Mechanical processing of cellulosic substrates is an important step in many processes such as nanocellulose production and pretreatment of biomass prior to enzymatic saccharification. Developing a deeper understanding of the way in which mechanical energy affects cellulose at the molecular and macromolecular scales will help optimize such processes. Previously, we demonstrated that relationships exist between the macromolecular geometry of cellulose fibrils and their propensity to concentrate stress into the formation of kink-defects that lower the overall free energy of the structure when constrained to curvatures above a certain threshold. In this presentation, I will describe recent developments towards understanding the mechanical induction of crystalline defects by 2 and 3-point bending tests performed both in-silico and with a scanning probe microscope. In addition to modeling and measuring the molecular mechanics of fibril bending, we incorporate quantum mechanical simulations to predict breakage of strained glycosidic bonds during the course of fibril bending. This phenomenon of mechanically-induced bond breakage may contribute to the enhanced enzymatic digestibly of biomass subjected to high-shear processing, such as disc-refining, by introducing new reducing and non-reducing ends for the initiation of processive hydrolysis. Finally, we investigate the reversibility of fibril bending and determine the threshold at which the mechanics of bent fibrils are permanently altered such that they may no longer spontaneously recover their initial configuration when the mechanical stress is released.

Understanding the mechanical induction of macromolecular defects in cellulose nanofibrils by molecular dynamics simulation and scanning probe microscopy

253rd National Meeting (2017)

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