Synthesis and Optical Properties of New End-Functionalized Polyquinolines S. P. Economopoulos, ²,‡ A. K. Andreopoulou, ²,‡ V. G. Gregoriou, ‡ and J. K. Kallitsis* ,²,‡ Department of Chemistry, UniVersity of Patras, Patras, 26500, Greece, and Foundation for Research and Technology-Hellas, Institute of Chemical Engineering and High-Temperature Processes (FORTH-ICE/HT), Patras 26500, Greece ReceiVed December 1, 2004 A novel monomer incorporating the quinoline moiety as the side group was synthesized and polymerized by employing free radical as well as atom-transfer radical polymerization (ATRP) techniques. In the latter case, two different initiators were used, resulting in dibenzyloxy- or dimethylester-end-functionalized polyquinolines. All polymers were characterized primarily using 1 H NMR, gel permeation chromatography, UV-vis photoluminescence spectroscopy, and cyclic voltammetry. A systematic luminescence study was performed in different solvents and concentrations, showing that the optical properties of the newly synthesized polymers depend on both the solution’s concentration and the ionic strength of the solvent. In addition, atomic force microscopy and scanning electron microscopy techniques also confirmed the close correlation between the film morphology and the solvent used for their preparation. Introduction Material science is focusing more and more toward the development of complex and architectural systems, possess- ing properties that arise from their detailed structure. The evolution of areas such as photonics and photovoltaics 1,2 strongly depends on the preparation of well-defined, non- conventional materials or the ideal combination of already existing ones, not in a traditional sense, but in ways that will produce new systems. Especially in applications such as polymeric light-emitting diodes (PLEDs) and plastic solar cells where more than one polymeric substances are neces- sary, but at the same time the blending of many is not always preferred due to miscibility reasons (e.g. thermodynamically), the design and preparation of polymers that bear, in a single chain, all the required functionalities are most preferable. In these two growing fields, the incorporation of hetero- atom-bearing moieties is claimed to be one of the most promising pathways since it brings out properties not easily found in all-carbon structures. One of the most well- established units of this kind is quinolines, which since their incorporation into polymers by Stille and co-workers 3-9 have attracted increased scientific attention due to their ease of synthesis 10 and excellent thermal and mechanical properties, but more importantly due to their interesting photonic, electronic, and conductive properties. 11-18 Further enrichment of their potential use in various applications came from experiments conducted by Jenekhe and Chen, concerning the observed self-assembly of diblock 19,20 and triblock 21 polyquin- oline-polystyrene copolymers. Until now, polyquinolines and their copolymers have been successfully used in PLEDs, 22-24 where they have been known to possess excellent electron transporting properties, organic photovol- taic devices 25,26 and selective chemosensors. 27 Moreover, these polymers can be pH-responsive due to the protonation of the imino group, 28,29 thus opening new uses as tunable * Corresponding author. 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