Mechanically Tough Pluronic F127/Laponite Nanocomposite Hydrogels from Covalently and Physically Cross-Linked Networks
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Mechanical properties of polymer hydrogels are critical to their performance as tissue engineering scaffolds especially in load bearing tissues and wound sealants. In this study, we aim to synthesize mechanically tough nanocomposite hydrogels by photo-cross-linking PEO-PPO-PEO triblock copolymer diacrylates (Pluronic F127 diacrylate) in the presence of silicate nanoparticles, Laponite. The resulting hydrogels have high elongations and improved toughness when compared to their polymer hydrogel counterparts. Oscillatory shear and creep experiments suggest that the silicate nanoparticles physically interact with the covalently cross-linked polymer networks and impart viscoelasticity to the hydrogels. Imaging the structures of deformed nanocomposite hydrogels with cryo-scanning electron microscopy (cryo-SEM) leads us to believe that stretched hydrogels have finer network structures with smaller pore sizes when compared to the unstretched ones. The structural transitions observed in cryo-SEM and the viscoelastic properties measured suggest that noncovalent, physical interactions between Pluronic F127 and Laponite may contribute to rearrangements of network structures at high deformations. Overall, we expect the relationships between mechanical properties and network structures to provide valuable knowledge for the future design of high-performance hydrogels with use in a variety of biotechnological, biomedical, and pharmaceutical applications. 2011 American Chemical Society.