A COMPARATIVE THERMODYNAMIC STUDY OF POLYELECTROLYTE AND HYDROGEN BONDED COMPLEXES IN AQUEOUS AND MIXED SOLVENTS

The significance of non-covalent interactions in guiding the association of natural and synthetic polymeric systems has been long recognized and, more recently, strategies based on weak interactions e.g., electrostatic forces, hydrogen bonds and the so called hydrophobic interactions have been formulated to create functional systems of diverse applications. In addition to the vast field of possible applications, the research of these model systems of synthetic polymers provides valuable information on the mechanisms of the interactions. We have selected a typical random polymer methacrylic acid/acrylamide MA/AAm. Results of thermodynamic studies of its complexation with poly (ethylene oxide) have been reported here. Comparisons have been made between complexing ability of copolymer methacrylic acid/acrylamide MA/AAm with a polyelectrolyte, poly (ethylene imine) and non - ionic homopolymers e.g., poly (vinyl pyrrolidone) PVP & poly (ethylene oxide) PEO. Further the systems have been studied in a mixed solvent (e.g., 90%: 10%; 80%: 20% water: Methanol respectively). Interpretations have been sought in terms of relative magnitude of the secondary binding interactions, cooperative interactions, neighboring group effect and hydrophobic interactions.