Hidrólise e caracterização de poliacrilamida hidrofobicamente modificada: avaliação da aplicabilidade na recuperação de petróleo

The hydrolysis reaction in alkaline conditions of the commercial polymer poly(acrylamide-co-metacrylate of 3,5,5-trimethyl-hexane) called HAPAM, containing 0.75 % of hydrophobic groups, was carried out in 0.1 M NaCl and 0.25M NaOH solutions, varying the temperature and reaction time. The polymers were characterized by 1H and 13C Nuclear Magnetic Resonance (NMR), Elemental Analysis and Size Exclusion Chromatography (SEC). The values of the hydrolysis degree were obtained by 13C NMR. The viscosity of HAPAM and HAPAM-10N-R solutions was evaluated as a function of shear rate, ionic strength and temperature. At high polymer concentration (Cp), the viscosity of HAPAM solutions increased with the ionic strength and decreased with the temperature. The viscosity of HAPAM-10N-R solutions increased significantly in distilled water, due to repulsions between the carboxylate groups. At high Cp, with the increase of ionic strength and temperature, occurred a decrease of viscosity, due to mainly the high hydrolysis degree and the low amount of hydrophobic groups. These results indicated that the studied polymers have properties more suitable for the application in Enhanced Oil Recovery (EOR) in low salinity and moderate temperature reservoirs

Micropartículas de poli (ácido lático-co-ácido glicólico) obtidas por spray drying para a liberação prolongada de metotrexato

Methotrexate (MTX) is a drug used in the chemotherapy of some kind of cancers, autoimmune diseases and non inflammatory resistant to corticosteroids uveits. However, the rapid plasmatic elimination limits its therapeutic success, which leads to administration of high doses to maintain the therapeutic levels in the target tissues, occurring potential side effects. The aim of this study was to obtain spray dried biodegradable poly-lactic acid co-glycolic acid (PLGA) microparticles containing MTX. Thus, suitable amounts of MTX and PLGA were dissolved in appropriate solvent system to obtain solutions at different ratios drug/polymer (10, 20, 30 and 50% m/m). The physicochemical characterizing included the quantitative analysis of the drug using a validate UV-VIS spectrophotometry method, scanning electron microscopy (SEM), infrared spectrophotometry (IR), thermal analyses and X-ray diffraction analysis. The in vitro release studies were carried out in a thermostatized phosphate buffer pH 7.4 (0.05 M KH2PO4) medium at 37°C ± 0.2 °C. The in vitro release date was subjected to different kinetics release models. The MTX-loaded PLGA microparticles showed a spherical shape with smooth surface and high level of entrapped drug. The encapsulation efficiency was greater then 80%. IR spectroscopy showed that there was no chemical bond between the compounds, suggesting just the possible occurrence of hydrogen bound interactions. The thermal analyses and X-ray diffraction analysis shown that MTX is homogeneously dispersed inside polymeric matrix, with a prevalent amorphous state or in a stable molecular dispersion. The in vitro release studies confirmed the sustained release for distinct MTX-loaded PLGA microparticles. The involved drug release mechanism was non Fickian diffusion, which was confirmed by Kornmeyer-Peppas kinetic model. The experimental results demonstrated that the MTX-loaded PLGA microparticles were successfully obtained by spray drying and its potential as prolonged drug release system.