Synthesis and characterization of thermolatent bases with varying activation temperatures

Abstract

Latent catalysts offer a powerful means to control both the start and progress of polymerization reactions by releasing the active species only upon exposure to a defined external stimulus, such as heat or light. While their application is well-established in coatings and adhesives, the concept is gaining traction for spatiotemporally controlling bond exchange reactions in dynamic polymer networks, particularly for balancing creep and flow properties. Latent catalysis does not only enable targeted property control in dynamic polymer networks, but also supports circular polymer strategies by allowing repair, reshaping, and recycling without loss of performance. These capabilities can extend the materials' lifetime, reduce the need for energy-intensive virgin polymer production, and contribute to lowering the carbon footprint of polymer manufacturing. In this study, we report on the synthesis and thermal characterization of a library of thermolatent Brønsted base generators (TBGs), designed to release catalytically active bases upon thermal activation. These TBGs consist of strong organic bases ionically bonded to carboxylate anions derived from acetic acid derivatives and dicarboxylic acids with varying chain length, which act both as stabilizing counterions and as thermally labile groups. This work systematically explores the relationship between molecular structure and thermal stability of TBGs, with particular focus on how structural variations in carboxylate anions and base cations influence the activation temperature. The synthesized compounds are highly stable under ambient conditions and decompose over a broad temperature range (60 °C to 290 °C), depending on the chemical structure of the acid as well as the base. The cleavage events observed during thermal activation results in an efficient and irreversible release of the base.