Development of base-dopable polymers

A series of new well-defined acidic poly(2,7-fluorene) derivatives have been synthesized by palladium-catalyzed Suzuki couplings. Upon deprotonation (i.e. base-doping), these conjugated polymers generate stable polymeric anions counter-balanced by alkali metal cations. The resulting polymeric salts exhibit interesting electronic and/or ionic conducting properties. For instance, base-doped poly-2,7′-((4-hexylphenyl) 9,9-dioctyl-2′,7-bifluorene-9′-carbonyl) exhibits an electrical conductivity of 10−2 – 10−3 S/cm while poly-2,7′-((4-hexylphenyl) 9-isobutylidene-2′,7-bifluorene-9-carbonyl) shows an electrical conductivity up to 10−1 S/cm in air, at room temperature. In the latter case, the high electrical conductivity is related to the good stability of the formed anions but also to the fact that all side chains are parallel to the plane of the polyfluorene backbone, leading to a more efficient interchain electrical transport. These attractive electrical properties confirm the great potential of these novel acidic fluorene-based π-conjugated polymers for various devices.