| Date | 25 September, 2018 |
| Time | 16:00-17:00 |
| Venue | Room 333, Building No.5, Yuquan Campus |
| Speaker | Costantino Creton |
| Abstract | In fracture of soft materials, the internal damage (bond scissionor plastic deformation of crystals or clusters) preceding crack propagation is very difficult to detect, because it is typically not readily visible optically and is not detectable by electron microscopy techniques. This has hampered physically based fracture models from being tested experimentally. Recently mechanochemistry has provided a powerful tool to do so1-3.Specific molecules have been developed that react to the application of a mechanical force by changing their light absorption when the applied force on the bond exceeds a critical value (spyropyran ->merocyanine),by emitting light upon bond scission (bis-adamantanedioxetane molecules) or by becoming fluorescent upon bond scission (pi-extended anthracene). If these molecules are incorporated into soft networks (generally as a dilute crosslinker) they can act as detectors of local bond scission or of a high stress region and be used to map damage zones4-5. In this work we will specifically discuss the incorporation of mechanosensitive molecules into multiple network elastomers that mimic well the behavior of soft filled materials. These marker molecules can be used to mark sacrificial bonds inside the material and providing therefore a signal of when the sacrificial bonds fails therefore imaging in 3D with confocal microscopy the locus of the damaged zone ahead of a crack. |
| Speaker | Current Research Area The focus of the research done in our group is the relationship between molecular and network structure of polymers (at the 10-50 nm length scale), mesostructure (at the micron scale) and macroscopic mechanical properties of polymers above their Tg. We focus on the design of soft polymer network architectures ranging from conventional rubbers, to softer self-adhesive materials all the way to very soft swollen hydrogels. We are interested in relating the polymer network architecture to its deformability, fracture and adhesion to surfaces with different functionalities. We are particularly interested in controlling independently stiffness (the modulus) and resistance to fracture (fracture toughness) through an appropriate molecular design of the network. |
