Expanding the Scope of Functional Group Tolerance in Direct Arylation Polymerization (DArP)

The synthesis of conjugated polymers via most traditional cross-coupling routes induces strict limitations on the monomer functionality subject to the strongly basic conditions typically used for installation of transmetallation groups. While direct arylation polymerization (DArP) alleviates the need for such steps, functionality that is polar, acidic, or strongly hydrogen bonding is subject to side reactions in the polymerization. Previous investigations of DArP with monomers bearing secondary amides at high temperatures revealed that these reactions can lead to defects and side reactions. In an effort to broaden the scope of monomer functionality compatible with DArP, this study reports a structure–reactivity investigation based on copolymers of 3,4-ethylenedioxythiophene and 9,9-dioctylfluorene bearing either alcohols, secondary amides, or diamidopyrimidine, to form poly(hydroxymethyl-EDOT fluorene) (PHMEDOTF), poly(amide-EDOT fluorene) (PAMEDOTF), and poly(diamidopyrimidine-EDOT fluorene) (PEDOT-DAPF), at 100 °C, 40 °C, and room temperature. At elevated temperatures, polymers were synthesized with molar masses up to 40.4, 30.1, and 19.6 kg/mol, respectively, and at room temperature, molar masses up to 26.3, 14.9, and 29.9 kg/mol were observed. The effect of the base used in the polymerizations was found to be critical, as PHMEDOTF showed improved reactivity when K2CO3 was used, even at room temperature. The previously observed defects in secondary amides caused by Cs2CO3 were prevented by employing low reaction temperatures. These developments allow for improvement in the accessibility of more functionally diverse conjugated polymers.