Bithiophenes polymers

M. Zagorska and B. Krische, Chemical synthesis and characterization of soluble poly(4,4 -dialkyl-2,2 -bithiophenes), Polymer, 31 1379-1383, 1990. 

Figure 9 Aromatic and quinonoid forms of fused bithiophene polymers.

It is predicted that the ground-state structures of the fused bithiophene polymers are of the aromatic forms, which are more stable than the quinonoid ones by 3.4-7.1 kcal mol. Optimized structural parameters for both aromatic and quinonoid forms are listed in Table 22. In the aromatic forms, the short bonds are longer than those of PT and the long bonds shorter. Especially, C(2)-C(3) (C(6)-C(7)), C(3)-C(4) (C(5)-C(6)), and C(4)-C(5) bonds of the aromatic forms become similar in length, showing quinonoid character. 

Table 22 Optimized geometrical parameters for the fused bithiophene polymers A1-A5 (bond lengths in A and bond angles in deg) aromatic A) and quinonoid (Q) forms...

Xiao D, Li Y, Liu L et al (2012) Two-photon fluorescent microporous bithiophene polymer via Suzuki cross-coupling. Chem Commim 48 9519-9521... 

Many thiophene derivatives have been polymerized in order to obtain new materials tailored for different purposes. Roncali [596] reviewed the enormous amount of literature regarding the synthesis, functionalization and applications of polythiophenes in 1992. Beside the polymerizations of thiophene and bithiophene, polymers from several thiophene oligomers, substituted thiophenes, thiophenes with... 

Combinations of polythiophenes and Cgo have also been utilised by the Santa Barbara group for more fundamental studies [211, 212], and by the Linkoping group for devices [213]. These devices actually comprise two different poly-thiophenes, poly(3-(4-octylphenyl)-2,2 -bithiophene), polymer II in Fig. 13, and poly(3- 2Lmethoxy-5 -octylphenyl thiophene), POMeOPT. The latter is used because it has a sidegroup reminiscent of anisole, which is known to interact with... 

Figure 2. Cyclic voltammograms of a poly(2,2 -bithiophene)-coated electrode in acetonitrile containing 0.1 M Bu4NC 04.34 (Reprinted from G. Zotti, C. Schiavon, and S. Zecchin, Irreversible processes in the electrochemical reduction of polythiophenes. Chemical modifications of the polymer and charge-trapping phenomena, Synth. Met. 72 (3) 275-281, 1995, with kind permission from Elsevier Sciences S.A.)...

As demonstrated in previous sections, the carbazole unit was introduced as a pendant group or as a chain member in major classes of EL polymers such as PPVs (95-105,141,177, 190) and PFs (62, 63, 242-245). A variety of 2,7-carbazole-derived polymers with different conjugated units, such as 2-alkoxy- and 2,5-dialkoxy-l,4-phenylene (549) and l,l -binaphtha-lene-6,6 -diyl (550 [658]), 2,5-pyridine (551), 2,7-fluorene (245 [345,346]), 2,5 -bithiophene (554 [345]), 5,8-quinoxaline (552), quinquethiophene-SjS -dioxide (450 [550]), 2,5-thiophene (553), 2,5-furan (555), and acetylene (556 [659]) were reported by Leclerc and coworkers... 

FIGURE 5.4 Chemical structures of photo- and electroluminescent polymers employed for polarized LEDs poly(2-methoxy-5-(2 -ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV) poly[2,5-dioctyloxy-l, 4-diethynyl-phenylene-a/t-2,5,-bis(2 -ethylhexyloxy)-l,4-phenylene] (EHO-OPPE) poly(p-phenylene), PPP poly(3-(4-octylphenyl)-2,2 -bithiophene), PTOPT poly(p-phenylene vinylene), PPV poly(3-alkylthio-phene vinylene), P3AT Acetoxy-PPY PPV-polyester, poly(9,9-dialkyl fluorene), PF. 

The sensor covalently joined a bithiophene unit with a crown ether macrocycle as the monomeric unit for polymerization (Scheme 1). The spatial distribution of oxygen coordination sites around a metal ion causes planarization of the backbone in the bithiophene, eliciting a red-shift upon metal coordination. They expanded upon this bithiophene structure by replacing the crown ether macrocycle with a calixarene-based ion receptor, and worked with both a monomeric model and a polymeric version to compare ion-binding specificity and behavior [13]. The monomer exhibited less specificity for Na+ than the polymer. However, with the gradual addition of Na+, the monomer underwent a steady blue shift in fluorescence emission whereas the polymer appeared to reach a critical concentration where the spectra rapidly transitioned to a shorter wavelength. Scheme 2 illustrates the proposed explanation for blue shift with increasing ion concentration. 

Fig. 1 Building units of conducting polymers, (1) polyacetylene (PA) (2) polypyrrole (PPy), polythiophene (PTh), polyfurane (PFu) (3) polyphenylene (PP) (4) polyaniline (PANI) 5 polyindole (PIND) (6) polycarbazole (PCaz) (7) polyazulene (Paz) (8) polynaphthalene (PNa) (9) polyanthracene (PAnth) (10) polypyrene (PPyr) (11) polyfluorene (PFiu) (12) poly(isothionaphthalene) (PITN) (13) poly(dithienothiophene) (14) poly(thienopyrrole) (15) poly(dithienylbenzene) (1G) poly(3-alkylthiophene) (17) poly(phenylene vinylene) (18) poly(bipyrrole) (PBPy), poly(bithiophene) (PBT) (19) poly(phenylenesulfide) (20) 4-poly(thienothiophene) (21) poly(thienyl vinylene), poly(furane vinylene) (22) poly(ethylenedioxythiophene) (PEDOT).

Studies by Heinze etal. on donor-substituted thiophenes or pyrroles [33] such as methylthio (= methylsulfonyl) or methoxy-substituted derivatives provide further clear evidence for this reaction pathway. They found, for instance, that 3-methylthiothiophene or 3-methoxythio-phene (2) undergo a fast coupling reaction. However, deposition processes or insoluble film formation could not be detected in usual experiments with these compounds, even at high concentrations. Similarly, the corresponding 3,3 -disubstituted bithiophenes (2a) do not polymerize, but the anodic oxidation of 4,4 -disubstituted bithiophenes (2c) produces excellent yields of conducting polymers. 

Organic molecules such as aniline, pyrrole and 2,2 -bithiophene have been intercalated and polymerized within the galleries of clay minerals, FeOCl, V2O5 gel and other layered hosts to yield multilayered inorganic/organic polymer nanocomposites... 

The step 7 monomer (0.61 mmol) and bis(trimethylstenyl)bithiophene (0.61) were dissolved in anhydrous DMF with gentle heating and then treated with tetrakis(triphe-nylphosphine) palladium(O) (about 10 mol% based on the total amount of reagents) and the mixture reacted at 85°C for 6 hours. The solution was cooled to ambient temperature, filtered, and the polymer isolated. It was then successively washed twice with hydrochloric acid/chloroform, twice with ammonia solution /CHC13, and twice with water/CHCl3. The polymer was then precipitated in methanol, dried, and 0.38 g of product isolated as a red polymer having an Mn of 25,000 Da. 

An alternative way to get better structural regularity might be to begin with bithiophene or terthiophene where some of the inter-ring bonds in the polymer are formed before the polymerization and these monomers have lower oxidation potentials (thiophene 1.6 V, bithiophene 1.2 V and terthiophene 1.0 V v SCE). Polymerizations of both bithiophene 143) and terthiophene 144) have been described but there is some doubt about whether the polymers derived from oligomers are more regular or... 

Thickness of the barrier layer, optimized at 220 nm [133], played a crucial role with respect to the chemosensor sensitivity, selectivity and LOD. So, eventually, the chemosensor architecture comprised a gold-film electrode, sputtered onto a 10-MHz resonator, coated with the poly(bithiophene) barrier layer, which was then overlaid with the MIP film. This architecture enabled selective determination of the amine at the nanomole concentration level. LOD for histamine was 5 nM and the determined stability constant of the MIP-histamine complex, XMn> = 57.0 M 1 [131], compared well with the values obtained with other methods [53, 136, 137]. Moreover, due to the adopted architecture, the dopamine chemosensor could determine this amine with the stability constant for the MIP-dopamine complex, XMip = (44.6 4.0) x 106 M-1 and LOD of 5 nM [133], which is as low as that reached by electroanalytical techniques [138]. The MIP-QCM chemosensor for adenine [132] also featured low, namely 5 nM, LOD and the stability constant determined for the MIP-adenine complex, XMIP = (18 2.4) x 104 M, was as high as that of the MIP-adenine complex prepared by thermo-induced co-polymer-ization [139]. The linear concentration range for determination of these amines extended to at least 100 mM. 

Early studies showed that polymers possessing some regiospecificity exhibit improved electrical and magnetic properties when compared to random polythiophenes [234]. In this instance, P3ATs 56 were synthesized by polymerization of 3,3 -dialkyl-2,2 -bithiophene 55 as shown in Scheme 55. Polymerization either electrochemically or via Lewis acid yielded predominantly HH-coupled polymers whose absorption maxima blue shifted -90 nm for 3,3,-dimethyl-2,2 -... 

The reaction of 5,5 -bis(pentaethyldisilanyl)-2,2 -bithiophene was chosen as a model compounds of poly[(tetraethyldisilanylene)bis(2,5-thie-nylene)]. After 77 h irradiation in benzene, they obtained 5-(pentaethyldi-silanyl)-2,2 -bithiophene (23%) and triethylphenylsilane (46%). The corresponding permethyl derivative was found to be photochemically inert. The inactivity of permethyl derivative is similar to the low photosensitivity of the permethyl polymer. 

Polymers 619 and 620 exhibit two absorption maxima located at 444 and 471 nm for 619 and 473 and 503 nm for 620. These transitions likely correspond to predominantly local transitions of the constituent dibenzosilole and mono/bithiophene copolymer building blocks. The absorption maxima of polymer 618-620 cast as thin films are 401 nm (618), 484 nm (619), and 493 nm (620). The fluorine-based copolymers exhibit maxima at 427 nm in solution and 440 nm as a thin film for 621 and 456 nm in solution (with strong shoulder at 502 nm) and 460 nm as a thin film for 622. Dibenzosilole-based copolymers 619 and 620 exhibit significant bathochromic shifts of ca. 30-50 nm compared to the fluorine-based polymers 621 and 622. 

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