Poly 3- thiophene structure

Since this book deals with thiophenes, we will not dwell on the more estabUshed small molecular organic semiconductors but will focus on oligo(thiophenes) and poly(thiophenes). Oligo(thiophenes) can be viewed both as materials with great potentials for devices, partly because of their high field-effect mobilities, and also as finite model systems for the poly(thiophenes). Structures of some oligo(thio-phenes) are shown in Fig. 2. 

The employment of substituted 2-aminothiophenes in such areas represents the latest discovery showing a great promise in materials chemistry for the generation of novel oligo- and poly- thiophene structures. 

Schematically show and compare the results of n-doping of a conventional semiconductor (e.g. Si with P) and a CP (e.g. poly(thiophene) with tetrafluo-roborate), using band structure diagrams, and molecular (for Si) and chain (for poly(thiophene)) structures. 

T. Yamamoto, A. Morita, Y. Miyazaki, T. Marayama, H. Wakayama, Z.H. Zhou, Y. Nakamura, T. Kanbara, S. Sasaki, and K. Kubota, Preparation of ir-conjugated poly(thiophene-2,5-diyl), poly(p-phenylene), and related polymers using zerovalent nickel complexes. Linear structure and properties of the TT-conjugated polymers, Macromolecules, 25 1214—1223, 1992. 

The synthesis of other poly(arylene ether)s containing thiophene units concerned the reaction of two activated halides containing thiophene (structures 8 and 9) with bisphenol A [44,45]. The polymers from the monomers of structures 8 and 9 and bisphenol A had intrinsic viscosities (NMP, 25 °C) of 1.23 and 0.43 dL/g and Tgs of 158 and 120°C, respectively. 

We have presented evidence to prove the structure of electrochemical ly generally poly(thiophene) from dithiophene both by independent synthesis and spectroscopy. Diodes and photodiodes were fabricated from lightly doped chemically and electrochemically synthesized PT. 

However, the particular synthetic requirements in the preparation of conjugated polymers have thus far severely limited the number of similarly hierarchically structured examples. Pu et al. reported different types of conjugated polymers with fixed main-chain chirality containing binaphthyl units in their backbone which exhibited, for example, nonlinear optical activity or were used as enantioselective fluorescent sensors [42—46]. Some chirally substituted poly(thiophene)s were observed to form helical superstructures in solution [47-51], Okamoto and coworkers reported excess helicity in nonchiral, functional poly(phenyl acetylenejs upon supramolecular interactions with chiral additives, and they were able to induce a switch between unordered forms as well as helical forms with opposite helical senses [37, 52, 53]. 

Poly(bithiophene) films from these two ionic liquids are morphologically similar (Figure 7.14), even though the redox behavior (Figure 7.9) is markedly different, suggesting that the dominant differences in the films produced are on an atomic or sub-micron rather than macroscopic level. The morphology ofthe poly (bithiophene) films appears to be similar to that described by Roncali et al. [74] who reported a thin film on the surface of the electrode, covered by a thick brittle powdery deposit, from the galvanostatic polymerization of bithiophene in acetonitrile. The nodular structures are smaller in the poly (bithiophene) films than in the poly (thiophene), which is consistent with the formation of shorter chain polymers [73], but this does not... 

A major reason for the failure of poly(acetylene)s in the above-mentioned applications is related to their inherent instability versus moisture and oxygen, and their high susceptibility to decomposition/rearrangement in the partially oxidized/doped state. Nevertheless, poly(ene)s stabilized by appropriate ligand systems and/or incorporated into cyclic structures are believed to exhibit similar stabilities to poly(thiophene)s, poly(pyrrole)s, poly(p-phenylene)s, PPV, and so on. In the following, we will outline the basic concepts of poly(ene)s as well as reviewing the structures that have been realized so far. 

Figure 4.8-1 Electronic structure and chemical structure of hole and electron polarons (a), hole and electron bipolarons (b), and hole and electron solitons (c). Examples of chemical structures refer to poly(thiophene) and poly(acetylene), respectively.

Depending on their structure, the polymers containing heterocycles have various applications. For example, poly(furfuryl alcohol) is used in composite materials with fillers such as sand and concrete, in copolymers with formaldehyde, etc. Some of the polymers from this group have special properties such as good electrical conductivity (after appropriate doping). Among these polymers are poly(thiophene-2,5-diyl) and particularly polypyrrole, CAS 109-97-7, (usually in carbon black doped with an organic acid anion). The structure of this polymer is shown below ... 

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. 

Table 2 contains idealized structures of some CPs with typical dopants and values for the conductivities of thin films. The exact structures of PPy and poly thiophene (PT) are unknown. Polyacetylene is the most crystalline and PANi can exist in several oxidation states with electrical conductivities varying from 10 S/cm to the values reported in Table 2. In its undoped state, PPS is an engineering thermoplastic with a conductivity of less than 10 S/cm. Upon doping with ASF5, conductivities as high as 200S/cm have been obtained after casting a film from a solution of AsFsP ...

Conducting electroactive polymers (CEPs) such as polypyrrole, poly thiophene, polyaniline, and sulfonated polyaniline (1-4 shown subsequently) are complex, dynamic structures that captivate the imagination of those of us involved in intelligent material research.1 2 3 4 5... 

Electrochemically prepared alkylated polythiophenes have been investigated by Gamier and coworkers.90 91 When comparing polythiophene and monosubstituted polyalkylthiophenes, these workers found an increase in crystallinity of the substituted thiophenes in comparison to the unsubstituted poly thiophene. The degree of crystallinity was low (5%), but the crystal structure was assigned to a hexagonal cell... 

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