Characterization of Native Vernonia Oil and the Preparation of Derivatives for Application as Performance Materials
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Date
2012-06-06
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Addis Ababa University
Abstract
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.
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Keywords
Characterization, Native Vernonia Oil, Preparation, Derivatives, Application, Performance Materials