Supramolecular nanostructures from self-assembly of T-shaped rod building block oligomers

Supramolecular polymers based on host-guest interactions for the construction of artificial light-harvesting systems

In the present work, artificial light-harvesting systems with a fluorescence resonance energy transfer (FRET) process were successfully obtained in the aqueous solution. We designed and synthesized an amphiphilic pyrene derivative with two 4-vinylpyridium arms (Pmvb), which can interact with cucurbit[8]uril (CB[8]) to form supramolecular polymer through host-guest interactions in aqueous solution. The formation of supramolecular polymers results in a significant enhancement of fluorescence, which makes Pmvb-CB[8] an ideal energy donor to construct artificial light-harvesting systems in the aqueous solution. Subsequently, two different fluorescence dyes Rhodamine B (RhB) and Sulforhodamine 101 (SR101) were introduced as energy acceptors into the solution of Pmvb-CB[8] respectively, to fabricate two different artificial light-harvesting systems. The obtained artificial light-harvesting systems can achieve an efficient energy transfer process from Pmvb-CB[8] to RhB or SR101 with high energy transfer efficiency.

Supramolecular Two-Dimensional Systems and Their Biological Applications

Various biological systems rely on the supramolecular assembly of biomolecules through noncovalent bonds for performing sophisticated functions. In particular, cell membranes, which are 2D structures in biological systems, have various characteristics such as a large surface, flexibility, and molecule-recognition ability. Supramolecular 2D materials based on biological systems provide a novel perspective for the development of functional 2D materials. The physical and chemical properties of 2D structures, attributed to their large surface area, can enhance the sensitivity of the detection of target molecules, molecular loading, and bioconjugation efficiency, suggesting the potential utility of functional 2D materials as candidates for biological systems. Although several types of studies on supramolecular 2D materials have been reported, supramolecular biofunctional 2D materials have not been reviewed previously. In this regard, the current advances in 2D material development using molecular assembly are discussed with respect to the rational design of self-assembling aromatic amphiphiles, the formation of 2D structures, and the biological applications of functional 2D materials.

The relationship between molecular structure and supramolecular morphology in the self-assembly of rod-coil molecules with oligoether chains

Controlling the morphology of rod-coil molecular aggregates is crucial for studying and obtaining functional materials with exceptional properties. In this paper, we report the construction of rod-coil molecular nanoaggregates with well-defined structures. The rod-coil molecules, labeled 1a-1d, consist of a rod section, composed of phenyl and biphenyl groups, and oligoether chains with 7 and 12 repeating units. The final assembled structures showed either oblique or hexagonal columnar structures, depending on the length of the coils in the bulk state. Interestingly, in water, molecules 1a and 1c self-assemble into scrolled nanofibers and cylindrical micelles. Instead, molecules 1b and 1d, which have methyl groups decorated at the interface of the rod and coil sections, self-organize into helical nanofibers and nanorings, respectively. Thus, controlling the length of the coil chains and inserting lateral methyl groups is an effective strategy to construct precise rod-coil molecular assemblies in the bulk and in aqueous solution.

Self-assembly of amphiphilic aryl-squaramides in water driven by dipolar π–π interactions

Amphiphilic aryl-squaramides self-assemble via unprecedented dipolar π–π interactions forming well-defined supramolecular aggregates and self-consistent hydrogels in water

Morphological Control of Coil-Rod-Coil Molecules Containing m-Terphenyl Group: Construction of Helical Fibers and Helical Nanorings in Aqueous Solution

Rod-coil molecules, composed of rigid segments and flexible coil chains, have a strong intrinsic ability to self-assemble into diverse supramolecular nanostructures. Herein, we report the synthesis and the morphological control of a new series of amphiphilic coil-rod-coil molecular isomers 1-2 containing flexible oligoether chains. These molecules are comprised of m-terphenyl and biphenyl groups, along with triple bonds, and possess lateral methyl or butyl groups at the coil or rod segments. The results of this study suggest that the morphology of supramolecular aggregates is significantly influenced by the lateral alkyl groups and by the sequence of the rigid fragments in the bulk and in aqueous solution. The molecules with different coils self-assemble into lamellar or oblique columnar structures in the bulk state. In aqueous solution, molecule 1a, with a lack of lateral groups, self-assembled into large strips of sheets, whereas exquisite nanostructures of helical fibers were obtained from molecule 1b, which incorporated lateral methyl groups between the rod and coil segments. Interestingly, molecule 1c with lateral butyl and methyl groups exhibited a strong self-organizing capacity to form helical nanorings. Nanoribbons, helical fibers, and small nanorings were simultaneously formed from the 2a-2c, which are structural isomers of 1a, 1b, and 1c. Accurate control of these supramolecular nanostructures can be achieved by tuning the synergistic interactions of the noncovalent driving force with hydrophilic-hydrophobic interactions in aqueous solution.

Supramolecular helical nanostructures from self-assembly of coil-rod-coil amphiphilic molecules incorporating the dianthranide unit

Coil-rod-coil amphipathic oligomers composed of a rigid dianthranide unit and a hydrophilic branched oligoether as the coil segment were synthesized. These amphiphilic molecules self-assemble into clew-like aggregates composed of fibres or helical nanofibers in aqueous solution. Subsequently, supramolecular polymers were produced from the above objects through charge-transfer interactions by adding 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (4F-TCNQ). Interestingly, temperature-sensitive supramolecular chirality was induced by lateral methyl units located at the interface of the rigid and flexible segments. However, upon addition of the electron-acceptor molecule, 4F-TCNQ, strong donor-acceptor interactions restrict any change in supramolecular chirality with temperature.

Surface functionalized nanostructures via position registered supramolecular polymer assembly

Versatile control of cylindrical nanostructures formed by supramolecular assembly of end-functionalized polymer blends is demonstrated not only in their orientation over large areas but also in their surface chemical functionalities. Two binary blends consisting of supramolecular analogues of diblock copolymers with complementary end-sulfonated and aminated groups are investigated, viz., mono-end-functionalized polymers of (i) one-end-sulfonated polystyrene (SPS) and one-end-aminated poly(butadiene) (APBD) and (ii) one end-aminated polystyrene (APS) and one end-sulfonated poly(butadiene) (SPBD). The orientation of the cylinders with respect to the substrate surface depends on the solvent annealing time; either hexagonally ordered vertical cylinders or in-plane ones are readily obtained by controlling the solvent annealing time. Selective chemical etching of one of the polymers provides four different chemically modified nanostructures, viz., hexagonally ordered cylindrical holes and cylindrical posts with either sulfonate or amine surface functional groups. Additional supramolecular assembly is successfully achieved by solution coating either polymers or organic dyes that complementarily interact with the functional groups on the nanostructures. Furthermore, the supramolecularly assembled nanostructures are controlled by confining them to topographically pre-patterned Si substrates with pattern geometries of various shapes and sizes to produce globally ordered vertical or in-plane cylinders with chemical functionalities on their surfaces.

Construction of Supramolecular Nanostructures from V-Shaped Amphiphilic Rod-Coil Molecules Incorporating Phenazine Units

A series of bent-shaped molecules, consisting of dibenzo[a,c]phenazine and phenyl groups connected together as a rod segment, and poly(ethylene oxide) (PEO) with a degree of polymerization (DP) of 6 as the coil segment, were synthesized. The self-assembling behavior of these molecules by differential scanning calorimetry (DSC), thermal optical polarized microscopy (POM), small-angle X-ray scattering spectroscopy (SAXS), atomic force microscopy (AFM), and transmission electron microscopy (TEM), revealed that carboxyl or butoxy carbonyl groups at the 11 position of dibenzo[a,c]phenazine noticeably influence self-organization of molecules into supramolecular aggregates in bulk and aqueous solutions. Molecules 1 and 2 with chiral or non-chiral PEO coil chains and the carboxyl group at the rod segments self-organize into a hexagonal perforated lamellar structure and a hexagonal columnar structure in the solid state. In aqueous solution, molecules 1 and 2 self-assemble into diverse lengths of nanofibers, whereas molecules 3 and 4 with butoxy carbonyl groups exhibit a self-organizing capacity to form diverse sizes of spherical aggregates.

Donor-acceptor interaction-driven self-assembly of amphiphilic rod-coil molecules into supramolecular nanoassemblies

Rigid-flexible amphiphilic molecules consisting of an aromatic segment based on pyrene and biphenyl units and hydrophilic polyethylene oxide chains self-assemble into lamellar, hexagonal columnar, and two-dimensional columnar nanostructures in the bulk state. In aqueous solution, these molecules self-assemble into nanofibers, spherical micelles, and multilayer nanotubes, depending on the chain or rod length of the molecules. Notably, ordered nanostructures of supramolecular polymers, such as single-layer curving fragments, nanofibers, and nanosheets, were constructed through charge-transfer interactions between the nanoobjects and an electron-acceptor molecule, 2,4,5,7-tetranitrofluorenone. These experimental results reveal that diverse supramolecular morphologies can be controlled by tuning rod-coil molecular interactions or charge-transfer interactions between the donor and acceptor molecules.

Construction of Supramolecular Assemblies from Self-Organization of Amphiphilic Molecular Isomers

Amphiphilic coil-rod-coil molecules, incorporating flexible and rigid blocks, have a strong affinity to self-organize into various supramolecular aggregates in bulk and in aqueous solutions. In this paper, we report the self-assembling behavior of amphiphilic coil-rod-coil molecular isomers. These molecules consist of biphenyl and phenyl units connected by ether bonds as the rod segment, and poly(ethylene oxide) (PEO) with a degree of polymerization of 7 and 12 as the flexible chains. Their aggregation behavior was investigated by differential scanning calorimetry, thermal optical polarized microscopy, small-angle X-ray scattering spectroscopy, and transmission electron microscopy. The results imply that the molecular structure of the rod building block and the length of the PEO chains dramatically influence the creation of supramolecular aggregates in bulk and in aqueous solutions. In the bulk state, these molecules self-organize into a hexagonal perforated lamellar and an oblique columnar structure, respectively, depending on the sequence of the rod building block. In aqueous solution, the molecule with a linear rod segment self-assembles into sheet-like nanoribbons. In contrast, its isomer, with a rod building block substituted at the meta-position of the aryl group, self-organizes into nanofibers. This is achieved through the control of the non-covalent interactions of the rod building blocks.

Self-organizing p-quinquephenyl building blocks incorporating lateral hydroxyl and methoxyl groups into supramolecular nano-assemblies

The self-assembling behavior of coil-rod-coil molecules 1a, 1b, and 2a, 2b was investigated using DSC, POM, SAXS, and AFM in bulk and aqueous solutions. These molecules contain p-quinquephenyl groups as rod segments incorporating lateral hydroxyl or methoxyl groups in the center positions and oligo(ethylene oxide)s as the coil segments. Molecules 1a and 1b, with lateral methoxyl groups in the rod segments, self-assemble into oblique columnar structures in the crystalline phase and transform into nematic phases. On the other hand, molecules 2a and 2b, with hydroxyl groups in the center of their rod segments, self-organize into hexagonal perforated lamellar and oblique columnar nano-structures in the crystalline and liquid crystalline phase, respectively. In aqueous solutions, these molecules aggregate into nano-ribbons and vesicles, depending on their lateral groups and oligo(ethylene oxide) chain lengths. These results imply that the lateral methoxyl or hydroxyl groups, present in the center of the rod segments, significantly influence the formation of various supramolecular nano-structures in the bulk state and in aqueous solution. This is achieved via tuning of the non-covalent interactions of the rod building blocks.

Synthesis and self-assembly of amphiphilic bent-shaped molecules based on dibenzo[a,c]phenazine and poly(ethylene oxide) units

Rod–coil molecules consisting of a dibenzo[a,c]phenazine unit and different lengths of PEO coils were synthesized, and their self-assembling behavior in both bulk and aqueous solutions was investigated.

Liquid crystalline assembly of coil-rod-coil molecules with lateral methyl groups into 3-D hexagonal and tetragonal assemblies

In this paper, we report the synthesis and self-assembly behavior of coil-rod-coil molecules, consisting of three biphenyls linked through a vinylene unit as a conjugated rod segment and poly(ethylene oxide) (PEO) with a degree of polymerization (DP) of 7, 12 and 17, incorporating lateral methyl groups between the rod and coil segments as the coil segment. Self-organized investigation of these molecules by means of differential scanning calorimetry (DSC), thermal polarized optical microscopy (POM) and X-ray diffraction (XRD) reveals that the lateral methyl groups attached to the surface of rod and coil segments, dramatically influence the self-assembling behavior in the liquid-crystalline mesophase. Molecule 1 with a relatively short PEO coil length (DP = 7) self-assembles into rectangular and oblique 2-dimensional columnar assemblies, whereas molecules 2 and 3 with DP of 12 and 17 respectively, spontaneously self-organize into unusual 3-dimensional hexagonal close-packed or body-centered tetragonal assemblies.