Hydrogels with dynamic linkers have garnered intense interest as extracellular matrix (ECM) mimics and injectable delivery vehicles due to their tailorable viscoelasticity, stress relaxation, and self-healing behavior. While dynamic hydrogels with a range of moduli and stress relaxation times have been developed, there remains a need to understand how linking chemistry affects gelation and nonlinear rheological properties. In this context, we have developed synthetic multi-arm poly(ethylene glycol) (PEG) hydrogels with three different dynamic covalent linking chemistries: boronic ester, hydrazone, and thia-conjugate addition bonds. This suite of dynamic covalent linkages allows control over the bond exchange kinetics across three orders of magnitude, which dictates hydrogel viscoelasticity under small amplitude oscillatory shear. Interestingly, the hydrogel moduli demonstrate unique scaling behavior at low concentrations. Furthermore, they exhibit non-monotonic flow curves under steady shear, with shear thickening behavior that depends on the crosslinking bond exchange kinetics and polymer concentration. At high shear, the dynamic hydrogels are injectable, with faster bond exchange kinetics leading to lower injection forces. Overall, these results provide insight to the molecular and structural characteristics that govern dynamic covalent PEG gelation, mechanics, and flow, while also expanding the types of scaffolds applicable to tissue engineering and therapeutic delivery.
Biography: Adrianne Rosales is an Assistant Professor of Chemical Engineering at the University of Texas at Austin. She is a co-lead of the Interdisciplinary Research Group “Fuel-Driven Pluripotent Materials” in UT Austin’s Materials Research Science and Engineering Center. She received her B.S. in Chemical Engineering from UT Austin and obtained her Ph.D. in Chemical Engineering from UC Berkeley. After completing her Ph.D. in 2013, she trained at the University of Colorado Boulder as an NIH NRSA post-doctoral fellow. Adrianne's group at UT Austin focuses on the development of bioinspired polymeric materials to model cellular microenvironments and engineer therapeutic technologies. This work has received emerging investigator recognitions from the Burroughs Wellcome Fund, the NIH, the NSF, and the American Chemical Society Polymeric Materials: Science and Engineering Division.