Surface composition of solution-cast films of diblock copolymers of poly(dimethylsiloxane) (PDMS) and nylon-6 as measured by using angle-dependent ESCA. Segregation of PDMS in the free surface region of the block copolymers was detected. The surface composition of these amorphous-semicrystalline block copolymers depends on both their polymer structure and the way the films are prepared. Mixed solvents can be used to control the competition between crystallization and microphase separation and, eventually, to adjust the surface composition of the solution-cast films. Annealing of the solution-cast films drives more PDMS into the surface region. The surface region comprised of the topmost 100 angstrom of the annealed films is pure PDMS for the PDMS-nylon-6 copolymer with a longer PDMS block length (202 repeat units) and a higher PDMS bulk concentration (34 mol %).