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Title: Structure Formation via Phase Transformations in Soft Materials
Authors: Liu, Jason Xufeng
Advisors: PriestleyArnold, RodneyCraig D. B.
Contributors: Mechanical and Aerospace Engineering Department
Keywords: colloids
phase separation
soft materials
thin films
Subjects: Materials Science
Issue Date: 2023
Publisher: Princeton, NJ : Princeton University
Abstract: Phase transformations underlie a plethora of phenomena in nature and in industry, and an understanding of the mechanisms underlying phase transformations allows us to elucidate biological processes as well as improve materials processing techniques. In this thesis, we experimentally explore several soft matter systems to elucidate the underlying physics of structure formation via phase transformations. We consider three classes of soft materials: structured polymer colloids, fibrillar biopolymer networks, and semicrystalline thin films. In our studies of structured colloids, we determine how the specific pathway from precipitation to vitrification dictates the resulting morphology of a polymer blend colloid. Through continuum simulations, free energy calculations, and experiments, we reveal how the colloid morphology changes with the trajectory taken through the phase diagram, all while the diagram itself evolves due to changing solvency conditions. In our attempt to understand the mechanics of intracellular phase separation, we induce liquid-liquid phase separation within fibrillar biopolymer networks as a synthetic analog to the cellular interior. With these experiments, we elucidate the mechanical interactions between droplets and the fibrillar network, finding that mesh-scale condensates constrained by the network grow in abrupt temporal bursts. Our experiments show that condensate restructuring and concomitant network deformation is contingent on the fracture of individual network fibrils, which is controlled by a competition between condensate capillarity and network strength. Finally, we investigate the structure of epitaxial polymer thin films deposited by matrix-assisted pulsed laser evaporation (MAPLE). We demonstrate that the heterogeneous confinement conferred by MAPLE deposition allows for the spatial separation of nucleation and growth, yielding a unique morphology of aligned epitaxial crystals. Amorphous material depletion during epitaxial crystallization is highly anisotropic, and we find that crystallization of the amorphous nanolayer becomes inhibited when bounded by epitaxial crystals.
Type of Material: Academic dissertations (Ph.D.)
Language: en
Appears in Collections:Mechanical and Aerospace Engineering

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