Fluorophosphazenes

Applications. Among the P—O- and P—N-substituted polymers, the fluoroalkoxy- and aryloxy-substituted polymers have so far shown the greatest commercial promise (14—16). Both poly[bis(2,2,2-trifluoroethoxy)phosphazene] [27290-40-0] and poly(diphenoxyphosphazene) [28212-48-8] are microcrystalline, thermoplastic polymers. However, when the substituent symmetry is dismpted with a randomly placed second substituent of different length, the polymers become amorphous and serve as good elastomers. Following initial development of the fluorophosphazene elastomers by the Firestone Tire and Rubber Co., both the fluoroalkoxy (EYPEL-F) and aryloxy (EYPEL-A) elastomers were manufactured by the Ethyl Corp. in the United States from the mid-1980s until 1993 (see ELASTOLffiRS,SYNTHETic-PHOSPHAZENEs). 

This material had poor hydrolytic stability and was no more than a laboratory curiosity. Treatment with sodium trifluoroethoxide and heptafluorobutoxide has recently been found to yield a useful fluorophosphazene polymer ... 

Tris(trimethylstannyl)amine reacts readily with fluorophosphazenes with cleavage of the Sn—N bond 119 e.g. 

An extensive study of the Friedel-Crafts phenylations of a wide variety of aminophosphazenes have been conducted [230-233]. Reactions at the PCI2 centre is generally sluggish. With the bulky secondary amino derivatives, hydrocarbon formation is the competing process [232]. Aryl fluorophosphazenes undergo Friedel-Crafts arylation readily [182, 234-236]. These reactions have been used to convert a P(Ar)F centre to a P(Ar)(Ar ) centre (Eqs. 43,44) [234]. 

Hexachlorocyclotriphosphazene (3.19) is prepared on an industrial scale by the interaction of phosphorus pentachloride with ammonium chloride in an organic solvent such as chlorobenzene. This compound, after careful purification and protection from moisture, is heated in the molten state at temperatures between 210 and 250 °C to induce polymerization.15-18 The mechanism of this reaction is discussed in a later section. Here it is sufficient to note that the process can also be applied, with minor variations, to cyclic phosphazo-phosphazenes (3.22a, 3.23), to cyclic fluorophosphazenes (3.24,3.25), and to cyclic carbo- (3.26), thio- (3.27), and thionyl (3.28) -phosphazenes. 

---