Tuning Curing, Latency, and Dynamic Behavior in Optically Clear Epoxy Vitrimers Using Organotin Catalysts

Achieving optically clear epoxy vitrimers based on transesterification remains a significant challenge. While epoxy vitrimer systems offer high thermomechanical performance, optical clarity is often compromised by catalyst-induced side reactions and network heterogeneities and has rarely been demonstrated in conventional epoxy–acid formulations, particularly after reprocessing. In this work, we examine how two commercially available tin oxides, monobutyltin oxide (MBTO) and dibutyltin oxide (DBTO), govern the curing pathways, topology, and relaxation behavior of transparent epoxy vitrimer networks. Differences in Lewis acidity, solubility, and steric hindrance result in different efficiencies for esterification and transesterification. MBTO strongly accelerates epoxy–acid polyaddition, whereas DBTO enhances latency and can favor interfacial exchange during heterogeneous vitrimerization. Both vitrimers remain reprocessable at 200 °C, achieving good thermomechanical recovery after reprocessing, consistent with the thermal robustness of the catalysts. Importantly, the original and reprocessed materials maintain high optical transparency across the UV–visible region, underscoring their potential in applications requiring clear, reprocessable materials. Overall, these results show that catalyst selection can tune reactivity, latency, and dynamic response, guiding the design of transparent, thermally resistant, and recyclable epoxy vitrimers.