Polyfluorenes alternating copolymers

Scheme 1 Synthesis of polyfluorenes via Yamamoto and Suzuki coupling. With Suzuki coupling (AA-BB type coupling reaction), the synthesis of strictly alternating copolymers is possible...

An industrial group have reported obtaining efficient red, green, and blue emission from polyfluorene-based alternating copolymers prepared by Suzuki polycondensation, but without publishing their structures [270,271]. 

The described synthesis of polyfluoren homopolymers allows also the design of alternating copolymers. Instead of the 2,7-dibromofluorene a variety of dibromoarenes ean be used in the Pd-catalyzed coupling polymerization reaction. An important group of... 

M Svensson, F Zhang, SC Veenstra, WJH Verhees, JC Hummelen, JM Kroon, O Inganas, and MR Andersson, High-performance polymer solar cells of an alternating polyfluorene copolymer and a fullerene derivative, Adv. Mater., 15 988-991, 2003. 

Veldman D, Ipek O, Meskers SCJ, Sweelssen J, Koetse MM, Veenstra SC, Kroon JM, van Bavel SS, Loos J, Janssen RAJ (2008) Compositional and electric field dependence of the dissociation of charge transfer excitons in alternating polyfluorene copolymer/fullerene blends. J Am Chem Soc 130 7721... 

K.G. Jespersen, F.L. Zhang, A. Gadisa, V. Sundstrom, A. Yartsev, and O. Inganas, Charge formation and transport in bulk-heterojunction solar cells based on alternating polyfluorene copolymers blended with fuUerenes, Org. Electr., 7, 235-242 (2006). 

M.-H. Chen, J. Hou, Z. Hong, G. Yang, S. Sista, L.-M. Chen, Y. Yang, Efficient Polymer Solar Cells with Thin Active Layers Based on Alternating Polyfluorene Copolymer/Fullerene Bulk Heterojunctions. Adv. Mater. 2009, 21,4238-4242. 

Andersson and coworkers have prepared solar cells based on blends of poly(2,7-(9-(2 -ethylhexyl)-9-hexyl-fluorene)-fl/t-5,5-(4, 7 -di-2-thienyl-2, l, 3 -benzothiadiazole) (223) and PCBM [416]. The polymer shows a Amax (545 nm) with a broad optical absorption in the visible spectrum and an efficiency of 2.2% has been measured under simulated solar light. The same group has also reported the synthesis of low bandgap polymers 200 (1 = 1.25 eV) and 224 (1 = 1.46 eV) which have been blended with a soluble pyrazolino[70]fiillerene and PCBM, respectively, to form bulk heterojunction solar cells of PCE of 0.7% [417] and 0.9% [418]. Incorporation of an electron-delident silole moiety in a polyfluorene chain affords an alternating conjugated copolymer (225) with an optical bandgap of 2.08 eV. A solar cell based on a mixture 1 4 of 225 and PCBM exhibits 2.01% of PCE [419]. 

Jespersen, K.G. et al. (2004) The electronic states of polyfluorene copolymers with alternating donor-acceptor units./. Chem. Phys., 121 (24), 12613-12617. 

Chain-growth catalyst-transfer polycondensation (CTP) is a rapidly developing polymerization method, as it allows, in many cases, the above-mentioned limitations of step-growth polymerizations to be overcome. CTP provides a straightforward access to well-defined conjugated homopolymers (e.g., polythiophenes (1), polyfluorenes (2), polyphenylenes (3), etc.), alternate donor-acceptor copolymer e.g., 4) and all-conjugated block polymers (e.g., 5), Chart 20.1. 

Svensson M, Zhang F, Veenstra SC, Verhees WJH, Hummelen JC, Kroon JM, Inganas O, Andersson MR (2003) High-ptaformance polymer solar cells of an alternating polyfluorene copolymer and a fnllerene derivative. Adv Mater 15 988... 

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