Tuning the Elevated-Temperature Creep Resistance of Reprocessable Polythiourethane Networks through Latent Catalysis and Stoichiometric Variations

The relatively rapid reaction of thiol and isocyanate groups results in thiourethane moieties and provides a route to synthesize both linear and network polythiourethanes (PTUs). PTU networks parallel the mechanical properties of conventional polyurethane (PU) networks and may be reprocessed with appropriate catalysis under mild conditions through both associative exchange and dissociative reversible dynamic mechanisms. Unfortunately, as conventionally made at stoichiometric balance, PTU networks exhibit poor elevated-temperature (T) creep resistance. Here, latent catalysis through the use of a thermally latent, protonated 1,8-diazabicyclo(5.4.0)undec-7-ene (DBUH⁺) complexed with tetraphenylborate (BPh₄^-) anion (DBUH·BPh₄) catalyst as well as stoichiometric variations during synthesis were employed to produce PTU networks that fully recover their crosslink density and associated properties after successive compression molding cycles. Additionally, our PTU networks exhibited excellent creep resistance at high T, indicating that thermal latent catalysis and stoichiometric variations may be used to tune the rheological and dynamic mechanisms responsible for elevated-T creep behavior, a phenomenon detrimental to the mechanical performance of PU-like networks.