Self-Destruct Thermosets: A Combination of the Comonomer Approach and Thermolatent-Base Compounds

Due to their enhanced chemical and mechanical properties, thermosets are playing a significant role in the worldwide plastic production business alongside linear polymers. However, their cross-linked structure prevents them from being recycled, reprocessed, or easily degraded. The introduction of weak/cleavable bonds into the backbone of networks via a comonomer approach was shown to impart degradability/recyclability of the object once treated with acid or base solutions. Yet, practical degradability is limited by the diffusion of this solution within the network. Many cases would rather require programmable destruction after the object's service life, with built-in degradability. We report here the introduction of stimuli-responsive latent species incorporated within the network prior to polymerization. These latent species are compatible with polymerization processes through thermal or photo-initiation (such as 3D-VAT printing). Under photothermal (NIR) or pure thermal activation at elevated temperatures (>100°C), the network depolymerizes into branched oligomers soluble in appropriate solvents. This approach was exemplified mainly using the radical copolymerization of dibenzo[c,e]oxepane-5-thione (DOT) with styrene and acrylic derivatives combined with different thermolatent 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) compounds, and was also shown to be compatible with the Ring-Opening Methathesis Polymerization (ROMP) copolymerization of dicyclopentadiene with cyclic olefins containing silyl ether combined with different thermolatent TBD compounds.