The thermal polymerization behavior of cyclic trimeric phosphazenes that bear organosilylmethylene or organosiloxymethylene side groups, of general formula N3P3C15R, gem-N3P3C14R2, and gem-N3P3C15R(CH3)R, where R = CH2SiMe3, CH2SiMe2OSiMe3, and CH2Si(Me)(OSiMe2)3O, has been studied. Species N3P3Cl6CH2SiMe3, gem-N3P3C14(CH2SiMe3)2, and gem-N3P3C14(CH3)R undergo a phosphazene ring-opening polymerization to yield phosphazene high polymers that bear organosilicon side groups. However, those compounds of formula N3P3C15R and gem-N3P3C14R2 where R = CH2SiMe2OSiMe3 and CH2Si-(Me)(OSiMe2)3O undergo thermally induced PCH2-Si and Si-0 bond cleavage reactions in preference to polymerization. The neopentyl derivative, N3P3C15CH2CMe3, polymerized at 250 °C, but gem-N3P3C14-(CH3)(CH2CMe3) did not. However, both compounds copolymerized with their organosilicon counterpart, i.e., with N3P3C15CH2SiMe3 and gem-N3P3C14(CH3)(CH2SiMe3), respectively. Possible explanations for these results are presented. The high polymers formed by these reactions were treated with sodium trifluoroethoxide to yield derivatives in which the hydrolytically sensitive P-Cl bonds were replaced by stable P-OCH2CF3 units. Under certain conditions these substitutions resulted in the concurrent cleavage of the PCH2-Si side group bonds to yield P-CH3 units in their place. Use of this technique has allowed the first synthesis of the polymer [[NP(OCH2CF3)2]2-[NP(CH3)2]]n. The behavior of the cyclotetrasiloxane side group under siloxane polymerization conditions is also discussed. The characterization, structure, and properties of the high polymers are also described.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry