Polymers Related to Polyphosphazenes

The poly(carbophosphazenes) that have been synthesized are amorphous rather than crystalline, and they appear to retain the same atom sequencing along the chain as in the cyclic trimer from which they are derived. Hence, repeating group scrambling during polymerization does not appear to be a significant component of the process. 

A third variant on the polyphosphazene skeletal structure is represented by the poly(thionylphosphazenes) (reactions (65) and (66)) in which every third phosphorus along the chain is replaced by a sulfur VI atom.266-272 These species are more hydrolytically stable than their sulfur IV analogues, probably because the presence of two side groups on sulfur provides additional protection for the main chain. 

It seems likely that phosphazene polymers with carbon or sulfur in the backbone are the forerunners of many new polymer systems that will be investigated in the coming years. 

The polyphosphazene systems comprise some of the most diverse macromolecules yet discovered. Because of space limitations, many aspects of polyphosphazene chemistry 

In many respects, the polyphosphazenes are the prototype inorganic backbone polymers, that exemplify the principles of ring-opening and condensation polymerization, macromolecular substitution reactions and their potential for molecular design, and an enormous range of derivatives with the same backbone but different organic side groups. 

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