| dc.contributor.advisor | Glatzhofer, Daniel T | |
| dc.creator | Kadam, Rahul Suryakant | |
| dc.date.accessioned | 2019-04-27T21:37:21Z | |
| dc.date.available | 2019-04-27T21:37:21Z | |
| dc.date.issued | 2011 | |
| dc.identifier | 99348380302042 | |
| dc.identifier.uri | https://hdl.handle.net/11244/319186 | |
| dc.description.abstract | 7Li and 19F Nuclear Magnetic Resonance Spectroscopy (NMR) was used to investigate of the nature of lithium triflate dissolved in mixtures of ether and amine solvents. The transport of ions in the liquid and polymer electrolytes is influenced by the presence of the heteroatoms in the polymer or the liquid. There has been considerable research reported in the literature as far as the oxygen- and nitrogen-based liquid electrolytes and solid polymer electrolytes are concerned. It is also reported in the literature that polymer electrolytes based on hybrid systems (oxygen and nitrogen heteroatoms) such as the MEEP (poly[ bis(methoxyethoxyethoxy)phosphazene]) have exhibited some of the best room temperature conductivities. Another ether-amine hybrid polymer, poly(N-(2-(2-methoxyethoxy)ethyl)ethyleneimine) (LPEI-G2) was reported in the literature to show high conductivities with added lithium triflate. Analysis of the LPEI-G2 polymer electrolyte showed evidence of lithium cation coordination to oxygen but no evidence of nitrogen coordination. To study this type of mixed ether-amine system further, model compounds and their mixtures with dissolved lithium triflate were studied using 7Li and 19F NMR as an investigative probe. Conductivities, changes in dielectric constant, and self-diffusion coefficients data were measured. The 7Li, 19F, conductivity, and self-diffusion data suggest that lithium triflate does not exist as a dissociated species and mostly forms clusters or aggregates. A model is presented which reconciles the different possible species clusters/aggregates with the 7Li, 19F, conductivity, diffusion coefficient, and dielectric constant data. Application of the Nernst-Einstein equation to the self diffusion data suggests 99.99% ionic association in an amine solvent (N,N,N',N'-tetramethylethylenediamine) as compared to an ether solvent (monoglyme) which showed 99.97% ionic association. The conductivity data supports the ionic association data derived from Nernst-Einstein equation. In amine solvents the conductivity is relatively low (~ 10-6 S/cm) and increases monotonically to (~ 10-4 S/cm) on the addition of ether solvents. Changes in the dielectric constant for samples with different fractions of nitrogen and oxygen heteroatoms suggest that the dielectric constant of the medium which dissolves the lithium triflate plays a role in the different species formed by the lithium triflate but that specific interactions of the salt with the solvent play a significant, possibly determinate role. The amine content forces formation of more or bigger clusters/aggregates that leads to lower conductivities. A chelation versus coordination effect was seen for molecules consisting of two nitrogens or oxygens compared to one nitrogen or oxygen, respectively. | |
| dc.description.abstract | In the course of this work a method to use Electron Paramagnetic Resonance (EPR) to study of dielectric properties of liquids was developed. The signal response of an EPR active species is attenuated by the medium it is in. Keeping all other parameters the same, the higher the dielectric constant of the medium, the lower the EPR signals response. This behavior is problematic in studying EPR active species in high dielectric media but can be capitalized upon to determine the dielectric constant or to monitor changes in the dielectric constant of the medium. Using a coaxial EPR cell design, the EPR signal of a stable nitroxyl radical compound (2,2,6,6-Tetramethyl-piperidin-1-oxyl radical) in a low dielectric constant solvent in the inner tube is attenuated by the solvent present between the inner and outer tubes (jacket medium). The attenuation increases monotonically with an increase in the dielectric constant of the jacket medium. Calibration curves can be constructed using jacket media of known dielectric constants ranging from 2 to 80 and the dielectric constant of a sample used as the jacket medium can be determined by interpolation. The application of this technique to determine the dielectric constants and/or composition of mixed solvents, to monitoring the rate of a reaction, and to the study of surfactant solutions is presented. | |
| dc.description.abstract | Finally, the synthesis and modification of poly(ethyleneimine) (PEI) polymers such as branched PEI (BPEI) and linear PEI (LPEI). The modification of BPEI was done by substituting allyl groups on the nitrogens as cross-linking sites. The allyl groups were cross-linked under UV light in the absence of initiators to eliminate any interference caused by the initiators in the ionic transport phenomena. The highest ionic conductivity of the crosslinked BPAEI/lithium triflate without any initiator was measured to be 1.12 X 10-7 S/cm and was compared to the cross-linked BPAEI/lithium triflate in the presence of initiator. No significant improvement in the conductivity of the BPAEI/lithium triflate cross-linked without any initiator compared suggested that the initiators did not have a strong influence on ionic transport in the BPAEI/lithium triflate electrolyte system. Linear poly(ethyleneimine) was partially substituted with different lengths (Gx where x = 1,2,3) of PEO-like tethers and partially substituted with allyl groups (LPAGxEI), cross-linked in the presence of lithium triflate as a salt, and the conductivity of the resulting cross-linked polymers was investigated. The highest conductivity for LPAG1EI was measured to be 2.7 X 10-7 S/cm. The highest conductivity for LPAG2EI was measured to be 4.4 X 10-6 S/cm. Comparison of the LPAG1EI and LPAG2EI electrolytes shows that increasing in the oxygen content in the polymers does improve the conductivity. Model compounds for LPEI-Gx polymers were synthesized and characterized using NMR. | |
| dc.format.extent | 250 pages | |
| dc.format.medium | application.pdf | |
| dc.language | en_US | |
| dc.relation.requires | Adobe Acrobat Reader | |
| dc.subject | Lithium cells | |
| dc.subject | Polyelectrolytes | |
| dc.subject | Electrochemistry | |
| dc.title | "Study of Lithium Triflate as an electrolyte in mixed ether-amine solvents" and "The use of Electron Paramagnetic Resonance Spectroscopy to study Dielectric properties of materials" | |
| dc.type | text | |
| dc.type | document | |
| dc.thesis.degree | Ph.D. | |
| ou.group | College of Arts and Sciences::Department of Chemistry and Biochemistry | |
