Thiophene polymer

In addition to useful polymers, thiophene derivatives have a variety of other interesting properties. Novel benzodiazepine analogues such as 46 and related compound 47 continue to... 

The electropolymerisation of the electrically conducting polymers thiophene (mentioned briefly aready in Chapter 5) and polypyrolle are thought to be produced by a scheme to that given in Fig. 6.22. (The scheme shows polypyrrole formation. Polythiophene is similar in that NH is replaced by S.)... 

They are all soluble in concentrated H2SO4, and most are soluble in NMP, DMAc, pyridine, and m-cresol at room temperature. The order of decreasing solubility is pyrrole-containing polymers > furan-containing polymers > thiophene-containing polymers. 

The highest mobilities achieved in solution-deposited polymer transistor devices have been exhibited by thiophene-containing polymers. Thiophene is an electron-rich, planar aromatic heterocycle, which can form a range of conjugated polymers when coupled appropriately [23, 24], The crystalline nature of many thiophene derivatives plays a role in their excellent charge transport properties. In this chapter, we will focus on copolymers of thiophene with the fused unit, thienothiophene, and their structural analogues. 

Thiophene was found in tar, gas and industrial benzene obtained from coal in the nineteenth century. A large number of thiophene derivatives are described in the literature and their physical properties, nucleophilic substitution and biological activity are still of current interest [ ] As for polymers, thiophene was oxidized by such acidic materials as orthophosphoric acid or a synthetic silica-alumina catalyst to yield liquid oligomer which consisted of its trimer containing a small amount of its pentamer. A report on this was published as early as 1883 [2], However, modem studies on polythiophene, aiming at the preparation of electrically conductive polymers, started at the beginning of the 1980s [3-5]. 

Heterocoagulation Heterocyclic Heterocyclic amines Heterocyclic azo dyes Heterocyclic compounds Heterocyclic dyes Heterocyclic polymers Heterocyclic thiophenes Heteroepitaxy Heterogeneous catalysis Heterogemte Heteroglycan Heterojunction... 

Polythiophene can be synthesized by electrochemical polymerization or chemical oxidation of the monomer. A large number of substituted polythiophenes have been prepared, with the properties of the polymer depending on the nature of the substituent group. Oligomers of polythiophene such as (a-sexithienyl thiophene) can be prepared by oxidative linking of smaller thiophene units (33). These oligomers can be sublimed in vacuum to create polymer thin films for use in organic-based transistors. 

Sulfonated styrene—divinylbensene cross-linked polymers have been appHed in many of the previously mentioned reactions and also in the acylation of thiophene with acetic anhydride and acetyl chloride (209). Resins of this type (Dowex 50, Amherljte IR-112, and Permutit Q) are particularly effective catalysts in the alkylation of phenols with olefins (such as propylene, isobutylene, diisobutylene), alkyl haUdes, and alcohols (210) (see Ion exchange). Superacids. 

Idemitsu Process. Idemitsu built a 50 t x 10 per year plant at Chiba, Japan, which was commissioned in Febmary of 1989. In the Idemitsu process, ethylene is oligomerised at 120°C and 3.3 MPa (33 atm) for about one hour in the presence of a large amount of cyclohexane and a three-component catalyst. The cyclohexane comprises about 120% of the product olefin. The catalyst includes sirconium tetrachloride, an aluminum alkyl such as a mixture of ethylalurninumsesquichloride and triethyl aluminum, and a Lewis base such as thiophene or an alcohol such as methanol (qv). This catalyst combination appears to produce more polymer (- 2%) than catalysts used in other a-olefin processes. The catalyst content of the cmde product is about 0.1 wt %. The catalyst is killed by using weak ammonium hydroxide followed by a water wash. Ethylene and cyclohexane are recycled. Idemitsu s basic a-olefin process patent (9) indicates that linear a-olefin levels are as high as 96% at C g and close to 100% at and Cg. This is somewhat higher than those produced by other processes. 

Polyheterocycles. Heterocychc monomers such as pyrrole and thiophene form hiUy conjugated polymers (4) with the potential for doped conductivity when polymerization occurs in the 2, 5 positions as shown in equation 6. The heterocycle monomers can be polymerized by an oxidative coupling mechanism, which can be initiated by either chemical or electrochemical means. Similar methods have been used to synthesize poly(p-phenylenes). 

The synthesis involves the nickel-catalyzed coupling of the mono-Grignard reagent derived from 3-alkyl-2,5-diiodothiophene (82,83). Also in that year, transition-metal hahdes, ie, FeCl, MoCl, and RuCl, were used for the chemical oxidative polymerization of 3-substituted thiophenes (84). Substantial decreases in conductivity were noted when branched side chains were present in the polymer stmcture (85). 

Styryl sulfonyl chloride Friedel-Crafts cyclization benzo[h]thiophenes from, 4, 873 Succinic anhydrides polymers, I, 277 mass spectrometry, 4, 585 structure, 4, 552... 

The polymers which have stimulated the greatest interest are the polymers of acetylene, thiophene, pyrrole and aniline, poly-p-phenylene, polyphenylvinylene and poly-l,6-heptadiyne. Of these materials polypyrrole has been available from BASF under the trade name Lutamer P160 since 1988. 

Hydrofining has all the advantages of acid treating without the disadvantages. For example, acid treating does not readily remove refractory sulfur compounds such as thiophene the treated products must be rerun to remove polymers with a consequent yield loss and disposal of the acid sludges is a serious problem. 

Like thiophenes, pyrroles are important n-components of conducting polymers... 

The Paal synthesis of thiophenes from 1,4-diketones, 4-ketoaldehydes and 1,4-dialdehydes has found great use in the synthesis of medicinally active compounds, polymers, liquid crystals and other important materials. Furthermore, the discovery of the catalyzed nucleophilic 1,4-conjugate addition of aldehydes, known as the Stetter reaction (Eq. 5.4.1), has enabled widespread use of the Paal thiophene synthesis, by providing 1,4-diketones from readily available starting materials. ... 

Polypyrrole, poly thiophene, polyfuran, polycarbazole, polystyrene with tetrathi-afulvalene substituents, polyethylene with carbazole substituents, and poly-oxyphenazine as electrochemically active polymers for rechargeable batteries 97CRV207. 

Structures of different conjugated polymers including various thiophenes (3,4,8,9,10,11) and pyrroles 12,5,6,7) that show color variation. (From A. A. Argun. R Aubert, B. Thompson, I. Schwendeman, C. L. Gaupp, J. Hwang. N. J. Pinto. D. B. Tanner, A. G. MacDiarmid, J. R. Reynolds "Multielectrochromism in Polymers Structures and Devices" Chem. Mater. 2004, 1B, 4401-4412). 

Polyacetylene is considered to be the prototypical low band-gap polymer, but its potential uses in device applications have been hampered by its sensitivity to both oxygen and moisture in its pristine and doped states. Poly(thienylene vinylene) 2 has been extensively studied because it shares many of the useful attributes of polyacetylene but shows considerably improved environmental stability. The low band gap of PTV and its derivatives lends itself to potential applications in both its pristine and highly conductive doped state. Furthermore, the vinylene spacers between thiophene units allow substitution on the thiophene ring without disrupting the conjugation along the polymer backbone. 

There have been very few examples of PTV derivatives substituted at the vinylene position. One example poly(2,5-thienylene-1,2-dimethoxy-ethenylene) 102 has been documented by Geise and co-workers and its synthesis is outlined in Scheme 1-32 [133]. Thiophene-2,5-dicarboxaldehyde 99 is polymerized using a benzoin condensation the polyacyloin precursor 100 was treated with base to obtain polydianion 101. Subsequent treatment with dimethyl sulfate affords 102, which is soluble in solvents such as chloroform, methanol, and DMF. The molar mass of the polymer obtained is rather low (M = 1010) and its band gap ( ,.=2.13 eV) is substantially blue-shifted relative to PTV itself. Despite the low effective conjugation, the material is reasonably conductive when doped with l2 (cr=0.4 S cm 1). 

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. 

There have been a number of different synthetic approaches to substituted PTV derivatives proposed in the last decade. Almost all focus on the aromatic ring as the site for substitution. Some effort has been made to apply the traditional base-catalyzed dehydrohalogenation route to PTV and its substituted analogs. The methodology, however, is not as successful for PTV as it is for PPV and its derivatives because of the great tendency for the poly(u-chloro thiophene) precursor spontaneously to eliminate at room temperature. Swager and co-workers attempted this route to synthesize a PTV derivative substituted with a crown ether with potential applications as a sensory material (Scheme 1-26) [123]. The synthesis employs a Fager condensation [124] in its initial step to yield diol 78. Treatment with a ditosylate yields a crown ether-functionalized thiophene diester 79. This may be elaborated to dichloride 81, but pure material could not be isolated and the dichloride monomer had to be polymerized in situ. The polymer isolated... 

The microstructure and architecture of polymers can also gready influence die properties of die polymers. For example, poly(3-substituted thiophene)s could have three microstructure joints s-trans (head to tail), s-trans (head to head), and s-cis (head to tail) (Fig. 9.3). The regioregular head-to-tail poly(3-substituted thiophene)s exhibit higher electrical conductivity values and higher... 

Linear Polymer with Chiral Units 9.4.2.1 Synthesis of Poly (thiophene) 11724a... 

Figure 4. Log intensity vs. potential plots (Tafel plots) obtained from the voltammograms of a platinum electrode submitted to a 2 mV s l potential sweep polarized in a 0.1 M LiC104 acetonitrile solution having different thiophene concentrations. (Reprinted from T. F. Otero and J. Rodriguez, Parallel kinetic studies of the electrogeneration of conducting polymers mixed materials, composition, and kinetic control. Electrochim, Acta 39, 245, 1994, Figs. 2, 7. Copyright 1997. Reprinted with permission from Elsevier Science.)...

A number of approaches are available to improve the morphology and homogeneity of electrochemically deposited conducting polymer films. Priming of the electrode surface with a monolayer of adsorbed or covalently bonded monomer leads to more compact deposits of polyaniline,87,88 poly thiophene,80 and polypyrrole.89,90 Electrode rotation has been shown to inhibit the deposition of powdery overlayers during poly(3-methylthiophene) deposition.81... 

The huge literature on the electronic conductivity of dry conducting polymer samples will not be considered here because it has limited relevance to their electrochemistry. On the other hand, in situ methods, in which the polymer is immersed in an electrolyte solution under potential control, provide valuable insights into electron transport during electrochemical processes. It should be noted that in situ and dry conductivities of conducting polymers are not directly comparable, since concentration polarization can reduce the conductivity of electrolyte-wetted films considerably.139 Thus in situ conductivities reported for polypyrrole,140,141 poly thiophene,37 and poly aniline37 are orders of magnitude lower than dry conductivities.15... 

---