The role of quenched disorder, interfaces and confinement on the glassy dynamics of colloidal suspensions, thermal liquids and films

glass transition, thin film, polymers, colloids, structural relaxation

Phan, Anh Duc

关键词: glass transition, thin film, polymers, colloids, structural relaxation;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/102444/PHAN-DISSERTATION-2018.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Understanding the slow activated glassy dynamics of colloidal and thermal (molecular, metallic, polymer) fluids in the presence of quenched disorder, interfaces and/or confinement is of fundamental science importance and relevant for materials applications. My overarching goal is to construct new, microscopic, force-level statistical mechanical theories to determine qualitatively and quantitatively the dynamics of confined systems using relatively simple models, make testable predictions and compare to experiments. The Elastically Collective Nonlinear Langevin Equation (ECNLE) theory for activated relaxation in the bulk serves as the starting point to predict dynamical arrest, the shear modulus and alpha relaxation time. First, I construct a new theoretical framework for the dynamics of bulk isotropic hard-sphere fluids and colloidal suspensions in the presence of randomly pinned particles, and also apply it to real thermal liquids. The randomly-pinned particle systems are also used to describe caging constraints at solid substrates in supported films. Second, I propose an improved treatment of collective elasticity effects in films to capture geometric asymmetry due to modified boundary conditions. Third, a new theory is constructed for how the local dynamic free energy that quantifies spatial caging constraints in glass-forming liquids at a surface and how such perturbations are propagated into the film. Fourth, novel predictions are made under anisotropic confinement in specific classes of films with a vapor interface(s), roughly and smooth hard substrates, and a vibrating (softened) pinned particle solid which reflect a complex interplay between glassy dynamics, elastic and topographic properties of surfaces, and physical adsorption. The spatial gradient of alpha relaxation time and glass transition temperature, interfacial and vitrified dead-layer thickness, spatial decoupling of relaxation in films from the bulk, elastic shear modulus, and characteristic length scales are calculated and are found to be in good agreement with simulations of simple models and experiments on molecular and polymeric liquids.