Coumarin based light responsive healable waterborne polyurethanes

Waterborne polyurethanes containing coumarin as chain extenders were successfully synthesized. Taking advantage of the photoinduced [2 + 2] cycloaddition reaction of coumarin moieties, this work evaluated the healing abilities of these materials. The photochemical process was analyzed by UV spectroscopy and the cycloaddition reaction kinetics was studied. In addition, the healing abilities of the synthesized waterborne polyurethanes were determined by means of scratch refilling studies and strain-stress tests. The irradiation conditions as well as the polymeric chain mobility on the fracture and the capacity to generate polymer networks by coumarin linkages were demonstrated to be the main factors affecting the healing process. The behavior of these systems was also determined under the direct irradiation of sunlight.