Solutions polythiophene properties

The other important electrochromic polymers are the polypyrroles and polythiophenes, obtained by polymerisation of the parent pyrrole and thiophene or, more importantly, their 3,4-substituted derivatives. The most widely studied of these two classes of polymers in electrochromic outlets are the poly thiophenes, which are readily synthesised by the reaction of the substituted monomer with FeClj in chloroform solution. The colour change properties of a variety of poly thiophenes in the presence of a counter-ion are shown in Table 1.14. ... 

The soluble polythiophenes are the first conducting polymers that can be taken above their glass transition without decomposition and it will be interesting to study morphology-property relationships. Heeger et al.262) have recently described conformational changes in solutions of poly-3-hexylthiophene which seem to involve a coil-helix transformation as the temperature is decreased or a poor solvent is added. 

Whereas in solution the photoluminescence efficiency (Of) of poly(3-alkylthiophenes) (PATs) is 3(Mf)%, it drastically drops to 1-4% and lower in the solid state due to the increased contribution of nonradiative decay via interchain interactions and ISC caused by the heavy-atom effect of sulfur (97MM4608). Optoelectronic devices of this type of compounds have been studied (98SCI(280)1741 06SM(156)1241). Fibers of poly(3-hex-ylthiophene) for photovoltaic applications have been described (07MI1377). Poly(3-octylthiophene) showed a TTA band at 800 nm (96JPC15309). The photophysical properties of some alkyl and aryl polythiophenes have been studied (03JCP(118)1550). The absorption maximum of poly(3-octylthiophene) is at 438 nm, while the fluorescence was... 

Regioregular poly(3-alkylthiophene)s have received a lot of attention, especially because of their high electrical conductivities in the doped state, and because of their unusual solvatochromic and thermochromic behavior . Hence, a lot of research has been focused on clarifying the structure of these materials, both in the solid state and in solution. Today, it is agreed that supramolecular aggregation of polythiophene chains plays an important role in their physical properties. 

Thin film transistor devices were fabricated by spin coating using a 1% solution of the selected polythiophene dissolved in chlorobenzene and drying in vacuo at 80°C for 20 hours. No precautions were taken to exclude oxygen, moisture, or light during device fabrication. From transistors with dimensions of 5000 x 60 m, electrical properties were determined as summarized in Table 1. 

Oxide, flouride, and polymeric films, as well as certain others, are used as protective coatings for HTSC materials (for example, see [505]). The electrodeposition of conducting polymers such as polypyrrole [433,491, 493, 506], polythiophene and its derivatives [493, 507], and polyaniline [478] is the most effective process. Anodic electropolymerization in acetonitrile solutions proceeds without any degradation of the HTSC substrate and ensures continuous and uniform coatings. Apparently, this method is promising not only for the fabrication of compositions with special properties based on HTSC [50, 28,295] as mentioned above, but also for the creation of junctions with special characteristics [507]. 

As with polyanilines, polythiophenes can either be prepared directly by electropolymerization, or by casting from solutions (for alkyl-substituted thiophenes). Most interest has focused on the latter because of their improved mechanical properties compared with those of electrochemically prepared films. The factors influencing the mechanical properties of PTh s are reviewed in this section. 

Studies of the chemical properties of polythiophenes have been limited. As with polypyrroles, a hydrophobic backbone is formed, and the polymer has ion-exchange properties. Modification of chemical properties by incorporation of appropriate counterions is not so readily addressable because polymerization must be carried out from nonaqueous solution and occurs at more anodic potentials compared to pyrrole. 

Bondarev SL, Bachilo SM, Dvornikov SS and Tikhomorov SA (1989) 2 - So fluorescence and transient S Sq absorption ofo//-tm s-/3-carotenein solid and liquid solutions. Photochem Photobiol, A Chemistry 46 315-322 Bouwman W, Jones A, Phillips D, Thibodeau P, Friel C and Christensen R (1990) Fluorescence of gaseous tetraenes and pentaenes. J Phys Chem 94 7429-7434 Bredas JL, Sdbey R, Boudreaux DS and Chance RR (1983) Chain-length dependence of electronic and electrochemical properties of conjugated systems Polyacetylene, polyphenylene, polythiophene, and poly pyrrole. J Am Chem Soc 105 6555-6559... 

Fig. 3.4. Two advanced polythiophene derivatives with liquid crystal properties. These materials are solution processable and can be processed into relatively large crystal domains through controlled thermal cycling, (a) PQT, where R is an alkane (in PQT-12, for example, R is (CHn)CH3) [21] (b) poly(2,5-bis(3-alkylthiophen-2-yl) thieno[3,2-b]thiophene), where R is also a variable length alkane chain 10-14 C long ([22])...

Another measure of the conformational flexibility of substituted polythiophenes is found in the determination of colligative properties of solutions of such polymers. Experimental studies have demonstrated poly(3-octylthiophene) in solutions to follow the... 

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