Morphology and structure of oriented polydiacetylene films: Molecular epitaxy of DCH

Abstract

The morphology and structure of oriented polydiacetylene films have been studied by optical and electron microscopy. The thin films are prepared under vacuum by epitaxial nucleation of the monomer crystal on single crystal substrates. Later on, a thermal topochemical polymerization preserves the orientation of the molecules and, hence, of the polymer chains. We thus obtain different types of organization of the chains depending on the interactions with the monocrystalline substrate. The films are polycrystalline. The higher nucleation density on organic substrates gives rise to a fine film texture. Third-order nonlinear characteristics have been measured; an anisotropy of 140 has been observed.