Side-group-exchange reactions have been studied for short-chain linear oligomeric phosphazenes, (RO)(4)P-[N=P(OR2)](n)OR (n = 6, 10, 20, and 40) as models for the linear high polymers (n similar to 15000). Specifically, the exchange behavior of oligomers where OR = OCH2CF3, OC6H5, OC6H4CHO-p, OC6H4CN-p, and OC6H4NO2-p with sodium trifluoroethoxide was examined. The ease of aryloxy group replacement by trifluoroethoxy increased with the electron-withdrawing character in the order OR = OC6H5 << OC6H4CHO-p < OC6H4CN-p < OC6H4NO2-p, but the reaction was efficient only if the phosphazene contained no more than 20 repeating units. However, attempts to force slower reactions by the use of excess sodium trifluoroethoxide induced secondary reactions at the trifluoroethoxy units already introduced to produce CF3CH2OCH2CF3 and generate -O-Na+ units in their place. The longest chain model underwent side-group-exchange reactions preferentially at the end units. These results are significant for the synthesis of phosphazene high polymers with fluoroalkoxy and aryloxy side groups.