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

Abstract

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