Inverse Cross-Link-Density/Activation-Energy Coupling in Poly(lactic acid) Dual-Dynamic Networks for Creep-Resistant...

Developing degradable poly(lactic acid) (PLA) covalent adaptable networks that simultaneously integrate mechanical robustness, creep resistance, reprocessability, and tunable multi-shape memory remains a major challenge, particularly when low-molecular-weight PLA is used as the sustainable precursor. Here, we report a poly(lactic acid) dual-dynamic network with inverse cross-link-density/activation-energy coupling constructed through a facile one-pot reaction of commercially available PLA diols, hexamethylene diisocyanate trimer, and 2,2'-diaminodiphenyl disulfide (DADS). The network architecture couples a densely cross-linked disulfide-containing dynamic network with low activation energy (E_a) and a loosely cross-linked PLA-rich dynamic network with high E_a. The dense low-E_a network provides mechanical reinforcement, low-temperature stability, and rapid thermally activated rearrangement, whereas the loose high-E_a network contributes extensibility, creep resistance, elastic energy storage, and high-temperature processability. By regulating PLA molecular weight and DADS/PLA ratio, the dual-dynamic networks show tunable glass transition, degradation rate, and rearrangement kinetics. Such unique hierarchical dual-dynamic network architecture with inverse cross-link-density/activation energy coupling endows the material with prominent stiff-toughness, reprocessability, creep resistance, and reconfigurable multi-shape memory capability. Moreover, adaptive medical fixation and photothermal-assisted therapeutic prototypes demonstrate the potential of these reconfigurable shape memory PLA networks with cytocompatibility for sustainable biomedical devices.