基于均苯三甲酸与对羟基吡啶的超分子水凝胶

以均苯三甲酸和对羟基吡啶为原料, 采用简便方法合成了一种新的凝胶因子, 并采用1H NMR、IR和元素分析确认其结构. 红外光谱中2849和1894 cm－1处出峰证明羧基与吡啶基间形成了氢键. 在凝胶化过程中, 凝胶因子可自组装形成纤维状网络结构. 随着凝胶因子浓度的增加, 纤维搭接逐渐致密, 凝胶网络密度逐渐增大, 可冻结水含量逐渐增加. 因此, 通过改变凝胶因子浓度可有效控制凝胶的结构及性能. 该凝胶因子在较低浓度下形成的超分子水凝胶在100 ℃下也能够稳定存在.     

A Library of Multipurpose Supramolecular Supergelators: Fabrication of Structured Silica,Porous Plastics,and Fluorescent Gels

Supramolecular gels find applications in various fields. Usually, a specific gelator is useful only for a specific application. This one‐gelator‐one‐application format is one factor that limits the usefulness of supramolecular gels. We report the synthesis of a library of gelators from a common core by using a click‐chemistry approach. Thus, the click reaction of β‐azido‐4,6‐O‐benzylidene–galactopyranoside ( 1 ) with various alkynes gave 11 different gelators having varying gelation abilities. Whereas gelators having alkyl‐chain substituents congealed alkanes and tetraethylorthosilicate (TEOS), the gelators having aromatic substituents congealed aromatic solvents. We exploited this difference in gelling behavior in the templated synthesis of silica rods and porous plastics. The styrene gel of gelator 2 j was polymerized, and the gelator was removed by washing to obtain porous polystyrene. The TEOS gel of gelator 2 b was polymerized to silica, and the gelator template was removed by calcination to give microstructured silica rods. We also developed fluorescent gelator 2 f by this method, which might find applications by virtue of its fluorescence in the assembled state.     

NMR study of the gelation of a designed gelator

The gelation of a designed gelator was investigated by different NMR methods, which showed a clear thermal hysteresis. Two very simple approaches for the NMR determination of the gelation point are suggested. One involves the observation of the NMR integral, and the other records the ratio of the diffusion coefficients between the gelator and the solvent. Differential behavior of the gelator protons are interpreted as a hint that a part of the gelator molecule might still be flexible as in the dissolved state.     

基于偏苯三甲酸与对羟基吡啶复合物的超分子水凝胶

基于偏苯三甲酸和对羟基吡啶合成了一种具有支化结构的凝胶因子,采用氢核磁、红外光谱及元素分析确认其结构.该凝胶因子熔体在冷却时可拉出数厘米的长丝,表明分子间形成了强相互作用.将凝胶因子的水溶液分别在25℃和0℃下自然冷却、以及在25℃的超声作用下冷却,凝胶因子自组装成纤维状网络结构并使水凝胶化,纤维网络的密度及凝胶的稳定性均按上述凝胶形成条件顺序增加.通过干凝胶能谱面扫描分析发现氮元素主要处于纤维内部,表明两亲性凝胶因子对分子自组装的影响.通过分析邻苯二甲酸与对羟基吡啶复合物、偏苯三甲酸的单晶结构表明,凝胶因子基于多种氢键识别作用组装成纤维结构.干凝胶的粉末X射线衍射分析表明在凝胶化过程中凝胶因子沿着特定方向进行组装.     

A novel low-molecular-mass gelator with a redox active ferrocenyl group: tuning gel formation by oxidation

A novel low-molecular-mass gelator containing a redox-active ferrocenyl group, cholesteryl glycinate ferrocenoylamide (CGF), was intentionally designed and prepared. It was demonstrated that the gelator gels 13 out of the 45 solvents tested. Scanning electron microscopy (SEM) measurements revealed that the gelator self-assembled into different supramolecular network structures in different gels. Chemical oxidation of the ferrocenyl residue resulted in phase transition of the gel from gel state to solution state. FTIR and (1)H NMR spectroscopy studies revealed that hydrogen bonding between the gelator molecules in the gel was one of the main driving forces for the formation of the gels.     

Self‐Assembled Fibers Containing Stable Organic Radical Moieties: Alignment and Magnetic Properties in Liquid Crystals

Macroscopically oriented stable organic radicals have been obtained by using a liquid–crystalline (LC) gel composed of an l ‐isoleucine‐based low molecular weight gelator containing a 2,2,6,6‐tetramethylpiperidine 1‐oxyl moiety. The LC gel has allowed magnetic measurements of the oriented organic radical. The gelator has formed fibrous aggregates in liquid crystals via intermolecular hydrogen bonds. The fibrous aggregates of the radical gelator are formed and oriented on cooling by applying a magnetic field to the mixture of liquid crystals and the gelator. Superconducting quantum interference device (SQUID) measurements have revealed that both oriented and nonoriented fibrous aggregates exhibited antiferromagnetic interactions, in which super‐exchange interaction constant J is estimated as ?0.89 cm^?1.     

Low-molecular-weight gelators: elucidating the principles of gelation based on gelator solubility and a cooperative self-assembly model

This paper highlights the key role played by solubility in influencing gelation and demonstrates that many facets of the gelation process depend on this vital parameter. In particular, we relate thermal stability ( T gel) and minimum gelation concentration (MGC) values of small-molecule gelation in terms of the solubility and cooperative self-assembly of gelator building blocks. By employing a van't Hoff analysis of solubility data, determined from simple NMR measurements, we are able to generate T calc values that reflect the calculated temperature for complete solubilization of the networked gelator. The concentration dependence of T calc allows the previously difficult to rationalize "plateau-region" thermal stability values to be elucidated in terms of gelator molecular design. This is demonstrated for a family of four gelators with lysine units attached to each end of an aliphatic diamine, with different peripheral groups (Z or Boc) in different locations on the periphery of the molecule. By tuning the peripheral protecting groups of the gelators, the solubility of the system is modified, which in turn controls the saturation point of the system and hence controls the concentration at which network formation takes place. We report that the critical concentration ( C crit) of gelator incorporated into the solid-phase sample-spanning network within the gel is invariant of gelator structural design. However, because some systems have higher solubilities, they are less effective gelators and require the application of higher total concentrations to achieve gelation, hence shedding light on the role of the MGC parameter in gelation. Furthermore, gelator structural design also modulates the level of cooperative self-assembly through solubility effects, as determined by applying a cooperative binding model to NMR data. Finally, the effect of gelator chemical design on the spatial organization of the networked gelator was probed by small-angle neutron and X-ray scattering (SANS/SAXS) on the native gel, and a tentative self-assembly model was proposed.     

基于均苯三甲酸与4-羟基吡啶的超分子水凝胶

以均苯三甲酸和对羟基吡啶为原料,采用简便方法合成了一种新的凝胶因子,并采用1H NMR、IR和元素分析确认其结构.红外光谱中2849和1894cm-1处出峰证明羧基与吡啶基间形成了氢键.在凝胶化过程中,凝胶因子可自组装形成纤维状网络结构.随着凝胶因子浓度的增加,纤维搭接逐渐致密,凝胶网络密度逐渐增大,可冻结水含量逐渐增加.因此,通过改变凝胶因子浓度可有效控制凝胶的结构及性能.该凝胶因子在较低浓度下形成的超分子水凝胶在100℃下也能够稳定存在.     

Biological Glucose Metabolism Regulated Peptide Self‐Assembly as a Simple Visual Biosensor for Glucose Detection

A glucose oxidase (GOx)‐mediated glucose metabolism was in vitro mimicked and employed to regulate the self‐assembly of peptide‐based building blocks. In this new stimuli‐responsive self‐assembly system, two peptide‐based building blocks, respectively, having aspartic acid (gelator 1 ) and lysine (gelator 2 ) residues were designed and prepared. When adding glucose and GOx to the aqueous solution of gelator 1 or the self‐assembled fibrillar hydrogel of gelator 2 to construct glucose metabolism system, the metabolic product (gluconic acid) can trigger the protonation of the peptide molecules and induce the phase transitions of gelators 1 (sol‐gel) and 2 (gel‐sol). Because this glucose metabolism regulated peptide self‐assembly is built on the oxidation of glucose, it can be used as a simple visual biosensor for glucose detection.     

Optically transparent hydrogels from an auxin-amino-acid conjugate super hydrogelator and its interactions with an entrapped dye

Low-molecular-weight organic hydrogelators (LMHGs) that can rigidify water into soft materials are desirable in various applications. Herein, we report the excellent hydrogelating properties of a simple synthetic auxin-amino-acid conjugate, naphthalene-1-acetamide of L-phenylalanine (1-NapF, M(w)=333.38?Da), which gelated water even at 0.025?wt?%, thereby making it the most-efficient LMHG known. Optically transparent gels that exhibited negligible scattering in the range 350-900?nm were obtained. A large shift from the theoretical pK(a) value of the gelator was observed. The dependence of the minimum gelator concentration (MGC) and the gel-melting temperatures on the pH value indicated the importance of H-bonding between the carboxylate groups on adjacent phenylalanine molecules in the gelator assembly. FTIR spectroscopy of the xerogels showed a β-sheet-like assembly of the gelator. Variable-temperature (1)H?NMR spectroscopy demonstrated that π stacking of the aromatic residues was also partly involved in the gelator assembly. TEM of the xerogel showed the presence of a dense network of thin, high-aspect-ratio fibrillar assemblies with diameters of about 5?nm and lengths that exceeded a few microns. Rheology studies showed the formation of stable gels. The entrapment of water-soluble dyes afforded extremely fluorescent gels that involved the formation of J-aggregates by the dye within gel. A strong induced-CD band established that the RhoB molecules were interacting closely with the chiral gelator aggregates. H-bonding and electrostatic interactions, rather than intercalation, seemed to be involved in RhoB binding. The addition of chaotropic reagents, as well as increasing the pH value, disassembled the gel and promoted the release of the entrapped dye with zero-order kinetics.     

Encapsulation of nanocrystals with responsive gels for spatial optical identification

A tripeptide (β-AspFF) gelator was designed and synthesised using solid-phase peptide synthesis. The as-prepared gelator formed a stable and clear multi-responsive gel in toluene solution. Encapsulating the quantum dots with β-AspFF effectively increased stability and antioxidisation ability which are beneficial for optical identification.     

In Situ Gel‐to‐Crystal Transition and Synthesis of Metal Nanoparticles Obtained by Fluorination of a Cyclic β‐Aminoalcohol Gelator

A new fluorinated version of a cyclic β‐aminoalcohol gelator derived from 1,2,3,4‐tetrahydroisoquinoline is presented. The gelator is able to gel various nonprotic solvents through OH???N hydrogen bonds and additional CH???F interactions due to the introduction of fluorine. A bimolecular lamellar structure is formed in the gel phase, which partly preserves the pattern of molecular organization in the single crystal. The racemate of the chiral gelator shows lower gelation ability than its enantiomer because of a higher tendency to form microcrystals, as shown by X‐ray diffraction analysis. The influence of fluorination on the self‐assembly of the gelator and the properties of the gel was investigated in comparison to the original fluorine‐free gel system. The introduction of fluorine brings two new features. The first is good recognition of o‐xylene by the gelator, which induces an in situ transition from gels of o‐xylene and of an o‐xylene/toluene mixture to identical single crystals with unique tubular architecture. The second is the enhanced stability of the toluene gel towards ions, including quaternary ammonium salts, which enables the preparation of a stable toluene gel in the presence of chloroaurate or chloroplatinate. The gel system can be used as a template for the synthesis of spherical gold nanoparticles with a diameter of 5 to 9 nm and wormlike platinum nanostructures with a diameter of 2 to 3 nm and a length of 5 to 12 nm. This is the first example of a synthesis of platinum nanoparticles in an organogel medium. Therefore, the appropriate introduction of a fluorine atom and corresponding nonbonding interactions into a known gelator to tune the properties and functions of a gel is a simple and effective tactic for design of a gel system with specific targets.     

Semiconducting Fabrics by In Situ Topochemical Synthesis of Polydiacetylene: A New Dimension to the Use of Organogels

A diyne functionalized 4,6‐O‐benzylidene β‐d ‐galactopyranoside gelator, which can align its diyne motifs upon self‐assembly (gelation) have been synthesized. The organogel formed by this gelator undergoes topochemical polymerization to polydiacetylene (PDA) under photoirradiation. This strategically designed gelator has been used to make semi‐conducting fabrics. By developing the organogel on the fabrics, the gelator molecules were made not only to self‐assemble on the fibers, but also to adhere to fabrics through hydrogen bonding. UV irradiation of the gel‐coated fabric/fiber resulted in the formation of PDA on fibers. The benzylidene motif could be deprotected to get PDA with pendant free sugars that strongly bind to the cotton fibrils through multiple hydrogen bonds. Conductivity measurements revealed the semiconducting nature of these fabrics.     

Molecular origin for helical winding of fibrils formed by perfluorinated gelators

A chiral low-molecular weight gelator, N,N'-diperfluoroheptanoyl-1,2(R,R)- or -1,2(S,S)-diaminocyclohexane, was prepared to form a gel of acetonitrile. The conformation of the gelator in fibrils was determined by vibrational circular dichroism spectra, providing a molecular model for self-assembly in a helical fibril.     

Hydrogen-bonding A(LS)2-type low-molecular-mass gelator and its thermotropic mesomorphic behavior

A unique cholesterol-based A(LS)₂-type gelator, which is a hydrogen-bonding complex based on an ALS-type non-gelator molecule 3-cholesteryl 4-(trans-2-(4-pyridinyl)vinyl)phenyl succinate and a counterpart 3-cholesteryloxycarbonylpropanoic acid, shows strong gelation ability in alcohol and aromatic solvents. The formed gel has a high T_g at low gelation concentration, and its xerogel shows fibrillar microstructure revealed by scanning electron microscopy (SEM). FTIR confirms the existence of intermolecular hydrogen bond in the gelator, and X-ray diffraction (XRD) analysis reveals that the gelator possesses a folded conformation in gel and self-assembles into the fibrillar structure mainly by van der Waals interaction between cholesteryl moieties of the gelator. Further more, the thermotropic behavior of the xerogel is studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM), which shows typical optical textures of liquid crystals.     

An amino acid-based gelator for injectable and multi-responsive hydrogel

A novel multi-responsive amino acid-based gelator is developed.     

由凝胶因子形成的十四酸异丙酯超分子凝胶制备与表征

采用双十八烷基-L-苯丙氨酸(Bis18-L-Phe)为凝胶因子,制备了具有热可逆性的十四酸异丙酯(IPM)超分子凝胶。IPM凝胶相转变温度(Tgel)随Bis18-L-Phe浓度增大而增加。偏光显微镜(POM)显示在整个IPM凝胶中形成了相互缠绕的针状聚集体。FT-IR光谱分析表明Bis18-L-Phe分子间酰胺的氢键作用是IPM凝胶形成的一个重要驱动力。IPM凝胶动力学研究表明凝胶时间随Bis18-L-Phe浓度的增大而缩短,随着温度升高而延长,因此IPM凝胶时间可以通过温度和Bis18-L-Phe浓度调控。     

Morphological studies of a (self-assembling oil gelator/liquid crystal) composite system

The aggregation structure of a novel (self-assembling oil gelator/liquid crystal) composite was investigated using light scattering studies and morphological observations. The oil gelator forms a self-assembled-networks aggregate in an organic solvent with a low molecular weight liquid crystal (LC). It became apparent from Hv light scattering patterns and polarizing optical microscopy that two types of LC molecular alignments exist in the composite: a random orientation and a spherulite type one in a nematic gel state. Also, optical and atomic force microscopic observations revealed that fibrils which formed bundles in the fibre-like and spherulite-like aggregates, were formed in the composite. The alignment of the liquid crystal molecules was related to the aggregation structure of the self-assembling oil gelator in a liquid crystal gel state.     

Morphological studies of a (self-assembling oil gelator/liquid crystal) composite system

The aggregation structure of a novel (self-assembling oil gelator/liquid crystal) composite was investigated using light scattering studies and morphological observations. The oil gelator forms a self-assembled-networks aggregate in an organic solvent with a low molecular weight liquid crystal (LC). It became apparent from Hv light scattering patterns and polarizing optical microscopy that two types of LC molecular alignments exist in the composite: a random orientation and a spherulite type one in a nematic gel state. Also, optical and atomic force microscopic observations revealed that fibrils which formed bundles in the fibre-like and spherulite-like aggregates, were formed in the composite. The alignment of the liquid crystal molecules was related to the aggregation structure of the self-assembling oil gelator in a liquid crystal gel state.     

A phase-selective,bis-urea organogelator with a curved bis-naphthalene core

A phase-selective,bis-urea organogelator with a curved bis-naphthalene core was synthesized and characterized.This gelator is capable of gelating a variety of hydrocarbons and oils.The resulting gels have been characterized by rheology,SEM,and molecular modelling.The gelator can be applied in the powder form for the recovery of a thin layer of petrol oil spill in water.