Synthesis and Self-assembling of Coumarin-based Low-molecular Weight Organogelators

Four coumarin derivatives（4a-4d） with different alkoxy chains were synthesized. It was found that compound 4d showed a better gelation ability than the other compounds, for example, it could self-assemble into organogels in various organic fluids via ultrasound treatment or heating-cooling process, whereas compound 4c could only gel in a few mixed solvents and compounds 4a, 4b could not form organogel. The results from fluorescent and FT-IR spectra indicate that π-π interaction had an effect on the formation of the organogels of compound 4d besides H-bonding and van der Waals interaction, which were the driving forces for the self-assembling of compound 4c in gel state. The gel of compound 4d in toluene could emit strong fluorescence under UV irradiation and the [2＋2] cyclo-addition was suggested by ^1H NMR and fluorescence spectroscopy. This light-sensitive organogel might find application in optical materials.

Poly(benzyl ether) dendrons without conventional gelation motifs as a new kind of effective organogelators

Two poly(benzyl ether) dendrons,decorated in their periphery with nitrile groups,were divergently synthesized and fully characterized.Their gelation properties were studied by using scanning electron microscopy(SEM),X-ray crystal structure analysis and concentration-and temperature-dependent 1 H NMR spectroscopy.It was found that the gelation capability of these dendrons was highly dependent on dendron generation,and the second-generation dendron G 2-CN proved to be highly efficient organogelator despite the lacking of any conventional gelation motifs,such as amides,long alkyl side chains and steroidal groups.The multiple strong-stacking interactions and hydrogen bonding interactions due to the peripheral isophthalonitrile motifs were proved to be the main driving forces to form the self-assembled gel.

Supramolecular self-assembly of two-component systems comprising aromatic amides/Schiff base and tartaric acid

The gelating properties and thermotropic behaviors of stoichiometric mixtures of aromatic amides 1,2,and the aromatic Schiffbase 3 with tartaric acid(TA)were investigated.Among the three gelators,2-TA exhibited superior gelating ability.Mixture 2-TA exhibits a smectic B phase and an unidentified smectic mesophase during both heating and cooling runs.The results of Fourier transform infrared spectroscopy and X-ray diffraction revealed the existence of hydrogen bonding and rc-ninteractions in 2-TA systems,which are likely to be the dominant driving forces for the supramolecular selfassembly.Additionally,it was established that all of the studied gel self-assemblies and mesophases possess alamellar structure.The anion response ability of the tetrahydrofuran gel of 2-TA was evaluated and it was found that it was responsive to the stimuli of F,Cl,Br,I,AcO.

Towards a universal organogelator:A general mixing approach to fabricate various organic compounds into organogels

Low-molecular-weight organogels(LMOG) have been attracting a surge interest in fabricating soft materials.Although the finding of the gelator molecules has been developed from serendipity to objective design,the achievement of the gelator molecules still needs good design and tedious organic synthesis.In this paper,we proposed a simple and general mixing approach to get the organogel for nearly all the organic compounds and even soluble nanoparticles without any modification.We have designed a universal gelator molecule,which forms organogels with more than 40 kinds of organic solvents from aploar to polar solvents.More interestingly,when other organic compounds or even nanomaterials,which are soluble in certain organic solvents,are mixed with this gelator molecule,they can form organogels no matter whether the individual compounds could form organogel or not.This method is applicable to nearly all kinds of soluble organic compounds and opens an efficient and universal way to fabricate gel materials.

Hydrogen Bonded Supramolecular Polymers in Both Apolar and Aqueous Media： Self-Assembly and Reversible Conversion of Vesicles and Gels

In a preliminary letter （Tetrahedron Lett. 2010, 51, 188）, we reported two new hydrazide-based quadruple hydrogen-bonding motifs, this is, two monopodal （la and lb） and five dipodal （2a, 2b and 3a--3c） aromatic hydrazide derivatives, and the formation of supramolecular polymers and vesicles from the dipodal motifs in hydrocarbons. In this paper, we present a full picture on the properties of these hydrogen-bonding motifs with an emphasis on their self-assembling behaviors in aqueous media. SEM, AFM, TEM and fluorescent micrographs indicate that all the dipodal compounds also form vesicles in polar methanol and water-methanol （up to 50% of water） mixtures. Control experiments show that lb does not form vesicles in same media. Addition of lb to the solution of the dipodal compounds inhibits the latter＇s capacity of forming vesicles. At high concentrations, 3b and 3c also gelate discrete solvents, including hydrocarbons, esters, methanol, and methanol-water mixture. Concentration-dependent SEM investigations reveal that the vesicles of 3b and 3c fuse to form gels and the gel of 3c can de-aggregate to form the vesicles reversibly.

Chiral self-assembly regulated photon upconversion based on triplet-triplet annihilation

Photon upconversion(UC)based on triplet-triplet annihilation(TTA)in quasi-solid or solid state has been attracting much research interest due to its great potential applications.To get effective UC,precisely controlled donor-acceptor interaction is vitally important.Chiral self-assembly provides a powerful approach for sophisticated regulation of molecular interaction.Here we report a chiral self-assembly controlled TTA-UC system composed of chiral acceptor and achiral donor.It is found that racemic mixture of acceptors could form straight fibrous nanostructures,which show strong UC emission,while chiral assemblies for homochiral acceptors emit weak upconverted light.The racemic assemblies allow efficient triplet-triplet energy transfer(TTET)and further realize efficient UC emission,while the homochiral assemblies from chiral acceptor produce twisted nanostructures,suppressing efficient triplet energy transfer and annihilation.The establishment of such chiral self-assembly controlled UC system highlights the potential applications of triplet fusion in optoelectronic materials and provides a new perspective for designing highly effective UC systems.

Organogelators based on p-alkoxylbenzamide and their self-assembling properties

A series of p-alkoxylbenzamides featuring a long alkyl chain have been synthesized and are readily to form stable gels in a variety of organic solvents. Their selfassembly properties and structure-property relationship were investigated by scanning electron microscopy, X-ray diffraction, IH nuclear magnetic resonance, and Fourier transform infrared spectroscopy. The gels formed were multi-responsive to environmental stimuli such as temperature and fluoride anion. The results show that a combination of hydrogen bonding, n-n stacking and van der Waals interaction result in the aggregation of palkoxylbenzamides to form three-dimension networks, depending on the length of the long alkyl chain.

Versatile Organogels of Aluminum Oxide Subnanosheets for Locking Solvents and Adhesion

Herein,we present a facile strategy to prepare versatile aluminum oxide subnanometer nanosheets with oleic acid and stearic acid ligands(OA-Al SNSs and SA-Al SNSs,respectively).The size effect endows subnanosheets with abundant acting sites,remarkable intermolecular interactions,and unique polymer-like properties,including flexibility,viscoelasticity,and sol-gel transitions,which is quite different from traditional inorganic materials.Consequently,subnanosheets could form freestanding organogels and OA-Al SNSs exhibit satisfying semisolidification of various solvents,making it an intriguing candidate for the safe storage and transportation of solvents.Furthermore,SA-Al SNSs exhibit excellent adhesive properties of high strength on diverse substrates,and it is easy to erase it without any damage,demonstrating the promising prospects in practical applications.

Novel four-hydrogen-bond assembled oligoamide dimer with pyrazoline moieties and its photoluminescent properties

In this paper, the synthesis and characterization of a triarylpyrazoline modified four-H-bonded molecular duplex are described. Its molecular structure has been confirmed by ^1H NMR and ESI-MS. The duplex emits strong pure blue light peaking at 448 and 452 nm under UV photoexcitation in solution and solid state, respectively, and its relative photoluminescence quantum efficiency in solution is determined as 0.778 using quinine sulfate as reference. In concentration of 〉40 mmol/L, the duplex can gelate DMSO, and the organogel formed shows good pure blue photoluminescence too. This novel duplex, for its well-defined structure and efficient photoluminescence property, is a prospective candidate for pure blue electroluminescent emitter.

Effects of Main-chain and Chain-ends on the Organogelation of Stearoyl Appended Pendant Valine Based Polymers

In this work, we investigated the effect of hydrophobic interactions between the polymeric backbone and chain-end groups on the self-assembly pathway of stearoyl appended side-chain valine（Val）-based poly（methacrylate/acrylate） homopolymers in different organic hydrocarbons. Gelation studies conducted revealed that while polymers with polyacrylate as backbone induces gelation in several organic hydrocarbons, polymers with polymethacrylate in the main-chain significantly hinders macroscopic gelation. Morphology of the organogels was analysed by field emission scanning electron microscopy（FESEM）, and mechanical strengths of the organogels were determined by rheological measurements. Reversible addition-fragmentation chain transfer（RAFT） polymerization chain transfer agents（CTA）s, [R1―S―C=（S）―S―R2] with different ―R1 and ―R2 groups, have been employed to study the effect of structural variation at the chain-end on macroscopic assembly mechanism. We found that the additional interactions between terminal groups via hydrogenbonding or π-π stacking interactions or both help to build up the self-assembly pathway and thereby produces mechanically stable organogels.

Benzohydrazide Derivatives: Gelation and Application in Oil Spill Recovery

The synthesis and gelation properties of a series of organogelators containing a benzohydrazide unit and two alkoxy chams(oBn) were reported herein. oBn(n=8, 10, 12) could form stable gels in commercial fuels(e.g., diesel), which were characterized by low critical gelation concentrations(CGCs) and good mechanical properties (G'>10^5 Pa). The gelation process was further studied by field-emission scanning electron microscopy(FE-SEM), Fourier transform infrared spectroscopy(FTIR) and X-ray diffraction(XRD), etc. It was demonstrated that in these organogels, molecules self^assembled into fibrils 3D-network, where hydrogen bonding, van der Waals force and π-π interaction were confirmed as the driving forces. As compounds oBn(n=8, 10, 12) show very good gelation properties in diesel, their applications in oil spill treatment have also been tested. It was found tliat oBw could achieve rapid (<30 s) and effective oil removal at room temperature, being good candidates for oil spill treatment in the future. Also, the removal efficiency could be as high as 95%.

Gelation capability of cysteine-modified cyclo(L-Lys-L-Lys)s dominated by Fmoc and Trt protecting groups

A series of symmetrical peptidomimetics （3-8） based on cysteine-modified cyclo（L-Lys-L-Lys）s were synthesized, and their gelation capability in organic solvents was dominated by fluorenylmethyloxycarbonyl （Fmoc） and triphenylmethyl （Trt） protecting groups and the exchange of thiol-to-disulfide as well. The peptidomimetics holding Trt （3 and 4） showed no gel performance, while the Fmoc groups promoted 5 and 6 to give rise to thermo-reversible organogels in a number of organic solvents. The self-assembled fibrillar networks were distinctly evidenced in the organogels by transmission electron micros- copy （TEM） and scanning electron microscopy （SEM） observations. Fourier transform infrared spectroscopy （FT-IR） and fluorescence analyses revealed that the hydrogen bonding and ^-rt stacking play as major driving forces for the self-assembly of these organogelators. A 13-turn secondary structure was deduced for the organogel of 6 by virtue of X-ray diffraction, FT-IR and circular dichroism （CD） measurements, and an interdigitated bilayer structure was also presented.