There is disclosed a process of etching the surface of polymeric materials made of polymers having at least one oxidatively degradable functionality which comprises treating said surface with a solution of at least one member of the etchant group consisting of nitronium, nitrosonium ions and complexes thereof, in a solvent containing less than 40 % by weight of water and nitroacidium ions and complexes thereof. The process further comprises use of cosolvents and swellants. It also includes pre and post etching steps directed to the preparation of the surface for etching and removal of the etchant respectively.
