SynopsisCarborane substituted polyphosphazenes were prepared by the thermal polymerization of phenyl-carboranyl penta chlorocyclotriphosphazene. Successive isothermal vacuum pyrolyses were conducted on the polymer and examined for structural changes by infrared spectroscopy.The degradation products were ascertained by gas chromatography-mass . . spectrometric analysis. It was found that the presence of the carborane group improves the thermal stability of the polymer by retarding the ring-chain equilibrium processes of decomposition. The alternating phosphorus and nitrogen atoms in the backbone of phosphazene polymers is responsible for the high degree of torsional mobility and accounts for the low glass transition temperature (Tg) values and the transparency of the polymer to ultraviolet radiation. lThe susceptibility of the phosphorus-chlorine bond to hydrolysis has been surmounted by nucleophilic substitution reactions ( Fig. 1) involving the replacement of halogen atoms of polydichlorophosphazenes by alkyl, aryl, amino, alkoxy, and aryloxy groups. 1-4 'Hydrolysis of the hexachlorocyclotriphosphazene trimer to the oxophosphazane (Fig. 2, . \ ref. 5), which is thermally unstable due to its P-N-P type bonding.The addition of the phenylcarborane group on thehexachlorocyclotriphosphazene ring followed by thermal polymerization and the replacement of remaining chlorine atoms with trifluoroethoxy groups (Fig. 3) result in an enhancement of the thermal stability of phosphazene polymers. Analytical EquipmentInfrared spectra were recorded on a Nicolet MX-l, Fourier Transform Infrared spectrometer. Gas chromatograp~y-mass spectrometric analysis of the polymer's decomposition products was accomplished using a Hewlett-Packard model #57l0A gas chromatograph with a 6-ft column packed with 3% OV 101 on 80/100 mesh Supelcoport AWDC and interfaced with an all-glass jet separator to a Hewlett-Packard model #5980A massspectrometer computer system. Successive pyrolyses of the polymer were conducted using a Chemical Data Systems model #120 Pyroprobe by heating the identical sample (2 mg) for 40 sec at ,the desired pyrolysis temperature. After analysis of the pyrolysis products the probe was allowed to cool before subjecting the polymeric residue to the next'pyrolysis temperature for the same time period. To the freshly prepared phenyl-lithiocarborane solution, the trimer (I) (2.2 gm, 6.3 mmoles) which was dissolved in 15 m1 anhydrous ether was added by drops with vigorous stirring at DoC within approximately 15 min. The mixture was allowed to warm slowly to ambient temperature and stirred for an additional 12 hr. The solvents were removed and the solid material,placed in a vacuum sublimator (60°C, evacuated to 0.05 rnm) after which the sublimable solid compounds were removed. The temperature of the oil bath was then increased to 5 l300e to yield a crystalline sublimate which was further purified by recrystallization from hexane (m.p. was l33°e) and confirmed by infrared spectroscopy (Fig. 5). Polymerization of Phenylcarboranyl-p...
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