Synthesis and condensation polymerization of N-silylphosphoranimines: new production methods for poly(alkyl/arylphosphazenes)

Abstract

The poly(alkyl/arylphosphazenes), (R$\sb2$P=N) $\sb{\rm n}$, are a class of phosphazene polymers in which the organic side groups are attached to the polymer backbone via P-C bonds. These materials are generally prepared via the thermal condensation polymerization of suitably constructed N-silylphosphoranimines. Phosphoranimines having trifluoroethoxy (1) or phenoxy (2) groups have been found to be the best poly(alkyl/arylphosphazene) precursors.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) In this investigation, aryloxyphosphoranimines 3 and 4, which can be used in future studies as model compounds or mechanistic probes, were prepared and characterized. These compounds were synthesized by oxidative bromination of a (disilylamino)phosphine followed by the nucleophilic substitution of the halogen atom by a lithiated phenol.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) Dihydroxybenzene derivatives 5 were prepared by a dehydrohalogenation reaction with 2 equiv of the dimethylbromophosphoranimine and 1 equiv of the dihydroxybenzene in the presence of 2 equiv of Et$\sb3$N.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) Other phosphoranimines having chloro (6) and trimethylsiloxy (7) groups were synthesized. These compounds are of interest as potential new precursors to poly(alkyl/arylphosphazenes). The diphenoxyphosphoranimine 8 was also prepared and characterized.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) The results of initial studies of a new production method for poly(alkyl/arylphosphazenes) based upon a catalyzed condensation polymerization of the phenoxyphosphoranimines (e.g., 3 and 4, R$\sp\prime$=R$\sp{\prime\prime}$=H) are described in this dissertation. The phenoxy precursor was heated at ambient pressure along with fluoride, phenoxide, and phosphine oxide catalysts. Initial investigations into the catalyzed condensation polymerization of the chloro- and trimethylsiloxyphosphoranimines 6 and 7 are also described here. The results of these studies indicate that the catalyzed polymerizations of N-silylphosphoranimines (especially with the NaOPh or HMPA catalysts) may be a more efficient route to the poly(alkyl/arylphosphazenes).