Charged colloids observed by electrophoretic and diffusion NMR

Abstract: The thesis deals partly with methodology including constructionof hardware and new pulse sequences in the field of electrophoreticNMR, and partly with practical use of ENMR anddiffusion NMR in the investigation of charged colloidal systems.Several sources of artefacts are investigated, including gas productionat the electrodes, electroosmosis and Joule heatingeffects that can cause convection. The electrophoretic doublestimulated-echo pulse sequence is introduced to suppress theseartefacts and to increase the feasible measuring range to higherelectric fields and conductivities.The interaction between the non-ionic polymer poly(ethyleneoxide) PEO and differently charged surfactants is investigatedusing the above mentioned methods. The investigated surfactantsare the anionic sodium dodecyl sulphate (SDS) andpotassium laurate (KC12), the cationic dodecyltrimethylammoniumbromide (CTAB) and the non-ionic octyl β-D-glucoside.ENMR is also used to investigate two different mixed micellesystems, with SDS as the charged surfactant component anddodecyl malono-bis-N-methylglucamide (C12BNMG) respectivelytetra(ethylene oxide) dodecyl ether (C12EO4) as the nonionicsurfactant component. A method to calculate the degreeof counter-ion dissociation, αdissociation, as a function of compositionis demonstrated.Finally diffusion NMR is used to compare transport dynamicsin gel electrolyte systems based on two differently grafted polymers;one amphiphilic system containing polymethacrylategrafted partly with polyethylene oxide and partly with fluorocarbonsand the corresponding nonamphiphilic system graftedwith only polyethylene oxide. Both systems contain the electrolytelithium bis(trifluoromethylsulfonyl) imide salt dissolved inγ-butyrolactone. The results show that the system based on theamphiphilic polymer has better transport dynamics and thereforeis more suited as material for battery