Chemical Upcycling of Polybutadiene Into Polyolefin-Based Dynamic Covalent Polymer Networks

The use of non-renewable petrochemical feedstocks for the production of specialty polymer materials is not a sustainable practice. However, the use of waste commodity thermoplastic polymers as a feedstock for the production of specialty monomers is an attractive alternative. In this work, we show that high molar mass polybutadiene can be upcycled into reprocessable thermoset materials that can be recycled and reshaped multiple times as a dynamic covalent polymer network (DCPN). First, a one-pot partial hydrogenation and ethenolysis protocol was used to chemically cleave polybutadiene chains into low molecular weight α,ω-dienes. These were subsequently incorporated in a thiol-ene cured thermoset material using multifunctional thiols. The thioether linkages, connecting the polyolefin segments, can be turned into covalent dynamic moieties upon alkylation at elevated temperatures. The dynamic behavior of these thioether linkages was demonstrated through rheological and reprocessing experiments at elevated temperatures, highlighting their potential for sustainable material design. This strategy has a clear potential for an "upcycling" paradigm of bulk polymer waste into specialty polyolefin-based thermosets and DCPNs with appealing recyclability potential.