The design of ionic side chain polymeric systems which present a mesomorphic thermotropic behaviour, is reviewed. The different ways for the introduction of charges in the polymeric system are described, namely ionic bonds, hydrogen bonds and also the use of low molecular salts. The mesomorphic phases identified in these polymeric systems are predominantly smectic in nature, mainly due to the preponderant role of ionic charges in the arrangement of the different constituents of the polymer within the layers. The corresponding structural models are described in detail to explain the thermotropic mesomorphic behaviour. In some specific cases, nematic or columnar phases can also be obtained.