Reprocessable Acid-Degradable Polycarbonate Vitrimers

Abstract

Vitrimers are cross-linked\npolymer networks containing linkages\nthat undergo thermally activated, associative exchange reactions,\nsuch that the cross-link density and overall network connectivity\nare preserved. Polycarbonates are industrially relevant polymers that,\nto our knowledge, have not yet been explored as vitrimers. We developed\nhydroxyl-functionalized polycarbonate networks that undergo transcarbonation\nexchange reactions at elevated temperatures in the presence of catalytic\nTi­(IV) alkoxides. The rate of transcarbonation within the networks,\nestimated through stress relaxation experiments, was tuned by adjusting\nthe catalyst loading or hydroxyl group concentration in the networks.\nThe polymer networks exhibit recovery of their tensile strength and\nplateau storage modulus (71–133%) after reprocessing. In addition\nto being reprocessable, the networks were hydrolyzed and decarboxylated\nin aqueous acid to recover 80 wt % of the precursor to the bifunctional\ncyclic carbonate monomer. These observations demonstrate that PC vitrimers\nare a novel class of strong, repairable polymers with more facile\nend-of-life degradation compared to other vitrimers and conventional\nthermosets. These characteristics, along with the high likelihood\nof deriving their monomers from bio-based sources, make PC vitrimers\noutstanding candidates for sustainable manufacture and use.