Dependence of the luminescent properties and chain length of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] on the formation of cis-vinylene bonds during Gilch polymerization

The presence of cis‐vinylene bonds in Gilch‐polymerized poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylene vinylene] is reported. Through fractionation, species with a weight‐average molecular weight of less than 37,000 exhibited an abnormal blueshift of photoluminescence spectra in toluene solutions, and this was attributed to the presence of cis‐vinylene bonds, as verified by NMR spectroscopy. Surprisingly, the fractionated species (∼1 wt %) with a weight‐average molecular weight of 5000 were mostly linked by the cis‐vinylene bonds. The concentration decreased with the molecular weight until a molecular weight of 37,000 was reached; at that point, the polymer chains contained mainly trans‐vinylene bonds. Obviously, the formation of cis‐vinylene bonds strongly inhibited the growth of polymer chains during Gilch polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2520–2526, 2005 The coil nature imposed by cis‐vinylene bonds formed during the Gilch polymerization of poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylene vinylene] strongly inhibits the growth of polymer chains and renders a blueshift of the photoluminescence spectrum.