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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Dynamics of Cyclic and Linear Poly(oxyethylene) and Threading Conformation in Their Blends

Nam, Sunghyun 15 November 2006 (has links)
Chemically identical but topologically different cyclic and linear polymers not only result in marked differences in dynamics, but also lead to unique transport properties of their blends, where cyclic polymers have chances to be threaded onto the linear polymers. This dissertation addresses the effect of ring architecture on dynamics using different time/length scale techniques: self-diffusion coefficients, NMR spin-spin relaxation time (T2) and bulk viscosity. In deuterated water, synthesized cyclic poly(oxyethylene) (CPOE) (400-1500 g/mol) diffused faster than corresponding linear POE (LPOE) and linear POE dimethyl ether (LPOEDE). However, the self-diffusion coefficients in melts were arranged in the following manner: LPOEDE > CPOE > LPOE, in excellent agreement with T2 and viscosity data, showing topological and chain end effects. Compared to LPOEDE, both CPOE and LPOE had higher activation energies for viscosity with less dependence on the molecular weight. In the blends of CPOE and LPOE for 900 and 1500 g/mol, the diffusion coefficient and viscosity in melts were higher and lower than the values predicted by a binary mixing rule, respectively. These deviations were attributed to the threading conformation, and the weight fraction of the threaded chains for 1500 g/mol was estimated by a three-term mixing rule. This threading conformation also appeared to influence such important bulk properties as the glass transition and spherulitic growth rate of the blends.

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