Catalyst‐Controlled Dual Dynamic Networks in Polyhydroxyurethanes from Six‐Membered Cyclic Carbonates

ABSTRACT External catalysts were used to promote dynamic exchange reactions within polyhydroxyurethanes (PHUs) derived from 6‐membered cyclic carbonates (6CCs). Owing to the presence of both carbamate and ester linkages in the network, two types of covalent exchange reactions; transcarbamoylation and transesterification can occur. A wide variety of catalysts were evaluated for their ability to promote exchange reactions, including dibutyltin dilaurate (DBTDL), potassium methoxide (MeOK), iron(III) acetylacetonate (Fe(acac) 3 ), 1,5,7‐triazabicyclo4.4.0dec‐5‐ene (TBD), 4‐dimethylaminopyridine (DMAP), zinc acetate (ZnOAc) 2 , and bismuth neodecanoate (Bi(neo) 3 ). PHU networks were extensively characterized by thermomechanical analysis (TGA, DSC, DMA, tensile testing), rheological measurements (stress relaxation and small amplitude oscillatory shear), infrared spectroscopy, swelling experiments, and reprocessing tests. Among the catalysts evaluated in this study, the PHU network prepared using potassium methoxide exhibited the best overall performance, combining superior mechanical properties with good reprocessability (up to three cycles), even at a low catalyst loading (2.5 mol%).