Thermal Ring Opening Polymerization
Polyphosphazenes are a broad class of macromolecules with the highly flexible inorganic phosphorus-nitrogen backbone.
The side groups R are chosen from a wide variety of organic, organometallic or inorganic units. More than 700 examples of these polymers have been synthesized, all with the same backbone but with different side groups. Thus, polyphosphazenes are the most versatile class or organic/inorganic polymers known.
A critical intermediate in the synthesis of polyphosphazenes is poly(dichlorophosphazene). This is usually obtained by the thermal ring-opening polymerization of hexachlorocyclotriphosphazene.
Ring-Opening Polymerization
From this one macromolecular intermedate, many different polymers may be generated. Macromolecular substitution reactions are readily performed on poly(dichlorophosphazene). The highly reactive nature of the P-Cl bonds allows the substitution reactions to occur in near quantitative yield. Over 30,000 substitution reactions typically occur on each polymer chain.
Macromolecular Substitution
The final properties of the polymer depend both upon the backbone and the side groups. Thus, this process allows the tuning of polymer and materials properties over a much broader range than is possible in most polymer systems.