POLYDIALKYLPHOSPHAZENES - NEW SYNTHETIC EFFORTS AND PROTONATION REACTIONS

Some dialkyl-or diaryl-phosphoranimines are so thermally stable that t heir thermal polymerization cannot be pursued; it follows that an alte rnative route to the synthesis of said polymers is to be found. The po lymerization of N-silyldiethylphosphoranimine with the aid of anionic initiators was studied. This reaction, compared with thermal polymeriz ation, proceeded at a lower temperature and with a shorter completion time. Low molecular weights and often bimodal distributions were found . M-w values obtained with Bu4NF and NaOPh were in the range 1000-10,0 00, with very narrow polydispersities. Since symmetrical disubstituted polyalkylphosphazenes with alkyl chains from C-2 up to C-5 are insolu ble in organic solvents, their solution characterization in usual solv ents was prevented. For this purpose, protonation reactions with organ ic and mineral acids were studied. The protonated polymers were found to be soluble in organic acids and in water. NMR spectra were register ed. The molecular weights of the polymers were determined in 20% (v/v) acetic acid. The method, tested on samples of polydimethylphosphazene whose molecular weight was determined independently by membrane osmom etry in chloroform solutions, was found to be reliable.