Precise synthesis of α,ω-chain-end-functionalized poly(dimethylsiloxane) with bromoaryl groups for incorporation in naphthalene-diimide-based N-type semiconducting polymers

Abstract

To date, poly(dimethylsiloxane) (PDMS)-based materials have been developed to utilize their unique properties, such as backbone flexibility and good solubility in organic solvents, in many applications. In the present study, we successfully synthesized multiblock copolymers consisting of PDMS, naphthalene-diimide (NDI), and bithiophene units by statistical terpolymerization. First, α,ω-chain-end-functionalized PDMS with 4-bromophenyl groups (BrPh-PDMS-PhBr) was obtained by metal-free controlled ring-opening polymerization of cyclotrisiloxane using a strong organo-base catalyst, followed by an end-capping reaction with (4-bromophenyl)chlorodimethylsilane. BrPh-PDMS-PhBr was found to be a key material in the statistical terpolymerization of BrPh-PDMS-PhBr, NDI, and bithiophene monomers based on the Migita-Kosugi-Stille coupling reaction. Indeed, three PDMS-containing multiblock copolymers were successfully synthesized with different PDMS compositions of 10, 16, and 36 wt%. In practice, the multiblock copolymer with 10 wt% PDMS content showed a typical n-type semiconducting character (μe = 1.5 × 10−3 cm2 V−1 s−1), according to the results of organic field-effect transistor (OFET) fabrication and evaluation, despite the incorporation of insulating PDMS segments along the π-conjugated main chains.