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Degradable epoxy-amine thermosets derived from cyclic-ketal monomers offer robust performance and facile end-of-use processing, enabling recovery of diketone building blocks and pristine carbon fiber from fiber reinforced polymer composites. 

Thiol–ene photopolymerization was exploited for the synthesis of poly(β-thioether ester ketal) networks capable of undergoing complete degradation under acid and/or basic conditions. Using the design of four novel bisalkene diketal monomers, we demonstrate the ability to tune degradation profiles under acidic conditions with timescales dictated by the structure of the diketal linker, while hydrolysis of the β-thioether ester functionality dominates the degradation profile under basic conditions irrespective of the diketal structure. All four poly(β-thioether ester ketal) networks exhibited degradation behavior characteristic of a surface erosion process. The networks showed mechanical (low modulus) and thermomechanical properties (low T g ) typical of thiol–ene thermosets with minimal influence from the structure of the diketal linkage. To highlight the advantages of endowing a step-growth network with ketal linker chemistry, we demonstrated the ability to recover diketone precursors from the thermoset degradation by-products and recycle these compounds into building blocks for additional thermoset materials. 

Abstract Hydrolytically degradable poly(β‐thioether ester ketal) thermosets are synthesized via radical‐mediated thiol‐ene photopolymerization using three novel dialkene acyclic ketal monomers and a mercaptopropionate based tetrafunctional thiol. For all thermoset compositions investigated, degradation behavior is highly tunable based on the structure of the incorporated ketal and pH. Complete degradation of the thermosets is observed upon exposure to acidic and neutral pH, and under high humidity conditions. Polymer networks composed of cross‐link junctions based on acyclic dimethyl ketals degrade the quickest, whereas networks containing acyclic cyclohexyl ketals undergo hydrolytic degradation on a longer timescale. Thermomechanical analysis reveals low glass transition temperatures and moduli typical of thioether‐based thermosets.