Glycidyl azide polymer (GAP) is an energetic alternative to hydroxyl-terminated polybutadiene (HTPB), but has poorer mechanical properties. Since HTPB-GAP mechanical blends are markedly biphasic, the use of block copolymers may be the solution to join the advantages of both. The copolymers were synthesized from the homopolymers by using two chain extenders: hexamethylene diisocyanate (HDI) and adipoyl chloride (AdCl). Both reagents gave homogeneous and stable polymeric mixtures, but with HDI there are risks of gelation during reaction. Therefore, the product obtained with AdCl is the best candidate to be used as binder or as compatibilizer in GAP-HTPB mechanical blends.