Date of Award
Doctor of Philosophy (PhD)
Materials Science and Engineering
Using computational modeling, we focus on the phase behavior of multicomponent systems incorporating enzyme and bottlebrush polymers where the agglomeration of multiple components occurs. We start with all-atom molecular dynamics (MD) simulations of lysozyme and polyethylene glycol (PEG) based polymer mixture to understand the mechanisms of preservation of lysozyme bioactivity at high temperatures with addition of PEG-derived bottlebrushes. We show that the PEG part of bottlebrushes phase separates at high temperature and shells the access of water to lysozyme, resulting in the preservation of lysozyme secondary structures. We then developed a coarse-grained model using a Dissipative Particle Dynamics approach to model bottlebrush polymers in solutions at long time/length scales. We studied the effects of solvent qualities, length of side chains and evaporation rate on the conformation of bottlebrushes and agglomeration process. The cluster definition is modified with three cut-off criteria indicating various degrees of interactions between bottlebrushes. Using these criteria we could distinguish the short-lived and long-lived clusters during the agglomeration process and demonstrate two pathways of cluster formation, from short-lived agglomerates during transient process or from globules that form long-lived clusters directly. Our results show that a decrease in the solvent quality first increases and then decreases the size of the clusters. The trends for MBBs with longer side chains are similar. For bottlebrush-polymer-solvent system, the slow evaporation rate results in formation of larger bottlebrush clusters with more stretched bottlebrush conformations compared with fast evaporation process. We then also performed simulations with nanoparticles in polymer matrices to have a better understanding of agglomeration status of these nanoparticles. These results point out how the aggregation processes of complex multicomponent systems could be controlled via adjusting the affinities between species.
Tu, Sidong, "Modeling Phase Behavior and Agglomeration in Polymer Systems Incorporating Complex Architectures: From Bottlebrush to Lysozyme" (2022). All Dissertations. 3101.
Author ORCID Identifier
Available for download on Thursday, August 31, 2023