Byers and coworkers demonstrated how the orthogonal activity of redox-switchable catalysis can be applied in the realm of crosslinking (FIG. ). For example, the building block, which is a bifunctional monomer, is a cyclic diester with a pendant epoxide. The cyclic diester moiety is polymerized upon exposure to an iron(II) complex to produce an epoxide-functionalized polyester. By adding an external oxidizing agent, Fe(II) is oxidized to Fe(III), and then concentrating the reaction mixture, ring-opening polymerization of the epoxide moiety occurs, interlinking the polyester chains and forming a crosslinked polymer network. Compared to linear poly(lactic acid), the cross-linked polymers show remarkably different thermal and physical properties. Moreover, the crosslinking method benefits from the switching capabilities of the iron complex. catalytic states to control the polymer sequence and microstructure. Redox-switchable catalysis towards the synthesis of a biodegradable crosslinked polymer network (i). Electrochemically controlled redox-switchable polymerization to synthesize a tetrablock copolymer (ii). CO2 controlled copolymerization of -butyrolactone, cyclohexene oxide/CO2 for triblock copolymers (iii). b| Polyethylene degradation via tandem (de)hydrogenation using γ-Al2O3 supported Ir complexes and alkane metathesis using Re2O7/Al2O3. The dehydrogenation/ hydrogenation process was catalyzed by the Ir compound while the olefin metathesis step was catalyzed by Re2O7/Al2O3.