Recent progress in self-healing polymers and hydrogels based on reversible dynamic B-O bonds: boronic/boronate esters, borax, and benzoxaborole

Intrinsic self-healing polymeric materials are substances that relieve external stress and restore their original mechanical properties after extreme damageviadynamic covalent bonding in the polymeric structure or the reversible association of supramolecular motifs. Boronic ester-based dynamic covalent bonds formed between boronic acids and diols impart excellent self-healing properties to the hydrogels, organic gels, elastomers, and plastics depending on the characteristics of the corresponding polymer. In addition, these bonds induce internal reorganization in the chemical/physical structure in response to changes in the biological signals and biomaterials, such as hydrophilicity, pH, and the presence of glucose. This multi-responsiveness to stimuli as well as the self-healing, injectability, and biocompatibility of boronic ester-based polymers have led to several technological achievements with applicability in biomedical fields, including drug delivery, medical adhesion, bioimplants, and healthcare monitoring. This review provides an overview of various self-healing polymeric materials based on reversible B-O bonds, with a focus on boronic/boronate esters, borax, and benzoxaborole and their properties, responses to external stimuli, and applications.