Аннотация:The effects of molecular mass of the linear polymer and of temperature on the conformational state of the complex formed in aqueous media by poly(methacrylic acid) gel and PEG were examined. It was found that as the concentration of PEG in solution increased, the gel first collapses (at PEG concentration below 0.5-1.5%) and then, at higher concentrations, reversible swelling of the gel takes place. Increasing the temperature and the molecular mass of PEG was found to expand the concentration range in which the gel is in the collapsed state. An important feature of reversible swelling of the gels of poly(methacrylic acid) interacting with PEG in a neutral medium is that a wide range of PEG concentrations exists, in which the gel may occur in the swollen and in the collapsed states.