Light‐driven self‐healing castor oil based polyurethane film with enhanced mechanical properties

To meet the need of alleviating the pressure of petrochemical industry and environmental protection, polyurethane (PU) made from castor oil (CO) as polyols, replacing petrochemical based crude material has attracted a lot of recognition over the past decades. For the sake of prolonging the service life of materials, it is also necessary to endow vegetable oil-based polymers with self-healing properties, which is seldom involved in present study. Currently, optically responsive self-healing system has attracted extensive attention because of its easy control and simple occurrence. However, the problem of low self-healing efficiency also puzzles the current research of this self-healing system. In this study, cinnamoyl group was introduced into bio-based PU as end blocking agent. The photoresponse reversible cycloaddition reaction of cinnamyl groups and the acceptable chain fluidity of CO provided the possibility for the self-healing properties of polymers. The dimerization degree of [2 + 2] cycloaddition reactions was as high as 58% under UV light for 36 h from UV-vis spectrum. Investigation of the optical healing property indicated that incision on the surface of certain PU sample was completely repaired and healing efficiency enhanced up to 93.1%, with the introduction of cinnamoyl group. What is more, the results from TGA, DMA and tensile tests suggested that the prepared PU samples showed excellent comprehensive performance.