Electrochemical Postfunctionalization of Thiophene–Fluorene Alternating Copolymers via Anodic C–H Phosphonylation

Abstract

Phosphonylated polymers are attractive materials due to their applications in chemical sensors and their unique electronic properties. Because of its mild reaction conditions and simple protocol, anodic phosphonylation is a favorable strategy for introducing phosphonate into the main chains of π-conjugated polymers. However, the precursor polymer for the reaction remains limited to poly(3-hexylthiophene), and in addition, the degree of substitution is still low. Here, we demonstrated the anodic phosphonylation of thiophene−fluorene alternating copolymers (P(Fl-Th)) using triethyl phosphite as a phosphonate source. The reaction proceeded efficiently in the presence of 2,6-lutidine, and the phosphonate was selectively introduced into the electron-rich thiophene moiety. The optoelectronic properties of the phosphonylated polymer were gradually varied by tuning the degree of substitution. Interestingly, various trialkyl phosphites, such as P(O n Bu) 3 , P(O i Pr) 3 , and P(OC 2 H 4 Cl) 3 , were suitable for the anodic phosphonylation. We also found that the phosphonate groups could be introduced into the fluorene moieties through the design of appropriate precursor polymers. Furthermore, constantpotential anodic phosphonylation instead of the constant-current method led to quantitative functionalization.