Self-Assembly, Nonlinearity, and Elastic Instabilities of Swollen Gels
Mechanical and Aerospace Engineering
Department Seminar Series
Dave C Swalm School of Chemical Engineering
Mississippi State University
Swollen polymer gels are used in a wide variety of applications ranging from bioimplants to food materials to drug delivery to tissue engineering. In this presentation, the non-linear mechanical responses, elastic instability, and failure behavior of two different gels: a physically crosslinked gel (triblock gel) and an ionically crosslinked gel (alginate gel) will be presented. The physical gel is thermoreversible in nature and consists of a triblock copolymer poly(methylmethacrylate)- poly(n-butylacrylate)-poly(methylmethacrylate) in a mid-block selective solvent. The gel structure evolution as a function of temperature captured using small angle neutron scattering will be discussed. Both small and large amplitude oscillatory shear experiments were used to investigate the rheological properties of these gels. Alginate gels display negative normal force, which has not been reported in literature earlier. Failure behavior of these gels initiated from a defect was investigated using cavitation rheology, a custom designed characterization technique. It involves growing a cavity at the tip of a syringe needle (~10 -1000 μm) located at any arbitrary location within a gel and monitoring the pressure at the onset of instability and fracture. The onset or critical pressure is directly related to the local mechanical properties of the material. Cavitation and shear-rheology results capture distinctly different non-linear behavior and failure responses for the triblock and alginate gels. The effect of graphene nanoplatelets on the self-assembly and mechanical properties of the triblock gel will also be presented.
Dr. Santanu Kundu is an Assistant Professor in the Dave C. Swalm School of Chemical Engineering of Mississippi State University since January 2012. Before joining Mississippi State Dr. Kundu performed postdoctoral research in the Sustainable Polymers Group (Polymers Division) of the National Institute of Standards and Technology (NIST) and at the Polymer Science and Engineering Department of the University of Massachusetts-Amherst. Dr. Kundu has received his PhD in Chemical Engineering from Clemson University in 2006. His PhD work, which linked flow, microstructure, and the processing of liquid crystalline carbonaceous materials, has been awarded the best dissertation in Carbon Science (2004-2006) by the Elsevier-Carbon journal. Dr. Kundu’s research interest is investigating the processing-structure-property relationships for various soft materials towards applications ranging from bioimplants to energy storage to water purification to structural composites. He is the recipient of the 2014 NSF Early Career Award.