P. Das, Erik M. Indra, L. Belfiore
Dec 1, 1997
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0
Influential Citations
8
Citations
Journal
Polymer Engineering and Science
Abstract
An allylphenoxy-substituted polyphosphazene has been modified via inorganic chemical concepts. The transition metal salt is bis(acetonitrile)dichloropalladium(II). The coordination complexes have been characterized using acid-base solution chemistry, sol-gel phase transitions, thermomechanical property measurements and infrared spectroscopy. Solid complexes of polyphosphazene and PdC1 2 cannot be dissolved in the original solvent (i.e., tetrahydrofuran) used during sample preparation. These polymeric palladium complexes also cannot be disrupted by a stronger base, like triphenylphosphine. There is a monotonic increase in the glass transition temperature at higher concentrations of palladium chloride. T g of the pure polymer increases by 21°C in the presence of 10 mol% palladium chloride. The increase in high-strain mechanical properties cannot be explained solely by a filler effect. At higher PdC1 2 concentrations, there is a direct correlation between the enhancement in T g , higher mechanical fracture stress, and increased infrared absorbance @ 1092 cm -l because of the formation of a palladium-π-complex with allylic substituents in the phenoxy sidegroup. Palladium chloride relinquishes its acetonitrile ligands after dissolution in THF, and the vacant sites in the first-shell coordination sphere of the transition metal are occupied by these allylic substituents in the sidegroup. This produces interchain coordination crosslinks, which modify the thermomechanical properties of polyphosphazene/ PdCl 2 complexes.