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theses

Organogels are thermal reversible semisolid materials that show great potential for use in foods to replace saturated fats and trans fats in processed foods. They are comprised of an organic liquid and low concentration (~ 2 wt%) of low molecular-mass organogelators (LMOGs) that spontaneously undergo formation of three-dimensional (3-D) self-assembled fibrillar networks (SAFiNs) capable of entrapping the solvent among the entangled nanofibers. SAFiNs formation requires the meticulous balance between contrasting solvent-gelator interactions. To elucidate the role of solvent properties on molecular gels formation, Hansen solubility parameters (HSPs) are used to correlate the nature of solvents to the gelation behavior of 12-hydroxystearic acid (12HSA). The hydrogen-bonding HSP (h) is found to be particularly useful in studying and predicting the solvent effect on 12HSA self-assembly and ultimately on gelation ability. Transparent 12HSA organogels only form in the solvents studied with hydrogen-bonding HSP less than 4.7 MPa1/2 while solution remains when h > 5.1MPa1/2. A strong linear correlation has also been established between h and critical gelator concentration (CGC). The macroscopic properties, microstructure and nanostructure of 12HSA molecular gels illustrate the importance of the nature of solvents that greatly affect SAFiN properties including: crystallinity, thermal properties, polymorphic forms, carboxylic dimer structure, domain size, fiber morphology and microstructure. Each of the aforementioned properties is influenced by h and to a lesser extent the polar component of the HSPs (p). 12HSA in solvents with a h < 4.4 MPa1/2 form transparent organogels that contain fibrillar crystal aggregates with the hexagonal polymorpic form. As the h of the solvent increases, the polymorph of 12HSA organogels undergoes transition from the hexagonal form to triclinic parallel form, which corresponds to the transitions observed in dimer structure, crystal morphology and the decrease in crystallinity.

ETD_5848

M.S.

Includes bibliographical references

by Songwei Wu

doi:10.7282/T3KH0PXX

ETD graduate

The author owns the copyright to this work.