Exploring the dual dynamic synergy of transesterification and siloxane exchange in vitrimers

Abstract

Despite the benefits of dynamic polymer networks with multiple dynamic bonds, identifying compatible combinations of dynamic chemistries that work synergistically to achieve desirable properties remains a significant challenge. This work focuses on the potential of utilizing both siloxane and ester dynamic bonds in epoxy-acid cured vitrimers to finetune chemical exchange reactions. We identified to what extent a common basic catalyst (TBD) can simultaneously activate siloxane and ester exchange in the corresponding epoxy-based vitrimers. Our results showed that TBD is not only able to facilitate network formation but also improved the dynamic behavior of the resulting networks dramatically, with an overall exchange rate that is faster than the sum of the individual exchange chemistries, as shown by stress-relaxation studies. It has been demonstrated that the siloxane and ester dynamic bonds work together in a synergistic way to facilitate topology rearrangement. The relative increase or decrease in mobility of neighboring chains, located around a specific dynamic bond within the polymer network, was investigated in detail by adjusting the concentration of dynamic bonds and catalyst. The herein reported strategy allows the production of dual dynamic polymer networks that exhibit much shorter relaxation times and thus improved (re)processability in comparison to vitrimers with one type of dynamic bond.