Some elastic and thermoelastic properties of two organophosphazene polymers

Samples of the alkoxyphosphazene polymer P(OCH₃)₂? N? ]_x and the aryloxyphosphazene polymer P(OC₆H₅)(O-p-C₆H₄C₂H₅)? N? ]_x were crosslinked using γ-radiation. The resulting elastomeric networks were characterized, in elongation, with regard to both their stress-strain relationships and their stress-temperature (“thermoelastic”) properties. Values of the ratio 2C₂/2C₁ of Mooney–Rivlin constants used to characterize the stress-strain isotherms were found to be similar to those of other elastomeric networks of comparable degree of crosslinking. The thermoelastic data show the energetic component of the retractive force to be positive for the alkoxy polymer, but negative for the aryloxy polymer. Although it is not difficult to suggest a possible molecular explanation for some of these thermoelastic results, a definitive interpretation would require reliable information on the conformational characteristics of the skeletal bonds in the polyphosphazene chain.