Fully soluble poly(p-phenylenevinylene)s via propagation control of the polymer chain conjugated lengths

PPV and its alkoxy-substituted derivatives are a well-established class of materials for polymeric light emitting diode application. MEH-PPV (poly[2-m ethoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene]s) as a typical example of the solution processable conjugated polymer for PLED device fabrication, po ssesses good solubility in common organic solvents. However, gelation or mi cro-gelation always occurs during the polymerization process, especially wh en the polymer is prepared from the bis-bromomethyl monomer through the Gil ch route. Herein, we present the synthesis of fully soluble MEH-PPV by the addition of molecular weight modifiers (chain stoppers or Gee radical scave ngers) in the polymerization system. The polymers synthesized in this work were characterized by FTIR, NMR, W-vis spectroscopy and GPC. The results in dicate that the molecular weights of the polymers can be effectively contro lled by the addition of chain stopper (benzyl bromide) or chain blocking an tioxidant (2,6-di-tert-butyl-4-methylphenol). The mechanism of polymerizati on in the presence of these additives is also discussed. (C) 2000 Elsevier Science S.A. All rights reserved.