Polymers Containing Phosphorus and Nitrogen in the Backbone

Polymers with different groups attached to the phosphorus atom can be obtained from phosphazene cyclic trimers or tetramers with mixed halogen and alkyl or aryl side groups by a similar procedure. Further attachment of side groups, such as fluoroalcoxy, can be achieved by treatment of the polymer with excess of sodium fluoroalkoxides [2], By this procedure are obtained, for example, poiy fluoroaikoxyphosphazenes) with the structure shown below  

In general, polyphosphazenes are not very resilient to heating, but their thermal decomposition occurs with a high degree of crosslinking and the formation of a dense structure that acts as a flame retardant [3], For some copolymers, the presence of phosphazene sequences enhances the thermal stability. Some other literature reports regarding thermal decomposition of these compounds are given in Table 17.2.1. 

Polymer polyldiphenoKy- Temp °C Results Phenoxy cyclic trimer ar d letramer. monoctiloropentaphenoxy cyclic Ref 

Besides the phosphazenes other polymers containing nitrogen and phosphorus are known [9]. Some of such polymers are used as flame retardant additives to other polymers (see Section 5.4). 

Bertsch, M. McKinley, Pittsburgh Conference, February 1998, Paper 1, p.1849. 

---