The synthesis and characterization of nine side-chain liquid crystalline copolysiloxanes containing trans-5-(n-undecanyl)-2-(4-cyanophenyl)-1,3-dioxane and 4-(alkanyloxyphenylazo)benzonitrile side groups are presented. The azobenzene dye contents in the copolymers range from about 5 to 20 wt.-%. The nature of the mesophase exhibited by the copolysiloxanes depends very much on the dye concentration. Three copolysiloxanes which contain about 5 wt.-% azobenzene dye, display a smectic A phase while the other six copolysiloxanes which contain more then 10 wt.-% azobenzene dye, exhibit a nematic phase. All the obtained copolysiloxanes show a very low glass transition temperature and a very wide temperature range of mesophase.