31P MAS NMR Spectroscopy of Hexachlorocyclotriphosphazene at Different Stages During Thermal Ring-Opening Polymerization

Thermal ring-opening polymerization of hexachlorocyclotriphosphazene was probed using P-31 magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The spectrum of unreacted hexachlorocyclotriphosphazene was compared with the spectra of a reaction mixture at 3, 8 and 17.5 h of polymerization. Signals from trimer, oligomer, polymer and hydrolysis products were identified in the spectra and used to observe changes in the mixture during polymerization. The signal of poly(dichlorophosphazene) exhibits a complex behavior where ten individual components were observed and analyzed by deconvolution. These lines were preliminarily assigned to species with differing chain lengths based on their chemical shifts and relative intensities. This work shows that P-31 MAS NMR has the potential to provide quantitative information about the rates of chain propagation and cross-linking during thermal ring-opening polymerization.