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Abstract The room temperature
stability of doped conducting poly(3-alkylthiophene),P3AT, films
with side chain numbers from 6 to 18 was studied. The UV/
Vis/ NIR absorption spectra were used to monitor the dedoping
process and calculate the dedoping rate. We found that dedoping
rate of poly(3-alkylthiophene) increases as the length of the
chain side increases. This result is consistent with the "
thermal undoping" which is attributed to the steric hindrance of
the long flexible side chains, which kick out the dopants.
Therefore, P3AT with longer alkyl side chain shows higher
dedoping rate. The stability of the polymer was also
dramatically influenced by the nature and stability of the
counteranions which were introduced into the polymer during
doping. P3ATs doped with AuCl3 were found to be more stable
than those doped with FeCl3. The mechanism of dedoping
reaction, derived from UV/Vis/NIR and ESR studies, can be
rationalized as bipolaronic states were first reduced to
polaronic states, polaronic states were then reduced to neutral
form. During dedoping , counteranion reacts with water to
produce small molecules, such as HCl, which diffuses out of the
polymer films and destroy the surface morphology of the films.
Moreover, some new polyalkylthiophenes derivatives,
functionalized with different side chains, were successfully
synthesized. The effects of the side chain on the stability of
doped polymer can be studied further in the future.
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