We synthesized star-shaped 18-arm polystyrene-block-poly(3-dodecylthiophene) copolymers ((PS-b-P3DDT)(18)) having lamellar microdomains, based on the cyclodextrin (CD) core. Without any surface modifications on a silicon substrate, thin films of (PS-b-P3DDT)(18) showed vertically oriented lamellar microdomains by thermal annealing. This is attributed to the entropic penalty induced by star-shaped chain architecture. In contrast, a parallel orientation was observed in the film morphology of the corresponding linear PS-b-P3DDT. We also found that the P3DDT crystals were confined in the lamellar microdomains of (PS-b-P3DDT)(18) as edge-on structure.