PLANAR-NONPLANAR CONFORMATIONAL TRANSITION IN CONJUGATED POLYMER-SOLUTIONS

Solutions of certain urethane substituted polydiacetylenes undergo dramatic, reversible color changes on addition of a nonsolvent. In some cases, the lowest energy optical transition of the polymer shifts by more than 5000 cm-1 (21 300 cm-1 to 15 900 cm-1 when the nonsolvent is added). The color changes are shown to be due to a planar-nonplanar conformational transition of the polymer backbone. The planar, fully-conjugated conformation is stabilized by intramolecular hydrogen bonding between urethane functionalities on adjacent substituent groups. © 1979 American Institute of Physics.