Irina Mahmad Rasid
The dynamic nature of the bonds in associating polymer networks has led to its use in the design of tough and self-healing hydrogels. While the ability of the materials to regain its original stiffness after a recovery period has been documented, such data provides no information on the molecular level processes occurring as the network is damaged, and subsequently as it heals. A luminescent hydrogel, cross-linked with dynamic metal-ligand coordinate complexes has been developed. Through this system, there is an opportunity to visualize and hence analyze these molecular level processes, as the optical and mechanical properties of the gel are inherently coupled. The system was designed such that the relative intensity of the emission in the 400-500nm range, as the hydrogel is stressed, is a measure of the degree of dissociation and re-association of the complexes. In this work, the opto-mechanical properties of the hydrogel was measured through a technique called rheo-fluorescence, where the bond states could be quantified as the material was stressed under steady shear over a range of shear rates.