Solvent effect on simple and high yield synthesis of polydichlorophosphazene precursor Cl3P=NSiMe3

Abstract

The condensation polymerisation of Cl3P=NSiMe3 at room temperature is one of the best methods for polydichlorophosphazene production. The living cationic nature of the polymerisation mechanism of this material enables unique features such as the preparation of well-defined block and star polymers or organic-inorganic hybrid copolymers. Therefore, a reproducible high yield synthesis of Cl3P NSiMe3 from readily available and cheap chemicals under mild conditions is an important issue to be solved. In this study, PCl5 was reacted with hexamethyldisilazane at 0 degrees C in various solvents to investigate the formation efficiency of Cl3P=NSiMe3. H-1 and P-31 NMR spectroscopic techniques were used to monitor the reaction progress and detect the available intermediates in the reaction mixture. Nonpolar solvents such as n-pentane highly decreased the formation of the side products such as Cl3P=NH and cyclic phosphazene derivatives. Thus, the isolated yield of Cl3P=NSiMe3 was increased up to 75%. The purity of Cl3P=NSiMe3 was over 97%, which was confirmed using H-1, P-31, C-13 and Si-29 NMR spectroscopic techniques. Moreover, the reaction carried out in toluene led to the direct fabrication of polydichlorophosphazene in one-pot from PCl5 and hexamethyldisilazane in high yield (similar to 94%) and without the isolation of any phosphazene intermediate.