Neutralization Degree Effect on Potentiometric Behavior of Poly(N-octyl-4-vinylpyridinium Bromide)

In this work, we synthesized Poly(4-vinylpyridine) (P4VP) by radical polymerization. A pair of copolymers containing the poly(4-vinylpyridine) were quaternized using octyl bromide to get P4VP-C8Br with degrees of quaternization of 48.8% and 72%. The P4VP and these two copolymers were characterized by 1H NMR, IR and ATG. Moreover, we studied the impact of the extent of quaternization and the concentration on the interaction of the P4VP-C8Br 48.8% and P4VP-C8Br 72% copolymers with proton H+ at 25 °C, within the neutralization range (0-1). In addition potentiometry technique was performed to evaluate this interaction for different concentrations and a phase diagrams of solubility was established in the concentration interval of (0.6×10-4 g/L - 3×10-4 g/L) for the two copolymers.The pKa variation versus copolymer concentration and it quaternization rate was examined. In the neutralization degree range (0 < α < 1), we noticed that the copolymer shows the modification in the structure and conformation caused by the presence of hydrophobic- hydrophilic and hydrophobic-hydrophobic interactions.