ABSTRACT Hydrophilic polymer matrix systems (HPMSs) are a highly relevant tool for drugs delivery whose bioavailability is impaired by low hydrosolubility. Besides this, when associated with nanoparticles these systems can provide better control over release profile of the active drug, maintaining the posology. Since polyvinylpyrrolidone (PVP) and zinc oxide (ZnO) are safe materials for use in the human body, we studied the effects of ZnO nanoparticle ratios on the characteristics of PVP matrix. For that purpose, nanocomposites were prepared by solution casting method and characterized by X-ray Fluorescence (XRF), Fourier Transform Infrared (FTIR), Thermal Gravimetric Analyses (TGA), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XDR) and Low-field Nuclear Magnetic Resonance (LF-NMR) technique, using relaxometry. We also analyzed the effects of the system on two broad-spectrum antimicrobial drugs. The characterization results of the new materials indicate good interaction of the nanoparticles with the polymer, and this fact suggests that these new materials may have a retarding effect on drug release. The results also showed no disruptive interaction of the matrix system important to the action of the antimicrobials.

RESUMO Nanocompósitos de polietileno linear de baixa densidade com argila montmorilonita organofílica (OMMT) de fonte brasileira foram obtidos com o objetivo de avaliar as propriedades físico-químicas. Foram produzidos e caracterizados nanocompósitos obtidos por extrusão nas concentrações 2, 2,5, 3, 3,5% e o polímero puro. As misturas foram injetadas e caracterizadas. As análises de TGA mostraram que a adição de nanoargila elevou a estabilidade térmica das amostras, principalmente a PELBD/OMMT2,0, cujo aumento foi de 5,6% comparado ao Branco. O DSC demonstrou que a incorporação não influenciou na temperatura de fusão com relação a amostra pura do PELBD, entretanto, aumentou o grau de cristalinidade das amostras, destacando-se a amostra PELBD/OMMT2,5 que apresentou grau de cristalinidade 9,48% maior que o branco. Os resultados de flamabilidade mostraram que a amostra PELBD/OMMT2,0 apresentou diminuição de 38% na velocidade de propagação de chama. No ensaio de tração, percebeu-se um aumento na rigidez das amostras com adição de OMMT, aumentando o módulo de Young e diminuindo o alongamento na ruptura com o aumento percentual de OMMT. Já a técnica de RMN mostrou que as amostras de até 2,5% de OMMT sugere a formação de um nanocompósito esfoliado, resultados comprovados por MEV/FEG, na qual amostras injetadas com uma quantidade superior a 2,5% de argila apresentaram as mesmas características de delaminação.

ABSTRACT Low density linear polyethylene nanocomposites with organophilic montmorillonite clay (OMMT) from Brazilian source were obtained with the objective of evaluating the physicochemical properties. Nanocomposites obtained by extrusion at the concentrations 2, 2.5, 3, 3.5% and the pure polymer were produced and characterized. The mixtures were injected and characterized. The TGA analyzes showed that the addition of nanoclay considerably increased the thermal stability of the samples, especially the PELBD/OMMT2,0, which increase was of 5.6% compared to White. Through DSC it was found that the samples with nanoclay incorporation suffered no change in melting temperature in relation to the pure sample of LLDPE, however, the incorporation of clay increased the degree of crystallinity of the samples, especially for the LLDPE/OMMT2,5 sample that showed a 9,48 % degree of crystallinity higher than the white one. The flammability results revealed that the LLDPE/OMMT2,0 sample showed a decrease of 38 % in the flame propagation velocity. In the tensile test it was noticed an increase in stiffness of the samples with addition of OMMT compared to the White one, increasing the Young's modulus and decreasing the elongation at fracture with the percentage increase of OMMT. On the other hand, the NMR technique showed that the samples of up to 2,5% of OMMT suggests the formation of an exfoliated nanocomposite.

Abstract Poly(vinyl alcohol) (PVA)-based chemically cross-linked xerogels, both neat and loaded with nanoparticulate hydrophilic silica (SiO2), were obtained and characterized mainly through time domain NMR experiments (TD-NMR). Fourier-transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD) analyses were employed as secondary methods. TD-NMR, through the interpretation of the spin-lattice relaxation constant values and related information, showed both cross-linking and nanoparticle influences on PVA matrix. SiO2 does not interact chemically with the PVA chains, but has effect on its molecular mobility, as investigated via TD-NMR. Apparent energy of activation, spin-lattice time constant and size of spin domains in the sample have almost linear dependence with the degree of cross-linking of the PVA and are affected by the addition of SiO2. These three parameters were derived from a single set of TD-NMR experiments, which demonstrates the versatility of the technique for characterization of inorganic-organic hybrid xerogels, an important class of materials.

In this work, proton NMR relaxometry was used to measure the behavior of spin-lattice relaxation time with T1H as the time constant, and also of spin-spin relaxation time with the time constant T2H. These relaxometry parameters were determined to better understand the changes in the main structures present in commercial and in nature forms of origanum. The T1H relaxation data showed that the structures which had higher molecular mass were more sensitive to degradation with increased temperature treatment. According to the values of the T2H parameter, up to 150 degrees no significant change in the mobility and organization of water was observed. These data infer that the ideal cooking temperature and tea preparation mode for this herb should be around 100 degrees for the sample not to lose its characteristics. Also, it is not advisable to cook this herb at higher than 150 degrees but better to consume it at room temperature, especially give commercial herb has already been dehydrated.

In this study, hybrid nanocomposites based on HIPS, high-impact polystyrene, were prepared in chloroform and in a 1:1 mixture of toluene and chloroform varying the quantity of organophilic montmorillonite. The morphology of the hybrid materials was investigated by X-ray diffraction (XRD) and proton relaxometry, determined in a low-field 1H nuclear magnetic resonance (NMR). The thermal characteristics were also obtained through thermogravimetric analysis. The emphasis of this study was to compare the effect of a pair of solvents against a single solvent in the formation/organization of the nanostructured materials when the solution method is applied. It was taken into consideration Interactions involving polymer-solvent, nanoparticle-solvent, and, principally, polymer-nanoparticle-solvent. The results show that the choice of solvent affects greatly the characteristic of the nanocomposites. Nanocomposites prepared with chloroform/toluene were more homogenous, more prone to exfoliate (for all organoclay concentrations), and had higher degradation temperature compared to the materials obtained with chloroform. It is clear from the data that the use of a solvent pair is important to produce good nanocomposites when using the solution method and that the clay proportion plays a role in the dispersion of organoclay in the polymer matrix.

The goal of this work was to investigate the production and properties of hybrid materials based on poly(lactic acid) (PLA), employing microcrystalline cellulose (MCC) and organophilic silica (R972) as fillers. The composites were obtained by solution casting to form films. Each nanoparticle was incorporated at 3 wt. %, relative to the polymer matrix. In this experiment, four films were obtained (PLA, PLA/MCC, PLA/R972 and PLA/MCC/R972). The films properties were evaluated by X-ray diffractometry, nuclear magnetic resonance, Fourier transform infrared spectroscopy and mechanical properties. The results showed that each nanoparticle, added individually or both combined, had different effect on the final properties of the films. Microcrystalline cellulose can act as nucleating agent for the crystallization of PLA. Silica promoted an increase in rigidity, due to the strong intermolecular forces, while MCC addition promoted an increase in the molecular mobility of the polymeric chains. The PLA/MCC/R972 film showed the highest crystallinity degree and tensile modulus. This film presented a T1H value between both values found for PLA/MCC and PLA/R972 films. The results indicated that silica R972 could promote a decrease of the surface tension between PLA and cellulose.

We investigated the effect of adding titanium dioxide nanoparticles (TiO2) to ethylene vinyl acetate (EVA) copolymer, containing 28% vinyl acetate groups, on the crystallinity and miscibility of the copolymer. Films of EVA/TiO2 containing 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 TiO2 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.

Nanocompósitos de amido de batata foram preparados pelo método de intercalação por solução, com a adição de argilas montmorilonita: organicamente modificada (Viscogel B8) e não modificada argila sódica (NT25) e de sílicas: modificada (R972) e não modificada (A200). Os nanocompósitos foram caracterizados pelas técnicas convencionais de difratometria de raios X e análise termogravimétrica. Foram caracterizados também por uma técnica denominada como não convencional, a ressonância magnética nuclear (RMN) de baixo campo, que é alternativa e efetiva na caracterização de nanocompósitos. Com ela, pode-se investigar a dispersão das nanocargas pelo grau de intercalação e/ou esfoliação, além de verificar a distribuição e modificações da mobilidade molecular da matriz polimérica. Os materiais nanoestruturados obtidos com as argilas apresentaram boa dispersão e formação de nanomateriais mistos, com diferentes graus de intercalação e esfoliação. Ao adicionar as sílicas na matriz de amido pode-se observar uma diminuição da mobilidade do material, este efeito foi observado para ambas às sílicas utilizadas. Utilizando a técnica de TGA verificou-se um ligeiro aumento na estabilidade térmica do material produzido em relação ao amido.

Nanocomposites of potato starch were prepared by the solution intercalation method with the addition of organically modified montmorillonite clay (Viscogel B and unmodified sodic clay (NT25) as well as modified and unmodified silica (R972 and A200, respectively), using water as the solvent. The nanocomposites were characterized by conventional techniques of X-ray diffraction and thermogravimetric analysis. They were also characterized using the non-conventional low-field nuclear magnetic resonance, which is an effective alternative technique for characterizing nanocompósitos. This technique allows one to investigate dispersion of nanofillers by the degree of intercalation and/or exfoliation, in addition to determine the distribution of nanoparticles in the polymer matrix and modifications of the molecular mobility of these fillers. The nanostructured materials obtained with the clays presented good dispersion and formation of mixed nanomaterials, with different degrees of intercalation and exfoliation. The mobility of the material decreased upon adding silica in the starch matrix, which applied to both types of silica. From the TGA technique, a slight increase in thermal stability of the nanocomposite was noted in relation to the starch matrix.

O acúmulo de resíduos poliméricos tem crescido nos últimos anos e os subsolos dos lixões já estão saturados com resíduos plásticos. Isso possivelmente se deve à elevada produção de resíduos sólidos de plásticos (cerca de 25 mil t/dia em 2008, segundo a Lei de Resíduos). Em vista disso, este trabalho apresenta uma análise comparativa do estudo do potencial de (bio)degradação de compostos de PVC utilizando um plastificante de origem vegetal renovável (PFR) com estrutura de éster de milho com massa molar 296,5 g.mol- 1 e dois plastificantes sintéticos, ftalato de dioctila (DOP) e adipato de dioctila (DOA), buscando inovar na obtenção de um composto de PVC com um plastificante de fonte renovável. Os resultados de FTIR evidenciaram maior interação do PFR com a resina de PVC para o teor de 30 phr, e para o teor de 40 phr observou-se que os plastificantes DOP e PFR apresentaram os mesmos valores de variação da banda atática. Já os ensaios mecânicos reforçaram os resultados de FTIR com maior compatibilidade para as composições contendo PFR. Uma maior estabilidade térmica no composto de PVC foi observada por TGA para a amostra contendo 40 phr de DOA, o que foi confirmado por RMN, e para a amostra com PFR nos teores de 30 e 40 phr. Por fim, uma perda significativa de massa foi observada nos ensaios de resistência à extração por solvente para os compostos contendo DOA, sendo que a amostra com 30 phr mostrou menor valor de extração. A biodegradação em solo simulado mostrou maior perda de massa para as amostras plastificadas com DOA (40phr) e PFR (40phr). Isso indica que é viável usar plastificante de fonte renovável nos compostos de PVC, devido à compatibilidade deste com esta resina.

The accumulation of polymeric waste in the environment has increased in recent years and landfills are already saturated with plastic waste, with an estimated production of ~25,000 t of solid plastic waste per day in Brazil, based on data for 2008. In this report, we describe a comparative analysis of the biodegradation of PVC compounds containing a renewable vegetable-derived plasticizer (RVP) with ester structure of corn and molar mass 296.5 g.mol- 1, or one of two synthetic plasticizers (dioctyl phthalate - DOP and dioctyl adipate - DOA). FTIR showed a greater interaction of RVP with the PVC resin at a content of 30 phr compared to the two synthetic plasticizers. In contrast, at 40 phr, the plasticizers DOP and RVP showed the same variation in the atactic band. Mechanical tests reinforced the results of FTIR by showing greater compatibility for compositions containing RVP. Thermogravimetric analysis showed that PVC compounds containing DOA at 40 phr were thermostable, as were compounds containing RVP at 30 and 40 phr. NMR confirmed the influence of the plasticizers on thermal stability. Compared to other combinations, samples plasticized with DOA showed significant loss of mass in tests of resistance to solvent extraction and biodegradation in simulated soil. These results demonstrate that RVP is compatible with PVC and suggest that this plasticizer could be a useful substitute for synthetic plasticizers in PVC-based products.

Poly (ε-caprolactone) (PCL) based hybrids containing different amounts of modified (Aerosil® R972) and unmodified (Aerosil® 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 (T1H) and hydrogen spin-lattice relaxation time in the rotating frame (T1ρH). 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.

Poly(3-hydroxybutyrate) (PHB) based on nanocomposites containing different amounts of a commercial organically modified clay (viscogel B7) were prepared employing solution intercalation method. Three solvents, such as: CHCl3, dimethylchloride (DMC) and tetrahydrofuran (THF) were used. The relationship among the processing conditions; molecular structure and intermolecular interaction, between both nanocomposite components, were investigated using a nuclear magnetic resonance (NMR), as a part of characterization methodology, which has been used by Tavares et al. It involves the hydrogen spin-lattice relaxation time, T1H, by solid state nuclear magnetic resonance, employing low field NMR. X ray diffraction was also employed because it is a conventional technique, generally used to obtain the first information on nanocomposite formation. Changes in PHB crystallinity were observed after the organophilic nanoclay had been incorporated in the polymer matrix. These changes, in the microstructure, were detected by the variation of hydrogen nuclear relaxation time values and by X ray, which showed an increase in the clay interlamelar space due to the intercalation of the polymer in the clay between lamellae. It was also observed, for both techniques, that the solvents affect directly the organization of the crystalline region, promoting a better intercalation, considering that they behave like a plasticizer.