Polythiophene soluble

The photovoltaic properties of PPV and PPV based soluble polymers have been quantitatively confirmed also for polythiophenes. The IN characteristics of ITO/ P30T/Au [60] and of ITO/P3HT/Au [61] diodes showed excellent rectification behavior and a high photosensitivity under reversed bias. 

Bao, Z. Lovinger, A. 1999. Soluble regioregular polythiophene derivatives as semiconducting materials for thin film field-effect transistors. Chem. Mater. 11 2607-2612. 

R.D. McCullough, P.C. Ewbank, and R.S. Loewe, Self-assembly and disassembly of regioregular, water soluble polythiophenes chemoselective ionchromatic sensing in water, J. Am. Chem. Soc., 119 633-634, 1997. 

Xue C, Cai F, Liu H (2008) Ultrasensitive fluorescent responses of water-soluble, zwitter-ionic, boronic acid-bearing, regioregular head-to-tail polythiophene to biological species. ChemEur J 14 1648-1653... 

Yao Z, Li C, Shi G (2008) Optically active supramolecular complexes of water-soluble achiral polythiophenes and folic acid spectroscopic studies and sensing applications. Langmuir 24 12829-12835... 

Positive charged water-soluble polythiophenes Negative charged water-soluble polythiophenes [220-222]... 

Sensitive, cationic, water-soluble polythiophenes have been utilized for biosensing. Leclerc et al. have created affinitychromic sensors with such polymers for transducing a variety of recognition events such as those between... 

Water-soluble derivatives of polythiophene have been made allowing counterions bound to the polymer backbone to self-dope with the protons (e.g., lithium and sodium ions) injecting electrons into the pi-system. Thus, combinations of sodium salts and proton salts (e.g., prepared from poly-3-(2-ethanesulfonate)thiophene) have been prepared that are both water-soluble and conducting. 

Further materials that have been evaluated as supports for solid-phase synthesis include phenol-formaldehyde polymers [239,240], platinum electrodes coated with polythiophenes [241], proteins (bovine serum albumin) [242], polylysine [243], soluble poly (vinyl alcohol) [244], various copolymers of vinyl alcohol [4,245,246], and soluble dendrimers [14,247]. 

While the polymers seem to be amorphous in the solid state, there are signs of a transition in solution, possibly from a disordered coil state to a helix, which involves a temperature-dependent colour change 266). This change is also associated with precipitation of a partly-crystalline form. The crystals and solution apparently co-exist over a rather wide temperature range, which is unusual because polymers generally show a rather sharp transition from solubility to insolubility. This may reflect a broad distribution of molecular weights in the polythiophenes. 

The range of soluble polythiophenes has been growing rapidly to include side chains up to docosane 267), ether and amide links in the side chains 268), and water-soluble polymers with sulfonated side chains (Table 1) which are claimed to be self-doping in that the sulphonate may act as the counterion to the delocalized chain cation 269,270). In principle, these polymers can be p-doped and undoped by the transport of a proton or a small cation rather than a large anion, and so may respond more rapidly. By treatment of an aqueous solution with NOPF6, a doped solution can be made, which slowly degrades. 

Against this background of infusible conducting polymers, the development of the soluble polythiophenes is most interesting. Glass transition temperatures have been reported as 48 °C for poly(3-butylthiophene) and 145 °C for poly(3-methyl-thiophene) 261). These polymers also show crystallinity in films and can be crystallized from solution. Solution studies indicate that there are two chain conformations 262) and the availability of a non-conjugated conformation may be a key to the low transition temperatures and solubility, when compared to the stiff-chain conjugated polymers. 

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. 

Polymer science is underdeveloped in terms of descriptions of the structure and properties of stiff-chain polymers. The conducting polymers fall mostly within this blind spot. They also present a number of novel possibilities such as the conversion from a flexible-chain precursor to a rigid-chain polymer, and the conversion between doped and undoped states in the soluble polythiophenes. Likewise, solid-state physics has yet really to tackle the transport of electrons in, and between, disordered, twisted chains. For each of the disciplines involved, the explosion of interest in conducting polymers has brouht a host of new question and new ideas. The process is far from over. 

The polymerization of thiophene, to yield intractable polythiophene 48, was first carried out in a controlled manner in the early 1980s [185-188]. Even in such an unyielding form, this polymer displayed many promising optical and electronic properties. Unfortunately, its lack of processibility precluded further exploration of these attractive attributes. Since then, the synthesis of soluble pol-... 

The materials (metals and conjugated polymers) that are used in LED applications were introduced in the previous chapter. The polymer is a semiconductor with a band gap of 2-3 eV. The most commonly used polymers in LEDs today are derivatives of poly(p-phenylene-vinylene) (PPV), poly(p-phenylene) (PPP), and polythiophene (PT). These polymers are soluble and therefore relatively easy to process. The most common LED device layout is a three layer component consisting of a metallic contact, typically indium tin oxide (ITO), on a glass substrate, a polymer film r- 1000 A thick), and an evaporated metal contact4. Electric contact to an external voltage supply is made with the two metallic layers on either side of the polymer. 

Molecular self-organization in solution depends critically on molecular structural features and on concentration. Molecular self-organization or aggregation in solution occurs at the critical saturation concentration when the solvency of the medium is reduced. This can be achieved by solvent evaporation, reduced temperature, addition of a nonsolvent, or a combination of all these factors. Solvato-chromism and thermochromism of conjugated polymers such as regioregular polythiophenes are two illustrative examples, respectively, of solubility and temperature effects [43-45]. It should therefore be possible to use these solution phenomena to pre-establish desirable molecular organization in the semiconductor materials before deposition. Our studies of the molecular self-assembly behavior of PQT-12, which leads to the preparation of structurally ordered semiconductor nanopartides [46], will be described. These PQT-12 nanopartides have consistently provided excellent FETcharacteristics for solution-processed OTFTs, irrespective of deposition methods. 

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