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Title: Novel biodegradable polyesters derived from carbohydrates
Author: Tang, Min
ISNI:       0000 0004 2680 8614
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2009
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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-raycrystallography. In Chapter 1, which is the introduction, some of the leadingbiodegradable polymers are introduced, in particular attention is paid to polyesterswhich are synthesised from carbohydrates. In addition, the standard polymerisationmethods for the polyester synthesis - ring opening polymerisation and steppolymerisation - are described. Chapter 2 details the synthesis and polymerisation ofacetic acid 5-acetoxy-6-oxo-tetrahydro-pyran-2-yl methyl ester. Three differentinitiating systems have been used for ring opening polymerisations; the kinetics and thepolymer product of the polymerisation are discussed. L-Lactide was used incopolymerisations with acetic acid 5-acetoxy-6-oxo-tetrahydro-pyran-2-yl methyl ester;the copolymers show distinct thermal properties and accelerated degradation ratescompared with poly(L-Lactide) (PLLA). Chapter 3 involves applying functionalisedcarbohydrates, with one free hydroxyl group, as the co-initiator for the ring openingpolymerisation (ROP) of L-lactide. The polymerisations were well controlled with linearrelationships between the percentage lactide conversion and the polymer?s molecularweight. The carbohydrates form the functionalised end group of the PLLA, which, inturn, improve the hydrophilicity of the resulting PLLA. These end-group functionalisedpolylactides have been used as the matrix for human-osteoblast-derived osteosarcomacells (SaOS-2 cells) culturing, and these studies proved that the carbohydrate endgroups were non toxic. Chapter 4 describes the synthesis of a series of othercarbohydrate 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. TheROP of these lactones resulted in formation of low molecular weight oligomers, exceptfor 2,3,4-tri-O-benzyl-D-xylonolactone, which can not be polymerised. Chapter 5describes the overall conclusions resulting from the experiments described in the thesis.Chapter 6 is the experimental section and thus provides a detailed description of thesynthesis of all the compounds prepared in the thesis and their analytical data. TheAppendices include two papers that have already been published, describing some ofthe work in the thesis; important additional NMR spectra and MALDI-ToF spectra; andthe complete X-ray crystallography data.
Supervisor: Williams, Charlotte ; Stevens, Molly Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral