Poly(arylene vinylene) Synthesis via a Precursor Step-Growth Polymerization Route Involving the Ramberg-Backlund Reaction as a Key Post-Chemical Modification Step

The synthesis of conjugated copolymers based on poly(fluorene vinylene) [PFV] and poly(fluorene vinylene-co-carbazole vinylene) [PFVCV] was achieved via a previously unexplored precursor three-step synthetic route involving the RambergBacklund reaction. The resulting pi-conjugated (co)polymers proved highly soluble in common organic solvents, such as DCM, THF, or CHCl3. The solution step-growth polymerization between 2,7-bis(bromomethyl)-9,9'-dihexyl-9H-fluorene [F-Br] and 2,7-bis(mercaptomethyl)-9,9'-dihexyl-9H-fluorene [F-SH] was carried out under basic conditions at 100 degrees C in a mixture of MeOH and THF. The resulting polysulfides were then subjected to an oxidation reaction using m-CPBA, which was followed by the RambergBacklund reaction in the presence of CF2Br(2)/Al2O3-KOH, thus achieving the desired PFV. Similarly, PFVCV could be synthesized through the same three-step sequence employing, in this case, 2,7-bis(mercaptomethyl)-9-(tridecan-7-yl)-9H-carbazole (C-SH) and F-Br. Conjugated polymers with apparent molecular weights up to 15 kg mol(-1) and exhibiting promising optical features were obtained following this convenient synthetic strategy.