Correlations have been established between mechanisms of molecular interaction, the energy of intermolecular bonds, nanoscopic free volume, phase state, and such macroscopic physical properties as linear and large-strain viscoelasticity, relaxation, water-absorbing capacity, and adhesive joint strength of pressure sensitive adhesives based on nonstoichiometric polyelectrolyte complexes. The polyelectrolyte complexes are formed by mixing of a polybase, copolymer of N,N-dimethylaminoethyl methacrylate with methyl methacrylate and butyl methacrylate (PDMAEMA-co-MMA/BMA), with a polyacid, copolymer of methacrylic acid and ethyl acrylate (PMAA-co-EA) in the presence of triethyl citrate (TEC) as a plasticizer. Rubber-like elasticity and pressure sensitive adhesion of the polyelectrolyte complexes on the macroscopic level have been demonstrated to be the result of specific coupling of such generally conflicting properties of polymer materials as sufficiently strong intermolecular cohesion energy with comparatively large free volume (vacant space between neighboring macromolecules) at the nanoscopic scale. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012