Thermally induced chromic effects (thermochromism) have been observed in polythiophene, polysilane2 and poly- diacetylene3 derivatives. These optical effects have been described in terms of a reversible transition between a coplanar (highly conjugated) and a nonplanar (less conjugated) con- formation of the main chain.4 Recently, a new chromic phenomena (ionochromism) has been reported in which a regioregular polythiophene derivative ...
