Chitin is a natural polymer which is extracted from a number of biological sources. This polymer is deacetylated to form the related polymer chitosan. The design and preparation of chitosan derivatives has been investigated to tailor the physical and chemical properties towards specific applications. To this end, this thesis describes the synthesis and characterisation of a number of chitosan derivatives. The prepared polymers contained either naphthalimide groups, thiol groups, poly(methyl methacrylate) side chains or poly(oligoethylene glycol methyl ether methacrylate) side chains.
Chitin was successfully extracted and purified from squid pens by literature methods to give polymers with DD values from 12 to 23%. The Kurita method was used to obtain chitosan samples with a range of DD values from 75 to 91%. The prepared polymers were characterised by microanalysis, IR, �H NMR and solid-state ��C NMR spectroscopy. The MW distributions of the chitosan samples were determined by GPC in 0.3 M AcOH/0.2 M AcONa(aq) solution with dextran standards.
The N-(naphthalimide)-chitosan derivatives were fluorescent materials and were typically prepared from the reaction of 4-bromonaphthalic anhydride with chitosan. This reaction was thoroughly investigated to find the optimal reaction conditions. The bromo groups were subsequently displaced by one of four nucleophiles: dimethylamine, piperidine, methoxide or vinylferrocene. The polymers were characterised by microanalysis, GPC, IR, �H NMR, UV-vis and fluorescence spectroscopy. The excitation and emission wavelengths and Stokes shifts were dependent on the substituent present in the naphthalimide group.
Chitin and chitosan were sequentially reacted with tosyl chloride, potassium thioacetate and sodium methoxide to form the thiolated derivatives. The success of the tosylation reaction was dependent on the synthetic route used and the DD of the polysaccharide. The thiolated chitin polymers were well defined although the samples were completely insoluble. The thiolated chitosan polymers were also characterised and were highly swollen in acetic acid solution.
These thiolated polysaccharides were used as macroinitiators for the free-radical polymerisation of MMA. The products obtained from the reaction of 6-mercaptochitin in DMSO with MMA were typically prepared with low yields and low amounts of grafting. The products prepared from 6-mercaptochitosan under the same conditions contained larger amounts of the synthetic polymers although the products were highly variable. MMA was subsequently polymerised with 6-mercaptochitosan in acetic acid buffer to form highly grafted copolymers.
Chitosan was reacted with the monomer OEGMA by ATRP to form chitosan-graft-poly(OEGMA) copolymers. Two synthetic routes were investigated. The "grafting-from" route involved. the formation of a chitosan macroinitiator and polymerisation of OEGMA with this polymer. The polymers contained a large amount of grafted side chains as estimated from the �H NMR spectra. However, the purification was not satisfactory as determined by the presence of two peaks in the GPC traces. The "grafting-to", route involved the formation of poly(OEGMA) by ATRP with activated initiators and subsequent attachment to chitosan. The prepared copolymers showed large differences in their appearance with even very low amounts of grafting. The purification of the polymers prepared by this method was successful with no detectable homopolymer as determined by GPC analysis.
| Identifer | oai:union.ndltd.org:ADTP/222194 |
| Date | January 2009 |
| Creators | Munro, Natasha Helen, n/a |
| Publisher | University of Otago. Department of Chemistry |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright Natasha Helen Munro |
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