Novel biodegradable polyesters derived from carbohydrates
Author(s)
Tang, Min
Type
Thesis
Abstract
This thesis concerns the synthesis of new biodegradable polyesters from carbohydrates.
All the new products have been characterised using nuclear magnetic resonance (NMR)
spectroscopy and mass spectrometry; some have been studied using X-ray
crystallography. In Chapter 1, which is the introduction, some of the leading
biodegradable polymers are introduced, in particular attention is paid to polyesters
which are synthesised from carbohydrates. In addition, the standard polymerisation
methods for the polyester synthesis - ring opening polymerisation and step
polymerisation - are described. Chapter 2 details the synthesis and polymerisation of
acetic acid 5-acetoxy-6-oxo-tetrahydro-pyran-2-yl methyl ester. Three different
initiating systems have been used for ring opening polymerisations; the kinetics and the
polymer product of the polymerisation are discussed. L-Lactide was used in
copolymerisations with acetic acid 5-acetoxy-6-oxo-tetrahydro-pyran-2-yl methyl ester;
the copolymers show distinct thermal properties and accelerated degradation rates
compared with poly(L-Lactide) (PLLA). Chapter 3 involves applying functionalised
carbohydrates, with one free hydroxyl group, as the co-initiator for the ring opening
polymerisation (ROP) of L-lactide. The polymerisations were well controlled with linear
relationships between the percentage lactide conversion and the polymer’s molecular
weight. The carbohydrates form the functionalised end group of the PLLA, which, in
turn, improve the hydrophilicity of the resulting PLLA. These end-group functionalised
polylactides have been used as the matrix for human-osteoblast-derived osteosarcoma
cells (SaOS-2 cells) culturing, and these studies proved that the carbohydrate end
groups were non toxic. Chapter 4 describes the synthesis of a series of other
carbohydrate lactones derived from D-glucono-1,5-lactone, D-xylose and 2-deoxy-Dribose;
the lactones include 2,3,4-tri-O-benzyl-D-xylonolactone, 6-methyl-2-oxotetrahydro-
2H-pyran-3-yl acetate, (S)-6-(benzyloxymethyl)-tetrahydropyran-2-one. The
ROP of these lactones resulted in formation of low molecular weight oligomers, except
for 2,3,4-tri-O-benzyl-D-xylonolactone, which can not be polymerised. Chapter 5
describes the overall conclusions resulting from the experiments described in the thesis.
Chapter 6 is the experimental section and thus provides a detailed description of the
synthesis of all the compounds prepared in the thesis and their analytical data. The
Appendices include two papers that have already been published, describing some of
the work in the thesis; important additional NMR spectra and MALDI-ToF spectra; and
the complete X-ray crystallography data.
All the new products have been characterised using nuclear magnetic resonance (NMR)
spectroscopy and mass spectrometry; some have been studied using X-ray
crystallography. In Chapter 1, which is the introduction, some of the leading
biodegradable polymers are introduced, in particular attention is paid to polyesters
which are synthesised from carbohydrates. In addition, the standard polymerisation
methods for the polyester synthesis - ring opening polymerisation and step
polymerisation - are described. Chapter 2 details the synthesis and polymerisation of
acetic acid 5-acetoxy-6-oxo-tetrahydro-pyran-2-yl methyl ester. Three different
initiating systems have been used for ring opening polymerisations; the kinetics and the
polymer product of the polymerisation are discussed. L-Lactide was used in
copolymerisations with acetic acid 5-acetoxy-6-oxo-tetrahydro-pyran-2-yl methyl ester;
the copolymers show distinct thermal properties and accelerated degradation rates
compared with poly(L-Lactide) (PLLA). Chapter 3 involves applying functionalised
carbohydrates, with one free hydroxyl group, as the co-initiator for the ring opening
polymerisation (ROP) of L-lactide. The polymerisations were well controlled with linear
relationships between the percentage lactide conversion and the polymer’s molecular
weight. The carbohydrates form the functionalised end group of the PLLA, which, in
turn, improve the hydrophilicity of the resulting PLLA. These end-group functionalised
polylactides have been used as the matrix for human-osteoblast-derived osteosarcoma
cells (SaOS-2 cells) culturing, and these studies proved that the carbohydrate end
groups were non toxic. Chapter 4 describes the synthesis of a series of other
carbohydrate lactones derived from D-glucono-1,5-lactone, D-xylose and 2-deoxy-Dribose;
the lactones include 2,3,4-tri-O-benzyl-D-xylonolactone, 6-methyl-2-oxotetrahydro-
2H-pyran-3-yl acetate, (S)-6-(benzyloxymethyl)-tetrahydropyran-2-one. The
ROP of these lactones resulted in formation of low molecular weight oligomers, except
for 2,3,4-tri-O-benzyl-D-xylonolactone, which can not be polymerised. Chapter 5
describes the overall conclusions resulting from the experiments described in the thesis.
Chapter 6 is the experimental section and thus provides a detailed description of the
synthesis of all the compounds prepared in the thesis and their analytical data. The
Appendices include two papers that have already been published, describing some of
the work in the thesis; important additional NMR spectra and MALDI-ToF spectra; and
the complete X-ray crystallography data.
Date Issued
2009-02
Date Awarded
2009-09
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Williams, Charlotte
Stevens, Molly
Creator
Tang, Min
Publisher Department
Chemistry and Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)