Abstract The problem of the relation of the swelling of vulcanizates to the nature of the liquid medium is very important in explaining the nature of vulcanization and determining the nature of the bond between the separate macromolecules in the vulcanizate. The relation of the swelling of vulcanizates to the molecular polarization of mixed liquids has been studied several times; however, the mechanism of the reaction of the polar component of a mixed liquid with the rubber molecules during swelling is still not very clear. According to contemporary theory, the swelling of polymers, particularly rubber, is thermodynamically analogous to the mixing of low-molecular liquids. Swelling is caused by a decrease of the free energy of the system: ΔG=ΔH−T⋅ΔS, which in the case of nonpolar polymers is due principally to an increase of entropy, T⋅ΔS, as a result of the separation of the molecular chains and their increased elasticity. For polar polymers, ΔH is the important factor. In this work rubber is regarded as a polymer in which the molecular chains are bound by nonequivalent bonds with varying amounts of energy, as appears in the swelling process, and not as a union of molecular chains surrounded by a uniformly strong field. It is evident from other studies that the latter assumption is not entirely correct. On the basis of a study of the protective action of antioxidants during the oxidation of rubber by oxygen, one of the authors regarded the mechanism of this action as the result of solvation of the antioxidant in the polar segments of the rubber molecule by the polar molecules.