Cationic Polyfluorene-<i>b</i>-Neutral Polyfluorene “Rod–Rod” Diblock Copolymers

Abstract

All-conjugated “rod–rod” diblock copolymers are an emerging class of polymeric materials of considerable interest for applications in chemical and biological sensors or as components for optoelectronic devices. Here, we report a novel cationic diblock copolymer containing a neutral polyalkylfluorene block covalently bound to a polar polyfluorene counterpart—poly[9,9-bis(6-trimethylammoniumhexyl)-2,7-fluorene]-b-poly(3-hexyl-2,5-thiophene) (PF6NBr-b-PF8)—which was synthesized in a sequential Suzuki–Miyaura polymerization and was made ionic with trimethylamine in a subsequent quaternization step. The optical properties of this material were investigated by UV/vis and photoluminescence spectroscopies in three different solvents: methanol, THF and THF/methanol 1:1. Atomic force microscopic (AFM) imaging experiments provided evidence for solvent-induced aggregation. The formation of vesicles and spherical particles is observed in layers from THF and methanolic solution.