Sunlight driven self-healing, reshaping and recycling of a robust, transparent and yellowing-resistant polymer†
For realizing sunlight stimulated self-healing, a crosslinked polyurethane carrying disulfide in the main chain is synthesized. Its macromolecular composition and architecture are optimized so that the included disulfide bonds can take part in the exchange reaction simply under illumination of the low concentration UV component of sunlight. Accordingly, the damaged polymer is allowed to be repeatedly healed in the sun in terms of strength restoration as a result of photo-triggered reversible exchange of disulfide bonds. Meanwhile, the elaborately introduced hydrogen bonding helps to quickly close cracks, favoring intimate contacts of the cracked surface and subsequent interaction of dangling chains across the interface, and eventually raising the effectiveness of the photo-reaction of the disulfide bonds in the solid phase. In addition, network rearrangement due to disulfide exchange enables multiple recycling and reshaping of the polymer under sunshine. The present proof-of-concept work would be hopefully developed into a cost-effective and environmentally friendly technology of design, fabrication and application of smart photo-sensitive polymers with high mechanical strength.