In summary, we report the synthesis of PE mimics containing Si-O bonds by a one-pot, sequential ROMP and hydrogenation process that leverages low loadings of Grubbs catalyst (0.004 mol %) and mild hydrogenation conditions (1 atm, room temperature). The polymers display thermal stability on par with HDPE, while the concentration of BSE units in the polymer chain and the steric bulk around each silicon atom influence the melting temperatures, crystallinities, and lamellar thicknesses of the copolymers, providing tunable handles to control processing parameters. Our method enables the synthesis of the highest-reported molecular weights for ROMP-derived HDPE mimics, which provides the first examples of such materials with mechanical properties on par with commercial HDPE. Tuning these parameters in tandem allowed us to synthesize copolymers with HDPE-like thermomechanical properties (Tm = 91 ºC, Xc = 40%, E = 494 MPa, σy = 21 MPa). Unlike conventional HDPE and reported PE mimics based on carbonyl-related functional groups, our PE mimics are shown to undergo mild, selective backbone deconstruction upon either Si-O bond cleavage or catalytic exchange, and the resulting deconstruction products can be repolymerized via step-growth polymerization to yield recycled PE mimics with the same chemical structure and molar mass as the original material. We note that this work represents the first example of step-growth repolymerization of ROMP-derived PE mimics, revealing that nearly identical molar masses and dispersities can be achieved via chemical recycling. This deconstruction strategy can be used to separate our PE mimics from commodity polyolefins in waste streams including PP, PET, and HDPE. The approach described here showcases how ROMP is a powerful tool for the synthesis of PE mimics of high molar mass and tunable functional group density, demonstrates how silyl ethers may expand the available chemistry of PE mimics, and provides novel applications of BSE exchange chemistry (e.g., for chemical recycling). Looking forward, step-growth repolymerization of telechelic oligomers into PE-like materials, which is demonstrated here for diols but could potentially be achieved for other functional oligomers generated from PE pyrolysis, could provide a "closed-loop" solution to PE waste.