Acta Phys. -Chim. Sin. ›› 2003, Vol. 19 ›› Issue (07): 580-583.doi: 10.3866/PKU.WHXB20030702

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Mechanism for the Reduction of Dichromate in the Polymerization of Aniline

Liao Chuan-Ping;Gu Ming-Yuan   

  1. State Key Laboratory of Metal Matrix Composites, Shanghai Jiaotong University, Shanghai 200030
  • Received:2002-11-11 Revised:2002-12-23 Published:2003-07-15
  • Contact: Gu Ming-Yuan E-mail:mygu@mail.sjtu.edu.cn

Abstract: The product of oxidative polymerization of aniline using dichromate as oxidant was proved to be polyaniline/Cr(OH)3 composites by methods of IR, XRD, elemental analysis and pyrolysis experiment.This conclusion is different from the idea in the literature that when aniline is oxidized the product of the reduction of dichromate is soluble Cr3+ that would not remain in the polyaniline product.The Cr(OH)3 content in the composites decreased from 38.4% to 1.3% along with the growth of solution acidity,as shown in Fig.1.The reduction Cr2O72- of was supposed to be composed of two steps:the reduction of Cr2O72- to Cr(OH)3 followed by the dissolution of Cr(OH)3 into acidic solution.The standard Gibbs free energy of the first step was calculated to be -582.11 kJ•mol-1,which is a very large negative value.The second step being the adsorption of polyaniline onto Cr(OH)3 retards its dissolution and leads to the formation of polyaniline/Cr(OH)3 composites.

Key words: Polyaniline, Dichromate, Reaction mechanism, Oxidation, Reduction