Thermodynamics of hydrogen bonding in polycomplexes of poly(4-vinylpyridine) with maleic acid-alt-ethylene copolymer

Hydrogen bonding formation in a polymer complex between poly(4-vinylpyridine) (P4VPy) and maleic acid-alt-ethylene (MA-alt-E) copolymer has been studied. Fourier transform infrared spectroscopic (FT-IR) studies have evidenced that the carboxylic groups of MA-alt-E interact with the pyridine ring of P4VPy. The existence of hydrogen bonding interactions in these systems is shown by the appearance of new bands at 1640 and 1503 cm^-1 and a broadening of the -C=C- band of the pyridinic ring. The thermodynamic analysis of the hydrogen bonding was performed through the estimation of the enthalpy of mixing in the polycomplex formation process. ΔH_M was determined by means of an association model developed by Painter and co-workers and by flow calorimetric direct measurements. These results showed a high negative value for the enthalpy of mixing, which is consistent with the blend miscibility given that ΔH_M is the main contribution to the change of the free energy of mixing, ΔG_M.