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Abstract: The thermal and electrochemical behaviours of PEMFC ionomers based on an aromatic backbone i.e., sulfonated polysulfones, sulfonated polyetheretherketones and sulfonated polybenzimidazoles, were investigated through their model molecules. Thermal degradation was characterized by weight losses and allowed inferring ionomer thermal degradations by chain breakings that cannot be detected by thermogravimetric analysis. In addition, cyclic voltammetry was used to characterize the electroactivity of some ionomers, related to their backbone and their ionic moieties. The use of model molecules is thus a useful tool for assessing both the thermal and electrochemical stability of ionomers. Lastly, due to the high concentrations used in liquid electrolytes as compared with an electrode/membrane interface it may be considered as an electrochemical aging test. [Copyright &y& Elsevier]

Graphical abstract Influence of cations and anions on the formation of gamma polar phase in polyvinylidene fluoride. Highlights • Polymer/Ionic liquids system can be treated as a ternary system. • The effect of the chemical nature of the cation and the anion may interfere on the crystalline phase formation of the PVDF polymer. • The acidity Brønsted difference of the ionic liquids result in different polarities in the main polymer chain. • A nanoestruturação por ILS promove RAF e MAF. • The existence of ILs in the RAF acts as an obstacle for the growth of larger structures. Abstract The ability of different microstructures from ionic liquids (ILs) governed by anions and cations has been a source of curiosity for composite systems. In this present study, the structural behavior of polyvinylidene fluoride (PVDF) mixed with phosphonium- and imidazolium-based ionic liquids (1 wt%) combined with different counter anions was investigated. The effect of the chemical nature of the cation and the anion on the resulting polar crystals was evaluated. Thus, the formation of polar phase after IL incorporation was highlighted with morphologic observation of spherulites of low-birefringence using polarizing optical (POM) and atomic force microscopies (AFM), and their crystalline structures were confirmed by infrared spectroscopy (FTIR) and Wide-angle X-ray diffraction (WAXS). However, the enhancement of polar γ-phase crystallization was mainly observed in presence of phosphonium-based ILs suggesting that the nanostructuration mechanism were amply dependent on the interacting abilities of ILs in PVDF matrix. In addition, we have also demonstrated that the presence of ILs within the crystalline lamellae, characterized by SAXS and DMA, oriented the chains allowing the formation of rigid amorphous fraction (RAF). For this reason, we proposed that the depression of spherulites size was due to the existence of ILs in the RAF acting as obstacle for the growth of larger structures. Finally, these different changes in the microscopic level structure bestowed a rather unique property which modified the mechanical performance of the polymer materials, especially the ability to sustain large deformation. [ABSTRACT FROM AUTHOR]

We present a Raman spectroscopic study of the conversion of soybean oil into biodiesel by methanol using the lipase B enzyme pseudomonas cepacia as the bio-catalyst and 1-alkyl-3-methylimidazolium ionic liquids (C n C 1 Im) as co-solvents, where the alkyl chain length is varied from ethyl ( n = 2) to decyl ( n = 10). We have limited this study to a low reaction temperature, 40 °C, and a low enzyme concentration to investigate the possibility of producing biodiesel with low energy and cost demands. We also demonstrate that Raman spectroscopy is a powerful and straightforward method to estimate the yield of the transesterification reaction, by analysis of the characteristic C O stretching mode found in the range ∼ 1730–1750 cm −1 . Our results indicate that both reaction yield and reaction rate increase with the chain length, but also that for chains longer than decyl further improvements are marginal. We discuss these results from the viewpoint of local interactions and local structure of the investigated ionic liquids. [ABSTRACT FROM AUTHOR]