Exploiting Acetal Moieties for the Synthesis of Degradable-On-Demand Polymeric Architectures.

Developing polymers with labile bonds has attracted increasing attention since it can favor the chemical recycling into oligomers or even the starting monomers that could be recovered and re-used. Different chemical bonds can break upon exposure to external stimuli, such as thermal, UV, or chemical triggers. Among these, the acetal bond can degrade under mild acidic conditions. This study focuses on the synthesis of polymers constituted by acetal moieties suitable for triggered depolymerization. In particular, the solvent-less polyaddition of 1,4-butanediol and 1,4-butanediol divinyl ether was developed and optimized using a heterogeneous catalyst (Amberlyst 15) at 100 °C. The best reaction conditions in terms of catalyst loading and reagent ratio were determined through a Design-of-Experiment aiming to achieve high conversion, low polydispersity, and desirable molecular weight. The resulting material presented an amorphous character and thermal stability up to 220 °C. It was confirmed responsive in an acidic environment, being completely hydrolyzed in 42 days, while remaining stable at neutral and basic pH. The obtained results represent a proof of concept for the design of pH-responsive materials through solventless, and scalable processes. The acetal moiety may be further exploited to achieve architectures presenting a sustainable end-of-life by implementing a recycling-by-design approach for new adhesives or novel degradable thermosetting materials.