Liquid-crystalline (LC) block copolymers of lamellar morphology were prepared via anionic polymerization of polystyrene-block-1,2-polybutadiene and subsequent introduction of a deuterated mesogen by polymer analogous reaction. Deuteron NMR measurements show that the first-order nematic/isotropic transition in the block copolymer is changed to a critical behaviour under the influence of shear. In the nematic phase the order parameter is reduced with respect to the homopolymer, and there is no evidence of an isotropic boundary layer of the LC-block at the nematic/isotropic interface.