Synthesis and self-assembly of fluorescent micelles from poly(ferrocenyldimethylsilane-b-2- vinylpyridine-b-2,5-di(2′- ethylhexyloxy)-1,4-phenylvinylene) triblock copolymer

A fluorescent ABC triblock copolymer containing poly(ferrocenyldimethylsilane) (PFS) and poly(2-vinylpyridine) (P2VP) moieties in the segments was synthesized via living anionic polymerization followed by quenching the living chains using a π-conjugated poly(2,5-di(2′- ethylhexyloxy)-l,4-phenylvinylene aldehyde (PDEHPV-CHO) homopolymer. The resulting triblock copolymer poly(ferrocenyldimethylsilane-b-2-vinylpyridine-b- 2,5-di(2′-ethylhexyloxy)-l,4-phenylvinylene) (PFS-b-P2VP-b-PDEHPV) underwent self-assembly in 2-propanol to form cylindrical micelles. 2-Propanol is a good solvent for P2VP, a modest solvent for PDEHPV, and a poor solvent for PFS. The cylindrical shape of the micelles is likely related to the semicrystalline nature of the PFS in the core. The PDEHPV block showed strong green-yellow fluorescence both for polymers dissolved as discrete molecules in tetrahydrofuran (THF), a good solvent for all three components, and as micelles in 2-propanol. The fluorescence quantum yields were 56% for the triblock copolymer in THF and ca. 17% for the micelles in 2-propanol. Because ferrocene units are powerful fluorescence quenching entities, we surmise that in both cases, the P2VP block acts as a spacer to minimize the quenching of PDEHPV fluorescence by the PFS block. Taking advantage of the fluorescence of the PDEHPV block, we were able to obtain images of the block copolymer micelles and their flower-like aggregates in 2-propanol solution by laser confocal fluorescence microscopy.