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 .