Polyphosphazene

Polyphosphazenes are inorganic polymers whose backbone consists of alternating phosphorus and nitrogen atoms ( - R1R2P = N- ). The substituents R1 and R2 are often alkoxy, amino, dialkyl- or diarylamino ( R2N ) or halogen radicals ( such as chlorides or fluorides).

Synthesis

The synthesis of polyphosphazenes can be done in different ways:

• Anionic ring-opening metathesis: polymerization of cyclic phosphazenes
• Cationic ring-opening metathesis: polymerization of cyclic phosphazenes
• Condensation of ammonia and phosphorus trichloride

Often the first chloro -substituted polymer is produced and this is then functionalized by nucleophilic substitutions.

Part of a poly ( difluorphosphazen ) chain as an example of a polyphosphazene ( NPF2 ) n

Properties

The properties are heavily dependent on the substitution at the phosphorus atoms, but often can be found the following properties:

• Elasticity
• Glass transition temperatures can be up to -100 ° C.
• Biocompatibility

Applications

Polyphosphazenes can be used as elastomers. In the future, medical applications could be considered. Thus, research is being done to use them as a framework for a faster bone regeneration. In this case, it would act as a supporting structure element, which can be degraded over time by hydrolysis in the body to phosphates and amines.