Photochromism and photoinduced bond-structure change in the conjugated polymer polydiacetylene

Abstract
The photoinduced change in absorption spectra has been measured on PDA-(12,8) (polydiacetylene) films for various photon energies and light intensities. The observed photochromic behaviors indicate that photoexcited electron-hole pairs in polymer backbone chains relax into a metastable state which develops into clusters with a local change in bond structure via a temperature-independent and self-activated multiple excitation process produced by light irradiation.