56 research outputs found
Multidimensional hierarchical self-assembly of amphiphilic cylindrical block comicelles
Cylindrical polymer micelles pack in 3D
When you control chemistry, solvents, temperature, and concentration, surfactants and block copolymers will readily assemble into micelles, rods, and other structures. Qiu
et al.
take this to new lengths through precise selection of longer polymer blocks that self-assemble through a crystallization process (see the Perspective by Lee
et al.
). They chose polymer blocks that were either hydrophobic or polar and used miscible solvents that were each ideal for only one of the blocks. Their triblock comicelles generated a wide variety of stable three-dimensional superstructures through side-by-side stacking and end-to-end intermicellar association.
Science
, this issue p.
1329
; see also p.
1310
</jats:p
Uniform patchy and hollow rectangular platelet micelles from crystallizable polymer blends
Growing patterned rectangular objects
The growth of patterned objects usually requires a template to aid the positioning of multiple materials. Qiu
et al.
used the seeded growth of a crystallizable block copolymer and a homopolymer to produce highly uniform rectangular structures (see the Perspective by Ballauff). Chemical etching, or dissolution, of uncross-linked regions of the rectangular structures produced perforated platelet micelles. The sequential addition of different blends and cross-linking/dissolution strategies allowed the formation of well-defined hollow rectangular micelles, which can be functionalized in a variety of ways.
Science
, this issue p.
697
; see also p.
656
</jats:p
Hierarchical Self-Assembly of Toroidal Micelles into Multidimensional Nanoporous Superstructures
Materials
with controlled porosity play a prominent role in industrial
and domestic applications. Although a rich array of methods has been
developed to tune the pore size over a broad range (from <1 nm
to >1 ÎĽm), the fabrication of functional materials with a
fully
open porous structure with sub-100 nm pore size has remained a significant
challenge. Herein, we report the hierarchical assembly of block copolymer
toroidal micelles with an intrinsic cavity into multidimensional nanoporous
superstructures (pore size 85–90 nm) by modulation of interparticle
interactions. The toroids aggregate into oligo-supermicelles or 2D
hexagonal arrays through van der Waals interactions upon drying on
a substrate, while synergistic hydrogen bonding interactions further
promote the formation of 3D nanoporous superstructures directly in
solution. Thus, toroidal micelles can be manipulated as a type of
distinctive building block to construct nanoporous materials
Transformation and patterning of supermicelles using dynamic holographic assembly
Although the solution self-assembly of block copolymers has enabled the fabrication of a broad range of complex, functional nanostructures, their precise manipulation and patterning remain a key challenge. Here we demonstrate that spherical and linear supermicelles, supramolecular structures held together by non-covalent solvophobic and coordination interactions and formed by the hierarchical self-assembly of block copolymer micelle and block comicelle precursors, can be manipulated, transformed and patterned with mediation by dynamic holographic assembly (optical tweezers). This allows the creation of new and stable soft-matter superstructures far from equilibrium. For example, individual spherical supermicelles can be optically held in close proximity and photocrosslinked through controlled coronal chemistry to generate linear oligomeric arrays. The use of optical tweezers also enables the directed deposition and immobilization of supermicelles on surfaces, allowing the precise creation of arrays of soft-matter nano-objects with potentially diverse functionality and a range of applications
Uniform Toroidal Micelles via the Solution Self-Assembly of Block Copolymer-Homopolymer Blends Using a "frustrated Crystallization" Approach
Toroidal
nanostructures are of growing importance due to their
unique geometry and potential utility in materials fabrication. Although
a variety of amphiphilic block copolymers has been shown to self-assemble
into toroidal micelles, the conventional methods used are often very
slow with little control over the size of the resulting nanostructures.
Here, we report a rapid and efficient synthetic route to prepare toroidal
micelles of near uniform diameter through the cooperative coassembly
of amorphous blends of polyferrocenylsilane block copolymer and homopolymer,
where the degree of polymerization of the core-forming metalloblock
in the former is greater than for the latter. The self-assembly process
is accomplished within a few minutes, and the ring size of the toroids
can be varied between 30 and 90 nm by adjusting the mass ratio of
the block copolymer and homopolymer. The kinetic stability of the
resulting toroidal micelles can be enhanced by frustrating core crystallization
through solvent modulation and the toroids can also be readily used
as templates to fabricate circular arrays of metal nanoparticles
Chiral Transmission to Cationic Polycobaltocenes over Multiple Length Scales Using Anionic Surfactants
International audienceChiral polymers are ubiquitous in nature, and the self-assembly of chiral materials is a field of widespread interest. In this paper, we describe the formation of chiral metallopolymers based on poly(cobaltoceniumethylene) ([PCE] ), which have been prepared through oxidation of poly(cobaltocenylethylene) (PCE) in the presence of enantiopure N-acyl-amino-acid-derived anionic surfactants, such as N-palmitoyl-l-alanine (C-l-Ala) and N-palmitoyl-d-alanine (C-d-Ala). It is postulated that the resulting metallopolymer complexes [PCE][C-l/d-Ala] contain close ionic contacts, and exhibit chirality through the axially chiral ethylenic CH-CH bridges, leading to interaction of the chromophoric [CoCp] units through chiral space. The steric influence of the long palmitoyl (C) surfactant tail is key for the transmission of chirality to the polymer, and results in a brushlike amphiphilic macromolecular structure that also affords solubility in polar organic solvents (e.g., EtOH, THF). Upon dialysis of these solutions into water, the hydrophobic palmitoyl surfactant substituents aggregate and the complex assembles into superhelical ribbons with identifiable "handedness", indicating the transmission of chirality from the molecular surfactant to the micrometer length scale, via the macromolecular complex
DNA-induced circularly polarized luminescence of helicene racemates
International audienceEnantiopure helicenes have been extensively investigated due to their outstanding chiroptical properties, while helicene racemates are considered as chiroptically silent. Here, we describe a facile method to produce circularly polarized luminescence (CPL) from helicene racemates via supramolecular association with DNA in aqueous solution. Racemic cationic helicene derivatives are immobilized in the grooves of commercially available double-stranded right-handed DNA, and the discrimination of left- and right-handed helicenes by chiral DNA is monitored by single molecule force spectroscopy. This subsequently leads to the generation of prominent CPL with dissymmetric factor |g(lum)| of close to 0.01, which is approximate to enantiopure helicenes. The strategy developed in this work avoids the tedious and expensive chiral resolution process and provides a distinctive insight into the fabrication of CPL-emitting systems
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