Water-Soluble Poly thiophenes

Another type of noncovalent interaction, namely electrostatic ones, has recently been exploited by Wang et al. in the fabrication of a hybrid film containing a water-soluble poly(thiophene) derivative and CdSe NCs.141 In this case CdSe NCs were functionalized with 11-mercaptoundecanonic acid (MUA) molecules prior to their self-assembly with side chain-functionalized poly(thiophene), that is, poly(3-(3 -thienyloxy)propyltrimethylammonium bromide) (P3TOPA). 

Polysubstituted thiophenes with other groups different to w-alkyl chain are also known. For example, alkylsulfonate, alkoxy, amide, poly(ether), and acylgroup were introduced in 3-position in thiophene and their electroobtained polymers were studied. A water soluble poly(alkane)sulfonatederivative of thiophene has also been reported [55] which would be an intrinsically conducting polymer (self-doped). Composites of poly(thiophene)s with poly(methylmethacrylate) and poly(vinylchloride) were prepared as... 

Liu, Z., Liu, L., Li, H., Dong, Q., Yao, S., Kidd, A.B., et al., 2012. Green polymer solar cell based on water-soluble poly[3-(potassium-6-hexanoate) thiophene-2,5-diyl] and aqueous-dispersible noncovalent functionalized graphene sheets. Solar Energy Materials and Solar Cells 97, 28-33. 

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. 

The sodium salts and the acids of poly-3(2-ethanesul-fonate) thiophene and poly-3-(4-butanesulfonate) thiophene are the first known examples of water soluble CPs many other examples of water-soluble, self-doped CPs are given in recent reviews. Indeed, it is well known that the incorporation of highly soluble sulfonate groups on the CP backbone is a common method of achieving water solubility in a doped CP. The two most popular routes are the use of sulfonated polymeric dopants and the polymerization of sulfonated monomers. 

Ambipolar behavior has also been observed in BBL and poly(thiophene-3-propionic acid, anunoninm salt).[297] 51a showed n-channel mobihties of 0.04-0.06 cm V s and 0.02-0.03 cm V s for p-channel operation. 51c showed valnes of 0.5-0.7 cm V s for n channel and 1.2-1.7 cm V s for p-channel with on/off ratios between 2 and 50 for devices operated in air. A similar mechanism involving ion-modulated electrochemical conduction, as described above for water soluble phthalocyanines was proposed by the authors. 

Ewbank, P.C., R.S. Loewe, L. Zhai, J. Reddinger, G. Sauve, and R.D. McCullough. 2004. Regioregular poly(thiophene-3-alkanoic acid)s Water soluble conducting polymers suitable for chromatic chemosensing in solution and solid state. Tetrahedron 60 (49) 11269-11275. 

Example 10 Polythiophene-Carboxylic Acid - Synthesis of Water-Soluble 2,5-Poly(thiophene-3-propionic Acid) and Poly(3-thiophene Methyl Acetate) (P3TMA)... 

The concept of self-doped conducting polymers was proposed some years ago with the synthesis of poly(3-thiophene-j8-ethanesulfonate) and poly(3-thiophene 5-butanesulfonate) (61) [278]. In these systems the charge-compensating anion is covalently bound to the polymeric backbone consequently, instead of anion incorporation, charge compensation upon doping involves the expulsion of cationic species. Furthermore, due to the presence of the sulfonate group, these polymers are the first examples of water-soluble PHCs. The polymers described in Ref. 278 were... 

Other 3-substituted thiophenes that have been polymerized include 3-methoxy [309-311], other 3-alkoxy [312], 3-phenyl [313,314], 3-(4-methoxyphenyl) [314], 3-(4-trifluoromethylphenyl) [314], 3-bromo [315], 3-alkylsulfonatethiophene [316-318], and others [319-323]. Poly-3-alkylsulfonate thiophenes are particularly interesting due to a striking property. Sodium poly-3-thiophene-j8-ethanesulfonate and sodium poly-3-thiophene-6-butanesulfonate and their conjugate acids are water soluble in both the doped and undoped states [317,318]. Ikenoue et al. [318] examined the conduction mechanism for this self-doped conducting polymer. 

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