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Dissertation Defense – Anise Grant
MSE Grad Presentation
Monday, May 20, 2019 - 10:00am
Prof. Vladimir Tsukruk, Advisor, MSE
Prof. Rajesh Naik, MSE
Prof. Zhiquin Lin, MSE
Prof. Meisha Shofner, MSE
Prof. Valeria Milam, ME
"Biopolymer and Synthetic Polymer Nanocomposite Reinforcement via Interfacial Assembly"
Protein biopolymer composites bring together the tunability and flexibility of protein matrices and functionality of filler components. Graphene-based biocomposites are particularly popular for design of aqueously processible and strong flexible electronics for sensing, nanowires, and semiconductors. However, a lot of trial and error is required to determine biopolymer and co-constituent chemistry as well as the assembly process needed for capitalize on their synergistic properties. The key to success is optimizing the material interface. This dissertation seeks to elucidate the mechanisms for favorable interfacial interactions and assembly that yield mechanical strength enhancement using silk fibroin from Bombyx mori silkworm cocoons, silk like protein suckerin from squid sucker ring teeth, and synthetic copolymers at inorganic interphases. Silk is a well-studied protein that serves as platform for identifying drivers of interfacial interactions between graphene and proteins, and then show how interface optimization leads to mechanical reinforcement. Inter-protein applicability is demonstrated using suckerin as well as the additive nature of some triggers for self-assembly and interfacial adhesion.
Specifically, this dissertation focuses on the assembly of silk fibroin from Bombyx mori silkworm cocoons, silk like protein suckerin from squid sucker ring teeth, and synthetic copolymers at inorganic interphases; the implications of assembly on mechanical performance; and how this relates to previous findings with SF. The main drivers of assembly and interfacial binding studied here include temperature, shear force, hydropathy, and pH. Surface topography and polymer chemistry/conformation were studied concurrently via atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). This data was supported by simulation to better define assembly mechanisms at the interface of biopolymers and inorganic 2D fillers and their timescales. Then, mechanical characterization via bulging tests and scanning probe microscopy methods (SPM), force distance spectroscopy (FDS) and quantitative nanomechanical mapping (QNM). Mechanical performance is evaluated at the macro and nanoscales using quantitative nanomechanical mapping, force distance spectroscopy, and buckling tests. Overall, this study draws a vital link between the structure of the biopolymer and 2D filler, processing applied, and mechanical performance ; thereby providing a roadmap for further optimization of biopolymer-based nanocomposites through interface-minded design.