The synthesis of multiblock copolymers containing liquid crystalline, semi aromatic polyester segments of poly( ethylene terephthalate-co-oxybenzoate), and polysulfone segments with different segment molecular weights was recently described. Such block copolymers should make it possible to combine properties of the base homopolymers, e.g., the high strength of liquid crystalline polymers (LCP) with the high thermostability of polysulfone (PSU). Investigations of melt rheology and relaxation behavior discussed here demonstrated that the properties of the block copolymers are intermediate between those of the homopolymers and can be tailored by using PSU and LCP segments of suitable molecular weight. The high melt viscosity of PSU is lowered by block copolymer formation, allowing good processability by injection molding. The material properties of the resulting samples are characterized by a combination of PSU thermostability and improved strength.