Fluorescent "barcode" multiblock co-micelles via the living self-assembly of di- and triblock copolymers with a crystalline core-forming metalloblock

J Am Chem Soc. 2011 Jun 15;133(23):9095-103. doi: 10.1021/ja202662u. Epub 2011 May 20.

Abstract

We describe the self-assembly in 2-propanol (2-PrOH) of the triblock copolymer, poly(ferrocenyldimethylsilane-b-2-vinylpyridine-b-2,5-di(2'-ethylhexyloxy)-1,4-phenylvinylene) (PFS(30)-b-P2VP(300)-b-PDEHPV(13), the subscripts refer to the degree of polymerization). The intense fluorescence of the PDEHPV moieties rendered the resulting cylindrical micelles and their aggregates visible in solution by laser confocal fluorescence microscopy (LCFM). Sonication yielded micelle fragments that could be grown into elongated fiber-like micelles 10 nm in width and nearly monodisperse in length by adding additional block polymer as a solution in tetrahydrofuran. The presence of the conjugated block in the corona promoted slow aggregation of the micelles into hierarchical flower-like structures, but this secondary assembly could be reversed by warming the solution to 50 °C for 30 min. When a solution of 500 nm long micelles of PFS(30)-b-P2VP(300)-b-PDEHPV(13) in 2-PrOH was treated sequentially with controlled amounts of the diblock copolymer PFS(30)-b-P2VP(300), and in intervals of 24 h, with additional aliquots of PFS(30)-b-P2VP(300)-b-PDEHPV(13), PFS(30)-b-P2VP(30), and PFS(30)-b-P2VP(300)-b- PDEHPV(13), uniform rod-like multiblock co-micelles were obtained with remarkable optical properties: a banded light-emitting "barcode" structure with fluorescent segments of the triblock copolymer separated by nonemissive segments made up of the diblock copolymer.