The design and characterisation of new electroactive polymers carrying functional (receptor) groups for ion recognition in the main or the side chain of the polymer are presented. For this purpose, thiophene polymer with an acetophenone group, 6-hydroxy-2-(2-(3thienyl)-ethoxy)-acetophenone (3-AcpT), as well as salen-based polymers such as poly [(6,6'-bis-(o-methoxyphenyt)-2,2'-bipyridine)Ni(II)] and poly [(N,N'-bis-(salicylidene)-ethylendiamine)Cu(II)] were studied. As spectroelectrochemical methods in situ ESR, ESR/UV-vis-NIR and FTIR spectroelectrochemistry were applied to follow both the paramagnetic and the diamagnetic species formed in redox reactions. Quantitative spectroelectrochemical analysis supports the preferable formation of ESR-silent (dicationic) chain segments upon oxidation in investigated polymer and copolymer structures, where the bipolarons and two interacting polarons in singlet state should be considered. The presented contribution besides the spectroelectrochemical characterisation discusses the potentiometric and voltammetric responses of salen-based polymers and copolymers in detection of Ni2+-ions. (C) 2004 Elsevier Ltd. All rights reserved.