Effect of the Nature and the Position of Defects on the Chiral Expression in Poly(3-alkylthiophene)s

Polymers produced with the most used controlled polymerization method with the simplest initiators, namely the Kumada catalyst transfer condensation polymerization (KCTCP) with Ni2+ salts, all have one regiodefect distributed along the polymer backbones. The irregularity created by these defects can be split up into three components, i.e., the nature of the defect, the position of the defect, and the additional inhomogeneity created by mixing polymers with the defect at different positions. In this research, the influence of these three parameters on the chiral expression of poly(3-alkylthiophene)s (P3ATs) is investigated separately for the first time. A series of chiral P3ATs with one tail-to-tail (TT) or head-to-head (HH) defect in different positions is synthesized by means of the Pd(RuPhos) protocol, and their chiral expression and that of their mixtures are studied via UV–vis and circular dichroism (CD) spectroscopy. For the polymers with an HH defect, it is found that the position at the very beginn...