Browsing by Author "Desalegn, Tegene"

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    Characterization of Native Vernonia Oil and the Preparation of Derivatives for Application as Performance Materials
    (Addis Ababa University, 2012-06-06) Desalegn, Tegene; Chebude, Yonas (PhD)
    In recent years, the interest in finding environmentally friendly or green biodegradable materials derived from natural resources as alternatives to non-biodegradable petroleumbased polymers has increased dramatically. Vernonia galamensis is a native plant of Ethiopia whose seeds contain a significant concentration of a unique naturally epoxidised triglyceride oil. This type of moiety is particularly useful as a cross-linking agent and synthetic building blocks and therefore, vernonia oil offers great potential for numerous applications. This thesis explores the synthetic possibilities of vernonia oil in order to try to maximise the prospects for its industrialisation. For this study, native vernonia galamensis seeds obtained from Haromaya University and Adet Agricultural Center were used. All the products obtained from vernonia oil are shown in Figure 1. Figure 1: Schematic representations of derivatives of vernonia oil The extracted vernonia oil, vernolic acid, vernonia oil methyl ester and vernanol were characterized using 1H NMR, 13C NMR, FTIR, MALDI-TOF MS, and TGA. The oil content of the plant and the concentration of the epoxy moiety were assessed. The vernonia oil derivatives such as vernolic acid, vernonia oil methyl ester, vernanol, were used as precursors in the synthesis of various value added products. One of the major objectives of this thesis is to conduct preliminary studies for the synthesis of polymeric materials using sugar fatty esters containing an epoxy group as the starting material. New epoxy starch and epoxy glucose fatty acid esters were prepared by esterification and transesterification reactions employing different reaction conditions, using both chemical and enzymatic synthesis and organic solvents and/or ionic liquids as solvents. Most of the products were found to be insoluble in NMR solvents, which complicated their characterisation. However, they were successfully characterised using a large array of techniques such as solid state NMR, FTIR, MS, DSC, TGA, powder XRD and SEM. All techniques confirmed the esterification of the sugars in a different degree of substitution, which were evaluated via titration methods. The stability of the epoxy group under the different experimental conditions was also evaluated. The degree of substitution and presence of epoxy group could also be related to properties such as the thermal stability or the morphology of the sample. The data collected helped to identify the most useful synthetic methods for further testing. Ring opening polymerisations of vernonia oil and vernonia oil methyl ester were also successfully carried out. These studies contain useful information that will be used in the future work for the design of the polymerisation reactions of the epoxidized sugar esters. Different modifications of vernonia oil and its derivatives were performed in order to increase the scope of applications of materials available from vernonia oil. These include epoxidation of vernonia oil, preparation of vernonia oil polyol and hydroxylation of VOME. In all cases, 1H NMR, 13C NMR, FTIR, ESI-MS results obtained confirmed the synthesis of the intended products.