Chemical modification of polyethylene glycols by antioxidants belonging to the class of sterically hindered phenols is used to obtain water-soluble conjugates differing in the structure of the joined antioxidant and molecular weight. The inclusion of hydrophobic end groups in polyethylene glycol molecules leads to a decrease in the lower critical mixing point of the solution as compared to the original polymer. Dilute solution viscometry and light scattering are used to determine the molecular-mass characteristics of the polymers and the hydrodynamic radii of single conjugate molecules. The mass fraction of single molecules in aqueous solutions of the conjugates is greater than 95%. The aggregates are micellar-type particles whose core is formed by the hydrophobic moieties of sterically hindered phenols. It is shown that the antiradical activity of the antioxidants 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propionic acid and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid, which are used for the modification, differs only slightly, whereas the activity of the relevant conjugates increases significantly.

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Macromolecular esters were synthesized from carboxy-substituted derivatives of spatially hindered phenols and hydrophilic polymers: dextran, hydroxyethylated starch, poly(ethylene glycols) of various molecular weight. The hybrid macromolecular antioxidants signifi cantly surpass in antiradical and antioxidant activity the low molecular weight analogs of the hindered phenols.This is indicative of the changed mechanism of the redoxprocesses in water and of the governing role therein of the supramolecular hydrated structures formed by the solvation of polymer molecules in water environment.