Abstract: Hydrophilic monomers in a supercooled, transparent state, are polymerized in the presence of water. The polymers have low levels of residual monomers and exhibit good mechanical strength. The process provides materials useful as contact lenses.

Abstract: A mixture of a specified siloxanylalkyl ester monomer and a specified vinyl monomer is polymerized by exposure to an ionizing radiation at low temperatures and the resulting polymer is worked with a lathe cut to form a contact lens. The contact lens obtained is free from any optical distortion, has good dimensional stability and exhibits high oxygen permeability. In a preferred embodiment, a monomer mixture comprising a siloxanylalkyl ester, a methacrylate or acrylate, N-vinylpyrrolidone, and a small amount of a dimethacrylate or diacrylate is exposed to a total dose of 1.times.10.sup.5 -5.times.10.sup.6 roentgens at a low temperature (-80.degree. C. to -20.degree. C. and at a dose rate of 8.times.10.sup.4 -2.times.10.sup.6 roentgens per hour, and the resulting polymer is worked into a contact lens by a suitable forming process involving cutting, grinding and polishing operations.