Polythiophene 3-octyl

The use of the heteroaryl Heck reactions extends beyond fine chemicals synthesis. Polythiophenes were prepared starting from 3-octyl-2-iodotiophene by heating in the presence of palladium acetate and tetrabutylammonium chloride (6.91.),122 The arylation of benzothiophene has also been achieved under the same conditions.123... 

Thermochromic behaviour with completely conjugated planar chains at low temperature (213 K) and with small conjugated chain segments, only a few rings in length, for a temperature of 463 K, is also reported for poly(3-hexylthiophene) [91]. Depending on the position of octyl-chains in poly(3-octylthiophene) co-planar and twisted polymer backbones were found [92]. Theoretical calculations predict a planar rod-like structure for polymethylthiophene [93]. The STM observations of side-chain substituted polythiophene were reported above [71]. 

The redox behavior of polythiophene and substituted polythiophenes (mainly 3-alkyl substituted) is closely related to that of polypyrrole, as might be expected. The cyclic voltammogram of polythiophene [42] shows that oxidation of the polymer occurs at 1.0 V versus SCE whereas reduction occurs at 0.9 V. Past 1.71 V, another peak appears, and if the potential of the film is taken beyond this value, deactivation of the film occurs. But in another aspect polythiophene differs from polypyrrole. It shows better redox activity when there is a substituent in the ring. In fact, the processibility (ability to spin cast films etc.) also improves, especially if there are hexyl or octyl groups substituted at the 3-position. 

Comparison with absorption and photoluminescence measured from regioregular polythiophenes in which oligothiophene sequences are delimited by n-octyl substituents placed in head-to-head fashion on... 

Irreversible undoping that led to the loss of electrical properties in doped poly(alkylthiophene)s on thermal treatment was reported by Inganas and co-workers. The rate of thermal undoping was observed to be faster in the case of longer chains substituted on the polythiophene when compared with nonsubsti-tuted polythiophene [128-131]. Random copolymers of methyl-and octyl-substituted polythiophene [132] and regular copolymers of dimer thiophene-co-octylphenylthiophene [133] demonstrated much better stability. 

A good example of such complex powder patterns in PL-ODMR and ADMR is shown in Figs. 22.7a and 22.7b, respectively, for the triplet state in poly(3-octyl-thiophene) (P30T), a derivative of polythiophene (see... 

The conductive properties of alkylated polythiophenes are known to be unstable, particularly at elevated temperatures. The mechanism of thermal undoping has been associated with thermal mobility. Consequently, various workers have considered synthesis of random copolymers (e.g., thiophene and 3-octylthiophene), with well-distributed octyl side groups leaving space around the main chains to accommodate dopants. 

---