Highly Stretchable, Self-Healable, and Adhesive Polyurethane Elastomers Based on Boronic Ester Bonds

Integrating stretchability, self-healability, and surface adhesive properties in a single material is attractive for expanding the applications in demanding fields. Herein, we have studied the metathesis kinetics of catechol-derived boronic esters and incorporated them into polyurethane (PU) networks to prepare a type of PU elastomeric vitrimers with excellent stretchability, healability, and adhesive properties. Two series of dynamic PU elastomers that have different cross-linking densities and varied fractions of catechol moieties were simply prepared by a solution casting method from the linear PUs containing pendent catechol groups and 1,4-phenylenediboronic acid. These elastomers possess excellent stretchability and moderate mechanical properties that can be readily manipulated by varying the cross-linking density and the number of residual catechol groups. Moreover, the elastomers are healable and reprocessable under mild conditions and show moderate adhesive capability. The effects of the cross-linking density and residual catechol fraction on the thermal relaxation profiles and adhesive strength of the elastomers were explored in detail. Finally, we have demonstrated the potential of this kind of dynamic PU elastomers for applications as stretchable, healable, and self-adhesive conducting composite materials.