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Synthesis, light emission, optical activities, and thermal stability of linear and hyperbranched acetylenic polymers

Authors Law, Chi Wang
Issue Date 2004
Summary New substituted acetylenes carrying functional groups (FG) {(C6H5)C≡CC6H4O(CH2)m-FG, (C6H5)C≡C(CH2)mC≡C-FG, (C6H5)C≡C(CH2)mC≡C-FG, (C6H5)C≡CCO2(CH2)m-FG, and (HC≡C)2Ge (C6H5)2 were designed and synthesized in satisfactory yields by multi-step reactions. Metathesis polymerizations, polycyclopolymerizations, and polycyclotrimerizations were effected by catalysts of WCl6-, MoCl5- and TaCl5-Ph4Sn, giving high molecular weight polymers in high yields (Mw up to 3.84 x 105 Dalton and isolation yield up to 99%). The structures and properties of the polymers were well characterized and evaluated by IR, NMR, UV, TGA, PL, EL, and CD analyses. All the polymers possessed high thermal stability in nitrogen and they started to lose weights at high temperatures up to 420℃. The polymers also experienced no molecular weight change even when they were heated to 200℃ in air. The chromophoric pendants had endowed the linear polyacetylenes with novel optical properties. Upon photoexcitation, the polymers emitted intense green light with quantum yields up to 99%. Multilayer EL devices with a configuration of ITO/Polymer:PVK/BCP/Alq3/LiF/Al were constructed, which emitted green light in high luminance of 303 cd/m2 and external quantum efficiency of 0.30%, which is enough for normal flat panel display. Incorporation of chiral appendages to the poly(phenylpropiolate) structures generated disubstituted polyacetylenes with strong helical chirality ([θ] up to -2.31 x 104 deg cm2 dmol-1) which decreased with the increase in the length of methylene spacers. The hyperbranched poly(phenylene germolene)s were practically nonluminescent when molecularly dissolved but became highly emissive when its solutions were cooled.
Note Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2004
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