Vitrimers are cross-linked polymer networks containing linkages that undergo thermally activated, associative exchange reactions, such that the cross-link density and overall network connectivity are preserved. Polycarbonates are industrially relevant polymers that, to our knowledge, have not yet been explored as vitrimers. We developed hydroxyl-functionalized polycarbonate networks that undergo transcarbonation exchange reactions at elevated temperatures in the presence of catalytic Ti(IV) alkoxides. The rate of transcarbonation within the networks, estimated through stress relaxation experiments, was tuned by adjusting the catalyst loading or hydroxyl group concentration in the networks. The polymer networks exhibit recovery of their tensile strength and plateau storage modulus (71-133%) after reprocessing. In addition to being reprocessable, the networks were hydrolyzed and decarboxylated in aqueous acid to recover 80 wt % of the precursor to the bifunctional cyclic carbonate monomer. These observations demonstrate that PC vitrimers are a novel class of strong, repairable polymers with more facile end-of-life degradation compared to other vitrimers and conventional thermosets. These characteristics, along with the high likelihood of deriving their monomers from bio-based sources, make PC vitrimers outstanding candidates for sustainable manufacture and use.
Bibliographical noteFunding Information:
This research was supported by the National Science Foundation (NSF) through the Center for Sustainable Polymers (CHE-1413862). This research made use of the IMSERC at Northwestern University, which has received support from the NSF (CHE-1048773); the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205); the State of Illinois, and the International Institute for Nanotechnology (IIN). This work made use of the OMM Facility supported by the NSF MRSEC program (DMR-1121262) at the Materials Research Center of Northwestern University.