Sulfone-containing polythioethers, compositions containing sulfone-containing polythioethers, methods of synthesizing sulfone-containing polythioethers and the use of sulfone-containing polythioethers in aerospace sealant applications are disclosed. The sulfone-containing polythioethers have sulfone groups incorporated into the backbone of the polythioether. Cured sealant compositions comprising the sulfone-containing polythioethers exhibit enhanced thermal resistance.