Fluorescent “Barcode” Multiblock Co-Micelles via the Living Self-Assembly of Di- and Triblock Copolymers with a Crystalline Core-Forming Metalloblock

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.

Colour-tunable fluorescent multiblock micelles

“…It is thus possible to illuminate each colour individually, all three simultaneously, or any combination of two colours along the nanostructures. Although several reports have described the preparation of cylindrical nanostructures with segregated fluorescent regions 12,14,39 , this represents the first example of such structures where full control over the length, number and emission colour of the fluorescent regions can be achieved. Although a wide range of nanoscale morphologies are accessible through BCP self-assembly, relatively few examples exist of methods for the preparation of non-centrosymmetric, non-spherical structures 40,41 .…”

“…Such materials are increasingly sought after as a method for invisibly identifying valuable objects or conveying sensitive information, and several examples of on/off nanoscale barcodes capable of binary encoding have been described 14,21,22,44 . Here, however, the ability to control the number of micelle blocks as well as fully tune the colour of each block allows for the preparation of nanomaterials with more complex patterns as well as vastly increased data density.…”

“…In particular, emerging strategies based on the self-assembly of block copolymers (BCPs) have enabled the construction of objects with multiple domains physically segregated on the nanoscale, making it possible to design multifunctional structures with a high degree of spatial control 8,9 . Such methods have enabled the synthesis of functional nanoscale materials of increasing complexity, including photonic crystals 10 , dispersants 11 , polymer vesicles 12,13 , monochromatic barcodes 14 and therapeutic nanoconstructs 15 .…”

Self-assembly concepts for multicompartment nanostructures

“…Functional groups copolymerized into the corona or attached in polymer analogue reactions may range from coordination sites for metal ions or nanoparticles, 334,335 reversible cross-linking sites 336 or optically active moieties. 337,338,52 The latter was demonstrated by attachment of light-emitting fluorophores to the corona bock followed by co-crystallization of various emitter sequences with exceptional precision regarding the location. In one example, poly(ferrocenyl dimethylsilane)-block-poly(2-vinylpyridine) (PFDMS-b-P2VP) diblock copolymers were fluorescently labeled by chain extension with oligomeric 2,5-di-(2´ethylhexyloxy)-1,4-phenylvinylene giving a labeled and unlabeled version of otherwise fully compatible block copolymers for consecutive epitaxial growth.…”

Understanding the CDSA of poly(lactide) containing triblock copolymers

“…[15][16][17][18] The size and morphology of the assemblies can be precisely adjusted with the instruction of a seed-growth methodology. [19][20][21][22] Various functional groups have also been incorporated, including fluorescent marking, 23 metal nanoparticle incorporation 24 and photo-responsibility, 25 demonstrating a diverse range of potential uses within drug delivery processes. 26 As a semi-crystalline polymer, PLLA is renowned for its outstanding biocompatibility and biodegradability, which allows use in bio-relevant applications.…”