Syntheses and thermal properties of (sulfonylbisphenoxy)-containing cyclotriphosphazene polymers

A (sulfonylbisphenoxy)-containing cyclotriphosphazene polymer system has been prepared by polycondensation of (phenoxy)chlorocyclotriphosphazene and 4,4'-sulfonylbisphenol. The syntheses by polycondensation using sodium salt of 4,4'-sulfonylbisphenol and by interfacial polycondensation were carried out for comparison. The characterization, thermal stability, and fire resistance of the synthesized polymers were studied. Thermogravimetric analysis showed that the polymers prepared were stable to above 400°C in nitrogen and exhibited high char contents at elevated temperature. The result indicated that the presence of a sulfonyl group was helpful for enhancing thermal stability and the presence of a phosphphazene ring was the cause of the high char residue at elevated temperature.