Abstract Electrospun fibers find a number of biomedical applications, like scaffolds for tissue engineering, as polymer nanofiber mats can mimic the extracellular matrix (ECM) of the body. In this research, non-woven mats composed of poly(L-lactic acid) (PLLA) fibers were obtained by low voltage (6 kV) electrospinning of PLLA/chloroform (CL)/sodium lauryl ether sulfate (SLES) solution. Tests were performed in two different collector/capillary distances and the produced fibers were evaluated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and cell viability. The results show the formation of three dimensional mats composed of porous fibers created by the addition of small amounts of aqueous solution of SLES surfactant; a higher crystallinity degree for longer collector/capillary electrospun distance and positive cell proliferation.

Polyaniline is a conducting polymer that has recently been studied regarding its potential in the removal of contaminants by heterogeneous photocatalysis. Since it is a polymer with a high absorption capacity of photons in the visible region, it promotes the photosensitization of catalysts that are typically inactive in solar systems. The increasing number of publications applying photocatalysis and composite catalysts based on polyaniline highlights the importance of this subject. This review systematizes the most important and specific contributions of composite catalysts formed by polyaniline. The main mechanisms proposed for photosensitization, which show the synergism between the phases of the composite, are summarized. Moreover, the relevance of morphology and conductivity of the composite catalyst, operating parameters (eg. pH, and light source contaminant) are some of the aspects discussed, revealing how these differ from traditional catalysts. Future prospects for the continuation and improvement of this issue mainly involve a greater variety of contaminant removal tests and understanding of relations between the structure of the material and its photocatalytic property.

Membranas baseadas em poli(aril éter cetona) sulfonada mostraram ser bastante promissoras para aplicação em células a combustível com membrana trocadora de prótons (PEMFC). O poli(éter-éter-cetona) sulfonado (SPEEK), com elevado grau de sulfonação (GS), apresenta alta condutividade de prótons, mas sofre perda de funcionalidade e condutividade em temperaturas altas e umidades baixas. O desenvolvimento de membranas híbridas é uma das possibilidades para melhorar o desempenho destes materiais. Neste trabalho foram preparadas membranas híbridas zirconizadas de SPEEK/copolissilsesquioxano fosfonado (CF) por casting, a partir de SPEEK com GS entre 60% e 70% e soluções de cloreto de zirconila (ZrOCl2) 1, 5, ou 10% (m/m). As membranas foram caracterizadas por espectroscopia na região do infravermelho (FTIR), difratometria de raios-X (DRX), análise termogravimétrica (TG), calorimetria exploratória diferencial (DSC), condutividade de prótons (σ) e microscopia eletrônica de varredura (MEV). A análise por energia dispersiva (EDS) confirmou a presença de Zr em domínios esféricos dispersos homogeneamente pelas membranas, enquanto análises de DRX mostraram que os produtos da zirconização são amorfos. Ensaios de impedância eletroquímica indicam aumento da condutividade protônica com a adição de CF e 1 ou 5% de ZrOCl2.

Membranes based on sulfonated poly(aryl ether ketone) are known to be very promising materials for Proton Exchange Membrane Fuel Cells (PEMFC). Sulfonated poly(ether-ether-ketone) (SPEEK), with high sulfonation degrees (SD), present high proton conductivity. However, they lose functionality and conductivity at high temperatures and low humidity. To enhance the performance of these materials, hybrid membranes have gained considerable attention. In this work, zirconized SPEEK/phosphonated copolysilsesquioxane (CF) hybrid membranes were prepared by casting, from SPEEK (60% < SD < 70%) and 1, 5, or 10 wt. (%) zirconyl chloride solutions. The membranes were characterized by infrared spectroscopy (FTIR), X-ray diffractometry (DRX), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), proton conductivity, and scanning electron microscopy (MEV). Energy-dispersive X-ray spectroscopy (EDS) analyses confirmed the presence of Zr in spherical domains along the membrane, while DRX showed that the precipitated zirconium compounds had an amorphous character. Electrochemical impedance measurements indicated an increased proton conductivity with the addition of CF and ZrOCl2.

Neste trabalho foi estudada a reação entre polietileno glicol (PEG) e uma resina epoxídica à base de diglicidil éter de bisfenol A (DGEBA), na presença de N,N-dimetilbenzilamina (DMBA), sendo os produtos desta reação avaliados por espectroscopia no infravermelho (FTIR), espectroscopia de ressonância magnética nuclear de próton (RMN-1H) e medidas de viscosidade cone-prato. Amostras curadas com um endurecedor à base de poliamina foram também submetidas a ensaios de tração e calorimetria exploratória diferencial (DSC). Os resultados das análises de viscosidade, FTIR e RMN (1H) confirmaram a ocorrência da reação entre grupos epóxi do DGEBA e grupos hidroxila do PEG na presença de DMBA, a 100 ºC. As análises de DSC e os ensaios de tração dos sistemas curados mostram que a reação de DGEBA com PEG gera um material com temperatura de transição vítrea (Tg) significativamente menor, em conjunto com o aumento da deformação na ruptura e decréscimo do modulo de elasticidade, quando comparados ao sistema epoxídico de referência (DGEBA).

In this work the reaction of polyethylene glycol (PEG) and epoxy resin (BADGE) in the presence of N,N-dimethylbenzylamine (DMBA) was studied. The reaction products were evaluated by infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and viscosity measurements. Samples cured with a polyamine-based hardener were also submitted to tensile tests and differential scanning calorimetry (DSC). The results of the viscosity analyses, FTIR and RMN (¹H) confirmed the reaction between DGEBA epoxy groups and PEG hydroxyl groups in the presence of DMBA, at 100 ºC. DSC analyses and tensile tests of cured systems showed that the reaction of DGEBA with PEG leads to a reduction of Tg, generating a more flexible material.

In this work, a varied amount of acetone was employed to dissolve an epoxy resin and then a route was followed to remove the acetone, simulating a frequently used method to disperse nanofillers in thermoset matrices. Analyses were then carried out to address the influence of residual acetone on the curing process and on the epoxy properties. The results showed a detrimental effect on the mechanical properties of the cured epoxy due to the presence of residual acetone and also a less brittle-like fracture of the specimen. Fourier transform infrared spectroscopy and thermogravimetric analyses were additionally used to characterize the cured resins and have also indicated the presence of a small amount of acetone. Nevertheless, rheological measurements indicated that 10.0 wt.% acetone addition on the resin causes a significant decrease in viscosity (around 50%) which may promote a better dispersion of nanofillers.