Even with as little as 10% DCPD content by mass the glass transition temperature increased to over 120 °C. In contrast, the 50-poly(S-r-CPD) made using the gas phase method had the lowest Tg because no DCPD was incorporated into the polymer, as it will remain in liquid form in the CPD reservoir in the reactor at 140 ºC and not be circulated into the molten sulfur. Importantly, using the optimized polymerization methods, no unreacted sulfur was detected by DSC and no sulfur blooming was observed after more than 1 year of storage of 50-poly(S-r-CPD) -a problem previously reported by Boyd other sulfur polymer systems . Raman spectroscopy, however, was used to detect crystalline S8 in some batches of 67-poly(S-r-CPD), which we regard as the practical upper limit of sulfur content for this system.