Behaviour of the poly(maleic anhydride-co-vinyl acetate) copolymer in aqueous solutions

The alternate copolymer obtained from maleic anhydride and vinyl acetate, p oly(maleic anhydride-co-vinyl acetate) (PMAVA), was studied by viscosimetri c and potentiometric methods. In aqueous solutions this copolymer is hydrol yzed to two neighbouring carboxyl groups in a structural unit and behaves a s a dibasic polyacid. The viscosimetric behaviour of PMAVA was studied in f unction of copolymer concentration, neutralization degree, concentration of the NaCl added and three samples of different molecular weights were synth esized. The rather low viscosity of the copolymer aqueous solution increase s with decreasing PMAVA concentration which makes evident the polyelectroly te character of this copolymer. By potentiometric titration the PMAVA solutions were studied both in the ab sence and in the presence of NaCl. The estimated values of pK(01) and pK(02 ) correspond to the first and to the second ionization stage, respectively. The electrostatic free energy of the polyion, G(e), was calculated with re ference to the number of the structural units in a macromolecule, in functi on of the neutralization degree. (C) 2001 Elsevier Science Ltd. All rights reserved.