Design and synthesis of aliphatic supramolecular polymers featuring amide, urethane, and urea hydrogen bonding units

Abstract

Functionalisation of polyurethane-urea oligomers with hydrogen bonding amide end groups leads to dramatic thermal, mechanical, morphological, and rheological changes of supramolecular polyurethane elastomers. This study reports the design, synthesis and characterisation of six new aliphatic thermally stable supramolecular polyurethanes (SPUs). It was found that introduction of the amide end groups affords a polymer network that is maintained by dynamic associations within the solid state of the material. Through atomic force microscopy (AFM), the aggregation of hard segments of these phase separated SPU networks was found to be more prominent with the introduction of the amide end groups. The strong hydrogen bonding associations between the amide end groups were complemented by urea-urea and urethane-urethane interactions from the main chains to enhance the self-assembly and phase separation of SPUs and also improve the mechanical, thermal and rheological properties with respect to other SPU elastomers that feature bisamide end groups. These thermally stable phase separated SPUs also displayed remarkable re-adhesive capabilities on both glass and aluminium substrates, for example, SPU2 exhibited unique reusability after seven adhesion cycles.