A method for producing polymerisable solution which comprises dissolving an ethylenically unsaturated zwitterionic monomer in a co-monomer system comprising a functionalised ethylenically unsaturated monomer in which the zwitterionic monomer is soluble, a siloxane group-containing monomer or macromer, and a crosslinking agent is disclosed. The polymerisable solution is biocompatible and can be used to produce polymers and articles such as contact lenses.
