Proton-monomeric ligand dissociation and metal-monomeric ligand stability constants of vinylacetic acid (VA) with some metal ions were calculated potentiometrically in 0.1KCI. Also, in the presence of 2,2'-azobisisobutyronitrile as initiator, the proton-polymeric ligand dissociation and metal-polymeric ligand stability constants were calculated. The effect of temperature on the dissociation of VA and the stability of its formed complexes were studied in monomeric and polymeric forms. The corre-sponding thermodynamic functions were derived and discussed. The dissociation process was nonspontaneous, endothermic, and entropically unfavorable. The formation of the metal complexes was found to be spontaneous, endothermic, and entropically favorable. (c) 2005 Wiley Periodicals, Inc.