CHROMIC PHENOMENA IN REGIOREGULAR AND NONREGIOREGULAR POLYTHIOPHENE DERIVATIVES

Chromic phenomena in various regioregular and nonregioregular polythio phene derivatives have been investigated both in the solid state and i n solution. Some structural, thermal, and optical measurements have re vealed a first-order-like conformational transition of the conjugated backbone (formation of twistons) which leads to important color change s. This thermally induced cooperative conformational transition of the main chain has been observed in both amorphous (even with branched si de chains) and semicrystalline regioregular polythiophene derivatives but did not occur in nonregioregular polymers. This single-chain pheno menon is strongly dependent upon the substitution pattern but is not n ecessarily driven by side-chain or main-chain crystallization, Noncova lent interactions between ether-substituted regioregular polythiophene s and ionic species can be used to stabilize the coplanar form of the backbone, leading to interesting ionochromic effects.