Varying Anionic Functional Group Density in Sulfonate-Functionalized Polyfluorenes by a One-Phase Suzuki Polycondensation

Abstract

A series of anionically functionalized polyfluorene-based conjugated polyelectrolytes were synthesized by the Suzuki polycondensation of the boronic ester 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-di(1-(2-(2-methoxyethoxy)ethoxy)ethyl)fluorene with the ionic and nonionic dihalides 2,7-dibromo-9,9-di(6-sodium sulfonate-hexyl)fluorene and 2,7-dibromo-9,9-di(1-(2-(2-methoxyethoxy)ethoxy)ethyl)fluorene. The latter monomer served as a diluent to control the ionic functional group density. The use of the triethylene glycol monomethyl ether derivatives made possible a one-phase polycondensation in a THF/methanol/Na2CO3(aq) mixture using Pd(PPh3)4. The one-phase nature of the polymerization was essential to balancing the reactivity of the dihalides so that they were both incorporated into the same polymer and so that the polymer composition became dictated by the monomer feedstock composition. In closely related two-phase reactions, a mixture of polymers, one ionic and one nonionic, was isolated wi...