Journal of Polymer Science Part A: Polymer Chemistry, Vol.42, No.8, 1820-1829, 2004
Green-emitting poly[(1,3-phenylenevinylene)-alt-(1,4-phenylenevinylene)]s: Effect of the substitution patterns on the optical properties
Green-emitting substituted poly [(2-hexyloxy-5-methyl- 1, 3-phenylenevinylene) -alt-(2,5-dihexyloxy-1,4-phenylenevinylene)]s (6) were synthesized via the WittigHomer reaction. The polymers were yellow resins with molecular weights of 10,600. The ultraviolet-visible (ILTV-vis) absorption of 6 (lambda(max) = 332 or 415 nm) was about 30 nm redshifted from that of poly[(2-hexyloxy-5-methyl-1,3-phenylenevinylene)-alt-(1,4-phenylenevinylene)] (2) but was only 5 nm redshifted with respect to that of poly[(1,3-phenylenevinylene)-alt-(2,5-dihexyloxy-1,4-phenylenevinylene)] (1). A comparison of the optical properties of 1, 2, and 6 showed that substitution on m- or p-phenylene could slightly affect their energy gap and luminescence efficiency, thereby fine-tuning the optical properties of the poly[(m-phenylene vinylene)-alt-(p-phenylene vinylene)] materials. The vibronic structures were assigned with the aid of low-temperature UV-vis and fluorescence spectroscopy. Light-emitting-diode devices with 6 produced a green electroluminescence output (emission lambda(max), similar to 533 nm) with an external quantum efficiency of 0.32%. Substitution at m-phenylene appeared to be effective in perturbing the charge-injection process in LED devices. (C) 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1820-1829, 2004.