M. Hua, S. Yang, S. Chen
Dec 1, 1997
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Journal
Chemistry of Materials
Abstract
The structure and properties of the poly[2-(3‘-thienyl)ethanesulfonic acid] (P3TESH) treated at temperatures from 20 to 70 °C were investigated by thermal analysis, ultraviolet−visible-near-infrared and infrared spectroscopies, electron spin resonance, solid-state 13C nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and conductivity measurements. P3TESH is susceptible to thermal undoping at low temperatures (40 °C for thin solid film). Upon undoping, the color of P3TESH changes from the original brownish green to brownish orange. The thermal undoping is irreversible due to a permanent structure change resulting from the nucleophilic attack of the −CH2CH2SO3- side chain at carbocations to yield C−O bonding and a coupling of the unpaired electrons in polarons on the main chains. As the solid film is subjected to undoping, its conductivity changes drastically from 10-2 to 10-7 S/cm. The sensitivity of P3TESH's color and conductivity changes are high compared to those of other conjug...