SYNTHESIS OF CYCLOPHOSPHAZENES AND POLYPHOSPHAZENES WITH PYRIDINE SIDE-GROUPS

New types of cyclo- and polyphosphazenes that bear pyridine side groups have been synthesized. The reactions of 2-(2-aminoethyl)pyridine and 2-(2-aminoethyl)amino)-5-nitropyridine with (NPCl2)3 were complex, with chlorine replacement being complicated by degradation and the formation of mixtures. However, the use of electron-withdrawing cosubstituents, such as phenoxy or trifluoroethoxy groups, allows straightforward chlorine replacement reactions induced by the aminoalkylpyridines to occur. The mono(alkylpyridine)-substituted cyclotriphosphazenes N3P3(OC6H5)(5)(NHCH2CH2(C5H4N)) (1) and N3P3(OC6H5)(5)(NHCH2CH2NH(C5H3N)NO2) (2) were synthesized as model compounds for high polymers. Polyphosphazenes of the general formula [NP(OCH2CF3)(x)(NHCH2CH2(C5H4N))(y)](n) were prepared by exposing [NPCl2](n) to sodium trifluorethoxide and 2-(2-aminoethylpyridine in a two-step reaction. All compounds were characterized by H-1, C-13, P-31 NMR spectroscopy, and elemental analysis. The cyclic trimers were also identified by mass spectrometry. Molecular weight estimations of the polymers were carried out by gel permation chromatography, and glass transition temperatures were determined by differential scanning calorimetry.