A method for synthesis of polyol from soybean oils has been developed using a two-step continuous route. The method involved epoxidation of soy oils and subsequent hydroxylation to produce polyols. The epoxidation was carried out using biphasic catalytic system (Na2WO4 / H2WO4) with 50 % hydrogen peroxide. The major advantages of this approach are that; the use of biphasic system allows easy separation of the products, does not require any chlorinated solvent (more environment-friendly), can be conducted at room temperature and requires relatively lower catalyst load. The functional groups of soy-polyol were identified using FTIR and NMR spectroscopy. This confirmed complete disappearance of the signature of the C=C double bonds, formation of the epoxy linkage following the epoxidation process, its further disappearance and incorporation of hydroxyl groups after the hydroxylation process. The hydroxyl number, hydroxyl functionality, acid value, iodine value and viscosity of the synthesized polyols were also determined.

Currently used small diameter synthetic vascular grafts are prone to high rates of failure related to thrombosis and neointimal hyperplasia. Biomimetic materials, based on the extracellular matrix (ECM) composition of native tissues, represent an attractive solution to address these complications. The inherent low thrombogenicity and cell signalling properties of elastin-like polypeptides (ELPs) make them a suitable option for these applications. In this thesis, ELP surface modification has been achieved through the use of elastin cross-linking peptide bioactive fluorinated surface modifiers (ECP-BFSMs). The synthesis of these low molecular weight fluorinated additives was described and their subsequent blending with a base polycarbonate-urethane (PCNU) was shown to successfully enrich the surface to allow for ELP surface cross-linking. The kinetic surface migration of fluorescent ECP-BFSMs was studied over a 2 week casting period by two-photon confocal microscopy. Contact angle and x-ray photoelectron spectroscopy (XPS) confirmed the surface localization of the ECP-BFSMs. Changes in contact angle and XPS spectrums following ELP surface cross-linking confirmed the success of the surface modification approach. The novel ELP surface modified materials were demonstrated to inhibit fibrinogen surface adsorption and platelet adhesion under physiological flow conditions and inhibit bulk platelet activation following blood-material contact. Moreover, these ELP modified surfaces were shown to promote increased endothelial and smooth muscle cell adhesion, spreading and retention over a 7 day culture period relative to their non-ELP analogs. Endothelial and smooth muscle cells seeded on the elastin-like materials were shown to express endothelial nitric oxide synthase (eNOS) and smooth muscle myosin heavy chain (SM-MHC) cell specific phenotypic markers, respectively. Furthermore, competitive inhibition experiments revealed that initial smooth muscle cell adhesion to ELP surface modified materials was mediated through elastin-laminin cell surface receptors binding to VGVAPG peptide sequences on the ELP molecules. Hence, these materials may have broad applicability in cardiovascular applications, from blood contacting materials to scaffold structures for vascular graft tissue engineering. Furthermore, this surface modifying additive approach represents a versatile technique that can be custom tailored for various biomimetic applications to generate stable bioactive ECM-like surfaces retained onto a relatively inert fluorinated background.

No description available.

No description available.

Currently used small diameter synthetic vascular grafts are prone to high rates of failure related to thrombosis and neointimal hyperplasia. Biomimetic materials, based on the extracellular matrix (ECM) composition of native tissues, represent an attractive solution to address these complications. The inherent low thrombogenicity and cell signalling properties of elastin-like polypeptides (ELPs) make them a suitable option for these applications. In this thesis, ELP surface modification has been achieved through the use of elastin cross-linking peptide bioactive fluorinated surface modifiers (ECP-BFSMs). The synthesis of these low molecular weight fluorinated additives was described and their subsequent blending with a base polycarbonate-urethane (PCNU) was shown to successfully enrich the surface to allow for ELP surface cross-linking. The kinetic surface migration of fluorescent ECP-BFSMs was studied over a 2 week casting period by two-photon confocal microscopy. Contact angle and x-ray photoelectron spectroscopy (XPS) confirmed the surface localization of the ECP-BFSMs. Changes in contact angle and XPS spectrums following ELP surface cross-linking confirmed the success of the surface modification approach. The novel ELP surface modified materials were demonstrated to inhibit fibrinogen surface adsorption and platelet adhesion under physiological flow conditions and inhibit bulk platelet activation following blood-material contact. Moreover, these ELP modified surfaces were shown to promote increased endothelial and smooth muscle cell adhesion, spreading and retention over a 7 day culture period relative to their non-ELP analogs. Endothelial and smooth muscle cells seeded on the elastin-like materials were shown to express endothelial nitric oxide synthase (eNOS) and smooth muscle myosin heavy chain (SM-MHC) cell specific phenotypic markers, respectively. Furthermore, competitive inhibition experiments revealed that initial smooth muscle cell adhesion to ELP surface modified materials was mediated through elastin-laminin cell surface receptors binding to VGVAPG peptide sequences on the ELP molecules. Hence, these materials may have broad applicability in cardiovascular applications, from blood contacting materials to scaffold structures for vascular graft tissue engineering. Furthermore, this surface modifying additive approach represents a versatile technique that can be custom tailored for various biomimetic applications to generate stable bioactive ECM-like surfaces retained onto a relatively inert fluorinated background.

Thesis (PhD)--University of South Australia, 2003

Thesis (PhD)--University of South Australia, 2003

Thesis (PhD)--University of South Australia, 2003

Pitting and delamination wear of ultra high molecular weight polyethylene (UHMW-PE) tibial plateaux for total joint replacements have habitually been attributed to a fatigue crack growth mechanism associated with a combination of high sub-surface cyclic shear stresses and degradation of the chemistry and structure of UHMW-PE caused by the gamma-irradiation sterilisation standard procedure. However, the exact mechanisms by which cracks initiate and grow in UHMWPE are not known and the relationships between these mechanisms and pitting and delamination are only assumptions based on qualitative observations. A fracture mechanics approach based on the J-integral concept of plane strain crack initiation toughness was therefore applied in order to firstly obtain the fracture toughness and crack growth stability of UHMW-PE and secondly to determine the mechanisms by which pitting and delamination occur in vivo. It was necessary to modify the existing standard ASTM E813-89 for the treatment of experimental J data in order to accommodate for the large crack tip plasticity and pronounced ductile tearing. This modified method was then applied to a detailed investigation of the influence of sterilisation and ageing on the chemical, physical and mechanical properties of UHMW-PE. Simulated shelf and in vivo environments enabling a rapid ageing of UHMW-PE corresponding to 10 years of natural ageing were developed. Sterilisation was either conducted by gamma-irradiation in air or nitrogen, or by gas plasma. In virgin UHMW-PE, cracks propagated by a succession of plastic deformation and craze nucleation over thin layers of material, yielding a very high value of J (90 kJ/m 2 ) at 37 : C. Gammairradiation in air followed by 10 years ageing resulted in a highly brittle material with a crack initiation fracture toughness reduced by 78% and a mechanical behaviour approaching that of a linear elastic material i.e. creation of a "cup-and-cone" in tension and formation of 45" shear lips in threepoint bending. On the other hand, gas plasma sterilised UHMW-PE could not be differentiated from unsterile UHMW-PE in either its physical nor mechanical properties. Qualitative correlations existed between the presence and location of highly oxidised regions and the crack initiation fracture toughness of the material. Quantitatively, the J-initiation toughness exhibited a hyperbolic decrease with increasing density and oxidation index while the tensile secant modulus linearly increased with density. From these empirical relationships, a model was created which described the variation of the fracture toughness with depth within a UHMW-PE sample. This model indicated that the zones of high density, oxidation and crystallinity correspond to the areas of maximum shear stress and minimum fracture toughness and that the propensity of UHMW-PE to suffer pitting, delamination and high wear rates through a fracture mechanism is significantly increased by extensive oxidative degradation.

Orientador: Nelson Eduardo Duran Caballero / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-05T10:26:59Z (GMT). No. of bitstreams: 1 Lemes_AnaPaula_M.pdf: 6068307 bytes, checksum: cde69555a9767e84a264aae77c5a0814 (MD5) Previous issue date: 2005 / Resumo: Neste trabalho foram desenvolvidos compósitos baseados em poli(3-hidroxibutirato-co-hidroxivalerato) (PHBV) e lignosulfonatos de diferentes massas molares. Os compósitos foram produzidos em um misturador mecânico, em diferentes composições (90:10, 80:20, 70:30 e 60:40). As propriedades térmicas dos compósitos foram investigadas por Calorimetria Diferencial de Varredura (DSC) e Termogravimetria (TGA). As análises de Microscopia Eletrônica de Varredura foram utilizadas para caracterizar a morfologia dos materiais. Os compósitos com maiores proporções de lignosulfonatos apresentaram diminuição no grau de cristalinidade e na temperatura de transição vítrea e menor estabilidade térmica. As análises de MEV mostraram uma baixa adesão interfacial entre os lignosulfonatos e a matriz de PHBV. Para promover uma melhor adesão interfacial entre a carga e a matriz, foi realizado um estudo utilizando um agente compatibilizante, que consistia na exertia de anidrido maleico (AM) na cadeia de PHBV (PHBV-g-AM). Para isto compósitos contendo 80 % de PHBV e 20 % de lignosulfonatos e proporções variadas de anidrido maleico foram produzidos em um misturador mecânico e em uma extrusora dupla rosca. Esses compósitos foram caracterizados por TGA e MEV. Na análise de TGA não foram observadas grandes alterações na estabilidade térmica. As análises morfológicas mostraram uma grande melhora na adesão entre carga e matriz. Os compósitos compatibilizados apresentaram um aumento de cerca de 125 % nos valores de tensão de flexão máxima e de 145 % nos valores de deformação na ruptura, em relação aos compósitos não compatibilizados. Amostras de PHBV e do compósito contendo 80 % de PHBV, 20 % de lignosulfonato e 1,5 % de anidrido maleico foram submetidas a testes de biodegradação em meio líquido e em solo. Os testes realizados em meio líquido mostraram uma redução de massa de 14,4 % para as amostras de PHBV e de 31,0 % para o compósito, após 65 dias de incubação. Nos testes realizados em solo a perda de massa foi de 7,6 % para as amostras de PHBV e 28,8 % para o compósito, após 50 dias de incubação. A perda de 20 % em massa dos compósitos foi atribuida à liberação de lignosulfonato. Em ambos os testes verificou-se que a presença do lignosulfonato não interfere na biodegradação da matriz de PHBV / Abstract: In this work, composites based on poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) and lignosulfonates of different molar weights were prepared by mechanical mixing of different compositions (90:10, 80:20, 70:30 and 60:40). Thermal properties of these composites were investigated by differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) was used to define the morphology of materials. The composites containing higher amounts of lignosulfonates showed a decreasing in crystallinity degree and glass transition temperatures, and lower thermal stability. SEM showed a poor interfacial adhesion between lignosulfonato and PHBV matrix. To improve the interfacial adhesion between filler and matrix, a study on compatibilizer utilization was carried out. The compatibilizer was formed by grafting of maleic anhydride (MA) in PHBV (PHBV-g-MA). The study was performed with composites containing 20 % of lignosulfonate, 80 % of PHBV and different amounts of maleic anhydride, prepared by mechanical mixing and by twin-screw. The thermal and morphological properties of composites were investigated by TGA and SEM, respectively. The TGA did not show significant change in the thermal stability of the composites as function of compatibilizer content. The SEM showed a high improvement in the adhesion between filler and matrix. The compatibilized composites exhibited an increase of 125 % in maximum stress values and 145 % in the strain values under rupture experiments. PHBV and composite containing 80 % of PHBV, 20 % of lignosulfonato and 1,5 % of maleic anhydride samples were submitted to biodegradation tests in aqueous and in soil media. Tests carried out in aqueous medium showed a decrease of 14, 4 % in the PHBV mass and 31,0 % in the composite mass, after 65 days of incubation. In the soil tests the weight loss was of 7,6 % for PHBV sample and 28,8 % for composite sample, after 50 days of incubation. Both tests showed that the presence of lignosulfonate did not interfere in PHBV matrix biodegradation / Mestrado / Físico-Química / Mestre em Química