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SynopsisHydrophilic gels have been prepared by polymerization of glycol methacrylate monoesters in the range of very low diester concentrations. The monomer mixture has been diluted with various solvents and the range has been investigated, in which swelling is independent of the dilution of the monomer mixture on polymerization. The quality of the gel is independent of the concentration and character of the solvent used in polymerization in a very broad range.Up to now, the formation of three-dimensional polymers in the presence of large solvent amounts has been studied mainly in systems with a high degree of crosslink age, especially with respect to the practical application of the results in modifying the properties of ion exchangers.' In the limiting case, the crosslinkage of 1% of the diolefinic component has been used. 2In both cases the formation of copolymers with no hydrophilic functional groups has been studied.Our work is aimed at the study of copolymers with hydrophilic functional groups and at the range of very low degrees of crosslinkage. Recently, these gels have become very interesting with respect to their application in medicine. 3For the preparation of these gels, the dimensional changes of the gel primarily formed after adjustment of equilibrium with water are especially interesting. This property may be influenced substantially by diluting the monomer mixture before polymerization. Experimental PartMonomers. Technical ethylene glycol monomethacrylate, 70-90% pure, containing 1.2-5.0% ethylene glycol bis-methacrylate as a crosslinking agent and ethylene glycol as the main residual impurity, produced by Povazske chemicke zavody in Zilina, was deprived of the main part of the diester by diluting with water in a ratio of 1 :4 by volume and by fivefold extraction of the aqueous solution with hexane in the volume ratio of 4: 1. After separating the hexane, the ester was isolated from the aqueous solution by salting out with sodium chloride; the glycol contained in the technical ester remaining in the salt layer. The isolation of the ester has been completed by double extraction of the salt layer with ether in a volume 4677

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