Mechanisms of Molecular Interactions in Polybase-Polyacid Complex Formed by Copolymers of N,N-Dimethylaminoethylmethacrylate with Alkylmethacrylates and Methacrylic Acid with Ethylacrylate

Mechanisms of molecular interaction in the blends of a polybase, a copolymer of N,N-dimethylaminoethylmethacrylate with methylmethacrylate and butylmethacrylate (PDMAEMA-MMA/BMA), with a polyacid, a copolymer of methacrylic acid with ethylacrylate (PMAA-co-EA), and plasticizer, triethylcitrate (TEC), have been investigated with FTIR Spectroscopy and potentiometry. To evaluate the strengths of hydrogen and ionic bonds in the polyelectrolyte complexes, quantum-chemical calculations were performed. According to this analysis, the energy of ionic and hydrogen bonding diminishes in the order: multi-component complexes involving protonated aminogroup of DMAEMA (ammonium cation) in the presence of chlorine counterion with ionized or unchanged carboxyl groups and water molecules (690-520 kJ/mol) > ternary H-bonded acid-base complexes associated with molecule of water (520-420 kJ/mol) > binary ionic complex of carboxylate anion and ammonium cation (404 kJ/mol) > H-bonded complex of carboxylate and ammonium ions (257 kJ/mol) > binary H-bonded complex of uncharged carboxyl group with ammonium cation (114 kJ/mol) > ternary H-bonded complex of uncharged carboxyl group, aminogroup and water molecule (43 kJ/mol) > binary H-bonded complex between nonionized carboxyl and amino groups (26 kJ/mol). Proton-donating capability of functional groups in the studied polyelectrolyte blends diminishes in the order: HN+(CH3)(2) - > HOOC- > HO-. The proton-donating capacity can be significantly improved in the presence of Cl- ions, the effect of which may be appreciably inhibited if Na+ cations are available in the blend or solution. Proton-accepting capability weakens in the order: uncharged aminogroup > carboxylate anion > uncharged carboxyl group > hydroxyl group. The results of quantum chemical calculations facilitate interpretation of FTIR spectra. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 1142-1165, 2009