Stilbene-containing liquid crystalline side chain homo- and copolysiloxanes: microphase separation and chemical modification to electroconducting materials

The phase behaviour of two classes of side chain polysiloxanes, containing respectively 4-cyano- and 4-alkoxy-4'-stilbene-ether mesogens, was studied over a wide temperature range by differential scanning calorimetry and wide angle X-ray diffraction, with special attention devoted to the characterisation of the microdomain phase morphology. Room temperature X-ray diffraction studies suggest for certain polymers with cyanostilbene mesogens the occurrence of microphase separation; this effect becomes significant as the amount of polysiloxane backbone versus the side chains increases. The onset of electrical conductivity was followed upon exposure of the polymeric films to various doping agents; conductivities up to 2x10(-1)Scm(-1) were measured when cyanostilbene-containing polymers were exposed to strong Lewis acids such as SO3 or SbF5. However, occurrence of some chemical degradation upon heavy doping and of electrode polarisation during DC conductivity measurements indicate that the observed electroconductivity is not purely electronic.