Emulsion templated poly(thiol-enes): Selective oxidation improves mechanical properties

Abstract

Porous thiol-ene polymer networks were prepared with different sulfur contents from high internal phase emulsions (HIPEs). A rigid thiol, tris [2-(3-mercaptopropionyloxy) ethyl] isocyanurate (TEMPIC), together with 1,6-hexanediol diacrylate (HDDA), was employed for this study. A modification of the polymer network was performed via the oxidation of the thioethers present in the polymer backbone to sulfoxides and sulfones. Infrared spectroscopy measurements confirmed that the selective oxidation of thioether groups was possible. Furthermore, the changes in thermomechanical properties were determined by dynamic mechanical analysis and thermogravimetric analysis. A significant increase in glass transition temperature from 4.9 to 41.5 °C for the resulting sulfone could be observed for networks with the highest sulfur content. Changes in mechanical properties were determined via tensile and compression testing and showed considerable improvement of tensile and compressive strength after the oxidation. The behavior of the materials upon hydrolytic stress was investigated and led to the highest mass loss for sulfone materials.