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Myongsoo Lee

Publications and source records attributed to Myongsoo Lee.

At least 19 recordsLinked to original sources
PubMed2006

Nanorings from the self-assembly of amphiphilic molecular dumbbells.

We have prepared amphiphilic dumbbell molecules consisting of hydrophobic alkyl chains and hydrophilic oligoether dendrons at each end of the rod segment. The molecular dumbbells, in aqueous solution, self-assemble into toroids as an intermediate nanostructure between spherical and long cylindrical micelles. The formation of toroidal structure is likely to originate from side by side connections of discrete bundles through the combination of strong hydrophobic interactions and anisotropic aggregation of rod segments.

Journal Article↗
PubMed2006

Tubular organization with coiled ribbon from amphiphilic rigid-flexible macrocycle.

We have synthesized an amphiphilic rigid-flexible macrocycle (fcoil = 0.68) consisting of hexa-p-phenylene and aliphatic polyether chain. The macrocyclic molecule in bulk state self-organizes into a 2-D body-centered rectangular structure (a = 4.3 nm and b = 6.3 nm). In aqueous solution, the macrocycle self-assembles into well-defined ribbonlike aggregates with a rod tilt relative to the ribbon normal at the initial stage. These elementary fibrils are further coiled to form a tubular structure consisting of coiled ribbons with a uniform diameter of about 20 nm and a regular pitch of 4.7 nm, as confirmed by TEM experiments. The internal diameter and the wall thickness of the nanotube are measured to be 14 and 3 nm, respectively.

Biomimetic Materials↗
PubMed2006

Assembling of dense fluorescent supramolecular webs via self-propelled star-shaped aggregates.

We report a novel mechanism of assembly of dendronized rod molecules into a dense supramolecular fluorescencent web featuring self-propelled mechanistic inward motion of star-shaped aggregates within a solution droplet. We suggest that such a motion (observed in real time) is caused by the self-repulsion of the growing star-shaped nuclei from the liquid-solid-air interface in the course of one-dimensional growth of the anchored arms. An intriguing mechanism discovered here involves microscopic (hundred micrometers) directional motion of the microscopic aggregates driven by one-dimensional molecular assembly, which opens a new venue for guided assembly of dense mesoscopic supramolecular webs. Such assemblies can serve as interesting microfluidic networks, a web of optical switches, and model systems for studying intercellular communication.

Journal Article↗
PubMed2005

Controlled self-assembly of carbohydrate conjugate rod-coil amphiphiles for supramolecular multivalent ligands.

Carbohydrate conjugate rod-coil amphiphiles were synthesized and their self-assembling behavior in aqueous solution was investigated. These amphiphiles were observed to self-assemble into supramolecular structures that differ significantly depending on the molecular architecture. The rod-coil amphiphiles based on a short coil (1) self-assemble into a vesicular structure, while the amphiphiles with a long coil (2) show a spherical micellar structure. In contrast, 3, based on a twin-rod segment, was observed to aggregate into cylindrical micelles with twice the diameter of molecular length scale. As a means to determine the binding activity to protein receptors of these supramolecular objects, hemagglutination inhibition assay was performed. The experiments showed that the supramolecular architecture has a significant effect on the binding activity. In addition, incubation experiments with Escherichia coli showed that mannose-coated objects specifically bind to the bacterial pili of the ORN 178 strain. These results demonstrate that precise control of the nano-objects in shape and size by molecular design can provide control of the biological activities of the supramolecular materials.

Animals↗
PubMed2005

Supramolecular reactor in an aqueous environment: aromatic cross Suzuki coupling reaction at room temperature.

[reaction: see text] We have investigated supramolecular reactors for the Suzuki coupling reactions of aryl halides with phenyl boronic acids by using self-assembly of amphiphilic rod-coil molecules in aqueous solution at room temperature. All the rod-coil molecules synthesized in this work showed to self-assemble into discrete micelles consisting of aromatic rod bundles encapsulated by hydrophilic poly(ethylene oxide) coils. We present a comparative study of rod-coil molecules' efficiency as supramolecular reactors for Suzuki coupling reaction. The closed-packed aromatic bundles play an efficient role in supramolecular reactors for the coupling reactions at room temperature. The supramolecular reactor based on hexa-p-phenylene confers unprecedented activity, allowing reactions to be performed at very low catalyst levels, without conventional heating or microwave.

Anisoles↗
PubMed2005

Transformation of isotropic fluid to nematic gel triggered by dynamic bridging of supramolecular nanocylinders.

We have synthesized an amphiphilic triblock coil-rod-coil molecule consisting of a rigid aromatic building block and poly(ethylene oxide). The coil-rod-coil molecule was observed to assemble into a cylindrical micelle structure in aqueous solution. Notably, addition of a small amount of a rod-coil-rod molecule into the cylindrical micellar solution can induce the anisotropic gelation due to dynamic interconnection of adjacent cylindrical micelles via hydrophobic and pi-pi interactions. Depending on the concentration of the rod-coil-rod molecule, the nematic gel can be reversibly switched into an isotropic solution of cylindrical micelles.

Benzene Derivatives↗
PubMed2005

Helical nanofibers from aqueous self-assembly of an oligo(p-phenylene)-based molecular dumbbell.

We have synthesized an amphiphilic dumbbell-shaped molecule consisting of dodeca-p-phenylene and aliphatic polyether dendrons as flexible end groups. The molecular dumbbell in aqueous solution self-assembles into well-defined left-handed helical cylinders with a diameter (8 nm) of a molecular length scale and a pitch length of 5.6 nm, as confirmed by TEM. These elementary helical fibrils are further assembled to give left-handed superhelical fibers with lengths up to several micrometers. Such a well-defined helical arrangement of conjugated rod building blocks may provide a new strategy for the design of one-dimensional nanostructured materials with biomimetic, electronic, and photonic functions.

Journal Article↗
PubMed2005

Amphiphilic treelike rods at interfaces: layered stems and circular aggregation.

Amphiphilic dendron-rod molecules with three hydrophilic poly(ethylene oxide) (PEO) branches attached to a hydrophobic octa-p-phenylene rod stem were investigated for their ability to form two-dimensional micellar structures on a solid surface. A treelike shape of the molecules was reported to be a major factor in the formation of nonplanar micellar structures in solution and in the bulk state (cylindrical and spherical). We observed that in these treelike amphiphilic molecules the hydrophilic terminated dendron branches assemble themselves in surface monolayers with the formation of two-dimensional layered or circular micellar structures. We suggested the formation of the planar ribbon-like structures with interdigitated layering within the loosely packed monolayers and circular, ringlike structures (2D circular aggregates) in the precollapsed state.

Journal Article↗
PubMed2005

Supramolecular barrels from amphiphilic rigid-flexible macrocycles.

Precise control of supramolecular objects requires the rational design of molecular components, because the information determining their specific assembly should be encoded in their molecular architecture. In this context, diverse self-assembling molecules including liquid crystals, dendrimers, block copolymers, hydrogen-bonded complexes and rigid macrocycles are being created as a means of manipulating supramolecular structure. Incorporation of a stiff rod-like building block into an amphiphilic molecular architecture leads to another class of self-assembling molecules. Aggregation of rod building blocks can generate various nanoscale objects including bundles, ribbons, tubules and vesicles, depending on the molecular structure and/or the presence of a selective solvent. We present here an unusual example of supramolecular barrels in the solid and in aqueous solution, based on the self-assembly of amphiphilic rigid-flexible macrocycles driven by non-covalent interactions. Preliminary experiments show that these amphiphilic macrocycles are membrane-active. The amphiphilic macrocycles might thus lead to an excellent model system for exploring biological processes in supramolecular materials.

Journal Article↗