The invention relates to an energy efficient, environmentally favorable process for the preparation of butyl ionomers that uses a common medium for both solution polymerization and subsequent bromination of butyl rubber. More particularly, the invention relates to a process that employs a common aliphatic medium for both solution polymerization and bromination of butyl rubber in the presence of a brominating agent and optionally for subsequent reaction with at least one nitrogen and/or phosphorus based nucleophile.