Amino end-terminated poly(L-lactic acid), poly(trimethylene carbonate), and polycaprolactone were synthesized via ring-opening polymerization techniques. The amino terminus was used to form a covalent link to poly(dichlorophosphazene), itself synthesized using a living cationic polymerization. The chlorine atoms in the polyphosphazene blocks were subsequently replaced by trifluoroethoxy groups. This is the first reported synthesis of block copolymers of polyphosphazenes linked to polyesters or polycarbonates. The molecular structure of each copolymer was established using multinuclear NMR techniques. Molecular weight analysis was used to provide confirmatory evidence that the two polymers chains were covalently linked. Thermal analysis results showed evidence that in the solid state the two blocks were phase-separated because the parent thermal transitions were detectable for each copolymer.