In the second study on melt-miscible syndiotactic polystyrene (sPS) and poly(phenylene oxide) (PPO) blends, the effect of processing conditions on morphology, ultimate tensile properties, and the mode of fracture is reported. Bulk samples of the blends were molded and then crystallized from melt as well as from the quenched state at different temperatures. The spherulitic morphology of the melt-crystallized blends, observed by scanning electron microscopy, revealed formation of complete, well-developed spherulites whose texture increased in coarseness with increasing crystallization temperatures. In all the cold-crystallized blends lamellar bundles formed a meshlike structure whose texture did not vary significantly with crystallization temperature. Depending on the crystallization temperature, 50/50 melt-crystallized blends showed varying tensile properties and different modes of failure. In the samples with the largest amorphous domain size of 0.6 mum, the amorphous ellipsoids were cold drawn into fibrils during tensile loading and very high tensile strengths were recorded. The tensile properties for the other melt-crystallized and all cold-crystallized blends did not vary substantially with the changing crystallization temperature. The micrographs of the fractured surfaces of the melt-crystallized blends suggested that, although intraspherulitic fracture occurred at low crystallization temperatures, interspherulitic fracture took place at high crystallization temperatures. The correlation of the morphology and mechanical properties suggests that meltmiscible blends have good interfacial adhesion between phases and that, by varying composition and processing conditions, it might be possible to control amorphous domain sizes, which is critical in achieving better mechanical properties. (C) 2003 Wiley Periodicals, Inc.