From Soft-Segment Engineering to Multifunctional Performance: A Study on Fully Degradable Poly(butylene adipate)-Based Polyurethanes

The development of sustainable electronics demands materials that combine high performance with designed degradability, yet achieving this balance remains a challenge. Here, we demonstrate that systematically engineering the soft-segment molecular weight in fully degradable, biobased polyurethanes (PUs) unlocks a suite of tunable properties for high-performance pressure sensing. By varying poly(butylene adipate) (PBA) diol molecular weight in networks containing isosorbide and acid-cleavable hexahydrotriazine, we establish that longer PBA chains enhance soft-segment crystallinity and elongation (up to 978%), while an optimal intermediate molecular weight (2000 g/mol) yields the highest tensile strength (25.7 MPa) and excellent biocompatibility. This optimized PU exhibits robust shape-memory behavior (Rf > 98%) and undergoes controlled dual degradation: enzymatic (up to 50% mass loss in 6 weeks) and complete acid-triggered dissolution, enabling quantitative recovery of conductive carbon black filler. A microstructured composite sensor fabricated from this material achieves high sensitivity (15.32 kPa–1) with fast response/recovery and successfully monitors human motion. This work establishes molecular design rules for degradable PUs and provides a viable pathway toward sustainable, high-performance flexible electronics.