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Papers by Maria Ines Bruno Tavares
Journal of Nanoscience and Nanotechnology, Apr 1, 2015
In this study, PVAL/sodic clay nanocomposite materials were obtained using different clay ratios.... more In this study, PVAL/sodic clay nanocomposite materials were obtained using different clay ratios. The nanocomposites were prepared by solution and in situ polymerization. They were characterized through proton relaxometry and X-ray diffraction, the latter technique used to determine the crystallinity of the PVAL matrix in the nanocomposites through the addition of unmodified montmorillonite clay. The relaxation data for the nanocomposite films obtained by solution intercalation showed a decrease in the proton spin-lattice relaxation values with increased clay proportion, forming a nanostructured material with high exfoliation degree, as a result of two phenomena: the higher molecular mobility of the polymer chains around the clay layers and the presence of paramagnetic metals in the clay layers, which accelerates the hydrogen relaxation process, causing a decrease in the relaxation value. The samples obtained through in situ polymerization were mixed nanocomposites (partly exfoliated and partly intercalated). The NMR relaxation data for the systems analyzed showed the solution intercalation process was more efficient than in situ polymerization in relation to the generation of nanostructured polymers with higher degree of exfoliated clay.
Applications of NMR Spectroscopy
Journal of Research Updates in Polymer Science
The purpose of this work was to study the molecular dynamics, morphology, mechanical and thermal ... more The purpose of this work was to study the molecular dynamics, morphology, mechanical and thermal performance of nanomaterials formed by poly(vinyl alcohol) and molybdenum trioxide (PVA/MoO3) obtained through solution casting method, focusing new materials with therapeutic applications since the molybdenum trioxide exhibit an excellent antibacterial activity and could be a pathway to prevent viruses. The obtaining materials were characterized by conventional techniques as X-ray diffraction, thermogravimetric and dynamical-mechanical analysis. The unconventional low-field NMR relaxometry was used to evaluate the molecular dynamic and morphology of these systems. The results obtained showed that the MoO3 addition into PVA matrix promote an increase on the thermal stability at higher temperatures and a progressive increase on the rigidity of the PVA systems. Also changes in the molecular mobility of nanomaterials determined through the proton spin-lattice relaxation time showed that low...
Materials Sciences and Applications
Journal of Thermal Analysis and Calorimetry, 2020
In this work, films of commercial PLA Ingeo 4043D with nano-zinc oxide particles (nano-ZnO) with ... more In this work, films of commercial PLA Ingeo 4043D with nano-zinc oxide particles (nano-ZnO) with average diameter around 100 nm and ZnO concentrations of 0.1, 0.25, 0.3 and 0.5 mass% were prepared by flat die extrusion. The addition of nano-ZnO had an objective to promote the crystallization of PLA, but it decreased the thermal stability of the films. Both neat PLA and PLA/nano-ZnO composites films did not crystallize during the cooling, but crystallize during a first heating, showing a cold crystallization process, which was significantly influenced by the heating rate. A low chain mobility was evidenced by the values of relaxation time (T 1 H). This low chain mobility avoided the high degree of crystallization of the films which were predominantly amorphous. For all films, an enthalpic relaxation phenomenon was detected during the first heating. The glass transition temperature (T g) was shifted to higher values as the heating rate and nanofiller content are increased. Addition of nano-ZnO in PLA films did not increase their crystallinity, indicating that it is not an effective nucleating agent for this low-crystallinity PLA grade.
... TRATAMENTO QUÍMICO RL Müller, FR Wagner, CM Mählmann, AL Rodríguez, LM Kipper, JAR Moraes ...... more ... TRATAMENTO QUÍMICO RL Müller, FR Wagner, CM Mählmann, AL Rodríguez, LM Kipper, JAR Moraes ... (5,13) Segundo Tita (13), o uso de bagaço de cana-de-açúcar promove um pequeno aumento na resistência ao impacto quando utilizado como reforço em matriz fenólica ...
Journal of Nanoscience and Nanotechnology, 2016
Tissue engeneering is a multidisciplinar field where the principles of engeneering and life scien... more Tissue engeneering is a multidisciplinar field where the principles of engeneering and life sciences can be applied to the development of biological subsitutes used to restore, keep or improve living tissues functions[1]. A biomaterial can be defined as a material designed to interface biological systems to evaluate, heal, enhance or substitute any tissue, organ or bodily function[2]. A limitation found in most polymers is that these materials lack the kind of properties that promotes cellular adhesion and proliferation. To improve the bioproporties and cellular interactions of those polymers, composites based on biodegradable synthetic polymers, modified biodegradable natural polymers and its blends have been proposed to prepare scaffolds [3]. Some of the most important properties of a biodegradable material include the absence of inflammatory or toxic response after its implantation, a reasonable shelf life, adequate mechanical properties for the desired application, whose variati...
Polymeric blends are interesting materials, from the thechnological point of view, due to their v... more Polymeric blends are interesting materials, from the thechnological point of view, due to their versatility and easy obtaining. Two biopolymers can be mixed to improve the hybrid's properties. Bioblends based on poly(beta-hydroxybutirate) (PHB) and poly(epsilon-caprolactone) (PCL) were obtained via solution casting under various PHB:PCL weight ratios. Bioblend's miscibility was assessed via time domain nuclear magnetic resonance (TD-NMR), through the observation of the longitudinal and transversal relaxation times constants, T1 and T2*, respectively. The experiment was conducte in a Maran Ultra spectrometer, operating at 0,54 T, at ambient temperature and employing the inversion-recovery (IR) and Magic Sandwich Echo Free Induction Decay (MSE-FID) pulse sequences. The experimental data were fitted in a commercial fitting software package (WinFit), assuming monoexponential decay for IR measurements and a set of exponentials, gaussians and Abraghamian curves for the fitting of ...
Polímeros
Four commercial flour samples with starch components were studied. They were characterized by Inf... more Four commercial flour samples with starch components were studied. They were characterized by Infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and low field NMR (T1H).
Solid-state nuclear magnetic resonance (NMR) techniques include hydrogen nuclear relaxation measu... more Solid-state nuclear magnetic resonance (NMR) techniques include hydrogen nuclear relaxation measurements, such as spin-lattice relaxation time in the laboratory frame (T1H). This relaxation parameter involves changes in thermal equilibrium of spin systems. The hydrogen relaxation times can be measured directly in a low-field NMR spectrometer. The efficiency of the process can be correlated with the structure and the value is intrinsically related to the system’s morphology. Consequently, the relaxation measurements can be used to evaluate nanoparticles’ dispersion in the polymer matrix, the interaction between both nanocomposite components, the molecular dynamics of the hybrid compound and also the formation of molecular domains in organic material. These techniques are thus good tools to analyze the molecular dynamics of polymer systems and nanocomposites. In this study, two nanocomposites, one based on virgin high impact polystyrene (HIPS) and organoclay and the other on recycled ...
Polímeros
Polycarbonate-organofilic clay nanocomposites were obtained via the melt intercalation method in ... more Polycarbonate-organofilic clay nanocomposites were obtained via the melt intercalation method in the blending chamber of a torque rheometer, under distinct values of shear and temperature. The influence of those processing parameters on the clay dispersion in the polymer matrix was probed by low-field nuclear magnetic resonance (NMR), using the T1H measurement technique and by wide angle X-ray scattering (WAXS). The differences in longitudinal relaxation times and in the X-ray reflection patterns were correlated with the formation of relaxation domains with particular molecular mobility, as progressively larger intercalated morphologies were found in the nanocomposites due to the increase of shear stress and temperature. 1H NMR has shown that both shearing and temperature have played a fundamental part on the polymer chains mobility, which explains the increase in the domain´s homogeneity following the increment of those processing parameters.
Polymer Testing, 2000
Natural fibers obtained from sugar cane have been analysed by carbon-13 high resolution solid sta... more Natural fibers obtained from sugar cane have been analysed by carbon-13 high resolution solid state nuclear magnetic resonance (NMR) employing different techniques such as: cross-polarisation magic angle spinning (CP/MAS); variable contact time experiment and proton spin-lattice relaxation time in the rotating frame. Molecular mobility information for distinct types of sugar cane fibers, as well as two different mixtures (one of the mixtures contains equal amounts of waste fibers and the other has a random distribution of these waste fibers) and their composites with poly(ethylene-co-vinyl acetate) (EVA) were obtained from those techniques. Mechanical measurements (stress-strain) were also recorded for all samples. Both NMR and mechanical measurements responses showed that the mixtures of natural fiber can be used as a matrix in the composites.
Journal of Nanoscience and Nanotechnology, Apr 1, 2015
In this study, PVAL/sodic clay nanocomposite materials were obtained using different clay ratios.... more In this study, PVAL/sodic clay nanocomposite materials were obtained using different clay ratios. The nanocomposites were prepared by solution and in situ polymerization. They were characterized through proton relaxometry and X-ray diffraction, the latter technique used to determine the crystallinity of the PVAL matrix in the nanocomposites through the addition of unmodified montmorillonite clay. The relaxation data for the nanocomposite films obtained by solution intercalation showed a decrease in the proton spin-lattice relaxation values with increased clay proportion, forming a nanostructured material with high exfoliation degree, as a result of two phenomena: the higher molecular mobility of the polymer chains around the clay layers and the presence of paramagnetic metals in the clay layers, which accelerates the hydrogen relaxation process, causing a decrease in the relaxation value. The samples obtained through in situ polymerization were mixed nanocomposites (partly exfoliated and partly intercalated). The NMR relaxation data for the systems analyzed showed the solution intercalation process was more efficient than in situ polymerization in relation to the generation of nanostructured polymers with higher degree of exfoliated clay.
Applications of NMR Spectroscopy
Journal of Research Updates in Polymer Science
The purpose of this work was to study the molecular dynamics, morphology, mechanical and thermal ... more The purpose of this work was to study the molecular dynamics, morphology, mechanical and thermal performance of nanomaterials formed by poly(vinyl alcohol) and molybdenum trioxide (PVA/MoO3) obtained through solution casting method, focusing new materials with therapeutic applications since the molybdenum trioxide exhibit an excellent antibacterial activity and could be a pathway to prevent viruses. The obtaining materials were characterized by conventional techniques as X-ray diffraction, thermogravimetric and dynamical-mechanical analysis. The unconventional low-field NMR relaxometry was used to evaluate the molecular dynamic and morphology of these systems. The results obtained showed that the MoO3 addition into PVA matrix promote an increase on the thermal stability at higher temperatures and a progressive increase on the rigidity of the PVA systems. Also changes in the molecular mobility of nanomaterials determined through the proton spin-lattice relaxation time showed that low...
Materials Sciences and Applications
Journal of Thermal Analysis and Calorimetry, 2020
In this work, films of commercial PLA Ingeo 4043D with nano-zinc oxide particles (nano-ZnO) with ... more In this work, films of commercial PLA Ingeo 4043D with nano-zinc oxide particles (nano-ZnO) with average diameter around 100 nm and ZnO concentrations of 0.1, 0.25, 0.3 and 0.5 mass% were prepared by flat die extrusion. The addition of nano-ZnO had an objective to promote the crystallization of PLA, but it decreased the thermal stability of the films. Both neat PLA and PLA/nano-ZnO composites films did not crystallize during the cooling, but crystallize during a first heating, showing a cold crystallization process, which was significantly influenced by the heating rate. A low chain mobility was evidenced by the values of relaxation time (T 1 H). This low chain mobility avoided the high degree of crystallization of the films which were predominantly amorphous. For all films, an enthalpic relaxation phenomenon was detected during the first heating. The glass transition temperature (T g) was shifted to higher values as the heating rate and nanofiller content are increased. Addition of nano-ZnO in PLA films did not increase their crystallinity, indicating that it is not an effective nucleating agent for this low-crystallinity PLA grade.
... TRATAMENTO QUÍMICO RL Müller, FR Wagner, CM Mählmann, AL Rodríguez, LM Kipper, JAR Moraes ...... more ... TRATAMENTO QUÍMICO RL Müller, FR Wagner, CM Mählmann, AL Rodríguez, LM Kipper, JAR Moraes ... (5,13) Segundo Tita (13), o uso de bagaço de cana-de-açúcar promove um pequeno aumento na resistência ao impacto quando utilizado como reforço em matriz fenólica ...
Journal of Nanoscience and Nanotechnology, 2016
Tissue engeneering is a multidisciplinar field where the principles of engeneering and life scien... more Tissue engeneering is a multidisciplinar field where the principles of engeneering and life sciences can be applied to the development of biological subsitutes used to restore, keep or improve living tissues functions[1]. A biomaterial can be defined as a material designed to interface biological systems to evaluate, heal, enhance or substitute any tissue, organ or bodily function[2]. A limitation found in most polymers is that these materials lack the kind of properties that promotes cellular adhesion and proliferation. To improve the bioproporties and cellular interactions of those polymers, composites based on biodegradable synthetic polymers, modified biodegradable natural polymers and its blends have been proposed to prepare scaffolds [3]. Some of the most important properties of a biodegradable material include the absence of inflammatory or toxic response after its implantation, a reasonable shelf life, adequate mechanical properties for the desired application, whose variati...
Polymeric blends are interesting materials, from the thechnological point of view, due to their v... more Polymeric blends are interesting materials, from the thechnological point of view, due to their versatility and easy obtaining. Two biopolymers can be mixed to improve the hybrid's properties. Bioblends based on poly(beta-hydroxybutirate) (PHB) and poly(epsilon-caprolactone) (PCL) were obtained via solution casting under various PHB:PCL weight ratios. Bioblend's miscibility was assessed via time domain nuclear magnetic resonance (TD-NMR), through the observation of the longitudinal and transversal relaxation times constants, T1 and T2*, respectively. The experiment was conducte in a Maran Ultra spectrometer, operating at 0,54 T, at ambient temperature and employing the inversion-recovery (IR) and Magic Sandwich Echo Free Induction Decay (MSE-FID) pulse sequences. The experimental data were fitted in a commercial fitting software package (WinFit), assuming monoexponential decay for IR measurements and a set of exponentials, gaussians and Abraghamian curves for the fitting of ...
Polímeros
Four commercial flour samples with starch components were studied. They were characterized by Inf... more Four commercial flour samples with starch components were studied. They were characterized by Infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and low field NMR (T1H).
Solid-state nuclear magnetic resonance (NMR) techniques include hydrogen nuclear relaxation measu... more Solid-state nuclear magnetic resonance (NMR) techniques include hydrogen nuclear relaxation measurements, such as spin-lattice relaxation time in the laboratory frame (T1H). This relaxation parameter involves changes in thermal equilibrium of spin systems. The hydrogen relaxation times can be measured directly in a low-field NMR spectrometer. The efficiency of the process can be correlated with the structure and the value is intrinsically related to the system’s morphology. Consequently, the relaxation measurements can be used to evaluate nanoparticles’ dispersion in the polymer matrix, the interaction between both nanocomposite components, the molecular dynamics of the hybrid compound and also the formation of molecular domains in organic material. These techniques are thus good tools to analyze the molecular dynamics of polymer systems and nanocomposites. In this study, two nanocomposites, one based on virgin high impact polystyrene (HIPS) and organoclay and the other on recycled ...
Polímeros
Polycarbonate-organofilic clay nanocomposites were obtained via the melt intercalation method in ... more Polycarbonate-organofilic clay nanocomposites were obtained via the melt intercalation method in the blending chamber of a torque rheometer, under distinct values of shear and temperature. The influence of those processing parameters on the clay dispersion in the polymer matrix was probed by low-field nuclear magnetic resonance (NMR), using the T1H measurement technique and by wide angle X-ray scattering (WAXS). The differences in longitudinal relaxation times and in the X-ray reflection patterns were correlated with the formation of relaxation domains with particular molecular mobility, as progressively larger intercalated morphologies were found in the nanocomposites due to the increase of shear stress and temperature. 1H NMR has shown that both shearing and temperature have played a fundamental part on the polymer chains mobility, which explains the increase in the domain´s homogeneity following the increment of those processing parameters.
Polymer Testing, 2000
Natural fibers obtained from sugar cane have been analysed by carbon-13 high resolution solid sta... more Natural fibers obtained from sugar cane have been analysed by carbon-13 high resolution solid state nuclear magnetic resonance (NMR) employing different techniques such as: cross-polarisation magic angle spinning (CP/MAS); variable contact time experiment and proton spin-lattice relaxation time in the rotating frame. Molecular mobility information for distinct types of sugar cane fibers, as well as two different mixtures (one of the mixtures contains equal amounts of waste fibers and the other has a random distribution of these waste fibers) and their composites with poly(ethylene-co-vinyl acetate) (EVA) were obtained from those techniques. Mechanical measurements (stress-strain) were also recorded for all samples. Both NMR and mechanical measurements responses showed that the mixtures of natural fiber can be used as a matrix in the composites.