Thermal gravimetric analysis (TGA) was used to assess the thermal stability of these BSE-based HDPE samples under ambient atmosphere. While most studies of PE-like materials have not investigated thermal stability, Wurm and coworkers reported that ROMP-derived PE mimics with orthoester backbone linkages displayed a decomposition temperature >100 ºC less than that of HDPE. We hypothesized that the high bond dissociation enthalpy of Si-O bonds may impart favorable thermal stability to BSE-based PE mimics. In support of this hypothesis, our samples displayed decomposition temperatures within ~10-20 °C of commercial HDPE even at the highest BSE loading (Figure ), with Et-substituted BSE showing slightly lower thermal stability compared to their i Pr counterparts, which may be due to its lower hydrolytic stability. We also note the absence of a two-stage decomposition profile, indicating that the BSE segments and methylene segments have similar thermal stability. The slightly reduced stability of our mimics compared to HDPE may be due to the presence of residual Ru, hydrolytic cleavage of the BSEs, or differences in the molar masses, and therefore chain end density, of the two samples. Nevertheless, these results support our hypothesis that BSEs, while susceptible to selective cleavage (vide infra), mostly maintain the thermal stability of HDPE.