期刊
SYNTHETIC METALS
卷 138, 期 3, 页码 429-440出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/S0379-6779(02)00471-X
关键词
polyaniline; polyacrylic acid; electrical conductivity; thermal degradation
This paper describes the effect of molecular weight of dopants on thermal degradation behaviour of electrical conductivity of polyacrylic acid (PAA) doped polyaniline (PANI). Two PAA with weight-average molecular weight (M,) of 5000 and 250,000, respectively, were used as dopants to synthesise PANI-PAA complexes by in situ oxidative polymerisation. PANI doped with the low M-w PAA has lower electrical conductivity. which is attributed to its smaller size of crystal islands due to the end group effect. When annealed at 180 degreesC, within a period of 2 h the conductivity of PANI doped with the high M-w PAA decreases continuously with the annealing time following sigma = sigma(0) exp [-(t(a)/tau)(1,2)] law, while the one doped with the low M-w PAA obeys this law only within 1 h of annealing. This indicates that the decrease of conducting island size is responsible for the thermal degradation of the conductivity of the complexes in a certain period and the length of this period depends on M-w of the dopants. TGA study shows that at 180 degreesC weight loss rates of the low and high M-w PAA doped PANI are about the same, which implies that the faster reduction of the conductivity in the low M-w PAA doped PANI is mainly due to its smaller initial crystal size. FTIR study shows that annealing leads to de-doping, but it is less pronounced in the high M, PAA doped PANI. (C) 2002 Elsevier Science B.V. All rights reserved.
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