Robert A. Montague

Synthesis of polyphosphazenes from phosphoranimines and phosphine azides

Abstract A number of phosphoranimines were prepared via the Staudinger coupling of the suitably substituted phosphite with trimethylsilyl azide. These compounds were polymerized under various conditions using fluoride initiators and then characterized by 1H and 31P nuclear magnetic resonance, size exclusion chromatography versus polystyrene standards, and differential scanning calorimetry. The condensation by-products of the polymerization were analysed by gas chromatography-mass spectrometry. Mechanistic details of these polymerizations are also discussed. N-Blocked phosphoranimines were prepared and used as chain terminators to control the molecular weights of these polymers. Several random copolymers were produced by the simultaneous polymerization of two phosphoranimines, and the first reported block copolymers were synthesized by the homopolymerization of one monomer followed by the subsequent addition of a second. The synthesis of the first soluble aryl-substituted polyphosphazenes via the phosphine azide route is also discussed.

The Conversion of Phosphoranimines to Polyphosphazenes in the Presence of Electrophiles

Abstract The application of electrophilic compounds as initiators for the polymerization of N-silylated phosphoranimines represents a new and rapid method for the synthesis of low to moderate molecular weight polyphosphazenes. Several Bronsted and Lewis acids were studied, and antimony pentachloride was found to be particularly effective. Complete conversion of a phosphoranimine monomer was observed within 2 hours under mild conditions (ca. 100°C) in solution polymerization with SbCl5. Poly[bis(trifluoroethoxy)phosphazenes] of molecular weight M n = 10,000 to 50,000 were obtained with low to moderate polydispersities (M w/M n = 1.2 to 2.5) and were characterized by NMR, IR, GPC, and DSC techniques. Kinetic and mechanistic evidence support SbCl5 as the true initiator, whereas the Bronsted haloacetic acids were found to initiate polymerization by the corresponding anions without the involvement of protons.

THE THERMAL-PROPERTIES OF POLYPHOSPHAZENES SYNTHESIZED BY THE ANIONICALLY INITIATED POLYMERIZATION OF PHOSPHORANIMINES

Abstract The thermal properties of a number of polyphosphazene random and block copolymers synthesized by the anionic polymerization of phosphoranimines have been examined by differential scanning calorimetry and correlated with variable-temperature wide-angle X-ray scattering. These studies show the effect of structure, molecular weight, composition, side groups and thermal history on the thermal transitions of these materials. In addition, annealing studies were performed to estimate the degree of crystallinity and attempts were made to detect microphase separation by small-angle X-ray scattering.