ELECTROCHEMISTRY OF DISULFIDE COMPOUNDS .1. ELECTROCHEMICAL POLYMERIZATION-DEPOLYMERIZATION PROCESS OF 2,5-DIMERCAPT-1,3,4-THIADIAZOLE

The electrochemical polymerization-depolymerization of an organodisulf ide compound, 2,5-dimercapt-1,3,4-thiadiazole (DMcT), was investigated under in situ conditions by quartz crystal microbalance (EQCM) and at omic force microscopy (AFM) measurements employed simultaneously with electrochemical voltammetry. The EQCM results, together with the cycli c voltammetric results, suggest that the polymerization and depolymeri zation processes of DMcT do not occur with the same coulombic efficien cy. The number of electrons consumed during the polymerization process is greater than that for the depolymerization process, indicating tha t some other chemical process occurs at the same time. The EQCM analys is and AFM observations indicated that the oxidation of DMcT, especial ly at higher potentials, involves not only a straightforward polymeriz ation process via S-S bonds but also an overoxidation or degradation ( decomposition) process of the poly(DMcT) deposited on the electrode su rface. The AFM images of the deposited poly(DMcT) show smooth/uniform and isolated/island growth at low (0.8 V) and high (1.4 V) potentials, respectively. Substantial decomposition of poly(DMcT) was confirmed f rom both EQCM and AFM analysis when the polymer was formed at high pot ential (1.4 V). This behavior can be regarded as a serious drawback wh en the material is used as battery material.