[Seminar] Microstructure of DNA-cross-linked hydrogels from time-temperature-superposition by Prof. Hill

Abstract:

DNA-cross-linked polyacrylamide hydrogels are termed ``smart" due to specific molecular recognition ability and base-pair reversibility. Little is known of their rheological properties, particularly on the longer timescales that influence their durability and classification as a liquid or gel in practical applications. This talk will present the linear-viscoelastic response of complementary-DNA-strand cross-linked polyacrylamide, with and without covalent N,N'-methylene(bis)acrylamide cross-linking. Unique characteristics of the gelation kinetics and viscoelasticity will be highlighted, particularly with respect to detailed complementary studies we have conducted on bis-cross-linked polyacrylamide. Interpretations based on the associative Rouse model of Indei and Takimoto (2010) will be explored, also drawing on the rheology of star-polymer melts for which the slowest relaxation time is hindered by arm entanglement/retraction dynamics.

Biography:

Reghan J. Hill is an associate professor in the department of chemical engineering at McGill University. He obtained his Ph.D. in chemical engineering from Cornell University (lattice-Boltzmann studies of inertial flow in porous media, under D. L. Koch) and undertook post-doctoral studies at Princeton University (electro-kinetics of fuzzy colloidal particles, under D. A. Saville and W. B. Russel). He presently teaches process control, foundations of soft matter, and heat-and-mass transfer.