The following protocol is for 50 wt % DIB polymer: Briefly, elemental sulfur (S8, 2 g, 7.81 mmol) was added to a vial and heated to 185 C in an oil bath under vigorous stirring. Once 185 C was reached, DIB (2.16 mL, 12.6 mmol) was injected, the whole mixture agitated with a glass rod and stirred for 4e5 min.