Regioregular Substituted Poly thiophenes

Regioregular alkyl-substituted poly(thiophenes) [46, 47] and oligo(thiophenes) [48] have also been synthesized, in which the alkyl chains are always substituted to the same type of /3-carbon atom, thus producing predominantly head-to-tail interactions, as shown in Fig. 5b, and therefore reducing steric interactions between the alkyl chains. 

An alternative, less sophisticated approach to regioregular substituted polythiophenes is the use of asymmetric 3,4-disubstituted thiophene monomers as substrates, resulting in the selective activation of either the 2- or 5- positions on the thiophene ring. Using this method, poly(3-alkoxy-4-methylthiophenes) with > 95% HT couplings have been prepared via FeCl3 oxidation.48 59... 

The microstructure and architecture of polymers can also gready influence die properties of die polymers. For example, poly(3-substituted thiophene)s could have three microstructure joints s-trans (head to tail), s-trans (head to head), and s-cis (head to tail) (Fig. 9.3). The regioregular head-to-tail poly(3-substituted thiophene)s exhibit higher electrical conductivity values and higher... 

Ochiai, K., M. Rikukawa, and K. Sanui. 1999. Novel highly ordered Langmuir-Blodgett films of regioregular poly(3-substituted thiophene). Chem Commun 10 867-868. 

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