The reaction of poly (difluorophosphazene), (NPF2)n, with phenyllithium, followed by treatment with sodium trifluoroethoxide, has yielded a new class of high polymeric organophosphazenes of formula [NP(C6H5)x(OCH2CF3)y], where x and y are 0.38 and 1.62, 0.64 and 1.36, 0.98 and 1.02, or 1.24 and 0.76, respectively. The macromolecules are the first examples of high molecular weight phosphazene polymers that contain a substantial number of organic groups bound directly to the skeleton through carbon-phosphorus bonds. The new polymers are nonelastomeric, film-forming materials with molecular weights (GPC average) above 1 X 106 and with glass transition temperatures at +7, +25, +45, and +60 °C, respectively. The structural characterization was by means of 31P and 1H NMR spectroscopy and by microanalysis. The replacement of fluorine in (NPF2)n by phenyl is accompanied by a skeletal cleavage reaction. However, chain cleavage is significant only after 70% or more of the fluorine atoms have been replaced by phenyl. Although fully phenylated polymers of formula [NP(C6H5)2], were prepared, the molecular weights were low (GPC average mol wt = 50 000-80000), with a glass transition temperature of +70 °C. The mechanisms of substitution and chain cleavage are discussed, and comparisons with the behavior of (NPC12)n are made. Thermolysis studies suggest that the phenyl side groups enhance the thermal stability of the polymers compared to the behavior of [NP(OCH2CF3)2]n.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry