CONDUCTIVITY DEGRADATION DUE TO THERMAL AGING IN CONDUCTING POLYANILINE AND POLYPYRROLE

Citation
S. Sakkopoulos et al., CONDUCTIVITY DEGRADATION DUE TO THERMAL AGING IN CONDUCTING POLYANILINE AND POLYPYRROLE, Synthetic metals, 92(1), 1998, pp. 63-67
Citations number
27
Categorie Soggetti
Physics, Condensed Matter","Material Science","Polymer Sciences
Journal title
ISSN journal
03796779
Volume
92
Issue
1
Year of publication
1998
Pages
63 - 67
Database
ISI
SICI code
0379-6779(1998)92:1<63:CDDTTA>2.0.ZU;2-6
Abstract
The decrease of the electrical conductivity of polyaniline and polypyr role due to thermal aging is reported. The d.c. conductivity is measur ed in the temperature range 300-80 K for aging times from 0 to 11 h at 120 degrees C in room atmosphere. The conductivity of polyaniline dec reases with aging time according to the law sigma = sigma(o)exp[-(t/ta u)(1/2)]. Polypyrrole diverges either from the above or sigma(o)-sigma alpha t(1/2). Moreover, polyaniline follows sigma = sigma(o)exp[-(T-o /T)(1/2)] law with T-o increasing with aging time. This can be explain ed by a conduction mechanism consisting of electron tunnelling between conducting grains embedded into an insulating matrix. Polypyrrole fol lows a sigma = sigma(o)exp[-T-1/(T + T-o)] law until about 5 h of agin g time. For longer heating its behaviour diverges from the predictions of known models of conduction in polymers. The above can be attribute d to differences of the aging process in the two compounds. In polyani line, aging is accompanied simply by a decrease of the grain size, the separation of which increases from 27 to 54 Angstrom after 10 h of he ating at 120 degrees C. In polypyrrole, for short aging times, the gra in size remains constant, their separation being about 60 Angstrom. Lo nger aging leads to a thermally activated conductivity whose mechanism is obscure. (C) 1998 Elsevier Science S.A.