A New Route for Poly(organophosphazene) Synthesis. Polymerization, Copolymerization, and Ring-Ring Equilibration of Trifluoroethoxy-and Chloro-Substituted Cyclotriphosphazenes

The phosphazene cyclic trimer, [NP(0CH2CF3)2]3 (X), copolymerizes with (NPC12)3 (I) to yield a new series of elastomers and also undergoes ring-expansion reactions at elevated temperatures. The copolymers were characterized by means of substitution reactions and 31P NMR analysis. The possibility that the polymerization involves a prior ligand exchange was investigated through studies of the thermal behavior of the cyclic phosphazenes, NaPsCWOCHaCFa) (V), NjPaCWOCHaCFah (trans nongem) (VI), NgPaClafOCHaCFah (trans nongem) (VII), N3P3Cl2(OCH2CF3)4 (cis nongem) (VIII), and N3P3C1(0CH2CF3)5 (IX). All these mixed substituent trimers underwent ring expansion reactions when heated, but only compounds V, VI, and VII yielded linear-type polymers. The gas, CF3CH2CI, was detected as a product from all systems that contained both P-Cl and P-OCH2CF3 bonds, with substantial quantities being released at temperatures above 250 °C. This process was apparently connected with the formation of trans-annular-linked cyclic compounds, cross-linked linear chains, or cyclolinear or cyclomatrix-type products. The mechanisms of these reactions are discussed.