End-functionalized π-conjugated polymers are highly desirable for the creation of multifunctional polymers or hybrid materials such as donor–acceptor diblock copolymers and surface-modified inorganic materials for organic photovoltaics. In order to prepare polymer chains bearing one or two end-functionalized groups, the following four approaches can be envisaged: (i) post-functionalization of a purified polymer; (ii) use of a functionalized initiator agent; (iii) termination reaction with functionalized quenching reagent using the same metal catalyst as the polymerization; and (iv) combination of initiator and quenching reagents (combining approaches (ii) and (iii)). The advantage of the first approach (i) is the selective functionalization of either the α- or ω-end, as well as both ends. However, there are some drawbacks with approach (i) in that two separate reactions for polymerization and end-functionalization are required. Also, in some cases, post-modification requires low-temperature conditions involving lithiation procedures, which can promote the aggregation of π-conjugated polymers in the reaction solution. Approaches (ii) and (iii) are effective for introducing one end-group on the polymer in a one-pot reaction. In comparison with the aforementioned approaches, approach (iv) has been relatively less investigated. In almost every approach mentioned above, C–C bond formation was used for end-functionalization. Reports concerning carbon-heteroatom end-functionalization are very limited and, to our knowledge, only C–P and C–Sn bond formation to produce end-functionalized poly(3-hexylthiophenes) (P3HTs) have been reported where approach (i) was used.
Amines are an end-group of interested, because amines are already been shown to ligate to desired nanoparticles for photovoltaic use. An amine is also desirable because it can be reacted to result in other functional groups of interest, such as alcohols and halogens. Amines also open the opportunity to react with biologically relevant substrates. When using the Kumada catalyst transfer polymerization (KCTP) for the controlled synthesis of P3HT, it is believed that the σ-aryl Ni complex remains on the growing end of the π-conjugated polymer. Thus, we hypothesized that we could introduce a C–N bond on the end of π-conjugated polymers in situ using a one-pot reaction by employing a combination of KCTP and a recently developed Ni-catalyzed C–N bond forming reaction.