An efficient continuum-space model for simulating polymer blends and copolymers is presented. In this model, the interactions are short-range and purely repulsive, thus allowing for excellent computational performances. The driving force for phase separation is a difference in the repulsive interaction strength between like and unlike mers. To demonstrate the effectiveness of the model, we study the phase behavior of a symmetric binary blend of polymers as well as the interface between the two immiscible phases. As predicted by theory, we find the critical interaction parameter to scaie with the inverse of the chain length of the polymers. The structure of the interface between two immiscible phases is investigated as a function of chain length and immiscibility. Capillary waves are observed and their measurementallows us to determine the surface tension accurately. Finally, the surface tension is related to the interface width.