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The main motivation of this work is to obtain poly (ionic liquids) (PILs) derived from poly (4-vinyl pyridine) of different hydrophobic character containing BF4−, PF6−, (CF3SO2)2 N− and CF3SO3− as counterions. PILs were synthesized from N-alkyl quaternized poly(4-vinylpyridine) P-4VP+-CnBr− with different alkyl chain length, n = 2, 4, 5 and different molecular weights (60.000 and 160.000 g/mol). The systems obtained were compared with the polyelectrolyte of origin, i.e., the N-alkyl quaternized poly(4-vinylpyridine). The molecular characterization of PILs was obtained by FT-IR, 1H NMR and 19F NMR. Moreover, the thermal analysis of these systems was by carried out by differential scanning calorimetry (DSC) and thermogravimetry (TGA) techniques. Thermal degradation profiles obtained from TGA measurements, varied according to the alkyl chain length, which in turn influenced the obtained values of glass transition temperature (Tg), due to greater or lesser segmental movement of the alkyl chain. The results obtained for the PILs studied were analysed according to alkyl chain length, molecular weight and counter-anion effects. Additionally, P-4VP+-C4 BF4− was used in a preliminary study of chromium (VI) removal from aqueous solution, showing a 72.2% removal of Cr (VI).

Adsorption of As (V) by poly ( N -octyl-4-vinylpyridinium) bromide (P4VPyC8), used as solid phase, was studied. Determination of As (V) was carried out by direct measurement of the fluorescence intensity on the solid phase. Adsorption variables were optimized for obtaining optimum values of pH and agitation time, where pH 9.0 and 60 min were established as optimum values. The adsorption of arsenic (V) was characterized by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. It was found that the fluorescence of the solid phase increases as the concentration of arsenic increases. Linearity was observed in the concentration range 6.80 to 90.0 μg L − 1 . The detection limit for determination of As (V) by this method was 2.24 μg L − 1 and the relative standard deviation (RSD) was 1.72%. The amount of retained As (V) was 0.154 mg/g of solid phase. The determination of As (V) in a sample of tap water by this method was well compared with the value reported by an external certified laboratory. Therefore, the method of analysis proposed here could be used as a screening methodology for monitoring the fulfillment of the norm for arsenic concentration in tap water.