文摘
The synthesis of dynamic covalent polymers with controllable amounts of sulfur鈥搒ulfur (S鈥揝) bonds in the polymer backbone via inverse vulcanization of elemental sulfur (S8) and 1,3-diisopropenylbenzene (DIB) is reported. An attractive feature of the inverse vulcanization process is the ability to control the number and dynamic nature of S鈥揝 bonds in poly(sulfur-random-(1,3-diisopropenylbenzene)) (poly(S-r-DIB) copolymers by simple variation of S8/DIB feed ratios in the copolymerization. S鈥揝 bonds in poly(S-r-DIB) copolymers of high sulfur content and sulfur rank were found to be more dynamic upon exposure to either heat, or mechanical stimuli. Interrogation of dynamic S鈥揝 bonds was conducted in the solid-state utilizing electron paramagnetic resonance spectroscopy and in situ rheological measurements. Time-dependent rheological property behavior demonstrated a compositional dependence of the healing behavior in the copolymers, with the highest sulfur (80 wt % sulfur) content affording the most rapid dynamic response and recovery of rheological properties.