Chalcogen Bond‐Induced Conformational Locking for Thermoplastic Polyurethane With Superior Puncture Force and Fracture Energy

ABSTRACT A fundamental and long‐standing issue in the design of polymers is how to transcend the constraints of conformational entropy within highly disordered polymer networks, thereby enabling the deterministic orientation of local chemical bonds. While such precision is common in crystalline systems, achieving it in amorphous polymers remains a challenge that often forces a compromise between strength and toughness. Herein, we report a molecular engineering paradigm based on supramolecular poly(urethane‐urea) elastomers synthesized via a two‐step polyaddition of poly(1,4‐butylene adipate), hexamethylene diisocyanate (HMDI), and 1,3,4‐thiadiazole‐2,5‐diamine as a chain extender. The sulfur atom in the thiadiazole ring engages in an intramolecular S···O chalcogen bond with the urea carbonyl oxygen, rigidifying the urea‐heterocycle motif into a highly stable coplanar conformation, extends π‐electron delocalization, and triggers resonance‐assisted hydrogen bonding (RAHB), elevating the hydrogen‐bond (H‐bond) binding energy to an unprecedented 10.4 kcal mol −1 . This electronic–mechanical synergy enables a massive leap in performance: the resulting elastomer achieves a tensile strength of ∼91 MPa alongside a fracture energy of ∼510 kJ m −2 and a record‐breaking puncture force of ∼185 N. This work not only establishes a new Pareto frontier for thermoplastic elastomers but also offers a universal design principle for super‐strong and ultratough polymers through the precise orchestration of electronic structure.