Emerson Oliveira da Silva

A molecular dynamic study of the starch obtained from the Mangifera indica Cv. Bourbon and Espada seeds by 13C solid state NMR

Abstract The molecular mobility of the starch obtained from Mangifera indica Cv. Bourboun and Espada , has been characterised by 13 C solid state nuclear magnetic resonance, using techniques, such as magic angle spinning (MAS) and cross polarisation magic angle spinning (CPMAS) NMR and by proton spin-lattice relaxation time in the rotating frame ( T 1 H ρ ). The CPMAS 13 C NMR spectra of these seeds showed three signals for Bourboun and two very broad signals for Espada . The seeds of the Mangifera indica Cv. Bourboun and Espada are heterogeneous amorphous polysaccharides that present, at least, two domains with distinct molecular mobility. These domains differ in size and chain packing. The variable contact time decay confirms that these starches are amorphous and present one predominant rigid domain. Mango fruits were also analysed by delayed contact time experiments, and the 13 C decays showed that the polysaccharides are heterogeneous and contain one rigid domain that controls the relaxation parameter.

Inorganic-organic hybrids based on poly (ε-Caprolactone) and silica oxide and characterization by relaxometry applying low-field NMR

®® A200) silica oxide were prepared employing the solution method, using chloroform. The relationships of the amount of nanofillers, organic coating, molecular structure and intermolecular interaction of the hybrid materials were investigated mainly using low-field nuclear magnetic resonance (NMR). The NMR analyses involved the hydrogen spin-lattice relaxation time (T 1 H) and hydrogen spin-lattice relaxation time in the rotating frame (T 1 ρH). The spin-lattice relaxation time measurements revealed that the PCL/silica oxide hybrids were heterogeneous, meaning their components were well dispersed. X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also employed. The DSC data showed that all the materials had lower crystallization temperature (Tc) and melting temperature (Tm), so the crystallinity degree of the PCL decreased in the hybrids. The TGA analysis demonstrated that the addition of modified and unmodified silica oxide does not cause considerable changes to PCL’s thermal stability, since no significant variations in the maximum temperature (Tmax) were observed in relation to the neat polymer.

Solid State NMR Evaluation of Natural Resin/Clay Nanocomposites

NMR nuclear relaxation times have been used by Tavares et al as a methodology to characterize the nano materials, especially nanocomposites, because NMR offers a great variety of relaxation parameters. The spin-lattice relaxation time, with a time constant T1, have been explored to get as much information as possible from the measurements of the spin-lattice proton relaxation (T1H), which can measure the fraction of available polymer/clay interface as well as the dispersion homogeneity of those interfaces actually formed. The spin-lattice has been evaluated since this relaxation time confirms the T1 and can give additional information to nanocomposite clay dispersion. The NMR relaxation times are sensitive to the chemical environmental, changes in the polymer matrix; chemical structure and interaction process, because they depend on the domain distribution and sample homogeneity, since they are measured in the solid state via intermolecular chains interaction and/or spin diffusion. The T1 relaxation time of the nanocomposite decreased very much in relation to the natural resin, according to the increase in the exfoliation clay process, forming a nanocomposite with polymer matrix around the clay lamella.

NMR and X-Ray Studies of Starches Derived from Tropical Fruit Seed Gelatinization Process

Gelatinization of the starch obtained from fruit seed such as mango and cumbaru was investigated applying an analytic methodology developed in the polymer nuclear magnetic resonance (NMR) laboratory at IMA/UFRJ, employing high resolution nuclear magnetic resonance spectroscopy in the solid state for hydrogen nucleus, using 1H HR-MAS pulse sequence. The results showed that NMR can be used instead of some techniques normally applied to study the gelatinization process, because 1H HR-MAS and relaxation time allow the evaluation of this process at the molecular level. NMR was also able to indicate the best gelatinization conditions. To start this study the glass transition (Tg) determination was a first step, because the Tg of seed starches are different than the Tg of starches derived from cereal, for example. The 1H HR-MAS NMR showed some useful information on the fruit seed starches gelatinization process. X-ray measurements were also used to support the data obtained from NMR technique. It was verified, from X-ray, that mango starch exhibits crystallinity in the A form and cumbaru showed a predominant amorphous phase. The use of 1H HR-MAS was shown to be a new, powerful method to follow the gelatinization process, because this process can be understood at the molecular level.

Nanoradiopharmaceuticals for breast cancer imaging: development, characterization, and imaging in inducted animals

Monoclonal antibodies as polymeric nanoparticles are quite interesting and endow this new drug category with many advantages, especially by reducing the number of adverse reactions and, in the case of radiopharmaceuticals, also reducing the amount of radiation (dose) administered to the patient. In this study, a nanoradiopharmaceutical was developed using polylactic acid (PLA)/polyvinyl alcohol (PVA)/montmorillonite (MMT)/trastuzumab nanoparticles labeled with technetium-99m (99mTc) for breast cancer imaging. In order to confirm the nanoparticle formation, atomic force microscopy and dynamic light scattering were performed. Cytotoxicity of the nanoparticle and biodistribution with 99mTc in healthy and inducted animals were also measured. The results from atomic force microscopy showed that the nanoparticles were spherical, with a size range of ~200–500 nm. The dynamic light scattering analysis demonstrated that over 90% of the nanoparticles produced had a size of 287 nm with a zeta potential of −14,6 mV. The cytotoxicity results demonstrated that the nanoparticles were capable of reaching breast cancer cells. The biodistribution data demonstrated that the PLA/PVA/MMT/trastuzumab nanoparticles labeled with 99mTc have great renal clearance and also a high uptake by the lesion, as ~45% of the PLA/PVA/MMT/trastuzumab nanoparticles injected were taken up by the lesion. The data support PLA/PVA/MMT/trastuzumab labeled with 99mTc nanoparticles as nanoradiopharmaceuticals for breast cancer imaging.

The Use of Montmorillonite Clays as Reinforcing Fillers for Dental Adhesives

The aim of this study was to obtaining an adhesive made of dimethacrylate copolymer and clay particles in different concentrations. The samples were prepared by light curing and were evaluated by XRD, FTIR and TGA as well as by measuring flexural strength, elasticity modulus and tensile resistance. The XRD and the mechanical test results indicated that the system with 0.2% clay is exfoliated, while the highest concentrations showed the agglomeration of these clays. FTIR was used to determine the conversion, and showed that use of clays particles are unable to significantly alter the polymerization until 1.0%. However, for the group containing 1.5%, there was a decline in this index. In the thermogravimetric analysis, only the groups with 0.2% of clays showed increased thermal resistance. In conclusion, the incorporation of clay at 0.2% concentration produces a well-dispersed system and can be applied as a dental adhesive.

EFEITO DA ADIÇÃO DE TIO2 NAS PROPRIEDADES TÉRMICAS E NA CRISTALINIDADE DO COPOLÍMERO DE ETILENO/ACETATO DE VINILA

0.25%–1% TiO2, relative to the total weight of EVA, were prepared from their solution. The obtained films were characterized by X-ray diffraction, low-field nuclear magnetic resonance, and differential scanning calorimetry. The addition of TiO 2 to the EVA copolymer was proved to cause changes in the crystallinity and mobility of the polymer chains of EVA, due to new intermolecular interactions and nanostructure organization.

NMR Assignment of Carbonyl and Olefinic Regions of Amescla Resin

The structural assignment of amescla resin was carried out using a methodology already established in a previous work published by Tavares and Silva. From the methodology, three structural fragments were determined, allowing us to conclude that this natural resin was polymerized from the double bond localized in the middle of the aliphatic chain.

The applicability of organomodified nanoclays as new fillers for mechanical reinforcement of dental composites

Objectives This study reports the evaluation of changes in crosslink structure and mechanical properties of dental microhybrid composite reinforced with clays when compared to silica nanofillers, which are already extensively used for this application. Materials and methods A standardized resin matrix with a glycerolate dimethacrylate, triethylene glycol dimethacrylate, and urethane dimethacrylate copolymers associated with a camphorquinone photoinitiator system was blended with 75 wt% filler content. As fillers, two organically modified clays (hydrophilic silica and organomodified silica) and a boron-aluminum-silicate glass with 4 µm were used to obtain nanohybrid nanocomposites. The samples were prepared by light curing and were evaluated by measuring flexural strength, elasticity modulus, hardness, tensile resistance, and crosslinking. Results The mechanical test results indicated that the system with 2.5% clay was better dispersed in the system, while the highest concentrations caused agglomeration of these clays. On the other hand, the silicas showed gradual gain in properties. The increase in concentration of all nanofillers reduced the crosslinking ability of the systems. This behavior can be explained because the clay’s presence makes the reaction medium more viscous or because the fillers act as points of light absorption and scattering.