Long Yi Jin

Synthesis and self-assembly of coil–rod–coil molecules with lateral methyl and ethyl groups in the center of the rod segment

Rod–coil molecules, consisting of a flexible and a rigid block, have a strong capacity to self-assemble into a variety of ordered nanostructures in the bulk state. In this paper, we report the synthesis and characterization of the self-assembly behavior of coil–rod–coil oligomers. These new materials consist of five biphenyls linked together with ether bonds as a rod segment and incorporate lateral methyl or ethyl groups in the center of the rod building block and poly(ethylene oxide) (PEO) with a degree of polymerization (DP) of 7, 12 and 17 coil segments. Structural investigation of these molecules by means of differential scanning calorimetry (DSC) and X-ray scattering (XRD) in the bulk state reveals that side chains, methyl and ethyl groups in the middle of the rod segment, dramatically influence the self assembly behavior in the liquid-crystalline phase. Molecules containing a lateral methyl group based on PEO coil chain (DP of 12 and 17) self-organize into a hexagonally perforated layer (HPL) structure in the liquid- crystalline phase, while the molecule with a lateral ethyl group based on PEO coil chain (DP of 7) self-assembles into a 2-D rectangular columnar liquid-crystal structure. On further increasing of the coil length of the molecule containing ethyl group, the molecules self-organize into a 1-D lamellar structure in the crystalline phase.

An ordered network polymer of bicontinuous cubic structure resulting from photo-polymerization of a coil-rod-coil molecule self-assembly

ConclusionsAn unusual strategy to generate an ordered network polymer from the self-assembly of reactive coil-rod-coil molecules was successfully achieved. The bicontinuous cubic structure of molecule4 was maintained by cross-linking the photo-polymerization self-assembly of4 in the liquid crystalline state. The result suggests that an approach to control a reactive supramolecular molecule structure and conversion to a polymer allows a novel, highly ordered 3-D nanostructural polymer to be produced.

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

Bent-shaped amphiphilic molecules 1–5, consisting of a dibenzo[a,c]phenazine unit and phenyl groups linked together as a rigid segment, and poly(ethylene oxide) (PEO) with a degree of polymerization (DP) of 6, 8 and 12 as flexible chains were synthesized and characterized. Their aggregation behavior was investigated using DSC, POM, SAXS, CD, TEM, and AFM in the bulk and aqueous solutions. Molecules 1–4 with various PEO coil chains self-organize into oblique columnar structures in the solid state. In aqueous solution, molecule 1 (with a DP of 6) self-assembles into spherical aggregates, whereas molecules 2, 3, and 5 (with coil chains longer than those of molecule 1) exhibit a self-organizing capacity to form cylindrical micelles or diverse lengths of fibers, depending on the PEO chain lengths. Interestingly, CD experiments, together with TEM investigations of molecules 4–5 incorporating lateral methyl groups at the interface of the rod and coil domains, showed that these molecules self-assemble into helical fibers. This indicates that lateral methyl groups lead to the formation of helical arrangement of the rod segments.

Ordered nanostructures from self-assembly of rod–coil oligomers with n-shaped rod and dendritic poly(ethylene oxide) coil segment

The n-shaped rod–coil molecules consisting of an anthracene unit and two biphenyl groups connected by acetylenyl bonds as a conjugated rod segment and dendritic poly(ethylene oxide)s with different cross-sectional areas were synthesised. These new molecular structures were characterised by using 1H NMR and MALDI-TOF-MS. The self-assembly of these molecules in the bulk state and in aqueous solution was investigated using differential scanning calorimetry, X-ray diffraction and transmission electron microscopy (TEM). In the bulk state, molecule 1a with a linear coil segment, self-organised into lamellar crystalline structures, whereas molecules 1b and 1c with di- and tetra-branched dendritic wedges did not solidify at room temperature. Dynamic light scattering and TEM experiments reveal that in aqueous solution, the molecules exhibit a strong tendency to organise into the thread-like fibres along the axial direction of cylindrical micelles or into the wide fibroid bundles via the aggregation of cylindrical micelles as the cross-sectional area of the dendritic coil segments increases.

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.

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.

Self-assembly of amphiphilic linear diblock rod-coil molecules by hydrogen bond and π-π stacking interactions

Aromatic amphiphilic molecules (1) consisting of three biphenyl groups linked together with ether bonds as a rigid rod segment and poly(ethylene oxide) with the number of repeating units of 17 as a coil segment were synthesized, and their self-assembly behavior in the bulk state and aqueous solution was investigated. In bulk, molecules 1 self-assembled into 1-D lamellar structure in the solid state or smectic A phase in the liquid crystalline phase via the cooperative effects of π-π stacking, micro-phase separation and hydrogen bond interactions. In dilute aqueous solutions, molecules 1 were observed to self-assemble into cylindrical micelles owned uniform diameter and length of hundreds of nanometers.

3-D hexagonal close-packed nano-structure from self-organization of triblock copolymer containing lateral ethyl groups in the middle of rod segment

AbstractWe report an unusual 3-D hexagonal supramolecular nano-structure via self-assembly of a coil-rod-coil molecule in the solid state. The rod-coil molecule consists of five biphenyls linked together with ether bonds as a rod segment, incorporating lateral ethyl groups in the center of the rod segment, and poly(propylene oxide) (PPO) with a degree of polymerization of 17 as coil segments. The molecular structure was characterized by 1H NMR and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy. The self-assembling behavior of the molecule was investigated by means of differential scanning calorimetry, polarized optical microscopy and small angle X-ray scattering reveals that the lateral ethyl groups in the center of rod segment and the PPO coil segments strongly induce the molecule to self-assemble into the 3-D hexagonal close-packed nano-structure in the solid state.

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.

Self-assembly of coil-rod-coil triblock copolymers depending on lateral methyl groups at the interface of rod and coil segments

AbstractTriblock coil-rod-coil compounds, consisting of four biphenyls and a p-terphenyl unit linked together with ether bonds as a rod segment, incorporating lateral methyl or ethoxymethyl groups at 2 and 5 positions of the benzene ring of p-terphenyl and poly(ethylene oxide) (PEO) with a degree of polymerization of 7, 12, 17, incorporating lateral methyl groups between the rod and coil segment as the coil segments, were synthesized. The compound structures were characterized with 1H NMR and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy. The self-assembling behavior of the compounds is investigated by means of differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and optical polarized micrograph (POM) in the bulk state. These compounds spontaneously self-assemble into lamellar, hexagonal perforated lamellar, rectangular columnar, and oblique columnar structures in the crystalline phase, and hexagonal perforated lamellar, bicontinuous cubic, and oblique columnar structures in the liquid crystalline phase, respectively. The results revealed that the lateral methyl groups attached to the interface of rod and coil segments strongly induce the compounds to self-assemble into various supramolecular nanostructures in the crystalline phase and the liquid crystalline mesophase.