Stability of Individual Polymeric Systems

The work of Kim et al. [110] focused on pofyacetylene fiber networks ranging in diameter from 60 to 80 nm. The dark red gel of low density foamlike polyacetylene doped with iodine showed a remarkably low temperature dependence of resistivity as compared to bulk polyacetylene film. Polyacetylene fiber networks were found to be more sensitive to air than the bulk polymer, because the resistance of the iodine-doped fiber network increased more rapidly than that of the bulk polyacetylene film on mqposure to air. 

Polythiophene and its derivatives show remarkable air stability in both oxidized and reduced form [111]. However, there are variable reports on their stability in different types of enviromnents. The ionization potential of poly thiophene is estimated to be above 5 eV, which is high enough to protect the polymer from forming a charge-transfer complex with otygen to cause oxidative instability. Both electrochemically as-prepared polythiophene and polythiophene redoped after ammonia compensation showed much better air stability compared to polyacetylene [112,113]. 

Polythiophene containing BFJ counterions showed a loss of dopant on exposure to ambient and slightly higher temperatures without any loss of conjugation however, at higher temperatures (around 175° C), it undergoes fast loss of dopant and then loss 

Source Adapted with permission from E Mohammad et al., Bull. Elec-trochem. 9(2/3), 109 (1993). Copyright 1993, CECRI, India. 

Initial electrical conductivity Counterion (fl cm ) T(°C) a (s-1) In vacuum Ambient air  

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