Thermally and mechanically robust self-healing supramolecular polyurethanes featuring aliphatic amide end caps

Abstract

A series of supramolecular polyurethanes (SPUs) were designed and synthesised with synergetic multifunctional hydrogen bonding aliphatic amide end-caps. Hydrogen bonding between the urethane, urea, and amide motifs in the polymers afford strong dynamic association between polymer chains in the solid state. Phase separation of the apolar and polar components of the polyurethanes also serves to reinforce their thermal and mechanical properties. The supramolecular polyurethane with bisamide-morpholine end caps associates via multiple hydrogen bonds and exhibits enhanced tensile and thermal properties when compared to the other materials. Variable-temperature infrared spectroscopy (VT-IR) and atomic force microscopy (AFM), were carried out to study the phase morphology of the polymers and revealed a correlation between increased phase separation and the introduction of amide motifs in the end-caps. These SPUs also exhibit excellent healing abilities, requiring temperatures >200 °C to recover their physical properties.