The morphology transition of binary mixtures of polystyrene-block-poly(butadiene)-block-poly(2-vinylpyridine)( SBV) triblock and polystyrene (PS) homopolymer thin films was investigated as a function of the volume fraction of added homopolymer and the annealing time in benzene vapor. It was found that the weight ratio of PS in the blends influenced the transition process. When PS content was >5%, the order-order transition (OOT) of core-shell cylinders (C) -> sphere in "diblock Gyroid" (sdG) -> sphere in lamella (sL) -> sphere (S) was observed, which was similar to ABC triblock copolymer except for the increased surface area of the PS phase. When PS content reached to 10-30%, the OOT in the sequence of C -> sL -> S was observed. The disappearance of the Gyroid phase is due to the change of the effective volume fraction. Further increasing the PS content, C phase also disappeared and sL -> S was expected to take place. (C) 2014 Wiley Periodicals, Inc.