Extending the Scope of “Living” Crystallization-Driven Self-Assembly: Well-Defined 1D Micelles and Block Comicelles from Crystallizable Polycarbonate Block Copolymers

Abstract

Fiber-like block copolymer (BCP) micelles offer considerable potential for a variety of applications, however, uniform samples of controlled length and with spatially tailored chemistry have not been accessible. Recently, a seeded growth method, termed 'living' crystallization-driven self-assembly (CDSA), has been developed to allow the formation of 1D micelles and block comicelles of precisely controlled dimensions from BCPs with a crystallizable segment. An expansion of the range of core forming blocks that participate in living CDSA is necessary for this technique to be compatible with a broad range of applications. Few examples currently exist of well-defined, water-dispersible BCP micelles prepared using this approach, especially from biocompatible and biodegradable polymers. Herein, we demonstrate that BCPs containing a crystallizable polycarbonate, poly(spiro[fluorene-9,5'-[1,3]dioxin]-2'-one) (PFTMC), can readily undergo living CDSA processes. PFTMC-b-poly(ethylene glycol) (PEG) BCPs with PFTMC:PEG block ratios of 1:11 and 1:25 were shown to undergo living CDSA to form near monodisperse fiber like micelles of precisely controlled lengths of up to ~1.6 m. Detailed structural characterization of these micelles by TEM, AFM, SAXS and WAXS, revealed that they comprise a crystalline, chain folded PFTMC core with a rectangular cross-section that is surrounded by a solvent swollen PEG corona. PFTMC-b-PEG fiber-like micelles were shown to be dispersible in water to give colloidally stable solutions. This allowed an assessment of the toxicity of these structures towards WI-38 and HeLa cells. From these experiments, we observed no discernable cytotoxicity from a sample of 119 nm fiber-like micelles to either the healthy (WI-38) or cancerous (HeLa) cell types. The living CDSA process was extended to PFTMC-b-poly(2-vinylpyridine) (P2VP), and addition of this BCP to PFTMC-b-PEG seed micelles led to the formation of well-defined segmented fibers with spatially localized coronal chemistries.

Elucidating the Ordering in Self-Assembled Glycocalyx Mimicking Supramolecular Copolymers in Water

“…23,24 Oppositely charged polypeptide supramolecular monomers were demonstrated by Besenius and co-workers to copolymerize into fibrous structures at neutral pH, whereas they disassembled at low and high pH. 25…”

Cellular uptake and targeting of low dispersity, dual emissive, segmented block copolymer nanofibers

“…Further addition of unimer to the seed micelles leads to epitaxial growth and low dispersity micelles with a length controlled by the unimer to seed ratio in a manner analogous to a living covalent polymerization of molecular monomers. 37 This process is uniquely suited towards the generation of nanoparticles that are otherwise hard to access, such as uniform 1D nanobers, [38][39][40][41][42][43][44] (and also 2D platelets) 45,46,48 as well as more complex assemblies. 50 For example, 'living' CDSA can also be used to generate hierarchical nanomaterials, such as segmented nanobers with spatially-dened functionalizable regions, 36,38,39,[49][50][51][52] as well as random-and gradient comicelles by the sequential or simultaneous seeded growth of different block copolymers with distinct coronal chemistries.…”

Rapid formation and real-time observation of micron-sized conjugated nanofibers with tunable lengths and widths in 20 minutes by living crystallization-driven self-assembly

“…Many uniform nanostructures have been created using various amphiphilic block copolymers (BCPs) with differing solubilities. [18][19][20] More recently, pioneered by Ian Manners group, an ingenious method termed Crystallization-Driven Self-Assembly (CDSA) was developed. The CDSA method enables the control of the nanostructure with excellent precision.…”