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Full-Text Articles in Engineering
Impact Of Chain Architecture On The Thickness Dependence Of Physical Aging Rate Of Thin Polystyrene Films, Gregory Brown, Elizabeth Lewis, Bryan D. Vogt
Impact Of Chain Architecture On The Thickness Dependence Of Physical Aging Rate Of Thin Polystyrene Films, Gregory Brown, Elizabeth Lewis, Bryan D. Vogt
Williams Honors College, Honors Research Projects
The dynamics of polymer thin films have been demonstrated to be significantly altered from the bulk, but the origins of such differences are not well defined. In this work, we seek to understand the differences in the structural dynamics (or physical aging) of polystyrene (PS) through branching and other well defined architectures (comb and centipede). The aging dynamics of ultrathin films (< 30 nm) differ from relatively thick films (100-150nm) with linear PS thin films aging more rapidly than the relatively “bulk-like” thick films. Ellipsometric measurements are used to characterize the physical aging rate of the films. The change in film thickness and refractive index as the films are held below the glass transition temperature (Tg) provides a simple measure of the physical aging. In this study, four different architectures (linear, comb, 4 arm star, and centipede) will be investigated. For each PS architecture, the aging rate will be determined for film …
Pigments For Improving Plant Health In Organic Systems, Gregory Keith Bartley Jr.
Pigments For Improving Plant Health In Organic Systems, Gregory Keith Bartley Jr.
Gregory Keith Bartley Jr.
Photosynthesis, arguably the most important biological process on earth, solely relies on the ability of pigments to capture, utilize, and convert the sun‟s energy to form life. The adequate conversion of light into harvestable food, fuel, and fiber regulates rates of population and economic growth. In order to meet the expanding needs of humanity with the earth‟s potential for agricultural production, new sustainable techniques for increased photosynthetic efficiency in plants must be implemented. The earth's pattern of light exposure is extremely dynamic, exhibiting constant changes in quantity and quality throughout time and space. For photosynthetic organisms, this meant evolving various …