Journal
ADVANCED MATERIALS
Volume 33, Issue 18, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202008057
Keywords
morphing hydrogel; dynamic covalent bonds; reconstructable network; polyelectrolyte; surfactant complex; coumarins
Categories
Funding
- National Natural Science Foundation of China [51773179, 51973189]
- Natural Science Foundation of Zhejiang Province of China [LR19E030002]
- Fundamental Research Funds for the Central Universities of China
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A hydrogel with reversible photo-crosslinks has been developed, allowing for the reprogramming of gradient structures and 3D deformations into various configurations. The hydrogel is fabricated by micellar polymerization of hydrophobic coumarin monomer and hydrophilic acrylic acid, with hexadecyltrimethylammonium chloride micelles enhancing local concentration of coumarin units and improving mechanical properties by forming polyelectrolyte/surfactant complexes. High-efficiency photodimerization and photocleavage reactions of coumarins enable reversible tuning of the network structure of the hydrogel, which can be patterned with different gradient structures through photolithography for versatile functionalities.
Morphing hydrogels have versatile applications in soft robotics, flexible electronics, and biomedical devices. Controlling component distribution and internal stress within a hydrogel is crucial for shape-changing. However, existing gradient structures of hydrogels are usually non-reconstructable, once encoded by chemical reactions and covalent bonds. Fabricating hydrogels with distinct gradient structures is inevitable for every new configuration, resulting in poor reusability, adaptability, and sustainability that are disadvantageous for diverse applications. Herein, a hydrogel containing reversible photo-crosslinks that enable reprogramming of the gradient structures and 3D deformations into various configurations is reported. The hydrogel is prepared by micellar polymerization of hydrophobic coumarin monomer and hydrophilic acrylic acid. The presence of hexadecyltrimethylammonium chloride micelles increases the local concentration of coumarin units and also improves the mechanical properties of the hydrogel by forming robust polyelectrolyte/surfactant complexes that serve as the physical crosslinks. High-efficiency photodimerization and photocleavage reactions of coumarins are realized under 365 and 254 nm light irradiation, respectively, affording reversible tuning of the network structure of the hydrogel. Through photolithography, different gradient structures are sequentially patterned in one hydrogel that direct the deformations into distinct configurations. Such a strategy should be applicable for other photolabile hydrogels toward reprogrammable control of network structures and versatile functions.
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