The thermal, optical and electrochemical properties of trans-poly(l -ethynylpyrene) (trans-PEP) and cis-poly(1-ethynylpyrene) (cis-PEP) have been studied as a function of polymer backbone configuration and internal stacking. Absorption spectra of the polymers showed that trans-PEP possesses a higher degree of conjugation than its homologue, cis-PEP. Intramolecular interactions occur between adjacent pendant pyrene units (associated pyrenes) present in each polymer, giving rise to static excimer emissions, strongest in cis-PEP because of the shorter distances between aromatic rings. Data resulting from excitation spectra and fluorescence decay profiles proved that such interactions take place in the ground state. Cyclic voltammetry of trans- and cis-PEP exhibited irreversible behaviors with different oxidation potentials as a result of their dissimilar geometry. (c) 2005 Elsevier Ltd. All rights reserved.