The thermodynamics of the interaction between water and swelling polymeric salts of 5-vinyltetrazole diethyl- and triethylamine was studied. Water swelling of polymeric salts is characterized by the negative values of the Gibbs free energy and the enthalpy of mixing, with the entropy values being positive. This fact suggests that the degradation of the polymer structure during the limited swelling of polymeric salts is mainly responsible for a change in the entropy of the system that is not fully compensated for by the formation of polymer-water structures.