Xianhong Wang

Thermal behaviors of doped polyaniline

Abstract Thermal behavior of polyaniline (PAn) doped with kinds of inorganic or organic acids under desired atmosphere were studied by TG, DSC and in-situ electrical conductivity measurements. The reason for the thermal stability of electrical conductivity of doped PAn was discussed.

Structure and properties of self-doped polyaniline

Summary form only given. Sulfonated Polyaniline (SPAn) with various sulfonation degrees (SD) has been synthesized by the reaction of polyaniline and concentrated sulfuric acid using silver sulfate as catalyst. Only when SD of the SPAn is over 45% can it be dissolved in dilute aqueous alkaline solution and display apparent self-doping property. The reversible conversion between SPAn and its ammonium salt, confirmed by in-situ UV-Vis and ESR, is another evidence for the self-doping property of SPAn. From the different self-doping behavior of SPAn and poly (o-aminobenzoic acid), it is concluded that the formation of relatively strong intra-molecular ionic bonds is responsible for the effective self-doping property. 4-Amino-2-sulfonic acid diphenylamine is synthesized through Ullmann condensation, and successfully electropolymerized in H/sub 2/O/CH/sub 3/ CN/Na/sub 2/SO/sub 4/ system. The resulted polymer is a typical alternative compolymer of aniline and m-amino-benzenesulfonic acid. The differences in FTIR spectra and cyclic voltamograms between SPAn and the above alternative copolymer indicate that the sulfonic acid groups are somewhat randomly distributed on the backbone aromatic rings.

SOLUTION PROPERTIES OF POLYANILINE AND ITS DERIVATIVES

Abstract Solutions of polyaniline (PAn), poly (ortho-toluidine) (POT) and poly (ortho-anisidine) (PAs) in N-methyl pyrrolidinonne (NMP) were examined by viscometric, gel permeation chromatographic (GPC) and rheological methods. Strong intermolecualr interaction and molecular aggregation are shown.

Thermal behavior of intrinsic polyaniline and its derivatrives

Abstract Thermal properties of polyaniline (PAn), polytoluidine (POT) and polyanisidine (PAs) were examined by TG and DSC techniques. The weight—uptake of POT at 200–300°C was observed and carefully discussed.

Synthesis and properties of poly (aniline-co-anisidine)

Summary form only given. Aniline and o-anisidine are chemically copolymerized at various temperature and monomer composition. Copolymerization reaction is confirmed by the solubility and electrochemical cyclic voltamograms of the resulted polymer. The pure copolymer can be separated from the homopolymers by THF/CHCl/sub 3/ two-step dissolution based on their solubility difference. O-Anisidine is more effective than o-toluidine to improve the solubility of Polyaniline. When the molar fraction of o-anisidine in monomer feed (f/sub 1/) is around 0.15-0.20, the resulted polymer is 100% soluble in THF, the corresponding tensile strength is more than 30 MPa and electrical conductivity remains at the magnitude of 10/spl deg/S/cm. When aniline and o-anisidine are copolymerized at low temperature (-5/spl deg/C), the resulted polymer is 100% soluble in THF, the tensile strength is more than 50MPa when f/sub 1/ is between 0.20-0.30 and its solution cast film shows apparent tensile yielding. GPC results demonstrate that the good solubility of the copolymer is related mainly to the steric repulsion between the methoxy groups. IR, /sup 13/C-NMR and F/sub 1/-f/sub 1/ (F/sub 1/ is molar fraction of anisidine in the copolymer) relationship indicate a random chain structure in the copolymer.

Synthesis and characterization of chlorinated polyaniline

Summary form only given. Chlorinated polyaniline (Cl-PAn) with different Cl content has been synthesized in aqueous HCl/(NH/sub 4/)/sub 2/S/sub 2/O/sub 8/ system. The chlorination degree depends on aqueous HCl concentration in the reaction medium. The optimum condition to prepare Cl-PAn with high solubility and electrical conductivity is 6. 6 N HCl, equivalent monomer and oxidant concentration and at room temperature. This kind of Cl-PAn is 100% soluble in THF both in undoped and doped state, and its electrical conductivity is around 10/sup -4/S/cm. GPC result indicates that it has low number average molecular weight (Mn = 3523) and narrow molecular weight distribution (Mw/Mn = 2.14). Elemental analysis, FTIR, UV-Vis spectra and cyclic voltamograms of Cl-PAn are similar to those of poly (o-chloroanitine), indicating that Cl-PAn has similar structure as poly(o-chloroaniline). GC-MS and FTIR spectra demonstrate that chlorination happens at first on the monomer, then the chlorinated aniline homopolymerizes or copolymerizes with aniline. Once HCl concentration is over 7N, bi- or tri- chlorine substituted aniline can be formed, leading to great decrease in polymer yield and electrical conductivity.

Conducting Langmuir-Blodgett films based on unsymmetrical alkylthiotetrathiafulvalene and alkylammonium-metal (dmit)2 complexes

Abstract Two kinds of complexes of unsymmetrical alkylthiotetrathiafulvalene and alkylammonium-metal (dmit) 2 were synthesized. Their Langmuir-Blodgett films have been deposited by vertical dipping method. After in situ iodine vapor treatment the film exhibited the conductivity of ca.2.5 × 10 −1 S/cm at room temperature.

Solution properties of polyantline and its derivatives

Summary form only given. The solutions of polyanitine(PAn), poly-o-toluidine(POT) and poly-o-anisidine(PAs) in N-methyl pyrrolidinone(NMP) and concentrated sulfuric acid are examined by viscometric and rheological measurements and GPC. The solution properties show tremendous concentration dependence. In the concentration below 0.25wt%, Mark-Houwink equation is obeyed for PAn with k = 1. 4 X 10/sup -4/ and /spl alpha/== 0. 93. Above 0.25wt% obvious interchain aggregation is observed for PAn solution in NMP, characteristic of the decrease of specific viscosity with concentration increase, the PAn solution in NMP behaves as Newtonian fluid when the concentration is below 5wt%. Over this concentration, it exhibits more and more pseudo-plasticity and the viscosity increases repidly with concentration, indicating that the gelation has taken place.

Investigation on the cross-linking reaction of poly(o-,m-)methylanilines

Summary form only given. The heat-treatment of poly(o-,m-)methylanilines in their base form was followed by IR, UV-Vis, TG, DSC and solubility measurements. TG, DSC and solubility measurements demonstrated that the heat-treatment of poly(o-,m-)methylanifines under nitrogen led to the occurence of the cross-linking reaction before the decomposition of polymeric backbone. IR and UV-Vis spectra revealed that the inter chain cross-linking reaction occures at nitrogen atoms on quinoid rings and the substitution pattern of aromatic rings remained almost unchanged. Based on the structure of the cross-linked polymer and EHMO-CO calculation, a possible cross-linking mechanism was proposed.

Molecular weight and properties of polyaniline

Summary form only given. Polyanifine (PAn) is fractionated through solvent dissolution into five fractions with molecular weight distribution from 2.4 to 4.7 and the molecular weight (MW) of each fraction is estimated to be from 1,000 to 40,000 by intrinsic viscosity in concentrated sulfuric acid using nylon-6 and PPTA(poly-para(phenytene terephthalamide)) as soft and stiff standard polymer, respectively. The electrical conductivity increases with MW for low MW fractions. When it reaches 10/sup 1/S/cm for NMP soluble-DMF insoluble fraction, it does not further in crease with MW. Tensile strength increases greatly with MW from 3OMPa (THF soluble acetone insoluble fraction) to 140 MPa (NMP soluble-DMF insoluble fraction), whereas that of the common polyaniline is only 55 MPa. Thus elimination of the low MW fraction is necessary to improve the tensile strength of PAn. GPC curve and intrinsic viscosity are combined to estimate the k and /spl alpha/ values in Mark-Houwink equation of PAn as 1.4 X 10/sup -4/ and 0. 93, respectively. The high a value indicates the extended molecular form of PAn in its NMP solution.