Fully Biobased Self-Healing and Recyclable Covalent Adaptable Networks Prepared via a Catalyst-Free Aza-Michael Reaction

In the present scenario, petroleum resource-based thermoset materials have become an environmental threat due to their permanent cross-linked structure that limits their recyclability. To overcome this problem, the development of covalent adaptable networks (CANs) containing dynamic covalent bonds has emerged in recent years that can be recycled under suitable conditions. However, the development of fully biobased as well as recyclable CANs following a green synthetic protocol is yet a great challenge and a dream toward a sustainable environment. With this goal, here, we report the development of fully biobased CAN films from acrylated castor oil (a low-cost vegetable oil derivative) and cystamine (a biobased diamine) via a catalyst-free aza-Michael reaction using disulfide linkage as the dynamic covalent bond. The CAN films show excellent thermoself-healing behavior and recyclability for at least 10 cycles while maintaining their material properties. In addition, the CAN films can be catalytically degraded, which can be further reprocessed to reconstruct the films. Furthermore, the CAN films are hydrophobic in nature, indicating that these biobased recyclable CAN films are useful for protective surface coating applications. Therefore, as a proof of concept, we further demonstrate the anticorrosive properties of a film having a maximum water contact angle of 102.4°, analyzed by a polarization method, electrochemical impedance, and a salt spray fog test under a corrosive environment. This work provides an economical as well as environmentally friendly route to develop multifunctional materials for a sustainable future.