Polymers’ light weight, low cost, and, importantly, stability under thermal, chemical, and mechanical stress make them valuable for a range of demanding applications. This stability, on the other hand caused environmental pollution. Since it is very difficult but also very expensive (REACH registration, etc.) to design brand-new materials that could both have the desired properties (mechanical, thermal, solvent resistance, etc.) and that are in the same time either recyclable and/or biodegradable, transforming already known materials to make them biodegradable/recyclable is more interesting. This approach relies on the introduction of labile bonds onto the polymer backbone. The degradation could thus occur from these weak bonds leading to oligomers that could be easily recyclable and/or bioassimilable. Degradation of commodity thermoplastics prepared by radical polymerization, like LDPE, PMMA and PS, is generally not possible due to the stability of their C−C backbone. A simple and useful method of incorporating weak bonds randomly onto the C−C polymer backbone is by radical copolymerization of vinyl monomers with cyclic monomers via radical ring-opening polymerization (rROP).