the present invention relates to polymeric compositions useful in the manufacture of biocompatible medical devices . more particularly , the present invention relates to certain cationic monomers capable of polymerization to form polymeric compositions having desirable physical characteristics useful in the manufacture of ophthalmic devices . such properties include the ability to extract the polymerized medical devices with water . this avoids the use of organic solvents as is typical in the art . the polymeric compositions comprise polymerized cationic hydrophilic siloxanyl monomers .