4-Alkyl-2,2’-bithiophene polymerization

Polythiophenes substituted regioregularly with alkyl chains were prepared by the polymerization of alkylated bithiophenes and terthiophene. Souto et al. polymerized 3,3 -dihexyl-2,2 -bithiophene (41) with iron(III)... 

Alkoxy-substituted bithiophenes have also been successfully polymerized, using Cu(C104)2 as oxidant.50 As with related FeCl3 oxidations of alkyl-substituted bithiophenes,51 these dimeric substrates are easier to oxidize than the corresponding substituted thiophene monomers, due to their lower oxidation potentials. 

However, electrochemically polymerized 3-alkyl-2,2 -bithiophenes (alkyl = hexyl, dodecyl) give conducting films whose electrical conductivities are independent of the length of the alkyl chains [485-487],... 

In the case of poly(3-alkyl-2,2 -bithiophene)s there are no head-to-head couplings or side chain clashes even for the regiorandom polymer (Figure 6). Oxidative polymerization of 4-alkyl-2,2 -bithiophenes with FeCla results in a completely regiorandom polymer which contains head-to-head couplings (17%),(57) but no side chain clashes (Figure 6). The absorption maximum for the poly(3-octyl-2,2 -bithiophene) is red shifted relative to poly(4-octyl-2,2 -bithiophene) as expected (Table VII) due to its lack of head-to-head linkages. In the solid state spectra, there are few differences between polymers derived from the 3-alkyl and 4-alkyl isomers.(28,54,67)... 

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