Mechano-responsive chameleon-gel integrated with dumbbell-shaped spiropyran cross-linker

• Published in: Materials letters 2024-04, Vol.361, p.136141, Article 136141
• Main Authors: Jeong, Hyewon, Cho, Sungwoo, Heo, Eun-jin, Woo, Chaewon, Gyu Shin, Sung, Ho Kim, Mun, Hyun Jeong, Jae
• Format: Article
• Language: English
• Subjects: Chameleon-gel; Cross-linker; Dumbbell-shaped spiropyran; Mechanical stress
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2024.136141

•Dumbbell-shaped spiropyran, SP-PEGDA cross-linker for hydrogels, induces stress-triggered color changes.•The SP-PEGDA cross-linker overcomes solubility challenges, acts effectively, preserves SP mechanophore function.•Chameleon-gels visualize internal stress with SP-PEGDA during controlled swelling/deswelling.•Mechano-responsive hydrogels exhibit reversible color changes, promising for sensing, imaging, and display. Stimuli-responsive hydrogels are being extensively studied altering their structures and physiochemical properties in response to external changes. However, technologies to visualize the internal stress of a gel generated by swelling and deswelling are still lacking. Here, we present a dumbbell-shaped spiropyran cross-linker synthesized by top-down grafting with poly(ethylene glycol) (PEG) acrylates. The cross-linker consists of spiropyran core that exhibits optical changes in response to mechanical stress, hydrophilic 2-arm PEGs that allow the cross-linker soluble in an aqueous solution, and acrylate units at each end of PEGs that cross-links the gel. As a result, the chameleon-gels integrated with the dumbbell-shaped spiropyrans were proved to visualize the internal stress generated by swelling and deswelling in a controlled manner. Overall, this new strategy to prepare the mechano-responsive hydrogel would be actively used in sensing, imaging, and display for drug delivery, tissue engineering, and environmental engineering, etc.