SynopsisSome physical and chemical properties of an ionic complex made from the weak polyelectrolytes carboxymethylated poly(viny1 alcohol) (PA) and aminoacetalized poly(viny1 alcohol) (PC) are investigated in comparison with those of another ionic complex made from the strong polyelectrolytes sulfated poly(viny1 alcohol) (PSA) and poly(viny1 alcohol) acetalized with diethoxyethyltrimethylammonium (PTC). It was found that when the complex PC-PA was heated at high temperatures, covalent amide bonding took place, whereas no significant change occurred in the case of the PTC-PSA complex. As a result of these structural changes, the degree of swelling of the PC-PA complex in water was markedly decreased, but that of the PTC-PSA complex was not changed by the treatment. The PC-PA complex was insoluble in water and in 1N HCl and 1N NaOH aqueous solutions even if not heat treated, but the PTC-PSA complex was soluble in such acidic and basic aqueous solutions but not in water if heat treated. The PC-PA and PTC-PSA films exhibited good mechanical properties.