Robust Self-Healable and Three-Dimensional Printable Thermoplastic Elastomeric Waterborne Polyurethane for Artificial Muscle and Biomedical Scaffold Applications

Waterborne polyurethanes (WPUs) with smart attributes like self-healing and shape-memory, reprocessability, and excellent integrated mechanical properties are the key connotations for advanced applications. Congenitally, these properties are associated with conflicting features, which makes it puzzling to optimize these paradoxical properties in a single material. Herein, this study introduces an easy but impactful strategy to answer this dilemma, which is based on the triple synergistic effect of 'dynamic hard domains (2-aminophenyl disulfide, 2-APDS)', 'asymmetric IPDI-IPDA (isophorone diisocyanate-isophorone diamine) architecture', and 'shape memory effect (SME)'. The loosely packed IPDI-IPDA moieties and the SME promote the reversible S–S metathesis reactions, resulting in high healing efficiency as well as mechanical strength, simultaneously. Based on this tactic, a series of robust self-healable WPUs (SHWPUs) was synthesized with good healing efficiency (70.22–79.94%), shape recovery (88.4–97.4%), excellent mechanical strength (16.09–26.23 MPa), high elongation at break (1604–2071%), outstanding toughness (188.3–216.6 MJ m–3), high fracture energy (46.74–66.33 kJ m–2), biocompatibility, and biodegradability. Outstandingly, a SHWPU film could lift a dumbbell of 25 kg, which is 53,648 times heavier than its own weight without any crack. Taking advantage of good shape recoverability, the elastomer was tested for "artificial muscle" contraction. Impressively, the SHWPU-1 film could vertically and successfully lift a 100 g load, which is 251.19 times heavier than its weight under ambient conditions. Moreover, a series of 3D printable gelatin/SHWPU-2 inks were prepared, which possess the potential for bone scaffolds. Additionally, this thermoplastic SHWPU could be reprocessed at 80 °C under 60–80 kg cm–2 pressure. Thus, the SHWPU elastomer exhibited all characteristics of advanced materials with smart attributes and eco-friendly nature.