SELMA MATHEUS LOUREIRO GUEDES
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Artigo IPEN-doc 28415 Manufacture of non-thrombogenic polymer surfaces by gamma irradiation to induce simultaneous grafting and heparinization of thin PVC films2021 - PANZARINI, LUZ C.G.A.; MORANDIM-GIANNETTI, ANDREIA de A.; GUEDES, SELMA M.L.Investigations regarding alternative methods for producing polymeric materials with hydrophilic properties have increased considerably. In this context, polymeric biomaterials with hemocompatible surface properties have been successfully obtained by grafting hydrophilic monomers onto commercial polymer films by simultaneous irradiation processes. In this study, simultaneous irradiation and grafting were used to produce a copolymer PVC-co-DMAEMA-co-heparin with hemocompatible surface properties. Characterization by FTIR of the graft copolymer indicates that the increase in monomer grafting levels inhibits the bonding sites to heparin. FTIR-PAS analyses of the graft copolymers showed that the highest graft levels were obtained for the irradiated samples containing 45% of monomer. Heparin, however, could only be detected in the irradiated samples containing 30% of DMAEMA. The analysis of the micrographs, on the other hand, showed that increasing the monomer concentration enhances surface roughness of the graft copolymers. Roughness however decreased with heparin addition. It was possible to verify that an excess of surface roughness of the graft copolymers inhibits anticoagulant properties of heparin, triggering thrombus formation. Platelet adhesion, on its turn, was not significantly affected by the presence of heparin when PVC-co-DMAEMA and PVC-co-DMAEMA-co-heparin, obtained from the systems containing 45% of monomer, are compared. The addition of heparin in the systems containing 30% of DMAEMA resulted in fewer thrombogenic surfaces.Artigo IPEN-doc 22537 Influence of a hindered amine stabilizer on optical and mechanical properties of poly(methyl methacrylate) exposed to gamma irradiation2010 - AQUINO, KATIA A.S.; ARAUJO, ELMO S.; GUEDES, SELMA M.L.The ability of Tinuvin 622, a Hindered Amine Stabilizer (HAS), in decreasing of radiation damage to commercial PMMA matrix used in manufacturing of medical supplies was examined. Effects of gamma irradiation in PMMA specimens irradiated at dose range of 10–60 kGy were assessed by comparison of the variation of viscosity average molar mass (Mv) of PMMA with Tinuvin 622 (PMMA- 622) when compared with PMMA without the additive (PMMA-control). Samples containing Tinuvin 622 presented smaller decrease of Mv as a function of dose. This phenomenon causes direct influence in the mechanical properties of PMMA. Above 10 kGy, both PMMA-control and PMMA-622 undergo changes in the yellowness index with increase of absorbed dose; however, the phenomenon was less pronounced for PMMA-622 samples. Electron Spin Resonance spectra showed that Tinuvin 622 induces a faster evolution of radicals formed in PMMA radiolysis followed by a decrease in radiation-induced degradation of the samples.Artigo IPEN-doc 22588 Gamma irradiation effects on poly(hydroxybutyrate)2006 - OLIVEIRA, LETICIA M.; ARAUJO, ELMO S.; GUEDES, SELMA M.L.Publicação IPEN-doc 00600 Selective hydrogen atom abstraction by hydrogen atoms in photolysis and radiolysis of alkane mixtures at 77K1977 - MIYAZAKI, T.; KINUGAWA, K.; EGUCHI, M.; GUEDES, S.M.L.Publicação IPEN-doc 00343 Selective hydrogen atom abstraction by hydrogen atoms in photolysis of cyclohexane-normal pentane mixtures at 77K1977 - MIYAZAKI, T.; GUEDES, S.M.L.; SILVA, L.G.A.; FERNANDES, L.Resumo IPEN-doc 05071 Radiation effect on the optical properties of DOP/PVC plastisol used as equivalent-tissue in radiation therapy1997 - PEZZIN, A.P.T.; SALMAN, K.D.; GUEDES, S.M.L.; MEI, L.H.I.Resumo IPEN-doc 04765 Dose effects on mechanical properties of gama-irradiated polydimethilsiloxane1996 - KODAMA, Y.; GUEDES, S.M.L.Resumo IPEN-doc 04776 Plasticizer effect on Mn of gama-irradiated PVC1996 - PANZARINI, L.C.G.A.; GUEDES, S.M.L.Resumo IPEN-doc 02937 Influencia da carga na estabilidade termica do polidimetilsiloxano1996 - KODAMA, Y.; MOREIRA, E.G.; GUEDES, S.M.L.; MATOS, J.R.Resumo IPEN-doc 04300 Vulcanizacao do latex de borracha natural induzida por radiacao ionizante1992 - CANAVEL, V.; SOUZA, A.; ARAUJO, S.C.; GUEDES, S.M.L.; ARAUJO, E.S.