Alternating -conjugated copolymer

Poly(dithiafulvene)s toward intelligent functional materials have been synthesized [76-78]. An alternating -conjugated copolymer (13) of ferrocene with dithiafulvene showed a unique redox property [76]. Although 13... 

Figure 5.17 (a) Generalized schematic of donor-acceptor units-based alternating conjugated copolymers (Reproduced from [153] with permission of The Royal Society of Chemistry) and (b) the band diagram of D-A alternating copolymer and its HOMO/ LUMO levels in relation to the consituent donor and acceptor units. Reprinted from Ref [152] with permission from WUey. 

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]. 

Li Y, Li Z, Wang C, Li H, Lu H, Xu B, Tian W (2010) Novel low-bandgap oligothiophene-based donor-acceptor alternating conjugated copolymers synthesis, properties, and photovoltaic applications. J Polym Sci Part A Polym Chem 48 2765-2776... 

Jenekhe and coworkers [430] synthesized a phenothiazine-containing alternating fluorene copolymer 352 by Suzuki coupling (Chart 2.89). The phenothiazine-3,7-diyl fragment in the polymer backbone interrupts the conjugation, and substantially blue shifts absorption... 

W. Wang, J. Xu, and Y.-H. Lai, Alternating conjugated and transannular chromophores tunable property of fluorene-paracyclophane copolymers via transannular tt-tt interaction, Org. Lett., 5 2765-2768, 2003. 

These are stable micelles that are formed with polymeric surfactants. Amphiphilic block copolymers such as the pluronics (polyoxyethylene-polyoxypropylene block copolymers) are able to self-assemble into polymeric micelles and hydrophobic drugs may be solubilized within the core of the micelle or, alternatively, conjugated to the micelle-forming polymer. Although micelles are rather dynamic systems that continuously exchange units between the micelle structure and the free units in solution, those composed of polyoxyethylene - poly(aspartic acid) have been found sufficiently... 

Alternating carbazole-quinoline 99 and phenothiazine-quinoline donor-acceptor conjugated copolymers and a corresponding oligomer were synthesized by Jenekhe et al. and their solution and sohd-state photophysics were investigated (Scheme 26) (01MM7315). 

Conjugated copolymers where suitable donor and acceptor segments or even blocks are chemically linked, have been demonstrated to fine tune the optoelectronic properties (e.g. bandgap, transport properties) and morphological features (e.g. phase segregation at a scale to match exciton diffusion length) to improve the optoelectronic performance and stability of related OPV devices. In particular, the donor-acceptor type alternating copolymers and donor-acceptor type block copolymers have special relevance in the context of above discussions. 

Yamamoto, T., H. Kotubo, M. Kobashi, and Y. Sakai. 2004. Alignment and field-effect transistor behavior of an alternative rr-conjugated copolymer of thiophene and 4-alkylthiazole. Chem Mater 16 4616-4618. 

Pai C-L, Liu C-L, Chen W-C, Jenekhe SA (2006) Electronic structiffe and properties of alternating donor-acceptor conjugated copolymers 3,4-ethylenedioxythiophene (EDOT) copolymers and model compounds. Polymer 47 699... 

Naka K, Uemura T, Chujo Y (2001) Alternating pi-conjugated copolymer of dithiafulvene with 2,2 -bipyridyl units. J Polym Sci Part A Polym Chem 39 4083 090... 

The synthesis of alternating jt-conjugated copolymers based on this electrochemical preparation of the above mentioned aryldizinc intermediates was obtained by their subsequent cross-coupling with unsaturated dihalogenated compounds using a palladium catalysis [39] ... 

Then, the use of nickel(II) or cobalt(II) complexes as catalyst associated to the sacrificial anode process allows synthesis of functionalized mono- or diorganozinc species in a simple and efficient manner. Alternating Jt-conjugated copolymers, based on this electrochemical preparation of intermediate aryldizinc species and their subsequent palladium-catalyzed coupling with unsaturated dihalogenated compounds, can be synthesized. Furthermore, aromatic ketones are synthesized efficiently via cobalt-catalyzed cross-coupling reaction between arylzinc bromides and acid chlorides. 

---