Degradable polyolefin materials enabled by catalytic methods
Plastics are essential to virtually any modern technology and therefore ubiquitious. However, when released to the environment they can persist for centuries. One pillar of a responsible future economy is therefore to endow important plastics with a non-persistent nature. Polyethylene (PE) is the largest scale synthetic material, used in transportation, energy storage, water cleaning, clothing and many other fields. However, it is most problematic concerning degradability.  This proposal addresses this major challenge by introducing photo- and hydrolytically degradable groups in the PE chain. Directly during catalytic PE synthesis, isolated keto groups will be generated by incorporation of small amounts of carbon monoxide. This yet unachieved goal is targeted via catalysts with extreme shielding and rigid ligand environments in heterobimetallic Ni(II) / main group metal complexes. A compartmentalized aqueous polymerization with precise control of high ethylene/CO ratios will yield the in-chain functionalized PE as nano- and microscale particle dispersions. Living catalytic polymerization in nanoparticles is pursued to achieve ultra high molecular weights and gradient PE chains forming nanodomains varying in ketone density. Aqueous heterophase oxidation with benign oxidants on all these nanoparticle will yield in-chain ester groups. Further types of hydrolytically cleavable groups are targeted via the complementary synthetic approach of step growth from seed- or microalgae-oil derived PE-telechelics. This yields linear PE with in-chain carbonate, acetal and anhydride groups. Basic materials properties of all polymers are determined by tensile tests. Degradation studies reflecting a marine environment will indicate the persistency behaviour and fate of microfragments, using macroscopic specimens and the above particles as models. Knowledge of the particle and bulk morphologies will be instrumental to understand the materials and degradation properties.