Conjugated polymers polythiophenes

Polymers, large molecules made up of smaller molecules in a repeating pattern, are used for many electrochromic materials. Conjugating polymers, which have alternating single and double bonds, are particularly suitable. Figure B shows the electrochemical oxidation of the conjugated polymer, polythiophene. Oxidation (in which electrons are removed) produces a semiconductive polymer. The neutral (unoxidized) polythiophene is red in color, whereas the semiconductive polythiophene (oxidized) is blue. In their neutral... 

It is possible to prepare three typical ti-conjugated polymers, polythiophene, polypyrrole and polyaniline, by means of electrochemical oxidation of the corresponding monomers in the presence of an electrolyte at ambient temperature. In 1990, Canham discovered that photoluminescent porSi materials could be formed by an electrochemical method that used a p-type c-Si wafer. Electrochemical methods are among the safest, most environmentally friendly and technically favorable processes eompared to Na/Li-based Wurtz coupling reactions (Chart 13.10). ... 

Keywords Applications of conjugated polymers Polythiophene Thiophene as electron donor... 

Within the conjugated polymers polythiophene is an important material for future technical applications, e. g. for LEDs, electronic devices, or optical switches [1]. In this context studies of light induced processes are of interest, especially details of the degradation of electronic energy within the ultrashort time scale of picoseconds and sub-picoseconds. 

Other polymers ia this category iaclude CJ-conjugated polygermylenes (20) and TT-conjugated poly acetylene, polythiophene, and poly(p-phenylenevinylene). The photoconductivity of many TT-conjugated polymers can be enhanced by dopiag with fuUerenes (21). 

Several attempts to use otganic polymeric semiconductors as the active component in photovoltaic devices have been reported during the last two decades. Interest in the photovoltaic properties of conjugated polymers like polyacelylcne, various derivatives of polythiophenes and poly(para-phenylene vinylene)s arose from... 

Polymers with n-conjugated backbones are an important class of materials that have captured the imagination of the scientific community due to their remarkable properties and exciting applications [91-95]. While most of the work on n-conjugated polymers has focused on all-carbon systems, there has been considerable interest in incorporating heteroatoms into the n-conjugated backbone (i.e.,polythiophene, polypyrrole, polyaniline) to tune their properties. 

Polythiophenes (including oligothiophenes) are one of the most studied and important classes of linear conjugated polymers [444,445], Versatile synthetic approaches to PTs (chemical [446] and electrochemical [447]), easy functionalization and unique, widely tunable electronic properties have been the source of tremendous interest in this class of polymers. 

Poly(monosulfide)s, 23 702-711 aliphatic, 23 702-704 aromatic, 23 706 conjugated polymers, 23 709 macrocyclic polythioethers, 23 707 poly(arylene sulfide)s, 23 704-706 poly(monosulfide ketone)s, 23 709-711 polythiophenes, 23 708 tetrathiafulvalene polymers,... 

The polaronic strategy has also been applied to polymers, incorporating m-phenylene units as coupling links in n-conjugated polymer chains of polyfthienylene ketone) (Dal Colle et al. 1999) as well as of polyarylamine, polyacetylene, and polythiophene (Kaisaki et al. 1991, Murray et al. 1994, Bushby et al. 1997a). Scheme 1.44 represents these polaronic polymers. 

Polyacetylene is very susceptible to attack by oxygen. The polymer loses its metallic lustre and becomes brittle when exposed to air. However, other conjugated polymers were found. Polypyrrole, polythiophene, polyaniline, polyphenylenevinylene (Figure 6.4), and others are conjugated polymers whose bonding and con-... 

Solitons are considered to be important defect states in these conjugated polymers (see Fig. 6.48). It has however been shown that correlation energy is the more important factor in giving rise to the energy gap in (CH) (Soos Ramasesha, 1983). Other polymers related to polyacetylene are polythiophene, polypyrrole, poly-phenylenesulphide, and polyparaphenylene (Section 3.3). Extensive measurements on doped polyacetylenes have been reported in the last five years and these materials, unlike other conducting polymers such as (SN), seem to have good technological potential. 

Against this background of infusible conducting polymers, the development of the soluble polythiophenes is most interesting. Glass transition temperatures have been reported as 48 °C for poly(3-butylthiophene) and 145 °C for poly(3-methyl-thiophene) 261). These polymers also show crystallinity in films and can be crystallized from solution. Solution studies indicate that there are two chain conformations 262) and the availability of a non-conjugated conformation may be a key to the low transition temperatures and solubility, when compared to the stiff-chain conjugated polymers. 

An extensive review of the synthesis of rc-conjugated polymers is presented using a tutorial approach to provide an introduction to the field intended for the undergraduate student and the experienced chemist alike. The many synthetic methodologies that have been used for the synthesis of conjugated polymers are outlined for each class of polymers with a focus on research from the 1990s. The effect of structure on electrical properties is detailed. Specific systems reviewed include the polyacetylenes, polyanilines, polypyrroles, polythiophenes, poly(arylene vinylenes), and polyphenylenes. 

Keywords Conducting polymers, Conjugated polymers, Polyacetylenes, Polyanilines, Polypyrroles, Polythiophenes, Poly(arylene vinylenes), Polyphenylenes... 

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