Chemical Synthesis Of Ring-substituted Polyanilines Doped With Functional Acids And Correlation Investigations Of Their Structures And Properties

The discovery of conducting polymer opens up a new field for the application of organic polymer. Polyaniline (PAn) is one of the most studied conjugated polymers due to its simple synthesis method, high electrical conductivity, good environmental stability and peculiar electrical, optical and magnetic properties. As a kind of new functional materials, PAn is promising in the applications to the field of energy storage, sensors, electrochromic displays, microsystem technologies, and corrosion protection etc. Until now PAns have developed in both theoretical and technological aspects to a great extent. Unfortunately there are still some problems unsolved when using the polymers as materials. The first is their poor processability and mechanical behavior. Because of the rigid nature of their chain backbone, PAns are difficult to dissolve and melt, especially their doping state. It is difficult to put into effect in practical application. The second is the difficulty to control the polymer structure, molar mass and aggregate state, which not only exerts an influence on polymer's properties, but also increases the difficulty in the correlation investigation of their structures and properties. Furthermore, it has been found that doping is a main approach to afford PAn some excellent properties, but it lowers stabilities and damages some properties of the polymers at the same time.In the faces of the three problems mentioned above, two modified approaches for PAns, i.e. ring-substitution and functional acid doping, were mainly investigated in this work. The modern physical techniques, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), 1H-nuclear magnetic resonance spectroscopy (1HNMR), thermogravimetry (TGA), scanning electron microscopy(SEM) etc, were used to the systematic studies of the effects of substituents and functional acid doping on the structures and properties of PAns. Moreover the electrochemical and electrocatalytic properties of the polymers were also studied to discuss the potential applications of PAnmodified electrodes.1 Chemical synthesis of some ring-substituted polyaniline derivativesUntil now there are just few ring-substituted polyaniline. Aimed at systematic studies of the steric and electronic effects of some substituents, poly-o-toluidine(POT), poly-m-methoxyaniline(PmMAn), poly-2-aminothiophenol(PAT), poly(aniline-co-aniline sulfonic acid)(An-co-SAn) were prepared and doped with different functional acids. The factors influencing on polymerization were discussed, and the suitable polymerizationconditions were determined. In our knowledge, there are little reports about the other polyaniline derivatives except for POT.It is shown that solution polymerization is favorable to obtain different acid-doped polymers with high doping efficiency in one step. The polymers obtained are easily studied in the subsequent research on the effects of dopant on the structures and properties. POTs doped with different functional acid were prepared by solution polymerization using ammonium persulfate(APS) as initiator and CoSO4 as catalyst. By comparing the molecular weight and conductivity of products, /Htoluenesulfonic acid(TSA) doped POT, with number-average molecular weight of 1.81 X106, can be prepared in the following conditions: 1.0 mol/L TSA solution as medium in ice bath, [APS]=[M]=0.1 mol/L, and reaction period 12h.PmMAn was successfully prepared by solution polymerization and emulsion polymerization. The optimal conditions of emulsion polymerization are as follows: [M]=0.119 mol/L, [SDS]=0.05 mol/L, [KPS]=0.074mol/L, reaction period 5.0h in ice bath. For the solution polymerization, optimal conditions were like as: 1.0mol/L HC1O4 solution as medium in ice bath, [mMAn]=[APS]=0.1 mol/L, reaction period 10h. Under these conditions, PmMAn(HClO4) with number-average molecular weight 1.160 106 can be obtained.By comparing the solution polymerization and emulsion polymerization of PAT, it is found that much APS must be used in...