page_title: Polyfluorene
section_title: Cross coupling polymerizations
hierarchical_section_title: Polyfluorene / Synthesis and design / Cross coupling polymerizations
caption_attribution_description: English: This is the synthetic route used to make the polymer in File:Polyfluorene derivative luminescence.png and File:Polyfluorene with oxadiazole.png
context_page_description: Polyfluorene is a polymer with formula
  n, consisting of fluorene units linked in a linear chain — specifically, at carbon atoms 2 and 7 in the standard fluorene numbering. It can also be described as a chain of benzene rings linked in para positions with an extra methylene bridge connecting every pair of rings.
  The two benzene rings in each unit make polyfluorene an aromatic hydrocarbon, specifically conjugated polymer, and give it notable optical and electrical properties, such as efficient photoluminescence.
  The term is also broadly applied to derivatives of this polymer, obtained by replacing some of the hydrogen atoms by other chemical groups, and/or by substituting other monomers for some fluorene unit. These polymers are being investigated for possible use in light-emitting diodes, field-effect transistors, plastic solar cells, and other organic electronic applications. They stand out among other luminescent conjugated polymers because the wavelength of their light output can be tuned through the entire visible spectrum by appropriate choice of the substituents.
context_section_description: The design of polymeric properties requires great control over the structure of the polymer. For instance, low band gap polymers require regularly alternating electron donating and electron accepting monomers.
  More recently, many popular cross-coupling chemistries have been applied to polyfluorenes and have enabled controlled polymerization; Palladium-catalyzed coupling reactions such as Suzuki coupling, Heck coupling, etc., as well as nickel catalyzed Yamamoto  and Grignard  coupling reactions have been applied to polymerization of fluorene derivatives. Such routes have enabled excellent control over the properties of polyfluorenes; the fluorene-thiophene-benzothiadiazole copolymer shown above, with a band gap of 1.78 eV when the side chains are alkoxy, appears blue because it is absorbing in the red wavelengths.
caption: The monomers used to obtain the complex polyfluorene derivative (copolymer of fluorene, oxadiazole and benzene). This Suzuki polymerization utilizes a palladium cross coupling between monomers with halogens and boronic esters.[13][35]
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