DERIVATIVES OF POLY THIOPHENES

The most well known derivatives of P(T), which are not simply substituted P(T)s, and the only ones discussed in this section, are poly(isothianaphthene) (P(ITN), also called poly(benzo[c] thiophene), its analogue poly(naphtho [c] thiophene), the 

A chemical oxidation procedure has been used by many workers for polymerization of P(ITN) directly from DHITN Jen and Elsenbaumer [611] used 02/FeCl3 as the oxidant Rose and Liberto [283(a)] used a multistep procedure Defieuw et al. [283(b)] used a modification of Wudl et al. s procedure, employing cone. H2SO4/O2 as the oxidant, the polymerization however taking as long as two weeks. Heeger, Wudl et al. [612(a)] polymerized P(ITN) electrochemically from the unstable ITN monomer. Perhaps the simplest and most practical synthesis of P(ITN) was that of Chandrasekhar et al. [74], which used a direct electropolymerization from DHITN itself this polymerization had important mechanistic implications, discussed in Chapter 5 (q.v.). 

Conductivities obtained by Chandrasekhar et al. for P(ITN) [74] were in the 1 to 3 S/cm range, to be compared with the maximum ca. 4 to 8 S/cm obtained by Defieuw et al. [283(b)] for the chemical polymerization. The spectroelectrochemical (SPEL) characteristics of P(ITN) have been presented in Chapter 3 (q. v.). One of the unique characteristics of this CP is that it is darker in its reduced state (at negative applied potential), and very thin films can be nearly transparent in the oxidized (+ applied potential) state. This is said to stem from its low bandgap, ca. 1.1 eV (cf. 2.1 eV for P(T)). Defieuw et al. [283(b)] used this property to cast films of P(ITN) from suspensions in aqueous H2S04/lambda carrageenan on to PET substrates for antistatic uses. Specialized P(ITN) syntheses and uses have been the subject of several patents [612(b)]. 

Poly(naphtho[c]thiophene) was synthesized by Wudl et al. [74] using a method similar to that for P(ITN), with the objective of an even further lowering in bandgap. This objective was not favorably realized, and because of its lesser practical utility and more difficult synthesis, this CP has seen little work since. 

Schlick et al. [613] recently studied the electropolymerization of a number of monomers containing a variety of alternating thiophene, vinylene and in once case, isothianaphthene units, some of which are illustrated in Fig. 14 7. The only monomers successfully polymerized were those shown in part (b) of this figure. 

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Among conducting polymers, various derivatives of poly thiophenes (PTs) have been investigated extensively because of their interesting semiconducting, electronic. 

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. ... 

For the devices presented here, the wrapped copolymer PPyVPV and a wrapped copolymer of poly thiophene and polyphenylene derivative, PTP, were used as the emitting materials SPAN and EB were used as the redox materials ITO and Al were used as electrodes. Figure 9.11 shows the schematic diagram of the device structure of the color-variable bipolar/ac light-emitting devices. 

Ahn T, Lee H, Han S-H (2002) Effect of annealing of poly thiophene derivative for polymer hght-emitting diodes. Appl Phys Lett 80 392... 

For the electrosynthesis of PEDOT and PPy, water was the preferred electrolyte solvent. Although some reports suggest that under special experimental conditions the aqueous electropolymerization of poly(thiophene) derivatives is possible, all attempts conducted in this study failed, including deposition at low pH values and using bithiophene which exhibits a lower oxidation potential than thiophene as the monomeric species [43, 44], Typically, boron trifluoride diethyl etherate and (fairly) anhydrous acetonitrile were used instead [34]. Although both solvents were successfully used to prepare poly(thiophene) inverse opals via the templated synthesis using poly(styrene) microsphere arrays, they tended to destroy the styrenic DG-structured scaffold [2 ]. 

A number of conjugated heterocyclic polymers, viz., poly(pyrrole) [9], poly(p-phenylene) [10], poly(thiophene) [11], and poly(aniline) [12] are also electrically conducting and continue to be developed and studied for electrochromic devices [13-14 see also the companion chapter in this volume] and ion switching devices [15-16], among others. Polymer films with high electrical conductivity have been generated by electrochemical polymerization of benzenoid, nonbenzenoid and heterocyclic aromatics, in particular from the derivatives of pyrrole, thiophene, carbazole, azulene, pyrene, triphenylene and aniline. The electrochemical approach for making these films is very versatile and it provides a facile way to vary the properties of the films. The realization of the applications for each electroactive polymer depends on the control and particularly the enhancement of the... 

Monomers that can be polymerized onto the core nanoparticles include those that upon polymerization can exhibit an inherent conductivity. A variety of copolymers or derivatives of poly(aniline) (PANI), poly(pyrrole), poly(thiophene), PEDOT, and poly(p-phen-ylene vinylene) can be used. 

M. Toba, Y. Takeoka, M. Rikukawa and K. Sanui. Synthesis and optical properties of poly(thiophene) derivatives with benzothiazole moiety. Synth. Met. 152(1-3), 197-200 (2005). 

Films of poly thiophene and its derivatives can be grown with thicknesses ranging from several angstroms to several millimeters. Tourillon [6] observed a linear... 

Polyphosphazenes with simple alkyl and aryl substituents directly attached to the backbone by P-C linkages can be prepared by the condensation polymerization of N-silylphosphoranimine precursors. These simple polymers can then be converted to a variety of functionalized polyphosphazenes by derivatization reactions. In this paper, the synthesis and characterization of some derivatives of poly(methylphenyl-phosphazene), [Me(Ph)P=N]and the copolymer, [Me(Ph)P=N]j [Me2P=N)y, are discussed. These polymers include grafted copolymers, water soluble carboxylated polymers, and polymers with silyl, vinyl, alcohol, ester, ferrocene, phosphine, thiophene, and/or fluoroalkyl groups. 

Polythiophene and its derivatives show remarkable air stability in both oxidized and reduced form [111]. However, there are variable reports on their stability in different types of enviromnents. The ionization potential of poly thiophene is estimated to be above 5 eV, which is high enough to protect the polymer from forming a charge-transfer complex with otygen to cause oxidative instability. Both electrochemically as-prepared polythiophene and polythiophene redoped after ammonia compensation showed much better air stability compared to polyacetylene [112,113]. 

Lee and Kertesz [50] used MNDO for geometry optimization and Hiickel theory for band structure calculations and applied them separately to the aromatic and quinonoid forms of poly thiophene (12) and derivatives with fused benzene 1, naphthalene 16, and anthracene 18 rings. The band gaps for the quinonoid and aromatic... 

The wide variety of coupling methods adapted from organic synthesis to condensation polymerization of just one CP can be appreciated from Fig. 5-12. for poly(pheny-lene). Typical condensations and eliminations adapted to syntheses of such CPs as poly(phenylene) and poly(phenylene vinylene) (P(PV)) are illustrated in Fig. 5-13. Fig. 5-14 shows the variety of precursor routes available to P(PV). More recently, the Yu group [86] has demonstrated application of Pd-catalyzed Stille and Heck reactions to the synthesis of poly(thiophene) (P(T)) derivatives (cf. Fig. 5-15. Besides the Grignard couplings such as shown in Eq. 1.6, Chapter 1, P(T) s can also be prepared via a variety of other procedures, such as Friedel-Crafts alkylation [87], and direct oxidation with FeClj as for P(Py) above. 

Fig. S-15 Pd catalyzed syntheses of Poly(thiophene) derivatives. After Bao and Yu...

The most studied candidate CP to date remains P(ANi), although P(Py) has also been well studied. Wrobleski et al. [617, 942] have studied a number of poly(3-alkyl thiophenes) and poly(3-thienylene acetates). Chandrasekhar et al. [934] have studied a number of poly(aromatic amines), such as derivatives of poly(diphenyl amine). 

The versatility of poly(phenylcne) chemistry can also be seen in that it constitutes a platform for the design of other conjugated polymers with aromatic building blocks. Thus, one can proceed from 1,4- to 1,3-, and 1,2-phenylene compounds, and the benzene block can also be replaced by other aromatic cores such as naphthalene or anthracene, helerocyclcs such as thiophene or pyridine as well as by their substituted or bridged derivatives. Conceptually, poly(pheny ene)s can also be regarded as the parent structure of a series of related polymers which arc obtained not by linking the phenylene units directly, but by incorporation of other conjugated, e.g. olefinic or acetylenic, moieties. 

Chaure, S. Yang, B. Hassan, A. K. Ray, A. K. Bolognesi, A., Interaction behaviour of spun films of poly[3 (6 methoxyhexyl)thiophene] derivatives with ambient gases, J. Phys. Appl. Phys. 2004, 37, 1558 1562... 

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. 

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