Blends of Polythiophenes

The emission spectrum of some PT and PBD polymer bilayer devices cannot be explained by a linear combination of emissions of the components. Thus, white emission of the PLEDs ITO/422/PBD/A1 showed Hof 0.3% at 7 V, and consisted of blue (410 nm), green (530 nm), and red-orange (620 nm) bands. Whereas the first and the last EL peaks are due to the EL from the PBD and the PT layers, respectively, the green emission probably originates from a transition between electronic states in the PBD layer and hole states in the polymer 

SCHEME 2.69 Synthesis of oligo(ethylene oxide)-containing PTs. (From Johansson, T., Mammo, W., Andersson, M.R., and Inganas, O., Chem. Mater., 11, 3133, 1999.) 

6 Polythiophenes for Structured and Polarized Polymer Light-Emitting Diodes 

Apart from the tunable color emission covering the full visible range, there are several other aspects supporting the interest in PTs for PLEDs. PTs are examples of classical conjugated polymers with intrinsic one-dimensionality of the polymer chain. Alignment can induce anisotropy in macroscopic properties such as electron transport or optical properties. Polarized 

EL with 4 el = 0.05% was observed in multilayer LB-film PLED ITO/399/A1, with a ratio in EL between the parallel and perpendicular orientations of 1.3 [523]. An even higher ratio of 2.4 was achieved in ITO/422/Ca/Al diode made from a stretch-oriented polymer film [524]. For more information on polarized LEDs, see Chapter 5 in this book. 

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Gadisa A, Svensson M, Andersson MR, Ingantls O (2004) Correlation between oxidation potential and open-circuit voltage of composite solar cells based on blends of polythiophenes/fullerene derivative. Appl Phys Lett 84 1609... 

Currently the best-performing heterojunction photovoltaic devices are made from blends of polythiophenes and PCBM [6,106]. Here, the charge-transfer states are stable with respect to triplet excitons, which comes at the cost of modest open-circuit voltages of 0.6V. Recent experimental evidence suggests that the high performance of PCBM polymer solar cells could also be attributed to the kinetic advantage in charge-transfer state separation that these cells have over those made from amorphous polymers. It is... 

Coated materials are evaluated in S-SBR and in 50 50 blends of S-SBR and EPDM rubbers. In blends, the partitioning of fillers and curatives over the phases depends on differences in surface polarity. In S-SBR, polythiophene-modified silica has a strong positive effect on the mechanical properties because of a synergistic reaction of the sulfur-moieties in the polythiophene coating with the sulfur cure system. In S-SBR/EPDM blends, a coating of polyacetylene is most effective because of the chemical similarity of polyacetylene with EPDM. The effect of... 

For silica in SBR, a polyacetylene coating gives the lowest filler-filler interaction, a good filler-polymer interaction, and the best dispersion compared to untreated and the other plasma-treated samples. However, for the stress-strain properties, the polythiophene-treated sample gives the best results. This shows the importance of sulfur moieties on the surface of the filler, which form a secondary network in the cured materials. In the blend of S-SBR and EPDM rubbers, the situation is less conclusive. The Payne effect, the bound rubber, and... 

Thermally activated PCBM diffusion and formation of crystalhne aggregates within blends with PPV derivatives were observed even at moderate temperatures [55,68,137]. In contrast, polythiophene based polymer-fullerene solar cells had an overall performance improvement upon thermal anneahng steps [171,172]. This improvement has been mainly correlated with an improved order in the film. This is especially true in the case of polythiophene, which is known to convert to a more ordered phase upon... 

The alteration of the optical properties for an electrochromic material involves the insertion or extraction of charge. These polymers can be classified into three types, depending on their specific optical states (1) absorption/transmission-type materials made of metal oxides, viologens or polymers such as PEDOT, including at least one colored and one bleached state for smart windows, (2) display-type materials made of polythiophenes without a transmissive state and (3) materials composed of blends, laminates and copolymers including more than two colored states [7],... 

Poly (thiophene)s are of particular interest as electfochromic materials owing to their chemical stability, ease of synthesis and processability. For the most part, current research has been focused on composites, blends and copolymer formations of several conjugated polyheterocyclics, polythiophene and its derivatives, especially PEIX)T. In one example, poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(2-acrylamido-2-methyl-l-propanesulfonate) (PAMPS) composite films were prepared by Sonmez et al. for alternative electrochromic applications [50]. Thin composite films comprised of PEDOT/PAMPS were reported to switch rapidly between oxidized and neufial states, in less than 0.4 s, with an initial optical contrast of 76% at A.max. 615 nm. Nanostructured blends of electrochromic polymers such as polypyrrole and poly(3,4-ethylenedioxythiophene) were developed via self-assembly by Inganas etal. for application as an electrochromic window [26]. Uniir etal. developed a graft-type electrochromic copolymer of polythiophene and polytetrahydrofuran for use in elecfiochromic devices [51]. Two EDOT-based copolymers, poly[(3,4-ethylenedioxythiophene)-aZ/-(2,5-dioctyloxyphenylene)] and poly[(3,4-ethylenedioxythiophene)-aft-(9,9 -dioctylfluorene)] were developed by Aubert et al. as other candidates for electrochromic device development [52],... 

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