Synthesis and characterization of poly (ionic liquid) derivatives of N-alkyl quaternized poly(4-vinylpyridine)

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).