Abstract
Many materials, including glasses and most polymers, are either non-crystalline or partially crystalline. In the low viscosity regime, diffusivity in non-crystalline systems can be modeled using the Stokes-Einstein relation, which connects diffusivity to the size of the diffusing species and the viscosity of the medium in which it is diffusing. When applying the Stokes-Einstein equation to polymer chains, the freely jointed chain model can be used to approximate the structure of an isolated polymer chain. For more complicated polymers with entangled networks, diffusion is more accurately description by reptation. Reptation refers to the snakelike motion of a polymer chain along its own axis. Ion exchange is an important interdiffusion process for modifying the surface properties of glasses. Ion exchange can lead to chemical strengthening of glass when smaller alkali ions from the glass are exchanged with larger alkali ions from a molten salt bath. Ion exchange also affects the refractive index of the glass and can be used to fabricate planar waveguides. Silver ion exchange can also create glass surfaces with anti-microbial properties to help prevent the spread of infectious diseases.
Published Version
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