SYNTHESIS AND PROPERTIES OF HIGH POLYMERIC PHOSPHAZENES WITH (TRIMETHYLSILYL)METHYL SIDE GROUPS

Poly(organophosphazenes) that bear Me3SiCH2 side groups were prepared via the reaction of [(trimethylsilyl)methyl]lithium with poly(phenylfluorophosphazene) ([NP(Ph)F(NPF2)2]n). Fluorine replacement occurred under mild conditions to yield polymers that contained up to 70% of the side groups as alklsilyl units. Subsequent reaction with CF3CH2ONa gave air- and moisture-stable polymers with the basic stoichiometry of [NP(Ph)0.34(OCH2CF3)1.66-x(CH2SiMe3)x]n. The polymers were analyzed by P-31, H-1, and F-19 NMR spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Replacement of the fluorine atoms by Me3SiCH2 side groups was accompanied by some skeletal cleavage. However, high molecular weight polymers were obtained by limiting the reaction time and temperature. Evidence was obtained that the organosilicon side groups are the sites of cross-linking reactions when the polymers are heated at temperatures above 200-degrees-C.