Are Electron-Withdrawing Groups Affecting Polyester Hydrolysis? A Comprehensive Study on Poly(thioether-ester)s and Poly(sulfone-ester)s

Improper plastic waste management and the increasing accumulation of microplastics remain major societal challenges, highlighting the need for new material solutions. Biodegradable polymers can contribute to mitigation in selected applications, such as agriculture, where postuse collection is impractical. In this context, strategies to accelerate environmental biodegradation are of growing interest. One promising approach is the incorporation of electron-withdrawing sulfone functionalities, which can increase the electrophilicity of ester carbonyl carbons and thereby enhance hydrolyzability, the rate-determining first step of biodegradation. However, the oxidation of thioethers to sulfones typically induces simultaneous changes in polymer hydrophilicity and crystallinity, complicating the isolation of purely electronic effects. Here, we systematically investigate the inductive effect of sulfone groups on ester hydrolysis. Four small-molecule model compounds derived from thiodiglycolic or thiodipropionic acid and benzylic alcohol were synthesized to isolate purely electronic effects from polymer morphology, oxidized, and examined under basic hydrolysis conditions, and density functional theory (DFT) calculations were employed to rationalize and quantify the experimentally observed trends. Complementary high-molecular-weight poly(sulfone-ester)s with varying distances between sulfone and ester groups but with similar hydrophilicity and crystallinity were compared for their hydrolysis and compostability. The poly(sulfone-ester)s exhibit accelerated hydrolysis, with thiodiglycolic-acid-based systems degrading faster than thiodipropionic-acid-based analogues. Together with a distance-controlled polymer design, this combined experimental–computational approach enables a direct assessment of sulfone-induced inductive effects on ester hydrolysis. The polymers show low cytotoxicity and good mechanical properties and compostability, making them promising candidates for fast-composting packaging materials.