The removal of residuals and oligomers from poly(2-hydroxyethylmethacrylate)

Poly(2-hydroxyethyl methacrylate) gels obtained by the cross-linking polymerization using four different free-radical initiators were washed with water. Chromatographically, the eluate appeared to be a mixture of low-molecular-weight compounds and of a small amount of the high-molecular-weight component. The UV and IR absorption spectra of compounds present in the eluate were compared with those of model compounds that were assumed to exist in the gel as impurities after the polymerization (monomers and oligomers of hydroxyethyl methacrylate, decomposition products of initiators). Time dependences of the removal of impurities from the gels by washing were measured. Most of the impurities were washed out within a few hours. In addition to the assumed impurities, the eluate was found to contain an unidentified compound that was still washed out after several months. Intracutaneous applications of this compound did not produce local irritation of the tested tissue.