Synthesis of Strong and Tough Supramolecular Elastomer based on Step Polymerization

Abstract

The development of high-performance functional polymers is of great importance in modern industry. In particular, the requirements for strength, toughness and other basic properties are more stringent. However, the methods for increasing strength and toughness are often the opposite. Therefore, from a molecular engineering perspective, a series of supramolecular polymers were synthesized in this work based on a stepwise polymerization, which involves mainly chemical reactions between hydroxyl, amino groups and isocyanate groups respectively. Since strong multiple hydrogen bonds are formed between the resultant urethane and urea groups, thereby an energy dissipation mechanism is conferred to the material. Meanwhile, the molecular structure was optimized to attenuate the adverse effect of chain entanglement on the toughness, resulting in three-arm polymers that exhibit excellent mechanical strength of 5280 kPa and toughness of 28850 kJ/m3. In addition, the aggregation of tertiary nitrogen atoms endows considerable fluorescence. More importantly, the existence of extensive internal hydrogen bonds can make it an adhesive with excellent bonded strength of 8.9 MPa when bonded with stainless steel, which can be used as a structural adhesive. This work is an important milestone in giving both high performance and functionality to the material through molecular structure design from the molecular synthesizing perspective.