Matrizes híbridas siloxano-poliéter incorporadas com argila montmorilonita para liberação controlada de fármaco

Pós-graduação em Química - IQ

Propriedades térnicas de géis e xerogéis híbridos de sílica/orgânico à base de GPTS-TEOS com diferentes concentrações de GPTS

In the present work the thermal characteristics of gels and xerogels of Silica/organic hybrids derived from different concentrations of GPTS-TEOS were investigated by thermal analysis (TG, DTA, and DSC). The preparation of gels of the Silica/organic hybrid matrix was held through the sol-gel process, consisting by the hydrolysis of alkoxides GPTS and TEOS in proportion (1:1) and (1:2) that was promoted in acidic conditions under reflux and stirring at 80oC/2h, producing the matrix in the colloidal state (sol). Gels were prepared by addition of NH4OH to the sol, promoting gelation of sol in sealed plastics containers. Part of the gels samples was analyzed by TG, DTS and DSC techniques in order to characterize water loss and degradation of the polymeric “epoxy” groups present in the structure of the silica derived from the GPTS alkoxide. Another set of samples was dried at 80oC/48h to obtain xerogels (dried gels) and analyzed by the same techniques. We obtained the characteristics temperatures of the matrix by the techniques DTA, DSC and TG, under measurements of thermal analysis until 800oC and 600oC in case of DSC. By thermal analysis (TG, DTA, and DSC) the main endothermic events (loss of water, melting, pyrolysis) and exothermic events (burning of the polymer) of the GPTS-TEOS matrix were determined

Obtenção de rochas sintéticas a partir de resíduos de vidro comercial e pó de granito

Pós-graduação em Engenharia Mecânica - FEG

Transição vesícula-micela em mistura aquosa de sais dialquilados de amônio quaternário com Pluronic® F127

Pós-graduação em Biofísica Molecular - IBILCE

Estudo da formação de domínios em membranas modelos induzidos por peptídeos antimicrobianos e sua ação interfacial

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da formação de domínios em membranas modelos induzidos por peptídeos antimicrobianos e sua ação interfacial

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Micropartículas de quitosana estruturadas com aerosil®: estabilidade, adsorção, encapsulação e liberação de substâncias ativas

Biodegradable microspheres used as controlled release systems are important in pharmaceutics. Chitosan biopolymer represents an attractive biomaterial alternative because of its physicochemical and biological characteristics. Chitosan microspheres are expected to become promising carrier systems for drug and vaccine delivery, especially for non-invasive ways oral, mucosal and transdermal routes. Controlling the swelling rate and swelling capacity of the hydrogel and improving the fragile nature of microspheres under acidic conditions are the key challenges that need to be overcomed in order to enable the exploration of the full pharmaceutical potential use of these microparticles. Many studies have focused on the modification of chitosan microsphere structures with cross-linkers, various polymers blends and new organic-inorganic hybrid systems in order to obtain improved properties. In this work, microspheres made of chitosan and nanosized hydrophobic silica (Aerosil R972) were produced by a method consisting of two steps. First, a preparation of a macroscopically homogeneous chitosan-hydrophobic silica dispersion was prepared followed by spray drying. FTIR spectroscopy, X-ray powder diffraction, differential scanning calorimetry, thermal gravimetric analysis, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (TEM) were used to characterize the microspheres. Also, the were conducted acid stability, moisture sorption capacity, release properties and biological assays. The chitosan-hydrophobic silica composite microspheres showed improved thermal degradation, lower water affinity, better acid stability and ability to retard rifampicin and propranolol hydrochloride (drug models) release under simulated physiological conditions. In vitro biocompatibility studies indicated low cytotoxicity and low capacity to activate cell production of the pro-inflammatory mediator nitric oxide. The results show here encourage further studies on the use of the new chitosan-hydrophobic silica composite microspheres as drug carrier systems via oral or nasal routes.

Acetilação do exopolissacarídeo (1→6)-β-D-glucana (lasiodiplodana): derivatização química e caracterização

Lasiodiplodan is an exocellular β-glucan with biological functionalities such as antioxidant, antiproliferative, hypocholesterolemic, protective activity against DNA damage induced by doxorubicin and hypoglycemic activity. Chemical derivatization of polysaccharide macromolecules has been considered as a potentiating mechanism for bioactivity. In this context, this work proposes the derivatization of lasiodiplodan by acetylation. Acetic anhydride was used as derivatizing agent and pyridine as catalyst and reaction medium. The derivatives obtained were evaluated by its water solubility, degree of substitution (DS), antioxidant potential, and characterized by infrared spectroscopy (FT-IR), thermal analysis, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. Acetylated derivatives with different degrees of substitution (1.26; 1.03; 0.66 and 0.48) were obtained, and there was correlation between the concentration of derivatizing agent and DS. FT-IR spectroscopy analysis confirmed the insertion of acetyl groups into derivatized macromolecules (LAS-AC) through of specific bands concerning to carbonyl group (C = O) and increase in C-O vibration. SEM analysis indicated that native lasiodiplodan presents morphological structure in the form of thin films with translucent appearance and folds along its length. Derivatization led to morphological changes in the polymer, including aspects thickness, translucency and agglomeration. Thermal analysis indicated the native sample and derivative with DS 0.48 presented three weight loss stages. The first stage occurred until 125 ° C (loss of water) and there were two consecutive events of weight loss (200 ° C - 400 ° C) attributed to molecule degradation. Samples with DS 1.26; 1.03 and 0.66 demonstrated four weight loss stages. The first stage occurred until 130 ° C (loss of water), following by two consecutive events of weight loss (200 ° C - 392 ° C) attributed to degradation of the biopolymer. The fourth stage was between 381 ° C and 532 ° C (final decomposition) with exothermic peaks between 472 ° C and 491 ° C. X-ray diffraction patterns showed that native and acetylated lasiodiplodan have amorphous structure with semicrystalline regions. Derivatization did not contribute to increased solubility of the macromolecule, but potentiated its antioxidant capacity. Acetylation of lasiodiplodan allowed to obtaining a new macromolecule with higher antioxidant potential than the native molecule and with technological properties applicable in various industrial sectors.

Poli-líquidos iônicos e complexos solúveis de Eu3+ e Tb3+ : bioimageamento celular seletivo

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Química, 2015.

O efeito do tratamento da atapulgita no desenvolvimento de compósito com o polietileno reciclado

The study aimed at the treatment of attapulgite for the development and characterization of composite recycled low density polyethylene - PEBD_rec embedded with natural attapulgite - ATP_NAT, sifted - ATP_PN and attapulgite treated with sulfuric acid - ATP_TR in different compositions (1, 3 and 5%) and compared with the PEBD_rec. The atapulgitas, natural, screened and treated, were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), particle size analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and determining the area specific surface (BET). The composites were characterized by thermogravimetry (TG), differential scanning calorimetry (DSC), Xray diffraction (XRD), torque rheometry, scanning electron microscopy (SEM) and traction. The composite PEBD_rec / ATP (natural, sieved and treated) were produced by mixing in the molten state in a single screw extruder matrix wire with subsequent reprocessing matrix tape. It was found that the screening of attapulgite not reduce the quantity of quartz and the acid treatment completely extracted dolomite aggregate impurities of the channels attapulgite, and increase their surface area. The addition of attapulgite in PEBD_rec acts as a catalyst, reducing the thermal stability of the polymer. The increased concentration of attapulgite, increases resistance and reduces the elongation at break and modulus of elasticity of the composite PEBD_rec / attapulgite

Avaliação tribológica dos polímeros NBR, PTFE e PTFE gravitado em contato com aço AISI 52100

Low cost seals are made of NBR, Nitrile Butadiene Rubber, a family of unsaturated copolymers that is higher resistant to oils the more content of nitrile have in its composition, although lower its flexibility. In Petroleum Engineering, NBR seal wear can cause fluid leakage and environmental damages, promoting an increasing demand for academic knowledge about polymeric materials candidate to seals submitted to sliding contacts to metal surfaces. This investigation aimed to evaluate tribological responses of a commercial NBR, hardness 73 ± 5 Sh A, polytetrafluoroethylene (PTFE), hardness 60 ± 4 HRE and PTFE with graphite, 68 ± 6 HRE. The testings were performed on a sliding tribometer conceived to explore the tribological performance of stationary polymer plane coupons submitted to rotational cylinder contact surface of steel AISI 52100, 20 ± 1 HRC Hardness, under dry and lubricated (oil SAE 15W40) conditions. After screening testings, the normal load, relative velocity and sliding distance were 3.15 N, 0.8 m/s and 3.2 km, respectively. The temperatures were collected over distances of 3.0±0.5 mm and 750±50 mm far from the contact to evaluate the heating in this referential zone due to contact sliding friction by two thermocouples K type. The polymers were characterized through Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The wear mechanisms of the polymer surfaces were analyzed by Scanning Electron Microscopy (SEM) and EDS (Energy-Dispersive X-ray Spectroscopy). NBR referred to the higher values of heating, suggesting higher sliding friction. PTFE and PTFE with graphite showed lower heating, attributed to the delamination mechanism

Mecanismos de desgaste de poliuretano em ensaios de microabrasão

Wear mechanisms and thermal history of two non-conforming sliding surfaces was investigated in laboratory. A micro-abrasion testing setup was used but the traditional rotative sphere method was substituted by a cylindrical surface of revolution which included seven sharp angles varying between 15o to 180o. The micro-abrasion tests lead to the investigation on the polyurethane response at different contact pressures. For these turned counterfaces with and without heat treatment. Normal load and sliding speeds were changed. The sliding distance was fixed at 5 km in each test. The room and contact temperatures were measured during the tests. The polyurethane was characterized using tensile testing, hardness Shore A measurement, Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Thermomechanical Analyze (TMA). The Vickers micro-hardness of the steel was measured before and after the heat treatment and the metallographic characterization was also carried out. Worn surface of polyurethane was analysed using Scanning Electron Microscope (SEM) and EDS (Electron Diffraction Scanning) microanalyses. Single pass scratch testing in polyurethane using indenters with different contact angles was also carried out. The scar morphology of the wear, the wear mechanism and the thermal response were analyzed in order to correlate the conditions imposed by the pressure-velocity pair to the materials in contact. Eight different wear mechanisms were identified on the polyurethane surface. It was found correlation between the temperature variation and the wear scar morphology.

Resposta térmica de um compósito PEEK+PTFE+Fibra de carbono+grafite

Composites based on PEEK + PTFE + CARBON FIBER + Graphite (G_CFRP) has increased application in the top industries, as Aerospace, Aeronautical, Petroleum, Biomedical, Mechanical and Electronics Engineering challenges. A commercially available G_CFRP was warmed up to three different levels of thermal energy to identify the main damage mechanisms and some evidences for their intrinsic transitions. An experimental test rig for systematize a heat flux was developed in this dissertation, based on the Joule Effect. It was built using an isothermal container, an internal heat source and a real-time measurement system for test a sample by time. A standard conical-cylindrical tip was inserted into a soldering iron, commercially available and identified by three different levels of nominal electrical power, 40W (manufacturer A), 40W (manufacturer B), 100W and 150W, selected after screening tests: these power levels for the heat source, after one hour of heating and one hour of cooling in situ, carried out three different zones of degradation in the composite surface. The bench was instrumented with twelve thermocouples, a wattmeter and a video camera. The twelve specimens tested suffered different degradation mechanisms, analyzed by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetry) techniques, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Rays (EDX) Analysis. Before and after each testing, it was measured the hardness of the sample by HRM (Hardness Rockwell M). Excellent correlations (R2=1) were obtained in the plots of the evaporated area after one hour of heating and one hour of cooling in situ versus (1) the respective power of heat source and (2) the central temperature of the sample. However, as resulting of the differential degradation of G_CFRP and their anisotropy, confirmed by their variable thermal properties, viscoelastic and plastic properties, there were both linear and non-linear behaviour between the temperature field and Rockwell M hardness measured in the radial and circumferential directions of the samples. Some morphological features of the damaged zones are presented and discussed, as, for example, the crazing and skeletonization mechanism of G_CFRP

Avaliação de sistemas lipidicos nanoestruturados utilizados como estratégia para melhorar as propriedades biofarmaceuticas do praziquantel no tratamento da esquistossomose

Pós-graduação em Nanotecnologia Farmacêutica - FCFAR

Funcionalização de celulose bacteriana com peptídeo RGD para reparação tecidual de pele

Pós-graduação em Química - IQ