Ring Expansion and Polymerization of Transannular Bridged Cyclotriphosphazenes and Their Spirocyclic Analogues

Harry R. Allcock, Michael L. Turner

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30 Scopus citations


The ring expansion and polymerization reactions of the transannular substituted cyclotriphosphazenes 1,3-[N3P3(OCH2CF3)4(X2R)] (X2R = 1,2-dioxyphenyl, 2,2′-dioxybiphenyl, 1,8-dioxynaphthyl, and 1,8-diaminonaphthyl) are described and are compared to the behavior of the analogous spirocyclic cyclotriphosphazenes 1,1-[N3P3(OCH2CF3)4(X2R)] (X2R = 2,2′-dioxybiphenyl, 1,8-dioxynaphthyl, and 1,8-diaminonaphthyl). When heated at temperatures above 200 °C, transannular 1,3-[N3P3(OCH2CF3)4(2,2′-O2C12H8)]and spirocyclic 1,1-[N3P3(OCH2CF3)4(2,2′-O2C12H8)], 1,1-[N3P3(OCH2CF3)4(1,8-O2C10H6)], and 1,1-[N3P3(OCH2CF3)4{1,8-(NH)2C10H6}] underwent ring-ring equilibration to yield higher cyclic species that ranged from the cyclic tetramer to dodecamer. When heated in the presence of 1% (NPCl2)3, as a polymerization initiator, small amounts of low molecular weight polymer are also formed. By contrast, thermolysis of transannular 1,3-[N3P3(OCH2CF3)4{1,8-(NH)2C10H6}], 1,3-[N3P3(OCH2CF3)4(1,8-O2C10H6)], and 1,3-[N3P3(OCH2-CF3)4(1,2-O2C6H4)] at temperatures above 200 °C, in the presence or absence of (NPCl2)3, resulted in ring-opening polymerization to give low molecular weight poly(organophosphazenes). The balance between ring-ring equilibration and ring-opening polymerization is discussed in relation to the ability of the transannular organic group to generate ring strain and destabilize the cyclic trimer with respect to the linear polymer.

Original languageEnglish (US)
Pages (from-to)3-10
Number of pages8
Issue number1
StatePublished - 1993

All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry


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