Polarity–Rigidity Modulation of Bio-Based Copolyesters for Water-Responsive Transient Adhesives with Recyclability and Biodegradability

Conventional adhesive materials often require compromises between bonding strength, easy removal, recyclability, and environmental sustainability. In this study, we propose a polarity–rigidity modulation strategy for the development of water-responsive transient adhesives capable of exhibiting both strong adhesion under dry conditions and rapid debonding upon water exposure. Bio-based poly(tartrate-co-itaconate-co-butylene-co-isosorbide) (PTIBI) copolymers were prepared via catalyst-free melt polycondensation while systematically varying backbone polarity and chain rigidity. The optimized PTIBI formulation displayed high lap-shear adhesion on polar substrates and underwent rapid, residue-free detachment when exposed to water without significant polymer degradation. Molecular dynamics simulations indicated that the interplay between polarity and rigidity simultaneously controls cohesive interactions and water affinity, facilitating hydration-induced weakening of interfacial adhesion while maintaining structural integrity. As a result, PTIBI enabled efficient material recovery and repeated reprocessing through a closed-loop recycling pathway. Furthermore, composting studies verified the biodegradable characteristics of the polymer system. The adhesive also demonstrated utility in sustainable manufacturing processes, including water-based and solvent-free fabrication of battery electrodes. These findings highlight polarity–rigidity modulation as an effective molecular design approach for next-generation sustainable adhesive and interfacial materials.