Poly organophosphazene s Prepared by Macromolecular Substitution of

6 Poly(organophosphazene)s Prepared by Macromolecular Substitution of [NPCbJn 

This type of a reaction is quite general. Thus, the reaction of [NPClajn with RONa (R = alkyl or aryl) affords the corresponding polymers [NP(OR)2]n- Similarly, the reactions of [NPCyn with primary or secondary amines affords the corresponding amino derivatives [NP(NHR)2]n and [NP(NR2)] (Fig. 3.33) [21-23]. 

Even exotic substituents such as those containing metal carbonyl units can be introduced by the nucleophilic substitution reaction (Fig. 3.34). 

Other representative examples of polyphosphazenes that have been prepared by the macromolecular substitution of [NPC Jn are shown in Figs. 3.35-3.36. 

There are two remarkable aspects of the macromoleeular substitution reaction that need to be mentioned. This involves about 30,000 nucleophilic substitution reactions per polymer molecule This means that for every reacting polymer molecule 30,000 chlorine atoms are being replaced. The obvious disadvantage of the parent polymer [NPCUln is turned around as 

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