Dissipative particle dynamics (DPD) simulations were used to investigate the interfaces of incompatible glycidyl azide polymer (GAP)/hydroxyl-terminated polybutadiene (HTPB) blends in the presence of block copolymers and plasticizers. They were GAP-b-HTPB copolymers and commonly used nitrate ester or inert plasticizers in the formulations of propellants. The results show that there were two abilities that determined the effects of the block copolymers and plasticizers on reducing the interfacial tension (?). These were the penetrability into each homopolymer phase and the ability for assembling at the interface. The plasticizers mainly depended on the first ability, and the block copolymers depended on the other ability. In addition, block copolymers with the different chain lengths had the different influences on ? of the GAP/HTPB blends. Moreover, this phenomenon could also be explained by the above two abilities. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012