Synthesis and characterizations
The synthesis of P3HTs with various regioregularities was performed by GRIM and oxidative polymerization methods. Table 1 shows the molecular weight distribution of the synthesized polymers. From the table, it is clear that P3HT synthesized by GRIM method have well defined molecular wt and narrow polydispersity.
This is because polymer chain growth in this route proceeds through selective oxidation of the propagating polymer end by the Ni complex catalyst [Ni(dppp)Cl2] .
In contrast, when FeCl3 is added to the monomer solution, the oxidation of the monomer is less selective which leads to the formation of less regioregularity and comparatively broad polydispersity (P3HT-70) polymers.
On the other hand, addition of monomer to FeCl3, results in the rapid non selective oxidation of monomers followed by fast and random polymerization reaction which in turn give rise to polymers with very low regioregularity and broad polydispersity (P3HT-58).
The percentage of regioregularity was estimated from 1H NMR .
The regioregularity of the P3HT obtained by GRIM method (P3HT-96), slow addition of FeCl3 to monomer (P3HT-70) and addition of monomer to FeCl3 (P3HT-58) is 96, 70 and 58% respectively.