Disputas: Lili Zhang
Cand. Scient. Lili Zhang ved Kjemisk institutt vil forsvare sin avhandling for graden ph.d. (philosophiae doctor): Solid-state NMR Characterization of Crystallinity and Dynamics in Polyethylene
Professor Shanmin Zhang, Physics Department, East China Normal University, China
Ph.D. Keith Redford, Conpart, Skjetten, Norway
Professor Ute Krengel, Department of Chemistry, University of Oslo
Leder av disputas: Professor Tyge Greibrokk
Veileder: Professor Eddy Walther Hansen, Professor Jaan Roots og Professor Qun Chen
This thesis investigates the morphology and spin dynamics of polyethylene (PE) by Solid-state Nuclear Magnetic Resonance (NMR). The work has been carried out as a collaboration between the Department of Chemistry, UiO and the Department of Physics, ECNU (East China Normal University).
The physical properties and applications of polymers are profoundly influenced by the degree of crystallinity. It is therefore crucial to determine the crystallinity as precisely as possible. Solid-state NMR spectroscopy has become a popular technique to determine this quantity. The crystallinity of LLDPE (Linear Low Density Polyethylene) obtained by carbon NMR was compared to the crystallinity derived from proton NMR. The figures were found to be compatible and also to agree with the crystallinity obtained by differential scanning calorimetry (DSC), a standard method widely applied in the industry. Furthermore, a new method of combined spin diffusion and cross polarization (CP) is proposed in the thesis.
The thesis also evaluates spin diffusion NMR experiments -which are usually applied to study microstructure in polymers- under different Magic-Angle Spinning rates and establishes a relationship between this rate and the apparent diffusion coefficient. In addition, a new model to study polymer chain transport (chain diffusion) is proposed and validated through experiments.
For mer informasjon, kontakt Astrid Waaler Kaas.