A series of all-conjugated diblock and triblock copolymers comprised of poly(naphthalene diimide) (PNDI)-based n-type and the poly(3-hexylthiophene) (P3HT) segments could be synthesized via the Kumada catalyst-transfer polycondensation process. The crystalline structures and chain orientation of the block copolymer thin films were systematically studied by grazing incident wide-angle X-ray scattering (GIWAXS). The GIWAXS results indicated that both the P3HT and PNDI segments in the block copolymers form exclusive crystalline domains in which the P3HT domain aligns with an edge-on rich orientation, and the PNDI domain aligns with a face-on rich orientation. In contrast, the blend films of the P3HT and PNDI homopolymers also show two distinguished crystalline domains in which the P3HT domain aligns with an edge-on rich orientation, and the PNDI domains align in different ways depending on the chemical structure of n-type polymers, that is, PNDI1Th is isotropically dispersed, while PNDI2Th aligns with a face-on rich orientation. In addition, the effect of thermal annealing on the crystalline behavior of the block copolymers is reported. The GIWAXS results indicated that thermal annealing increases the crystallinity of both segments without affecting their chain orientation. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1139-1148