Regioregular PATs

The deleterious effects of non-HT coupling was first examined by Elsenbaumer et al. [55]. It was shown that the polymerization of a 3-butylthiophene-3 -methyl-thiophene dimer which contains a 63 37 mixtiu e of a HT HH couphngs leads to a three-fold increase in electrical conductivity over the random copolymerization of butylthiophene and methylthiophene (50 50) reaction. Therefore increase in HT coupling leads to a more highly conductive PAT. 

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FIGURE 9.25 Transition metal-catalyzed polymerizations to regioirregular (A) and highly regioregular PATs by the McCullough (B) and Rieke (C) routes. 

Methods of Synthesis Mechanism of the Nickel-Catalyzed Cross-CoupUng Reaction Synthesis of Regioregular PATs with Functionalized... 

Synthesis of Regioregular PATs with Functionalized Side Chains... 

Careful conductivity studies for rr-P3HT, doped with iodine, give conductivities in the range of 50 to 100 S/cm. Regioregular PATs show conductivities as high as 650 S/cm, with typical conductivities of several hundreds, while PATs show conductivities as high as 700 S/cm. 

In the polymerization of alkylthiophenes, the reactivity and thus the routes that lead to PATs are almost the same as for PT, but the challenge here is not as much the solubility but the regioregularity. Great efforts have been put into preparing fully regioregular PATs (HT-HT) for their better performance in PSCs [46-51]. 

It is important to note that care must be taken in determining the molecular weights of PATs using GPC. It has been reported by Berry, Yue, and McCullough that extensive aggregation occurs in regioregular PATs and this can lead to errors in the GPC [52]. We have seen samples of PATs that have of 130K by GPC (THF). 

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