NOVELTY - Heterocyclic monomers for use in the production of ionic conductive membranes, comprise benzimidazole compounds with a protecting group on the nitrogen at position 1 and a trifluorovinyl group at position 2.    USE - Fuel cells in which the electrolyte is an ionic conductive membrane made from polymers of these monomers are used for driving motor vehicles (claimed).    ADVANTAGE - Enables the production of conductive membranes which permit the effective migration of protons at operating temperatures above 100degrees C (e.g. 200degrees C) at atmospheric pressure, even in the absence of water; these membranes can be produced in high yield and show no problems due to elution since the heterocyclic units involved in proton migration are anchored in the membrane structure.    DETAILED DESCRIPTION - Monomers with a benzimidazole group for use in the production of ionic conductive membranes, having a structure with at least one unit of formula (I).    R = protecting group.    INDEPENDENT CLAIMS are also included for    (1) a method (M1) for the production of monomers (I) by (a) reacting an o-phenylenediamine with a fluoromonomer such as hexafluoropropene (HFP) in presence of a solvent such as acetonitrile to give a fluorinated benzimidazole derivative (10), (b) protecting the nitrogen (N1) with a benzyl, trialkylsilyl or carbamate group and then (c) dehydrofluorinating the protected compound by reaction with a base to give a protected monomer (6b', 6c')    (2) protected polymers (17) containing the above monomer units    (3) a method (M2) for the production of these protected polymers from monomers (6b', 6c')    (4) deprotected polymers (18) based on the above protected polymers, with hydrogen atoms instead of the protecting group (R) in (17)    (5) a method (M3) for the production of (18) by replacing the protective groups (R) with hydrogen atoms    (6) ionic conductive membranes made from these deprotected polymers (18)    (7) electrochemical devices, fuel cells and electrolysers with these membranes as the electrolyte.