AbstractRecently, more and more attention has been focused on new techniques for energy production also in view of environmental problems. A noticeable device is small fuel cell that converts chemical energy into electric energy by electrochemical reaction of hydrogen with oxygen, and exhibits a high‐energy efficiency. Conventional small fuel cells have been classified into phosphoric acid‐type fuel cells, molten carbonate‐type fuel cells, solid oxide‐type fuel cells, solid polymer type fuel cells, etc., according to the type of electrolyte used. The target of this work is the development of a new process to build up polyelectrolyte membranes, for polymer type fuel cell (PEM), by sulfonating syndiotactic polystyrene in its clathrate form. The polyelectrolyte membranes of this paper are inexpensive and exhibit good long‐term stability and ion exchange capability.