In this contribution a series of novel multiblock-co-ionomers consisting of hydrophobic (partially fluorinated) and hydrophilic (sulfonated) domains has been prepared and characterised in terms of their applicability as fuel cell membranes. The synthesis of these multiblock-co-ionomers is a four-step procedure including (1) the sulfonation of the monomer 4,4'-difluorodiphenylsulfone, (2) the preparation of hydrophilic telechelic macromonomers by molecular-weight controlled step-growth polycondensation of the sulfonated monomer with various bis(thio)phenols, (3) the preparation of a hydrophobic telechelic macromonomer and (4) the coupling of both telechelic macromonomers to yield microphase-separated block-co-ionomers. This study focuses on the investigation of the influence of various linkage groups and atoms within the hydrophilic domains of the multiblock-co-ionomers. Both the telechelic macromonomers and the multiblock-co-ionomers were structurally investigated by H-1- and F-19-NMR spectroscopy and gel permeation chromatography (GPC). All multiblock-co-ionomers of this series could be cast into membranes and their membrane properties (ion-exchange capacity, specific resistance, swelling ratio, water uptake, thermal and oxidative stability) were measured and discussed in dependence of the various linkage groups within the hydrophilic domains. (c) 2007 Wiley Periodicals, Inc.