Chain folding in liquid-crystalline main-chain polymers with a smectic phase

Thermotropic main-chain liquid-crystalline polymers (LCPs) composed of azob enzene or azoxybenzene mesogens and flexible spacers with and without a phe nyl side group have been characterized by gel permeation chromatography, di fferential scanning calorimetry, and X-ray diffraction. The polymers exhibi t smectic phases in the well-accessible temperature range from room tempera ture up to 160 degrees C. The morphology of thin films on a solid substrate was studied by X-ray reflectometry and scanning force microscopy (SFM). Th e smectic layers are mainly oriented parallel to the film surface. On the b asis of X-ray reflectometry and SFM. investigations, it is concluded that, at least in thin films, the polymer main chains are not extended like in th e common model for main-chain LCPs, but almost regularly folded.