Thermochromism in Optically Active Polyaniline Salts

Optically active polyaniline salts PAn.(+)-HCSA (HCSA = 10-camphorsulfonic acid) have been shown to have different conformations for their polyaniline chains depending on whether they are synthesized chemically or electrochemically. These conformations are assigned as “compact coil” and partial “expanded coil”, respectively. An “expanded” to “compact” coil transformation is induced by heating to 140 °C for 10 min, as evidenced by UV−visible and circular dichroism spectral studies. At temperatures greater than 180 °C, progressive dedoping of the PAn.(+)-HCSA salt films occurs, with the formation of racemic emeraldine base.