Structural properties of oriented polydiacetylenes: AFM and time-resolved spectroscopy characterizations

We report a new approach for the growing of polydiacetylene thin films which leads to better oriented samples as seen by atomic force microscopy (AFM) imaging, as well as static and time-resolved optical spectroscopy. With these two techniques, we characterized the morphology and structure of the films as well as the intramolecular relaxation times. The linear optical characterization of poly [1,6-di(N-carbazolyl)-2,4-hexadiyne] (pDCH) samples, grown on a hot crystalline substrate, shows a significant red shift of the excitonic π → π* transition. The dynamic measurements allow the determintion of the relaxation mechanisms of the pDCH chain. Two types of mechanisms have been distinguished: the coherent electronic dephasing and the excitonic population relaxation. The dynamics of both processes is influenced by the structural properties of the polymer backbone. This study suggests that the quality of the epitaxial deposition is important for the determination of the intrinsic dynamical properties of the polymer materials.