Poly(N-octyl-4-vinylpyridinium bromide) copolymers in aqueous solutions: potentiometric and thermodynamic studies

Abstract

AbstractIn this work, the P4VP was synthesized by radical polymerization. The quaternization of this polymer by octyl bromide leads to the two copolymers [poly(N-octyl-4-vinylpyridinium bromide] named P4VPC8Br 48.8% and P4VPC8Br 72%. The thermodynamic behavior associated with the potentiometric titration of the copolymers, was reported in the temperature range (293.16–333.16 K) and as a function of the concentrations (0.25×10−4 mmol/dm3 12.3×10−4 mmol/dm3). The free energy of dissociation ΔGdiss variation versus the neutralization degree shows the negative value due to the steric and electrostatic effect of the alkyl chains. The positive values of ΔH and ΔS confirmed the spontaneity and disorder of the reaction. The critical concentration C* of the two copolymers was determined from the enthalpy ΔH0 and entropy ΔS0 changes. The transition in conformation of the copolymer chains was influenced by the presence of hydrophobic-hydrophilic and hydrophobic-hydrophobic interactions.