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 conjugated polymers. Such
characteristics allow P3TESH to be
useful for the permanent recording of a temperature increase in the
low-temperature range.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.