**3. Conclusions**

Four *N*-alkyl phosphoranimines were synthesized and found to be effective chain capping agents for polyphosphazenes prepared by anionic initiation of a phosphoranimine monomer. The NMR and GPC data support their incorporation into the chain as end groups. The use of chain-capping/terminating compounds in the anion-initiated polymerization of a phosphoranimine monomer has been demonstrated and may provide a useful technique for further functionalization of polyphosphazenes. For example, it may be possible to add alkenyl groups to short phosphazene chain ends as a route to prepare inorganic/organic graft copolymers, as well as to prepare block copolymers with controlled molecular weight.

#### **4. Materials and Methods**
