Soluble conducting polymers

In the field of soluble conducting polymers new data have been published on poly(3-alkylthiophenes " l They show that the solubility of undoped polymers increases with increasing chain length of the substituent in the order n-butyl > ethyl methyl. But, on the other hand, it has turned out that in the doped state the electro-chemically synthesized polymers cannot be dissolved in reasonable concentrations In a very recent paper Feldhues et al. have reported that some poly(3-alkoxythio-phenes) electropolymerized under special experimental conditions are completely soluble in dipolar aprotic solvents in both the undoped and doped states. The molecular weights were determined in the undoped state by a combination of gel-permeation chromatography (GPC), mass spectroscopy and UV/VIS spectroscopy. It was established that the usual chain length of soluble poly(3-methoxthythiophene) consists of six monomer units. 

G Gustafsson, Y Cao, GM Treacy, F Klavetter, N Colaneri, and AJ Heeger, Flexible light-emitting diodes made from soluble conducting polymers, Nature, 357 477-479, 1992. 

Oxireductases in the Enzymatic Synthesis of Water-Soluble Conducting Polymers... 

The use of enzymes as biocatalysts for the synthesis of water-soluble conducting polymers is simple, environmentally benign, and gives yields of over 90% due to the high efficiency of the enzyme catalyst. Since the use of an enzyme solution does not allow the recovery and reuse of the expensive enzyme, well-established strategies of enzyme immobilization onto solid supports have been applied to HRP [22-30]. A recent work reported an alternative method that allows the recycle and reuse of HRP in the biocatalytic synthesis of ICPs. The method is based on the use of a biphasic catalytic system in which the enzyme is encapsulated by simple solubilization into an IL. The main strategy consisted of encapsulating the HRP in room-temperature IPs insoluble in water, and the other components of the reaction... 

The mechanism for the SPAN layer changing the emission properties of the PPy VPV polymer is attributed to the formation of new emissive species due to protonation of the pyridyl units by SPAN. These species was identified by both absorption and PL experiments. Figure 9.15 shows the absorbance spectra of a PPy VPV layer, a SPAN layer, and a bilayer of PPy VPV/SPAN. SPAN is a self-doped, water-soluble conducting polymer with a room-temperature conductivity of 10-2 S/cm.18 It has a wide optical window from green to near infrared PPy VPV... 

Substituted PANIs (polymers of functionalize aniline molecules), on the other hand, have also become an alternative choice to obtaining the desired properties of processability and solubility. For example, the polymerization of a derivatised aniline such as 2-methoxyaniline, results in a soluble conducting polymer. In general, substituent groups present in the units of the polymer chain cause decrease in the stiffness of the polymer chain to result in better solubility. Unfortunately such improvements by substitution of groups in the phenyl ring or A -position of polyaniline units are also accompanied by decrease of conductivity. Nevertheless, aniline substituted with two methoxy groups, 2,5-dimethoxyaniline, has been reported to contrarily produce a soluble polymer, poly(2,5-dimethoxyaniline), PDMA, with a conductivity similar to PANI [57]. 

Other workers have used additives to enable the preparation of effectively water-soluble conductive polymer colloids. As early as 1986, Bjorklund and Liedberg102 observed that when pyrrole was oxidized by FeCl3 in the presence of aqueous methylcellulose (MWt 100,000), a PPy/methylcellulose sol was formed that could be characterized by scanning electron microscopy. Thin films could be obtained from the sol, exhibiting a conductivity of ca. 0.2 S cm-1. Subsequently, a range of neutral, water-soluble steric stabilizers such as poly(vinylalcohol), poly(ethyleneoxide) (PEO), or poly(vinylpyridine) have been successfully... 

An alternative approach52 involves polymerization of conventional polymer in the presence of a soluble conducting polymer (alkylated thiophene) to form a semi-interpenetrating network. The polythiophene was dissolved in solutions of styrene and divinyl benzene conductivities in the range 0.01-0.10 S cm-1 were obtained. 

Bryce, M. R., Chissel, A., Kathirgamanthan, R, Parker, D., Smith, N. R. M., Soluble, Conducting Polymers from 3-Substituted Thiophenes and Pyrroles , J. Chem. Soc. Chem. Commun. (1987) 466-467. 

Figure 11.7. Structure model for soluble conducting polymers. [Reproduced from ref 69 with kind permission of Carl Hanser,]...

Several. sessions at the ICSM 1988 in Santa Fe, titled Soluble conductive polymers. 

G. Gustafsson, Y. Cao, G. M. Treacy, F. Klavetter, N. Colaneri, A. J. Heeger, Flexible Light-Emitting Diodes Made from Soluble Conducting Polymers. Nature 1992, 357,477-479. 

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. 

In the next section, the deciding basic requirement for the existence and character and for the nanoscale properties of these materials—principal insolubility—will be discussed. This discussion is necessary because the vast majority of the scientific community dealing with the conductive polymers still hopes of obtaining truly soluble conductive polymers one day—a goal that has no chemical or physical basis and would, if it were realistic, prevent their use in nanotechnology. 

With the end of the battery research, the need for processing became evident, as new ideas connected with LEDs emerged. These demanded a kind of solvent-based processing technique. On the basis of work by Elsenbaumer et al. [44], a variety of soluble conductive polymers and solvents, even for doped polyaniline, have been proposed. This question was discussed shortly in Section 1.2. Here, only conductive polymers will be discussed. 

Soluble conducting polymers can be solvent cast to form coatings. The addition of appropriate substituents to the polymer backbone or to the dopant ion can impart the necessary solubility to the polymer. For example, alkyl or alkoxy groups appended to the polymer backbone yield polypyrroles [117,118], polythiophenes [118], polyanilines [119,120], and poly(p-phenylenevinylenes) [97] that are soluble in common organic solvents. Alternatively, the attachment of ionizable functionalities (such as alkyl sulfonates or carboxylates) to the polymer backbone can impart water solubility to the polymer, and this approach has been used to form water-soluble polypyrroles [121], polythiophenes [122], and polyanilines [123]. These latter polymers are often referred to as self-doped polymers as the anionic dopant is covalently attached to the polymer backbone [9]. For use as a corrosion control coating, these water-soluble polymers must be cross-linked [124] or otherwise rendered insoluble. 

The use of polymeric blend composites for corrosion protection of AA 2024-T3 has been reported, including composites formed by incorporating water-soluble conducting polymers (either polymethox-yaniline sulfonic acid or poly(4-(3-pyrrole) )butane sulfonate) into various binders (a cross-linked polyvinyl alcohol, a waterborne epoxy, a modified water-dispersible polyester, and a UV-curable urethane acrylate binder) [149]. The preparation of epoxy and polyaniline composite coatings has been described, using either nanodispersed EB particles [91] or EB that was first dissolved in selected amine hardeners before adding the epoxy resin [98]. Even with very low EB loadings, these workers reported enhanced corrosion protection for steel. 

Bryce, M.R., et al. 1987. Soluble, conducting polymers from 3-substituted thiophenes and pyrroles. 7 Chem Soc Chem Commun (6) 466. 

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