Castor Oil-Based UV Curable Polyurethane Acrylate: Solvent-Free Processing, Self-Healing, Controlled Degradation for Flexible Wearable Electronics

Abstract

Biobased polyurethane acrylate has broad application prospects in the field of wearable electronics due to its designable molecular structure, low cost and excellent sustainable properties. However, traditional plant oil-based polymers generally have disadvantages such as insufficient self-healing efficiency, insulation and nonconductivity, poor mechanical properties, and a tendency to cause electronic waste pollution, which limit their practical application. Here, we designed a simple, efficient and green preparation strategy, using a compound system of renewable castor oil (CO) and polycaprolactone diol (PCL) as a biodegradable soft segment, addressing the issue of poor processability caused by the high viscosity of castor oil while enhancing the material’s flexibility. Based on the dynamic cross-linked network constructed by intermolecular hydrogen bonds and reversible disulfide bonds, the prepared BPUA-4 exhibited high strength (11.04 MPa) and elongation at break (294%). Furthermore, through ionic liquid functionalization modification, this material exhibits excellent scratch self-healing efficiency (>83% at 80 °C for 48 h). Thanks to the dense cross-linked structure formed by ultraviolet curing and the protection of hard chain segments, the ester bonds of this material will only undergo significant degradation in a strongly alkaline environment with pH = 14 or under the action of lipase CALB, and the mass loss rate after 30 days can exceed 30%. The sensor devices constructed based on this composite material can accurately detect various human movement signals and show good application potential in the fields of health monitoring and smart wearable devices.