Highly Adhesive and Tough Thermoplastic Polyurethanes Using a Furandicarboxamide Rigid Chain Extender with Noncovalent Interactions

Preparing polyurethane hot-melt adhesives (HMA) with high bonding strength and toughness is still a huge challenge. As an indispensable component in polyurethane synthesis, the chain extender greatly influences the molecular chain structure, microphase structure, and mechanical properties of resultant polyurethane, so it is crucial to design a chain extender with suitable molecular structures. In this work, a bio-based furandicarboxamide diol chain extender was prepared and used to synthesize thermoplastic furandicarboxamide-based polyurethane (PUFD). The furandicarboxamide group acted as a multiple hydrogen-bonding motif that could endow polyurethane with excellent elongation at break and breaking strength. It was noteworthy that the resultant PUFD-HMA exhibited ultrahigh adhesive strength on a variety of substrates, including metals, composites, and plastics. The strong adhesion was ascribed to the formation of multiple noncovalent bonds between the groups on the polyurethane molecular chain and the surface of the substrate. Meanwhile, rebonding was easily achieved by reheating the separated substrate and PUFD-HMA could retain 75% of its original adhesion strength after 5 repeated uses. It is expected that the molecular design strategy of this work may also be applicable to other polyurethane elastomer or adhesive systems.