Discotic liquid crystalline triblock copolymers: Interplay of liquid crystal architecture with microphase separation

A triblock copolymer has been prepared in which a main chain polymeric discotic liquid crystal is capped at both ends with blocks of poly(ethylene oxide). It has been characterized by GPC, DSC, polarizing microscopy, small- and wide-angle X-ray diffraction, electron microscopy, and rheometry. The copolymer undergoes microphase separation, giving a nanostructured material consisting of a hexagonal array of poly(ethylene oxide) rods in a matrix of columnar liquid crystal. It is found that the alignment of these rods is determined by that of the liquid crystal. Hence, under shear, both the columns of the discotic and the rods of poly(ethylene oxide) align perpendicular to the shear direction. At lower temperatures the poly(ethylene oxide) regions crystallize, and a lamellar structure is obtained.