis of PANI-AuNPs composite were measured. The absorption of the-AuNPs composite with time was also studied and compared to the growth of the composite film using the QCM technique. The results indicated that the kinetics of the chemical synthesis of PANI-AuNPs composite is according with the kinetics of composite film formation.Finally, PANI-AuNPs composite was prepared by using H₂O₂ both as reductant of HAuCl4 and oxidant of aniline. The polymerization of aniline dependence on the reaction time of H₂O₂ and HAuCl4 was investigated. Quartz crystal microbalance (QCM) and UV-Visible spectrophotometer were used to observe the polymerization reaction rate in real time, and Fourier Transform infrared (FT-IR) spectroscopy was used to characterize the structure of the prepared composite. The results show that the rates of polymerization of the composite were affected by the reaction time between H₂O₂ and HAuCl4, and the gold nanoparticles have catalysis on polymerization of aniline.