Conjugated polymers incorporating thieno thiophene

Ong et al. have synthesized solution-processable alkyl-substituted poly(ter- and quarterthiophenes) 203-205 [369-371] and realized OFETs with hole mobilities up to0.14cm V s and on/off ratio over 10 in the case of203 [369]. Similar results have been reported by others [372]. Another approach consists in limiting rr-electron delocalization by incorporation of building block, such as thieno[2,3-b]thiophene that interrupts the conjugated pathway in the chain. The solution-processable polymers 206 leads to OFETs with hole mobility of 0.12-0.15 cm V s [373]. 

Unlike the other TT isomers, incorporation of thieno[2,3-h]thiophene, a cross-conjugated system, into conjugated oligomers or polymers suppresses the effective conjugation length and hence increases its ionization potential, that is, lowers the HOMO energy level and increases the stability of the materials [77]. 

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