ABSTRACT
Phosphazenes are ring or chain compounds consisting of alternating phosphorus-nitrogen atoms with two substituents attached to phosphorus. Representative structures are shown below. In these structures, R can be a halogen, organo, or organometallic substituent; X is generally a halide or metal halide counterion. The physical properties of phosphazenes vary considerably with molecular weight and choice of substituents (R). Many of the cyclic phosphazenes are either liquids or low-melting crystalline solids. As the molecular weight is increased, either by the size of the substituent or the number of P-N repeat units, one can obtain oils and greases; ultimately, elastomers and thermoplastics are formed.
