Studies on the mechanism of phosphazene ring-opening polymerization (ROP)

Bilge S.

Turkish Journal of Chemistry, vol.35, no.5, pp.745-756, 2011 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 35 Issue: 5
  • Publication Date: 2011
  • Doi Number: 10.3906/kim-1105-16
  • Journal Name: Turkish Journal of Chemistry
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, TR DİZİN (ULAKBİM)
  • Page Numbers: pp.745-756
  • Keywords: ROP, polyphosphazenes, carboranes, spectroscopy, PHOSPHONITRILIC COMPOUNDS, POLYPHOSPHAZENES, KINETICS, ALKOXY
  • Ankara University Affiliated: Yes

Abstract

In this study, the ring-opening polymerization (ROP) of cyclic trimer N3 P3 Cl6 catalyzed by [Et3 Si(N3P3 Cl6)][CHB11 H5 Br6] (3) obtained from the reaction of N3 P3 Cl6 (1) and Et3 Si(CHB11 H5 Br 6) (2) at room temperature was investigated. This provided a unique opportunity to explore the polymerization mechanism. The coordinatively unsaturated cation [N3 P3 Cl5]+ is responsible for the ROP of N3 P3 Cl6, and is formed by the intramolecular elimination of Et3 SiCl from 3. The detection of Et3 SiCl by 1H-NMR as the catalysis proceeded offers new evidence for the formation of [N3P3 Cl 5]+. The progress of the catalysis was followed using 31P-NMR and revealed the build-up of a polymer. Cyclic phosphazenes with rings larger than that of N3 P3 Cl6 [(Cl2 P=N)n (n= 4-7)] were observed fairly early in the course of the ROP. The propagation of that polymerization at room temperature proceeded via a living cationic mechanism.