Physical properties and thermal transition of polyaniline film

The effect of solvent and dopant on the thermal transition of polyaniline ( PANI) has been investigated principally by dynamic mechanical analysis (DMA ). Solvent (NMP) containing film was found to exhibit three thermal transit ions in tan delta curve (142, 198, and 272 degreesC). The two lower transit ions were disappeared when NMP was removed. Hence, the third peak was sugge sted to be real glass transition of PANI. The shape of DMA spectra was vari ed with thermal curing temperature, which is directly related to NMP conten t. Two other peaks seemed to be due to the evaporation of solvent existing as different environment (free NMP and hydrogen-bonded NMP), which was trac ed by TGA, FT-IR, and DMA with altering the curing temperature. It was sugg ested that the third peak was composed of cross-linking reaction between ad jacent chains as well as glass transition of polyaniline backbone. NMP free films were prepared by two methods (repeating doping-dedoping cycle and th ermal curing). In these films, only one tan delta was observed at over 250 degreesC. When the NMP free film was doped, the DMA peak observed over 250 degreesC was broadened and shifted toward lower temperature. (C) 2001 Elsev ier Science B.V All rights reserved.