Hypervalent iodine-based dynamic and self-healing network polymers

Abstract

Linear polymers with multiple carboxylate pendant groups (copolymers of styrene and acrylic acid) participate in ligand-exchange reactions with (diacetoxyiodo)benzene and the reaction yields network polymers with (diacyloxy)iodoarene-type crosslinks. The unreacted carboxylate groups that are present in the polymers can participate in further ligand-exchange reactions with the hypervalent iodine(III) centers at the crosslinks, which makes the materials dynamic and self-healing. The application of strong shear force leads to gel disintegration but when the external force is removed, the gels are regenerated again, as proved by rheology studies. When exposed to UV light or heat (microwave irradiation), the gels are “set” (i.e., become permanent) due to the homolytic cleavage of the weak hypervalent I–O bonds present at the crosslinks, followed by irreversible radical coupling of adjacent polymer-bound C- and/or O-centered radicals.