The copolymerization of a cyclic hydrocarbon with a cleavable comonomer via ROMP, followed by hydrogenation of the copolymer backbone, is an established strategy to produce PE-like materials; however, most previous reports use a stoichiometric amount of initiator (e.g., 1 equiv. of Grubbs 1 st or 2 nd -generation complex per polymer chain), which leads to high metal content, and/or perform hydrogenation in a second step, which adds cost and time. Additionally, chemical recyclability of such polymers has not been demonstrated, nor have their tensile properties been directly compared to commercial HDPE. Here, we developed a protocol using a chain transfer agent-cis-4-octene-and an in situ hydrogenation process to access PE-mimics in one pot with very low loadings of ROMP initiator (0.004 mol%). BSEbased monomers with Et or i Pr Si-substituents (EtSi8 or i PrSi8) were synthesized from commercially-available materials according to literature protocols; copolymerization of these monomers with cyclooctene (CO) via ROMP was investigated (Scheme 1). Three copolymers with varied BSE content were synthesized using each BSE comonomer to give 6 polymers in total (CO/R2Si8 = 10, 50, 100, Scheme 1, Table ) following the same general procedure: CO, cis-4-octene CTA (0.33 mol% relative to the moles of alkenes; [RSi8 + CO]0 : [CTA] = 300), and BSE comonomer were dissolved in 2methyltetrahydrofuran (2-MeTHF; 1M relative to the total monomer concentration) under inert atmosphere; Grubbs 3 rdgeneration bis-pyridyl complex (0.004 mol% relative to the moles of alkenes; [RSi8 + CO]0 : [G3] = 25,333) was added and the reactions were stirred at room temperature for 2 h. Quantitative conversions of both monomers and complete BSE incorporation were observed by 1 H NMR spectroscopy (Figures ). The reactions were quenched with excess ethyl vinyl ether. While the resulting Fischer carbenes have been shown to be active hydrogenation catalysts at high hydrogen pressures, we found that adding a small amount (0.1 mol % relative to the moles of alkenes; [RSi8 + CO]0 : [Cat.] = 1,000) of Wilkinson's chlorotris(triphenylphosphine)rhodium(I) complex directly to the crude reaction mixture enabled complete hydrogenation under much less energy-intensive conditions (room temperature in 24 h using 1 atm H2).