Copolymers of epichlorohydrin (ECH) and 1,2-epoxyhexane (EpH) have been synthesized via cationic ring-opening polymerization using BF(3)xTHF as a catalyst. Structures of the resulting polymers have been confirmed by IR and NMR spectroscopy and GPC. In a subsequent reaction with NaN3 in DMSO, the halogenated precursors were completely azidated, which was confirmed by the same spectroscopic methods. The introduced pendant n-butyl chains act as an internal plasticizer by lowering the glass transition temperature (T-g) of the copolymers compared to the reference compound glycidyl azide polymer (GAP). Compared to GAP in a similar molecular weight range, the copolymers also showed reduced viscosity. These properties make the described copolymers interesting candidates for use as energetic binders in cast-cure applications.