Hydrolytically degradable poly(beta-thioether ester ketal) thermosets via radical-mediated thiol-ene photopolymerization

Thiol-ene photopolymerization was exploited for the synthesis of poly(beta -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 beta -thioether ester functionality dominates the degradation profile under basic conditions irrespective of the diketal structure. All four poly(beta -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.