4 years ago

Hyperelastic Tough Gels through Macrocross-Linking

Hyperelastic Tough Gels through Macrocross-Linking
Christopher John McAdam, Stephen C. Moratti, Lyall R. Hanton, Shailesh K. Goswami
The wet and soft nature of hydrogels makes them useful as a mimic for biological tissues, and in uses such as actuators and drug delivery vehicles. For many applications the mechanical performance of the gel is critical, but gels are notoriously weak and prone to fracture. Free radical polymerization is a very powerful technique allowing for fine spatial and temporal control of polymerization, but also allows for the use of a wide range of monomers and mixtures. In this work, it is demonstrated that extremely tough and extensible hydrogels can be readily produced through simple radical polymerization of acrylamide or acrylic acid with a poly(ethylene oxide) macrocross-linker. These gels, with a water content of 85%, are extremely elastic with an extension much more than 15 000% at 9 MPa true stress. They can be compressed over 98% at a stress of 17 MPa. They are notch-insensitive, and the usual trouser tear test does not work because the tear simply does not propagate. This highly extensible nature seems to be related to very long chain lengths between cross-links and efficient incorporation of chains into the network. Through the use of multiarmed cross-linkers it is possible to produce acrylamide and acrylic acid hydrogels of remarkable stretchability and compressibility. The resulting gels can be compressed to over 98% at a strength of 16 MPa, and stretched to 150× their original length with good recovery. Conventional cross-linkers also perform worse; the reason for this needs to be determined.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/marc.201700103

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