Synthesis, Characterization and Enzyme Degradation Study of a New Biodegradable Copolymer of Poly(L-lactide) and Poly(L-glutamic acid)

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dc.contributor.advisor Easteal, Allan en Huang, Ning Fang (Anna) en 2007-07-20T09:38:20Z en 2007-07-20T09:38:20Z en 2003 en
dc.identifier THESIS 04-041 en
dc.identifier.citation Thesis (PhD--Chemistry)--University of Auckland, 2003 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract Polylactide is a widely used biodegradable polymer which finds many uses in biomedical applications such as surgical sutures, implant materials and drug carriers. However, the rather low hydrophilicity of polylactides, due to the presence of apolar methyl substituents, decreases their compatibility with soft tissues and lowers their biodegradability. This problem may be overcome by introduction of hydrophilic segment, e.g. poly(amino acid)s, into the polylactide chain. This thesis describes the synthesis, characterization and enzyme degradation of a novel biodegradable copolymer comprising poly(L-glutamic acid) and polylactide segments. First, the preparation of protected poly(y-benzyl-L-glutamate) (PBLG) bearing NH2 group at both ends with narrow molecular weight distribution was conducted. Under appropriate conditions, the PBLG then initiated the ring-opening polymerization of L-lactide to produce block copolymer, using low toxicity stannous octoate as catalyst. The kinetics of the polymerization was studied, and the characterization of the copolymer was performed by the use of 1H and 13C NMR FT-IR and GPC (gel permeation chromatography). A tri-block structure of the copolymer was deduced. The thermal behavior of the copolymers was investigated by DSC, and the morphology of crystallized polymer films was examined by polarized light microscopy. The composition of the copolymer affected not only the degree of crystallinity but also the morphology of the crystals. Since both the PBLG and polylactide segments are hydrophobic, PBLG was deprotected by catalytic hydrogenation using Pd/C (10%) as catalyst. Films of poly(L-glutamic acid) and polylactide copolymers were found to degrade in enzyme (Proteinase K) solution. Amorphous films lost weight even on the first day of degradation, and weight loss reached 73% on the 8th day for one sample. In comparison, the solvent cast films only lost weight 22% by the 10th day. Crystallization led to slower degradation. Degradation rate was also controlled by the hydrophilic/hydrophobic composition of the copolymer. Finally, the biodegraded samples were characterized by FT-IR, NMR DSC and SEM (scanning electronic microscopy). en
dc.language.iso en en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA99119875614002091 en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights.uri en
dc.title Synthesis, Characterization and Enzyme Degradation Study of a New Biodegradable Copolymer of Poly(L-lactide) and Poly(L-glutamic acid) en
dc.type Thesis en Chemistry en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en

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