Selenophene-containing copolymers

Many selenophene-containing copolymers are available. Most of them were developed as conductive materials, but recent polymers are finding other applications such as light-emitting and photovoltaic materials. Copolymer 14 [57, 58], which consists of selenophene and thiophene, was developed by electropolymerization of 2-thienylselenophene. The conductivity of 14 under doping was of the order of 10 -10 Scm and is almost the same as that of polyselenophene. 

Copolymers 20 and 21, which include selenium atoms in their polymer chains, were also studied [67]. However, even when doped with iodine or antimony pentafluoride, these polymers exhibited conductivities lower than 10 Scm .  

Polyaniline has always been at the forefront of interdisciplinary research on account of its unique reversible prototropic dopability, excellent redox recyclability, chemical and environmental stabiUty, low cost and easy preparation [68], However, the intractable insolubility of polyaniline in common organic solvents is the most significant factor hampering commercial use. As a backbone modification of polyaniline, polymer 22 was synthesized by chemical polymerization of p-selenienylaniline with FeCb [69]. The polymer was soluble in THF, DMF, NMP and DMSO and exhibited a reversible prototropic doping process. Upon doping with iodine, the pellet powder sample showed a low conductivity of 8.0 x 10 S cm .  

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Palladium cross-coupling reactions of a-haloselenophenes are a useful tool for the preparation of selenophene-containing copolymers <2005PSA823, 2005MM244>. 

Although polythiophenes are best utilized as solution-processable high-performance p-type semiconductors [102], polyselenophenes are of no use as FET materials because of their insolubility. However, it was recently reported that selenophene-containing copolymers 47-50 could form thin films with a solution-processable method and showed p-channel FET responses with hole mobilities of the order of 10 " -10 cm V s [103]. When the thin films were annealed after spin coating, the mobilities were enhanced by one order of magnitude. 

Recently, Kim et al. reported that a FET using the copolymer of fluorene and selenophene, poly(9,9 -dioctylfluorene-a/t-biselenophene) (51), as an active layer exhibited a high hole mobiUty of 0.012 cm V s which is better than the performance of the fluorene and thiophene copolymer counterpart [104]. It is speculated that the high mobility of 51 is a result of the close molecular packing and the well-defined orientation of selenophene-containing polymer chains. 

Because isoindigo homopolymer is a typical n-type semiconductor, [14] in order to obtain p-type isoindigo-based polymers, electron-rich groups should be introduced to increase the HOMO level of the desired polymers. The donor-acceptor interactions of electron-deficient isoindigo units and electron-rich units may enhance the interchain ti-ti stacking interactions. Selenophene-(2-4) and thiophene-containing (2-5 to 2-11) units are used to construct the copolymers (Scheme 2.2). Units 2-4—2-7 and unit 2-10 are centrosymmetric, and units 2-8, 2-9 and 2-11 are... 

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