Phosphorus-Containing Polymers—The Phosphazenes

Abstract

Rubber-like networks made from polyphosphazene chains were reported as early as 1897 by Stokes.¹ One particular compound, poly(dichlorophosphazene), came to be known as “inorganic rubber” because of the similarity of many of its mechanical properties to those of natural rubber. Thermal decomposition of the polymer did not commence until about 300°C, but rapid hydrolysis to inorganic salts in moist air precluded any practical applications. Much effort was devoted to overcoming this problem by the synthesis of analogous polymers without halogen groups, or by attempting total replacement of the halogen groups in the polymer itself. The early attempts were frustrated by the insoluble, intractable nature of the materials produced and the consequent difficulties of chemical modification and processing. The first report of the preparation of a linear, high-molecular-weight poly(dichlorophosphazene), which was completely soluble in benzene, was made by Allcock and Kugel in 1965.² The chloro groups of this polymer could be completely replaced by others to yield products of good hydrolytic stability.