Nuclear Magnetic Resonance Methods to Study Soft Matter Dynamics and Microstructure
Doctoral thesis, 2012
Soft matter is of great importance for food, hygiene and pharmaceutical products. Gels are an example of soft matter and are found in e.g. diapers, that are able to take up large amounts of liquids. Translational motion such as diffusion and/or flow is the fundamental mechanism for transport of solutes or solvents e.g. within gels and is strongly dependent on their microstructure. In addition, interactions e.g. solutes binding to the gel surface, may alter diffusion in soft matter. In order to tailor-made materials, it is necessary to have a detailed knowledge of how microstructure and interactions influences mass transport in soft matter.
Different nuclear magnetic resonance methods were applied to monitor mass transport in a variety of microstructures during steady and non-steady state conditions. Water dynamics were monitored during capillary formation in alginate gels using
1H magnetic resonance imaging. This method allowed the water at the gelation front, where the growth of capillaries occurred, to be followed as a function of time. It was found that there are enhanced water dynamics at the gelation front and that the rate of gel formation occurs faster and produces a denser gel in the case of capillary formation.
1H and 19F chemical shift imaging was applied to study the dynamics of water and fluoride ions dynamics during gelation of a non-aqueous cellulose solution, which forms a gel upon addition of water. The rate of gelation was followed tracking the water signal as a function of time and position.
3D 1H diffusion tensor imaging combined with 3D 2H spectroscopic information mapped the microstructure of shear-induced multi-lamellar vesicles as a function of time. Furthermore, the half-life time could be estimated in a spatially resolved manner and it was found that shear-induced multi-lamellar vesicles seems to decay faster close to surfaces.
The interaction of water with silica surfaces was studied with 17O relaxation measurements as a function of amount silica and salt. Upon the addition of salt, a gel is formed and a reduced amount of surface “bound” water is reported. The information obtained was then used to rationalize the diffusion of water in this systems in the framework of the cell model.
KC
Opponent: Philip W. Kuchel
Author
Diana Bernin
Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry
SuMo Biomaterials
Chemical Shift Imaging NMR to track gel formation
Journal of Colloid and Interface Science,;Vol. 344(2010)p. 238-240
Journal article
Magnetic resonance analysis of capillary formation reaction front dynamics in alginate gels
Magnetic Resonance in Chemistry,;Vol. 49(2011)p. 627-640
Journal article
Många produkter inom hygien- och läkemedelsbranschen består till största delen av mjuka material, vanligtvis uppbyggda av geler. Geler är i sin tur uppbyggda av långa molekylkedjor som bildar ett nätverk av trådar omgivna av någon vätska. Nätverken benämns mikrostrukturer och hålrummen mellan kedjorna kallas porer. Genom en karaktärisering kan man förstå sammanhanget mellan mikrostruktur och upptagning/frisättning av molekyler. Detta är viktigt för att kunna skapa mjuka material med skräddarsydda egenskaper.
I detta arbete har olika metoder av kärnmagnetisk resonansspektroskopi (NMR) använts för att karaktärisera mikrostrukturer och mäta molekylers rörelse i dessa. Kärnmagnetisk resonanstomografi (MRI) har använts för att få information om molekylers rörelse i en pixel av en bild. Detta arbete har också visat att MRI kan användas för att undersöka förflyttningen av vatten vid bildande av små rör i en gel som exempelvis kan användas för att bygga upp cellvävnader. Även inträngningshastigheten av vatten när en gel bildas och halveringstiden av sfäriska mikrostrukturer har kunnat bestämmas med MRI. Utöver detta har interaktionen mellan vatten och en yta av olika mikrostrukturer undersökts för att studera påverkan av vattens rörelse genom mikrostrukturen.
NMR/MRI är väl fungerande metoder för karaktärisering av mikrostrukturer och tillför därmed betydelsefull kunskap som kan användas för att skapa nya mjuka material såväl som till att optimera egenskaperna hos olika produkter.
Soft matter is of great importance for hygiene and pharmaceutical products. Translational motion such as diffusion and/or flow is the fundamental mechanism for mass transport within a soft matter microstructure. In order to tailor-made materials, it is necessary to have a detailed knowledge of how microstructure and interactions influences mass transport in soft matter. Nuclear magnetic resonance (NMR) methods were applied to monitor mass transport in microstructures during steady and non-steady state conditions. Water dynamics were monitored during capillary formation in alginate gels using 1H magnetic resonance imaging. Water at the gelation front was followed as a function of time and enhanced water dynamics at the gelation front in case of capillary formation were found. 1H and 19F chemical shift imaging was applied to study dynamics of water and fluoride ions during gelation of a non-aqueous cellulose solution. 3D 1H diffusion tensor imaging combined with 3D 2H spectroscopic information mapped the microstructure of shear-induced multi-lamellar vesicles as a function of time. The half-life time could be estimated, showing that shear-induced multi-lamellar vesicles decay faster close to surfaces. Interactions of water with silica surfaces were studied with 17O NMR. Upon the addition of salt, a gel is formed and a reduced amount of surface “bound” water is reported. The information obtained was then used to rationalize the diffusion of water in these systems.
Subject Categories
Chemical Sciences
ISBN
978-91-7385-778-9
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 3459
KC
Opponent: Philip W. Kuchel