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Synthesis and properties of conjugated hyperbranched polymers

Authors Haeussler, Matthias
Issue Date 2006
Summary Hyperbranched polymers are a young but hot research field in polymer science. Despite copious scientific efforts, synthetic protocols for the preparation of high molecular weight polymers with a high degree of branching are still limited. In this thesis, we have developed new, simple methodologies for the preparation of conjugated hyperbranched polymers. The resulting macromolecules show novel thermal, optical, and magnetic properties, which may find an array of high-technology applications. Homopolycyclotrimerization of aliphatic diynes, catalyzed by single-component transition metal catalysts at room temperature, give hyperbranched poly(alkenephenylene)s with high molecular weights (Mw up to ~2.7 x 105) in high yields (normally >80%). The resulting poly(alkenephenylenes) resemble structural features similar to glycogen, a natural occurring hyperbranched biopolymer, and show outstanding thermal stability. Homo- and copolycyclotrimerization of new aromatic diyne and triyne monomers furnish completely soluble hyperbranched poly(arylenes) (hb-PAs) in high yields (up to 99.9%) and with high molecular weights (Mw up to ~2.9 x 105). The hb-PAs show interesting optical and thermal properties: the polymers emit bright blue lights when irradiated, efficiently limits intense 8-ns laser pulses, exhibit high thermal stabilities, and carbonize in high yields when heated up to 900 °C under nitrogen. Homopolycouplings of aryltriynes and their copolycouplings with monoyne are effected by CuCl in air under Glaser-Hay oxidative coupling conditions, giving soluble hyperbranched polyynes (hb-PYs). The resulting hyperbranched polyynes (hb-PYs) are strong blue emitters, shows high light refractivity, function as negative photoresist, and form hexagonal arrays of breath figures by blowing moist air over their carbon disulfide solutions. Their peripheral terminal triple bonds can be 100% end-capped by aromatic rings via palladium-catalyzed coupling with aryliodides. The carbon-rich polyynes are readily curable, thermally stable, and pyrolytically carbonizable. Complexations of the acetylene moieties with cobalt carbonyls metallify the hb-PYs. UV irradiation of the thin films of the organometallic polymers through a Cu-negative mask photobleaches the exposed regions with features in the size range of ~10-100 μm and change their refractive index dramatically. Thin films of the cobalt-containing hb-PYs effectively induce the growth of carbon nanotubes. Ceramizations of the cobalt-polyyne complexes afford soft ferromagnetic materials with high magnetizability and low coercivity. A series of hyperbranched poly(ferrocenylene)s containing elements of group 14 and group 15 are prepared by polycoupling of dilithioferrocene with tri- or tetrachlorides of the elements under salt-elimination. All the polymers show good thermal stability with high decomposition temperatures and graphitize into iron-containing ceramics by pyrolyzation at 1000 °C under nitrogen in high char yields. Calcination of the organometallic polymers furnishes iron and iron-alloy nanoparticles embedded in a graphite matrix.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006
Language English
Format Thesis
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